Structure and Functions in living organisms Flashcards
pass gcse
nucleus
controls the cells activity (by making proteins)
contains the chromosomes (strands of DNA which carry genes which code for a protein)
cell membrane
boundary between the cytoplasm and the cell’s surrounding.
controls what substances enter and exit the cell.
cytoplasm
jelly-like liquid where reactions occur
mitochondria
carries out aerobic respiration, which produces ATP
ribosomes
synthesize (assemble) proteins and amino acids
chloroplasts
contain chlorophyll, absorb light energy and use it to carry out chemical reactions of photosynthesis making biological molecules for plants.
cell wall
helps keep plants in a fixed shape
vacuole
filled with a water liquid called cell sap, stores dissolved sugars, mineral ions and other substances.
similarities of plants and animal cells
nucleus
cytoplasm
mitochondria
cell membrane
ribosomes
differences of plants and animal cells
plants only:
cell wall (cellulose)
vacuole
chloroplasts
what is the acronym of chemical molecules in carbs, lipids and protein
CHO CHO CHON
carbohydrate structure
large molecules made up of smaller basic units.
starch and glycogen from simple sugars (smallest unit of carbs).
complex carbs are made up of 1000s of simple sugars joined together.
lipid structure
large molecules made up of smaller basic units.
fatty acids and glycerol.
made of 3 fatty acids joined to a glycerol.
protein structure
large molecules made up of smaller basic units. made of many amino acids joined together.
20 different amino acids can be joined together in any order to create millions of different proteins.
the shape of a protein helps it carry out its job
why are starch and glycogen good storage molecules
less soluble as simple sugars so have less effect on osmosis
what uses starch and glycogen
plants store glucose as starch
animals and fungi store glucose as glycogen
practical - investigate food samples for the presence of glucose
glucose - benedicts test
1. add benedicts solution to a sample of food
2. place in water bath at 80’c for 5 mins
3. colour changes from blue -> brick red
functions of lipids
- thermal insulation
- electrical insulation (around nerve cells)
- buoyancy
- part of cell membranes
- energy storage (can be used in respn)
functions of proteins
- structural molecules
- controlling chemical reactions (enzymes are proteins)
- messenger molecules (hormones are proteins)
- combatting disease (antibodies are proteins)
- transport (haemoglobin and cell membrane proteins)
practical - investigate food samples for the presence of starch
starch - iodine test
1. add a few drops of orange iodine solution to the sample on a spotting tile
2. color changes from orange to blue/black
practical - investigate food samples for the presence of proteins
protein - buriets test
1. add 2cm water to a food sample and shake
2. add buriets solution
4. original colour -> pale purple
practical - investigate food samples for the presence of lipids
lipid - emulsion (ethanol)
1. food sample is placed in test tube
2. add a small volume of absolute ethanol and shake to dissolve any lipid in the alcohol
3. add equal volume of water
4. original colour -> cloudy white
what is an enzyme
a biological catalyst for metabolic reactions
how does temperature affect enzyme function
as temperature increases the enzyme and substates have more kinetic energy which means they move faster so have more successful collisions
once temperature has got to a certain point the temperature breaks the bonds that hold together the amino acids (which make the proteins) which changes the shape of the enzyme.
this is denaturing
once the enzyme has denatured the substrate can no longer fit in the active site (as it has lost its shape) meaning that the reaction will stop
practical - investigate how enzyme activity can be effected by changes in temperature
amylase digests starch
- mix 10cm of 10% starch solution with 5cm of 5% amylase in a boiling tube.
- heat in a water bath
- every minute add 1 drop of this solution to 1 drop of iodine in a spotting tile
- repeat using different temps of water baths
when the starch has been fully digested (so none is present) iodine will stay orange
diffusion
the random movement of particles from a high to a lower concentration
so particles of O2 will move out of the lungs into the RBCs as the lower conc of O2 is in the RBCs
active transport
the movement of molecules from a low to high concentration using ATP
plants use active transport in their root hair cells to absorb mineral ions.
organisms have special carrier proteins in the cell membrane. These use ATP to provide the energy to move the substances across the membrane against the concentration gradient.
osmosis
the movement of water molecules from a high potential to a lower potential across a partially permeable membrane
how does surface area to volume ratio affect movement of substances in and out of cells
A larger surface area speeds up the rate of diffusion as there are more opportunities for the molecules to move, which is why surfaces such as alveoli in lungs are so large. Surface area to volume ratio is more significant, as the two counteract (oppose) each other: an efficient exchange surface has a surface area which is very large compared to the distance the molecules must travel. SA:V is increased when structures are small.
how does distance affect movement of substances in and out of cells
Diffusion takes longer if the molecules have to travel further. Therefore cells are small (smaller volume reduces distance).
how does temperature affect movement of substances in and out of cells
At higher temperatures, molecules have more kinetic energy and so move faster.
how does concentration gradient affect movement of substances in and out of cells
If there is a very large difference in concentration between to areas, molecules will diffuse from the higher to the lower concentration quickly. If the concentration gradient (difference) is small, diffusion will happen more slowly.
practical - investigate diffusion and osmosis using living systems
- Make a 5 different concentration of sucrose solutions
- Measure 5cm3 of each dilution into separate test tubes.
- Use a cork borer to cut out six potato chips and cut down the sections into identically sized chips. Dry each chip using a paper towel to remove excess
water but do not squeeze. - Weigh each before the start of the experiment.
- Place a potato chip in each test tube (one per sucrose concentration) and leave
for 20 minutes. - Remove each potato chip, dry gently using paper towel, and weigh them in turn.
- Calculate the percentage change in mass for each sucrose solution.
practical - investigate diffusion and osmosis using non-living systems
- Add sucrose solution to a section of Visking tubing – a selectively permeable substance used to model a cell membrane.
- Weigh the Visking tubing and its contents.
- Add the Visking tubing to a beaker of water.
- Leave for 1 hour.
- Pat the Visking tubing dry to remove excess water.
- Reweigh the Visking tubing and its contents.
what does photosynthesis do
plants produce glucose from simple inorganic molecules – carbon dioxide and water – using light energy
word equation for photosynthesis
water + carbon dioxide -> (light energy) oxygen + glucose
chemical equation for photosynthesis
6CO2 + 6H2O → C6H12O6 + 6O2
how do CO2 levels affect photosynthesis rate
adding more CO2 increases rate of reaction because there are more molecules for the enzymes to collide with. there is a point where it doesn’t matter how much CO2 there is as other factors are now limiting
How does light intensity effect the photosynthesis rate
adding more light (increasing brightness) increases rate of reaction because there is more energy for the reaction to occur. there is a point where it doesn’t matter how much light there is as other factors are now limiting
How does temperature affect the rate of photosynthesis
increasing temperature increases the rate of reaction because the enzymes and substrates have more kinetic energy up until a point where the temperature increases too much when the enzymes will denature
how is the SA of the leaf specialized for photosynthesis
large SA and thin, to maximize SA of the leaf absorption of sunlight by the photosynthesis cells. it also increases the amount of stomata, so CO2 can diffuse quicker
how is the upper epidermis of the leaf specialized for photosynthesis
upper epidermis is transparent which allows light to pass through to the mesophyll
how is the palisade of the leaf specialized for photosynthesis
palisade mesophylls are long and thin and tightly packed. they contain large numbers of chloroplasts which maximize sunlight absorption. the palisade mesophylls is the main site of photosynthesis
how is the stomata of the leaf specialized for photosynthesis
stomata allow gas to diffuse into the air spaces of the leaf. this allows a short diffusion distance for CO2. also can close to reduce water loss (at night)
how is the xylem of the leaf specialized for photosynthesis
xylem transports the water into the leaves. this provides a short distance for the water to diffuse into the photosynthesis cells
why do plants need mineral ions
to grow
why do plants need magnesium ions
for chlorophyll
why do plants need nitrate ions
for amino acids
practical 2.23 - evolution of oxygen from a water plant
- Take a bundle of shoots of a pondweed
- Submerge them in a beaker of water
- Use a light a set distance from the plant (measure with a ruler)
As oxygen is produced, the bubbles of gas will appear - count the number of bubbles over a set time, eg 60 secs
Repeat steps for different distances of the light
and calculate mean
what are the components of a balanced diet
carbohydrates, proteins, lipid, vitamins, minerals, water, dietary fiber
what foods give carbs
bread, potatoes, pasta, rice, cereals, fruit
what food give protein
meat, eggs, fish, quinoa, quorn
what foods give lipids
butter, cooking oils, cream, avocados
functions of carbs
fuel for respiration
functions of proteins
growth and repair of cells and tissues
fuel for respiration
functions of lipids
store of energy
fuel for respiration
insulation for (thermal and electrical)
sources of iron
red meat, liver, spinach
sources of vit A
fish liver oil, liver, butter, carrots
sources of calcium
milk and dairy products
sources of vit C
fresh fruit and vegetables
functions of iron
forms part of hemoglobin which binds to oxygen
sources of Vit D
dairy products, oily fish
functions of calcium
needed to form bones and teeth
functions of vit A
making a chemical retina and also protects the surface of the eye
functions of vit C
needed for cells and tissues to stick together
functions of vid D
needed to absorb calcium and phosphate ions from food
iron deficiency
amenia
calcium deficiency
rickets
vit A deficiency
night blindness and damaged corena
vit C deficiency
scurvy
vit D deficiency
rickets caused from weak bones
functions of water
water is an essential solvent and is used to transport the components of blood and is crucial for temperature regulation by sweating
functions of dietary fibre
fiber helps the movement of food through the intestine, preventing constipation and bowel cancer.
how does age affect energy requirements
Young people need more energy requirements as it is used for growth and muscle development
how does activity levels affect energy requirement
When a person is more active there is more energy requires as there are more muscle contractions which requires more respiration as it needs more energy
how does pregnancy affect energy requirement
Energy requirements increase as energy is needed to support fetus, and the larger mass the mother needs to carry
ingestion
taking food in through the mouth and swallowing
digestion
breaking down large insoluble molecules into smaller pieces (physical digestion) and smaller soluble molecules
absorption
movement of small soluble molecules out of the gut and into the blood by diffusion and active transport
egestion
passing out undigested food out through the anus
assimilation
building larger biomolecules from the small soluble molecules in all cells
what are the first 2 parts of the digestive system
mouth + oesophogus
what happens in the mouth
mechanical + chemical digestion + swallowing
mechanical - food is broken down into smaller molecules by chewing. this increases SA for enzymes and prevents discomfort when swallowing
chemical - saliva is released by the salivary glands. saliva makes food easier to swallow and it contains amylase
swallowing - before swallowing food is shaped into a ball and pushed to the back of the mouth by the tongue. this ball is called a bolus. there is a flap called epiglottis which blocks food from entering the trachea
what is chemical digestion
food broken down into smaller soluble molecules by enzymes, bile and acids
what is mechanical digestion
food broken down via physical methods such as churning, grinding and chewing
what happens in the oesophagus
long tube that connects the mouth and the stomach. the bolus is pushed down/through by peristalsis
what is peristalsis
the gut muscles contracting and relaxing to form a wave to push the bolus down/through the oesophagus.
circular muscles contract + longitudinal muscles relax
circular muscles relax + longitudinal muscles contract
what happens in the stomach
the gastric glands in the stomach walls secrete pepsin which starts to digest protein
contractions of the stomach wall causes the contents to mix maximizing the contact between the enzymes and food
the stomach is acidic because HCl is released from the gastric glands as the optimum pH for pepsin is acidic. the low pH would burn through the stomach walls so they are covered in mucus to prevent this. the HCl also kills most bacteria and fungi present in the food.
what happens in the small intestine
both digestion and absorption happen in the small intestine
made up of duodenum and ileum
what happens in the duodenum
the final place of chemical digestion.
the pancreas makes several enzymes and secretes them into the duodenum.
trypsin, amylase, lipase
the duodenum also contains glands which secrete the enzymes they produce into the duodenum
maltase, peptidase
the duodenum also contains bile
what is bile
bile is produced by the liver and stored in the gall bladder
- neutralizes the stomach acid because the duodenum enzymes work best at 7-8 pH
- emulsifies lipids - breaks down the large droplets into smaller droplets, increasing SA for lipase to digest the fat
what happens in the ilium
absorption begins. the small soluble molecules are absorbed. some by diffusion but some such as glucose by active transport.
how is the ilium optimized for diffusion
large SA - folding of the ileum, villi & microvilli (folds on the surface of cells lining the villi) increase SA
short diffusion distance - the villi cells are one cell thick
high concentration gradient - provided by capillary network and lacteals removing absorbed molecules
what happens in the colon
site of all reabsorption of water
what happens the rectum
the faeces are stored in the rectum and egested from the anus
whats execretion
the removal of waste products by chemical reactions
eg urea removed by the kidneys and sweating
what does the pancreas do
produces and secretes amylase, trypsin, lipase into the duodenum
secretes an alkaline fluid into the duodenum to neutralize the acidity of the stomach
practical 2.23 - show chlorophyll is required for photosynthesis
- Drop a variegated leaf in boiling water (heated by a bunsen burner)
This denatures the enzymes in the leaf and breaks down the cell walls (meaning photosynthesis stops) - Turn off the bunsen burner
- Transfer the leaf into hot ethanol in a boiling tube for 5-10 minutes
This removes the chlorophyll so color changes from iodine can be seen more clearly - Rinse the leaf in cold water
This is done to soften the leaf tissue after being in ethanol - Spread the leaf out on a white tile and cover it with iodine solution
In a variegated leaf, the green parts of the leaf will turn blue-black as photosynthesis is occurring in these areas of the leaf as they contain chlorophyll.
The area of the leaf that was white will remain orange-brown as it does not contain any chlorophyll and so could not photosynthesize, while the green area will turn blue-black
these results show chlorophyll is essential to photosynthesis
practical 2.23 - show that a plant requires light to photosynthesis
Destarch a plant by placing it in a dark cupboard for 24 hours
This ensures that any starch already present in the leaves will be used up and will not affect the results of the experiment
Following de-starching, cover a leaf of the plant with aluminium foil and place the plant in sunlight for a day
Remove a covered leaf and a uncovered leaf and test for starch using iodine using the method below
- Drop a the leaves in boiling water (heated by a bunsen burner)
This denatures the enzymes in the leaf and breaks down the cell walls (meaning photosynthesis stops) - Turn off the bunsen burner
- Transfer the leaves into hot ethanol in a boiling tube for 5-10 minutes
This removes the chlorophyll so color changes from iodine can be seen more clearly - Rinse the leaf in cold water
This is done to soften the leaf tissue after being in ethanol - Spread the leaves out on a white tile and cover it with iodine solution
the uncovered leaf will turn blue/black because it had access to light in order to photosynthesis.
the covered leaf will stay orange/brown because it did not have access to light which stops photosynthesis occurring
practical 2.23 - show a plant requires CO2 to photosynthesis
place one leaf into a conical flask containing soda lime (which absorbs CO2)
place another leaf into a conical flask without anything in
- Drop a the leaves in boiling water (heated by a bunsen burner)
This denatures the enzymes in the leaf and breaks down the cell walls (meaning photosynthesis stops) - Turn off the bunsen burner
- Transfer the leaves into hot ethanol in a boiling tube for 5-10 minutes
This removes the chlorophyll so color changes from iodine can be seen more clearly - Rinse the leaf in cold water
This is done to soften the leaf tissue after being in ethanol - Spread the leaves out on a white tile and cover it with iodine solution
the leaf in the soda lime will remain orange/brown as there was no CO2 which is required to photosynthesis
the leaf without soda lime will turn black/blue as there is CO2 so it can photosynthesis
how is the small intestine adapted for absorption
villi and micro villi
very long which increase SA and time for diffusion and active transport
peristalsis mixes food together and keeps things moving
why do leaves normally contain starch
leaves are the site of photosynthesis which produces glucose.
any excess glucose is stored as starch which is why the starch test proves photosynthesis is occurring
starch ->
starch –(amylase)–> maltose
maltose ->
maltose –(maltase)–> glucose
protein ->
protein –(pepsin)–> peptides
protein ->
peptides –(trypsin)–> amino acids
lipid ->
lipid –(lipase)–> glycerol and 3 fatty acids
practical 2.33B - investigate the energy content in a food sample
BANANA CHIP
- attach a boiling tube to a clamp stand
- Use the measuring cylinder to measure out 25cm3 of water and pour it into the boiling tube
- Record the starting temperature of the water using the thermometer
- Weigh the initial mass of the food sample
- Set fire to the sample of food using the bunsen burner and hold the sample 2cm from the bottom of the
boiling tube until it has completely burned - Record the final temperature of the water
- (Once cooled) weigh the mass of any remaining food and record
- Repeat the process with different food samples
A larger increase in water temperature indicates a larger amount of energy contained by the sample
We can calculate the energy in each food sample using the following equation:
Energy transferred (J) =
(mass of water (g) x 4.2 x temperature increase (°C)) ÷ (mass of food (g))
how do living organisms produce ATP
respiration!!
how do cells get energy to carry out their life processes
ATP from respiration
what is cell respiration
cells constantly break down food molecules to produce ATP
this happens continuously because without it the cell would have no energy and die
does cell respiration happen in plants
yes it is part of the process as they photosynthesis to create glucose and then respire the glucose to create energy
what is the difference between anaerobic and aerobic respiration
aerobic respiration requires O2 whereas anaerobic respiration does not
aerobic respiration completely breaks down glucose whereas anaerobic respiration does not
aerobic respiration releases a lot of energy whereas anaerobic respiration only produces a little
what are carbohydrases
they are enzymes that break down carbohydrates into simple sugars
amylase and maltase
what are proteases
they are enzymes that break down protein into amino acids
pepsin, trypsin, proteases
what are lipases
they are enzymes that break down lipids into glycerol and fatty acids
lipase
word equation for aerobic respiration
oxgyen + glucose —> water + carbon dioxide
chemical equation for aerobic respiration
C6 H12 O6 + 6O2 → 6CO2 + 6H20
why does aerobic respiration produce more ATP than anaerobic respiration
aerobic respiration fully oxidizes glucose whereas anaerobic respiration doesn’t
word equation for anaerobic respiration in animals
glucose —-> lactic acid
word equation for anaerobic respiration in plants + fungi + bacteria
glucose —-> ethanol + carbon dioxide
2.39 practical - investigate the evolution of CO2 and heat for respiring seeds
- place some alive seeds soaked in Milton solution (bleach which kills any bacteria present which would also
respire affects results) in a thermos flask - place some dead seeds (boiled to denature enzymes) soaked in Milton solution in another thermos flask
- Make sure the cotton wool is plugging the top of each flask
- place a thermometer and the flasks
- place a delivery tube into the flasks and collect the gas produced
- Record the initial temperature
- After 4 days, record the final temperature
The thermometer in the flask with the germinating seeds should show an increase in temperature
the dead seeds should remain at room temperature
This is because the alive seeds are respiring and producing heat energy in the process
This shows that respiration is an exothermic reaction
The dead seeds are not respiring because they are dead, so the temperature remains the same
bubble the collected gas though limewater which will turn cloudy is CO2 is present
the gas produced from respiration is CO2 so the gas from the alive seeds will turn limewater cloudy
the gas from the dead seeds won’t as they haven’t produced CO2 as they can’t respire
what is coronary heart disease
coronary arteries supply heart muscle tissue with blood. this blood provides muscle cells with O2 and glucose for aerobic respiration and the blood also removes CO2 produced from aerobic respiration.
fatty deposits will build up in your artery walls which narrow the lumen (space for blood) in the arteries. this reduces the amount of blood that can pass through to the arteries and therefore the amount of blood that reaches the heart muscle cells.
less blood reaching the working muscle cells means that less O2 (and glucose) meaning the cells respire aerobically less have to respire anaerobically more. anaerobic respiration produces lactic acid which is poisonous.
this poisoning of the heart muscle cells will lead to a heart attack
what factors make coronary heart disease more likely to happen
diet - eating lots of saturated fats increases blood cholesterol and increases the risk of fatty deposits
smoking - increases blood pressure and increases the risk of fatty deposits forming
high blood pressure - damages artery lining and increases the rick of fatty deposits occurring
obesity - being obese will increase blood pressure
chemicals in cigarettes
nicotine
tar
carbon monoxide
+ more than 4000 others
effects of nicotine
narrows blood vessels leading to an increased blood pressure
increases heart rate
both of these effects can cause blood clots to form in arteries leading to a heart attack or a stroke
effects of carbon monoxide
CO binds permanently to haemoglobin (forming carboxyhaemoglobin) which reduces the capacity to carry oxygen
this puts more stress on the breathing system as breathing frequency and depth need to increase to get the same amount of oxygen into the blood
also puts more strain on the circulatory system to pump blood faster around the body and increases the risk of coronary heart disease and strokes
effects of tar
tar is a carcinogen
carcinogens are chemicals that can alter the DNA and increase the risk of cancer (rapid, uncontrolled cell growth)
how does smoking affect the cilia cells and etc
in a healthy person the trachea and bronchi are specialized to prevent dirt and bacteria entering the lungs.
goblet cells produce mucus which traps dirt and pathogens
the cilia of the lining cells waft the mucus up the airways
the chemicals from smoking destroy the cilia.
at the same time the mucus production will increase because of the smoke (with all of the bad stuff in it)
the destroyed cilia cells cannot then waft the mucus up so the mucus builds up resulting in a cough (smokers cough) and increases the risk of infection.
bronchitis is a disease resulting in the build up of infected mucus in the bronchi and bronchioles
how does smoke damage the alveoli
the smoke breaks down the alveoli’s walls and so fuse together forming larger irregular air spaces. this decreases SA and so less oxygen diffuses into the blood
2.50 practical - investigate breathing in humans, including the release of CO2 and effect of exercise
- get 2 or more students
- Work out student A’s breathing rate at rest
- Count their number breaths for 15 seconds and multiply by 4
- Repeat several times to calculate an average
- Student A should then exercise for a set time (at least 4 minutes)
- Immediately after exercising, count the breaths taken in 15 seconds and multiply by 4 to obtain the
breathing rate per minute - Compare the result to the breathing rate at rest in order to work out the change in breathing rate as a
result of exercise - Repeat this last step every minute after exercise for 5 minutes
Repeat the process for student B
Frequency of breathing increases when exercising
This is because muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them (and carbon dioxide removed) to keep up with the energy demand
If they cannot meet the energy demand they will also respire anaerobically, producing lactic acid
After exercise has finished, the breathing rate remained elevated for a period of time
This is because the lactic acid that has built up in muscles needs to be removed as it lowers the pH of cells and can denature enzymes catalyzing cell reactions
It can only be removed by combining it with oxygen - this is known as ‘repaying the oxygen debt’
This can be tested by seeing how long it takes after exercise for the breathing rate to return to normal
The longer it takes, the more lactic acid produced during exercise and the greater the oxygen debt that needs to be repaid and therefore the more unfit the student is
how is water absorbed by the root hair cells
plants take in water from the soil through the root hair cells. the root hair cells (RHC) are specialized to increase their surface area which then increases rate of active transport.
the plant actively transports the mineral ions from the soil into the root hair cells. the mineral ions lower the water potential of the root hair cells. the water will then osmosis from the soil to the RHCs as the RHCs have the lower water potential. (osmosis - water moves from high to low conc)
this gradient is maintained as the water is continually being taken up by the xylem.
transpiration
water lost from the leaves, mainly from the stomata due to evaporation off of the leaf surface
(water evaporates into the air spaces in the spongy mesophyll then diffuses out of the stomata)
how is transpiration rate affected by humidity
Very humid air contains a great deal of water vapour – there is a smaller concentration gradient, so transpiration slows down.
In dry air the diffusion of water vapour from the leaf to the atmosphere will be rapid.
Transpiration therefore increases if humidity decreases.
how is transpiration rate affected by wind speed
In still air, the region around a transpiring leaf will become saturated (full) with water vapour so that no more can escape from the leaf –causing transpiration to slow down.
In moving air, the water vapour will be blown away from the leaf as fast as it diffuses out. This will speed up transpiration.
Transpiration therefore increases as wind speed increases.
how is transpiration rate affected by temperature
On a hot day, water will evaporate quickly from the leaves of a plant as the water molecules have more kinetic energy.
Transpiration therefore will increase as temperature increases
how is transpiration rate affected by light intensity
Light itself does not affect evaporation, but in daylight the stomata of leaves are open to supply carbon dioxide for photosynthesis.
This allows more water to diffuse out of the leaves and into the atmosphere
2.58B practical - investigate the role of wind in determining the rate of transpiration for a leafy shoot
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - place a hairdryer so its blowing on the plant to recreate wind
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
2.58B practical - investigate the role of increased temperature in determining the rate of transpiration for a leafy shoot
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - make the room hot
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
2.58B practical - investigate the role of humidity in determining the rate of transpiration for a leafy shoot
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - surround the plant in a clear plastic bag
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
2.58B practical - investigate the role of light in determining the rate of transpiration for a leafy shoot
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - make the room dark
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
what is excretion
the removal of toxic waste products that have been made by cells
what do the lungs excrete
CO2
what do the kidneys excrete
Urea
what does the skin excrete
Urea
what are the organs of excretion
skin, lungs, kidneys
what does the kidney do
excrete toxic waste products and substances in excess
osmoregulation
whats osmoregulation
the process of maintaining water and salt concentrations across membranes in the body
example of homeostasis
what are the 3 parts of the kidney
cortex - the outmost region
Medulla - the inner section of the kidney
Renal pelvis - the tube linking the kidney to the ureter
where are the nephrons
in the kidney
Nephrons start in the cortex of the kidney, loop down into the medulla and back up to the cortex
where do the contents of the nephron go
drain into the renal pelvis and the urine collects there before it flows into the ureter to be carried to the bladder for storage
structure of the nephron
The nephron is made up of a kidney tubule which has several sections:
glomerulus inside the bowman’s capsule
Proximal convoluted tubule
Loop of Henlé
Distal convoluted tubule
Collecting duct
what is the proximal convoluted tubule
section of nephron after the bowmans capsule and before the loop of henle
what is the distal convoluted tubule
section of nephron after the loop of henle and before the collecting duct
how does the kidney excrete
Ultrafiltration
Selective reabsorption of glucose
Reabsorption of water and salts
what is ultrafilterisation
Arterioles branch off the renal artery and lead to each nephron, where they form a knot of capillaries (the glomerulus) sitting inside the cup-shaped Bowman’s capsule
The capillaries get narrower as they get further into the glomerulus which increases the pressure on the blood moving through them (which is already at high pressure because it is coming directly from the renal artery which is connected to the aorta)
This eventually causes the smaller molecules being carried in the blood to be forced out of the capillaries and into the Bowman’s capsule, where they form what is known as the filtrate
This process is known as ultrafiltration
The substances forced out of the capillaries are glucose, water, urea, salts
Some of these are useful and will be reabsorbed back into the blood further down the nephron
what is in the glomerular filtration
glucose, water, urea, salts
selective reabsorption of glucose
After the glomerular filtrate enters the Bowman’s Capsule, glucose is the first substance to be reabsorbed at the proximal convoluted tubule
This takes place by active transport (by specialized cells)
The pct is adapted for this by having many mitochondria to provide energy for the active transport of glucose molecules
Reabsorption of glucose cannot take place anywhere else in the nephron as the gates that facilitate the active transport of glucose are only found in the proximal convoluted tubule
whats in urine
water, urea, ions
what happens in the loop of Henle
Salts are reabsorbed by diffusion and active transport as well as water by osmosis
also makes the medulla salty which makes osmosis more efficient
what is absorbed in the distal convoluted tubule
The distal convoluted tubule (DCT) assists in the regulation of potassium, sodium, calcium, and pH levels in the body.
order of organisation
organelle - a component within a cell that carries out a specific task (mitochondria)
cell - basic functional and structural units in a living organism
tissues - a group of cells of similar structure working together to perform a particular function
organs - made from a group of different tissues working together to perform a particular function
organ system - made from a group of organs with related functions, working together to perform body functions within the organism
how is enzyme function affected by changes in pH
If the pH is too high or too low, the bonds that hold the amino acid chain together to make up the protein can be disrupted/destroyed
This will change the shape of the active site, so the substrate can no longer fit into it, reducing the rate of activity
Moving too far away from the optimum pH will cause the enzyme to denature and activity will stop
2.14B practical: investigate how enzyme activity can be affected by changes in pH
amylase digests starch
- mix 10cm of 10% starch solution with 5cm of 5% amylase in a boiling tube.
- add in a few drops of a solution with a specific pH
- every 10s add 1 drop of this solution to 1 drop of iodine in a spotting tile
- repeat using different pH solutions
when the starch has been fully digested (so none is present) iodine will stay orange
when the iodine stays blue it shows the enzyme has been denatured as it is not capable of breaking down the starch so the starch is still present giving a positive test result.
what is the role of diffusion in gas exchange
in single celled organisms gases can exchange sufficiently by just diffusing straight through the cell membrane
in multi celled organisms, there are exchange surfaces and organ systems that maximise the exchange. eg lungs or leaves
gain nutrients in the digestive system
gain oxygen in the lungs
remove waste products in the lungs and kidneys
what is gas exchange
the exchange of gases from an organism to the enviroment or vice versa
how is the gas exchange of CO2 and O2 related to respiration and photosynthesis (in plants)
plants need O2 and CO2 for respiration and photosynthesis.
FOR RESPN
the O2 diffuses from a high conc outside the leaf to a lower conc inside the leaf.
the CO2 diffuses from a high conc inside the leaf to a lower conc outside the leaf
the reverse happens for photosynthesis
how is the structure of leaves adapted for gas exchange
adapted to maximise gas exchange of CO2 (released in respiration but used in photosynthesis), O2 (released in photosynthesis but used in respiration) and water vapour (released in respiration and transpiration)
adaptation of whole leaf
- thin leaves which give short diffusion distance
- flat leaves which provide a large surface area to volume ratio
- leaves have many stomata which allow movement of gases in and out of the air spaces by diffusion
adaptations of specific bits
- leaves contain air spaces which allow gas movement around the other mesophyll cells and a shorter diffusion distance
- stomata can open and close allowing CO2 in when there is sunlight for photosynthesis and then shut when there is no sunlight to stop excess loss of water
- upper epidermis is transparent which allows light to penetrate to the palisade mesophyll
- palisade cells are long, thin and tightly packed. They contain large numbers of chloroplasts. This maximises absorption of sunlight energy. (palisade mesophyll is main site of photosynthesis)
- xylem transports water absorbed in roots to the leaves which provides a short diffusion distance for the water to move into the photosynthesis cells
- spongy mesophyll are loosly packed creating air gaps. they also are coated in a thin layer of water which allows the gases to dissolve
what is the role of the stomata in gas exchange
stomata open to allow CO2 to diffuse into the leaf for photosynthesis. they also allow other gases to diffuse in and out
stomata will also close when there is little light as the plant has no need for CO2 for photosynthesis as there is not enough light to allow the process to happen. they will also close when there is little water as water will diffuse out or conditions that allow water to diffuse out quickly (windy or hot or dry air) if they are open
how do guard cells work
the guard cell opens and closes the stomata by actively transporting ions into GCs cytoplasm, then the ions lower the water potential making water to move in making the cell turgid so the stomata open
In the light the guard cells photosynthesise. The concentration of sugars increases, the water potential in the guard cells falls and so water moves into the guard cells by osmosis. They become turgid (swollen) - this causes the guard cells to become banana shaped, due to the inflexible inner cell wall, and opens the stomata.
Photosynthesis stops in the dark. As the sugar concentration falls (due to respiration), water potential increases and water moves out of the guard cells. They become flaccid and the stomata close.
what is the net exchange of O2 and CO2 during the day and night
Plants can only photosynthesise when they have access to light, however, cells respire all the time
This means that gas exchange in plants varies throughout a 24 hour period
During the daytime plants both respire and photosynthesise
The rate of photosynthesis tends to be higher than the rate of respiration (unless there is a low light intensity)
Therefore there is net diffusion of carbon dioxide into the plant and net diffusion of oxygen out of the plant during the day
During the nighttime, plants only respire
This means that there is a net movement of oxygen into the plant and net diffusion of carbon dioxide out of the plant during the night time
At low light intensities, the rate of photosynthesis is equal to the rate of respiration
This means that there is no net movement of oxygen or carbon dioxide in either direction
2.45B practical: investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator
Measure out 20 cm3 hydrogencarbonate indicator into 4 boiling tubes
Put some cotton wool into each boiling tube
Label the boiling tubes A-D and set them up as follows:
Tube A - No leaf (control tube)
Tube B - Place a leaf in the tube and leave in the light
Tube C - Place a leaf in the tube and wrap it in aluminium foil to block out the light
Tube D - Place a leaf in the tube and wrap it in gauze to allow partial light
Put a bung into the top of each tube
Leave all 4 tubes in the light for 30 minutes
After 30 minutes, we would expect the following results:
Tube A - The control tube should remain an orange/red colour to show that the carbon dioxide is at atmospheric levels
There has been no net movement
Tube B - This tube was placed in the light with a leaf which is photosynthesizing and respiring
Because the rate of photosynthesis is greater than the rate of respiration, the hydrogencarbonate indicator will turn purple as there is less carbon dioxide than atmospheric levels
Tube C - This tube had a leaf inside, but was wrapped in aluminium foil meaning that no sunlight could reach the leaf
No light means that this leaf will not photosynthesize but will still be respiring and therefore producing carbon dioxide. The indicator will turn yellow as carbon dioxide levels increase above atmospheric levels
Tube D - This tube had a leaf inside and was wrapped in gauze allowing partial light
This means that the rate of photosynthesis equals the rate of respiration so there was no net change in carbon dioxide levels and the indicator remained orange/red
structure and function of the thorax
ribs - bone structure which protects internal organs
intercostel muscles - muscles between ribs which control the movement of the ribs
diaphragm - sheet of conective tissue and muscle at the bottom of the thorax to allow inhalation and exhalation
trachea - windpipe that connects the mout and nose to the lungs
bronchi - large tubes branching off the trachea with one bronchus for each lung
bronchioles - bronchi split to form smaller tubes connected to the alveoli
alveoli - tiny air sacs where gas exchange takes place
pleural membranes - thin layers that cover each lung that reduce friction between the lungs and chest wall
what is the role of the intercostal muscles and the diaphragm in ventilation
During inhalation
The diaphragm contracts and flattens
The external set of intercostal muscles contract to pull the ribs up and out:
This increases the volume of the chest cavity (thorax)
Leading to a decrease in air pressure inside the lungs relative to outside the body
Air is drawn in
During exhalation
The diaphragm relaxes it moves upwards back into its domed shape
The external set of intercostal muscles relax so the ribs drop down and in
This decreases the volume of the chest cavity (thorax)
Leading to an increase in air pressure inside the lungs relative to outside the body
Air is forced out
The external and internal intercostal muscles work as antagonistic pairs (meaning they work in different directions to each other)
When we need to increase the rate of gas exchange (for example during strenuous activity) the internal intercostal muscles will also work to pull the ribs down and in to decrease the volume of the thorax more, forcing air out more forcefully and quickly – this is called forced exhalation
There is a greater need to rid the body of increased levels of carbon dioxide produced during strenuous activity
how are alveoli adapted for gas exchange
There are many rounded alveolar sacs which give a very large surface area to volume ratio
Alveoli (and the capillaries around them) have thin, single layers of cells to minimise diffusion distance
A good blood supply ensures constant supply of blood high in carbon dioxide and low in oxygen maintaining the concentration gradient
A layer of moisture on the surface of the alveoli helps diffusion as gases dissolve
why can simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell
In order for any organism to function properly, it needs to exchange substances, such as food molecules and waste products, between itself and its environment
This exchange of substances occurs across the cell membrane
There are three transport processes that living organisms use for exchange: diffusion, osmosis and active transport
Unicellular (single-celled) organisms like amoeba have very large surface areas (SA) in comparison to their volumes
This means that the distance between the surface of the organism to its centre is very small
As a result, unicellular organisms do not need to have specialist exchange surfaces or transport systems; as diffusion, osmosis and active transport through the cell membrane occur at a sufficient rate to meet the organisms needs
why is there a need for a transport system in multicellular organisms
The bodies of these organisms contain many layers of cells, meaning that the distance between the surface of the organism to its centre is relatively long and the diffusion distance is too great to rely on diffusion alone
Diffusion to all of the cells would take far too long
Diffusion cannot occur at a sufficient rate to meet the needs of the organism, so larger organisms usually have transport systems
The transport system in animals is the circulatory system which carries the necessary substances around the body in the blood
what is the role of the phloem
transporting sucrose and amino acids from the leaves (where they are made in photosynthesis) to other parts of the plant
the cells are living cells and are not hollow. The substances move from cell to cell through the pores in the end walls in each cell
what is the role of the zylem
transporting water and mineral ions from the roots to other parts of the plant
composed of dead cells which form hollow tubes
Xylem cells are strengthened by lignin and so are adapted for the transport of water in the transpiration stream
what is the vascular bundle
the zylem and phloem in a plant (they are always arranged together in the root, stem and leaves)
what is the composition of blood
red blood cells
white blood cells
platelets
plasma
Over half of the volume of the blood is made up of plasma
The majority of the other half is made up of red blood cells
The remaining fraction consists of white blood cells and platelets
what is the role of plasma
Plasma is a straw coloured liquid which the other components of the blood are suspended within
Plasma is important for the transport of many substances including:
Carbon dioxide - the waste product of respiration, dissolved in the plasma as hydrogencarbonate ions and transported from respiring cells to the lungs
Digested food and mineral ions - dissolved particles absorbed from the small intestine and delivered to requiring cells around the body
Urea - the waste substance produced in the breakdown of proteins by the liver. Urea is dissolved in the plasma and transported to the kidneys
Hormones - chemical messengers released into the blood from the endocrine organs (glands) and delivered to target tissues/organs of the body
Heat energy - created in respiration (an exothermic reaction), heat energy is transferred to cooler parts of the body or to the skin where heat can be lost
adaptations of the red blood cells
Red blood cells are specialised cells which carry oxygen to respiring cells
They are full of haemoglobin, a protein that binds to oxygen to form oxyhaemoglobin
They have no nucleus which allows more space for haemoglobin to be packed in
The shape of a red blood cell is described as being a ‘biconcave disc’ this shape gives them a large surface area to volume ratio to maximise diffusion of oxygen in and out
phagocytes
Phagocytes engulf and digest pathogens
Phagocytes have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it
This is a non-specific immune response
Phagocytes can be easily recognised under the microscope by their multi-lobed nucleus and their granular cytoplasm
lymphocytes
Lymphocytes produce antibodies
Antibodies are Y-shaped proteins with a shape that is specific (complementary) to the antigens (sticky outie bits) on the surface of the pathogen
This is a specific type of immune response as the antibodies produced will only fit one type of antigen on a pathogen
Antibodies attach to the antigens and so stick several pathogens together (more efficient for phagocytes to engulf)
This means the pathogenic cells cannot move very easily or reproduce
At the same time, chemicals are released that signal to phagocytes that there are cells present that need to be destroyed
Lymphocytes also produce antitoxins to neutralise toxins released by pathogens
Lymphocytes can easily be recognised under the microscope by their large round nucleus which takes up nearly the whole cell and their clear, non-granular cytoplasm
what is the role of platelets
Platelets cause blood to clot when the skin is cut which prevents pathogens or microorganisms entering and also stops blood loss
Platelets are fragments of cells
When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding
A series of reactions occur within the blood plasma
Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot
The clot eventually dries and develops into a scab to protect the wound from bacteria entering
Scab formation seals the wound with an insoluble patch that prevents entry of microorganisms that could cause infection
It remains in place until new skin has grown underneath it, sealing the skin again
structure and function of the heart
The heart organ is a double pump
Oxygenated blood from the lungs enters the left side of the heart and is pumped to the rest of the body (the systemic circuit)
The left ventricle has a thicker muscle wall than the right ventricle as it has to pump blood at high pressure around the entire body,
Deoxygenated blood from the body enters the right side of the heart and is pumped to the lungs (the pulmonary circuit)
The right ventricle is pumping blood at lower pressure to the lungs
A muscle wall called the septum separates the two sides of the heart
Blood is pumped towards the heart in veins and away from the heart in arteries
The coronary arteries supply the cardiac muscle tissue of the heart with oxygenated blood
As the heart is a muscle it needs a constant supply of oxygen (and glucose) for aerobic respiration to release energy to allow continued muscle contraction
Valves are present to prevent blood flowing backwards
The pathway of blood through the heart
Deoxygenated blood coming from the body flows through the vena cava and into the right atrium
The atrium contracts and the blood is forced through the tricuspid (atrioventricular) valve into the right ventricle
The ventricle contracts and the blood is pushed through the semilunar valve into the pulmonary artery
The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place
Low pressure blood flow on this side of the heart prevents damage to the capillaries in the lungs
Oxygenated blood returns via the pulmonary vein to the left atrium
The atrium contracts and forces the blood through the bicuspid (atrioventricular) valve into the left ventricle
The ventricle contracts and the blood is forced through the semilunar valve and out through the aorta
Thicker muscle walls of the left ventricle produce a high enough pressure for the blood to travel around the whole body
how does the heart rate change during exercise
The heart pumps blood around the body in order to supply oxygen and glucose to respiring cells
The blood also removes waste products from the respiring cells
During exercise, the cells of the muscles respire more rapidly in order to provide energy for muscle contraction
Respiration may be aerobic if exercise is moderate, or anaerobic if exercise is more intense
An increase in respiration means an increase in requirement for oxygen and glucose as well as an increase in production of waste products that need to be removed
The nervous system responds to this requirement by stimulating the following changes
Heart rate increases to deliver oxygen and glucose and remove waste more frequently
The volume of blood pumped out of the heart also increases to deliver bigger quantities of oxygen and glucose
At the end of a period of exercise, the heart rate may remain high for a period of time as oxygen is required in the muscles to break down the lactic acid from anaerobic respiration
This is how the oxygen debt is paid off
how does the heart rate change under the influence of adrenaline
binding to specific receptors on heart cells called beta-1 adrenergic receptors. When adrenaline binds to these receptors, it triggers a series of reactions inside the cell causing the heart to beat faster. This effect prepares the body for action, especially in situations where a quick response may be needed allowing the muscles to have a good supply of oxygen for respiration
what factors increase the chance of coronary heart disease
High cholesterol - Speeds up the build up of fatty plaques in the arteries leading to blockages
Smoking - Chemicals in smoke cause an increase in plaque build up and an increase in blood pressure amd Carbon monoxide also reduces the oxygen carrying capacity of the red blood cells
diet - eating lots of saturated fats increases blood cholesterol
high blood pressure - damages the artery lining and increases the risk of fatty deposits forming
structure and function of arteries
Carry blood at high pressure away from the heart
Carry oxygenated blood (except the pulmonary artery)
Have thick muscular walls containing elastic fibres
Have a narrow lumen
Blood flows through at a fast speed
Thick muscular walls containing elastic fibres withstand the high pressure of blood and maintain the blood pressure as it recoils after the blood has passed through
A narrow lumen also helps to maintain high pressure
structure and function of veins
Carry blood at low pressure towards the heart
Carry deoxygenated blood (other than the pulmonary vein)
Have thin walls
Have a large lumen
Contain valves
Blood flows through at a slow speed
A large lumen reduces resistance to blood flow under low pressure
Valves prevent the backflow of blood as it is under low pressure
structure and function of capillaries
Carry blood at low pressure within tissues
Carry both oxygenated and deoxygenated blood
Have walls that are one cell thick
Have ‘leaky’ walls
Speed of blood flow is slow
Capillaries have walls that are one cell thick (short diffusion distance) so substances can easily diffuse in and out of them
The ‘leaky’ walls allow blood plasma to leak out and form tissue fluid surrounding cells
main blood vessels of the circulatory system
heart - vena cava + aorta
lungs - pulmonary artery + vein
liver - hepatic artery + vein
kidney - renal artery + vein
order of the circulatory system
heart -> lungs -> heart -> liver -> (gut -> liver) -> kidneys -> other organs -> heart
waste products and their loss from the stomata
Oxygen and carbon dioxide can be both reactants and waste products within a plant
The amount or intensity of light affects the waste products within plants
During the day, when there is sufficient light:
The rate of photosynthesis is higher than the rate of respiration
More oxygen is released than used in respiration
Less carbon dioxide is released than used in photosynthesis
Net effect - oxygen is in excess and a waste product
During the night, when there is insufficient light:
There is no photosynthesis, only respiration
Oxygen is used in respiration and carbon dioxide is produced
No photosynthesis means that no carbon dioxide is used
Net effect - carbon dioxide is in excess and a waste product
Whichever gas is in excess diffuses out of the plant via the leaf organ
The gases exit through the stomata
structure of urinary system
blood goes through the kidneys where urea and other substances are filtered out.
these substances are transported through the ureters into the bladder
then they are transported via the urethra which carries urine to the outside
how is water reabsorbed in the blood from the collecting duct
collecting duct responds to ADH to vary how much water is reabsorbed
When ADH binds to receptors on the principal cells of the collecting duct, vesicles containing aquaporins fuse with the cell membrane. These aquaporins are protein channels that increase the permeability of the collecting duct, allowing more water to be reabsorbed into the blood by osmosis
what is the role of ADH
If the water content of the blood is too high then less water is reabsorbed, if it is too low then more water is reabsorbed
This is controlled by the hormone ADH
Any change to the water level of the blood is detected by the hypothalamus, which then sends a signal to the pituitary gland
The pituitary gland in the brain constantly releases a hormone called ADH
How much ADH is released depends on how much water the kidneys need to reabsorb from the filtrate
ADH affects the permeability of the tubules to water
If the water content of the blood is too high:
The pituitary gland releases less ADH which leads to less water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become less permeable to water)
As a result, the kidneys produce a large volume of dilute urine
If the water content of the blood is too low:
The pituitary gland releases more ADH which leads to more water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become more permeable to water)
As a result, the kidneys produce a small volume of concentrated urine
what is the large intestine
colon and rectum
how are organisms able to respond to changes in their environment
homeostasis
what is homeostasis
the maintenance of a constant internal environment
examples of homeostasis:
body water content
body temperature
what does a co-ordinated response require
stimulus, receptor and effector
how does the nervous system control responses
information is sent as electrical impulses down neurones at high speeds allowing rapid responses to stimuli
it coordinates activities of sensory receptors, decision making centers and effectors
it is used to control functions that need instant response
how does the endocrine system control responses
information is sent as chemical substances (eg hormones) in the blood stream and so can circulate the whole body
hormones transmit information from one part of the organism to another and bring about a change (they provide a signal that triggers a response)
they alter the activity of one or more specific target organs
hormones control functions that do not need instant responses
hormones are produced by endocrine glands
differences between the endocrine and nervous system
nervous system is made up of Nerves (bundles of neurones), brain, spinal cord
endocrine system is made up of glands
nervous system sends electrical impulses
endocrine system sends chemical hormones
nervous system is very fast acting
endocrine system is slower acting
nervous system has a short duration of effect
endocrine has a longer duration effect
what does the central nervous system consist of
the brain and spinal cord which are linked to sense organs by nerves
how do rapid responses happen
stimulation of receptors in the sense organs which send electrical impulses along nerves into and out of the CNS
what is the role neurotransmitters at synapses
neurones don’t touch each other
Where the dendrites of two neurones meet (to make a connection between the neurones) a junction known as a synapse is formed
at the synapse there is a very small gap between the neurones (synaptic gap)
the electrical impulses cannot travel directly from one neurone to the other to the next due to the gap
Instead, the electrical signal is briefly converted to a chemical signal that can cross the gap
The chemical signalling molecules used to transfer the signal between neurones at a synapse are known as neurotransmitters
Once these neurotransmitters cross the synaptic cleft and meet the neurone on the opposite side, the signal is converted back into an electrical impulse, which can then pass along the neurone
how is an impulse passed across a synapse
The electrical impulse travels along the axon of the first neurone (known as the presynaptic neurone)
This triggers the end of the presynaptic neurone to release chemicals called neurotransmitters from vesicles
These vesicles fuse with the presynaptic membrane, releasing their contents into the gap
The neurotransmitters diffuse across the synaptic cleft and bind with receptor molecules on the membrane of the second neurone (known as the postsynaptic membrane)
This stimulates the second neurone to generate an electrical impulse (which then travels down the second axon)
The neurotransmitters are then destroyed to prevent continued stimulation of the second neurone (otherwise the neurotransmitters would cause repeated impulses to be sent)
Synapses ensure that impulses only travel in one direction, avoiding the confusion that would be caused within the nervous system if impulses were able to travel in both directions
structure and functioning of a simple reflex arc illustrated by withdrawal of a finger from a hot object
the hot object touching the skin (stimulus)
temperature receptors detect change in temperature (receptor)
sensory neurone sends electrical impulses to the spinal cord (coordinator)
sensory neurone connects a synapse to a relay neurone which then connects to a motor neurone
impulse travels along motor neuron and out of the spinal cord to the arm muscles (effector)
muscle contracts and arm moves off hot object (response)
what is a reflex response
A reflex response (also known as an involuntary response) does not involve the conscious part of the brain as the coordinator of the reaction
Awareness of a response having happened occurs after the response has been carried out
Responses are therefore automatic and rapid – this helps to minimise damage to the body and aids survival
Pain-withdrawal, blinking, and coughing are all examples of reflex responses that help us to avoid serious injury, such as damage to the eye or choking
what is a reflex arc
the pathway of a reflex response (specifically, the pathway taken by electrical impulses as they travel along neurones)
function of the eye in focusing on near objects
When an object is close up:
The ciliary muscles contract (the ring of muscle decreases in diameter)
This causes the suspensory ligaments to loosen
This stops the suspensory ligaments from pulling on the lens, which allows the lens to become fatter
Light is refracted more
role of the skin in temperature regulation - too hot
sweat glands - are active, they secrete sweat which evaporates from the skin carrying heat away from the body cooling the skin
muscles - not shivering
hairs - the hair erector muscles in the skin relax , causing the hairs to lie flat which stops them from forming an insulating layer as they can’t trap any air which allows air to circulate over the skin and allows heat loss via radiation
capillaries near skin - dilate due to the shunt vessel constricting so more blood flows closer to the skin allowing more heat loss via radiation (vasodilation)
function of the eye in responding to changes in light intensity - bright light
The pupil reflex is a reflex action carried out to protect the retina from damage
In bright light, the pupil constricts (narrows) in order to prevent too much light from entering the eye and damaging the retina
bright light:
photoreceptors (receptor) detect brighter light (stimulus)
brain (coordinator)
radial muscles relax (effector)
circular muscles contract (effector)
pupils constricts (response)
less light enters the eye
role of the skin in temperature regulation - too cold
sweat glands - no sweat released as less heat is lost if no sweat is evaporated
muscles - contract to cause shivering as this increases muscle respiration which then releases heat energy
hairs - hair erector muscles contract causing hairs to stand on end which forms an insulating layer over the skins surface trapping air between the hairs preventing heat being lost by radiation
capillaries - constrict near the surface so more blood flows along the shunt vessel further away from the skin so less heat loss via radiation
source, role and effect of adrenaline
produced in adrenal gland
targets lots of organs (heart, iris, liver muscles)
effect - fight or flight response so increased breathing rate, heart rate, eye dilation, liver muscles -> causes glycogen to convert to glucose in preparation for respn
source, role and effect of insulin
produced in pancreas
targets the liver
effect - causes glucose to convert to glycogen for storage (glycogen is less soluble so does not effect osmosis)
source, role and effect of testosterone
produced in testes
targets the testes
effect - sperm production (and causes secondary sexual characteristics)
source, role and effect of progesterone
produced corpus luteum in ovaries
targets the ovaries
effect - maintains the uterus lining and inhibits LH and FSH production
source, role and effect of oestrogen
produced in the ovaries
targets the ovaries
effect - causes regrowth of uterus lining and inhibits FSH production and stimulates LH production. Causes secondary sexual characteristics
source, role and effect of ADH
produced in the pituitary gland (brain)
targets the kidney (collecting duct)
effect - causes water to be reabsorbed by increasing the permeability of the collecting duct
source, role and effect of FSH
produced in pituitary gland (brain)
targets the ovaries
causes the egg to mature and stimulates oestrogen production
source, role and effect of LH
produced in the pituitary gland (brain)
targets the ovaries
triggers ovulation and the release of progesterone
do plants respond to stimuli
yes
examples of stimuli plants respond to
light + gravity
what is geotropic
a response to gravity
roots grow downwards into soil away from light to gravity (negative phototropic response - grows away from light) (positive geotropic response - grows to gravity)
what is phototropic
a response to light
shoots grow up towards light (positively phototropic - grows to light) (negatively geotropic - grows away from gravity)
role of auxin in plants
is produced in the tips of the growing shoots
auxin then diffuse down to where cell division occurs (just below the tip)
auxin diffuses to the shaded part of the cell division area and causes the cells to elongate and grow faster
this means that the shaded side is longer than the sunny side so the shoot bends towards the sun
(if there is even light then the auxin diffuses evenly and so all cells elongate evenly so it grows straight up)
function of the eye in responding to changes in light intensity - dim light
The pupil reflex is a reflex action carried out to protect the retina from damage
In dim light, the pupil dilates (widens) in order to allow as much light into the eye as possible to improve vision
dim light:
photoreceptors (receptor) detect dimmer light (stimulus)
brain (coordinator)
radial muscles contract (effector)
circular muscles relax (effector)
pupils dilates (response)
more light enters the eye
function of the eye in focusing on near objects
When an object is far away:
The ciliary muscles relax (the ring of muscle increases in diameter)
This causes the suspensory ligaments to tighten
The suspensory ligaments pull on the lens, causing it to become thinner
Light is refracted less
cornea
transparent lens that refracts light as it enters the eye
iris
controls how much light enters the pupil
lens
transparent disc that can change shape to focus light onto the retina
retina
contains light receptor cells – rods (detect light intensity) and cones (detect colour)
optic nerve
sensory neuron that carries impulses between the eye and the brain
pupil
hole that allows light to enter the eye
ciliary muscles
a ring of muscle that contracts and relaxes to change the shape of the lens
suspensory ligaments
ligaments that connect the ciliary muscle to the lens
fovea
centered point where light is focused onto retina
blind spot
spot where there are no photoreceptor cells
what is a stem cell
an unspecialised cell which can differentiate and divide into many types of cells but also just mitotically divide into more stem cells
can be found inside long bones, embryos and in plants
importance of cell differentiation in the development of specialised cells
stem cells are undifferentiated however they can differentiate into specialised cells which then construct organs
undifferentiated cells receive signals which stimulates the transcription of certain genes allowing them to become specialised (so they can carry out specialised functions)
advantages of using embryotic stem cells in medicine
(very early stages of an (embryo) fertilised egg as it begins to divide a few times)
can differentiate into any type of cells and divide mitotically
scientists can collect them and grow them in a lab and then instruct which genes to be transcribed to decide how they are specialised allowing them to become whatever type of cell is needed for the transplant
disadvantages of using embryotic stem cells in medicine
ethical issues with using them as they can be sourced from unused embryos produced from IVF and these embryos could have turned into humans
as embryo is not from patient the patients body may reject the embryotic cells (as the embryo cells have different antigens then the patient which causes WBCs to recognise them as foreign and so the WBCs will kill the cells) which can result in failure of medicine or the patient may have to take immune suppression medication which could cause other illness
advantages of using adult stem cells in medicine
comes from your own body so the antigens from the stem cells will match the ones from the rest of your body so less likely to be rejected
no ethical concerns
less likely to become cancerous
disadvantages of using adult stem cells in medicine
can only differentiate into some cells (eg bone marrow stem cells can only become blood or bone cells)
don’t multiply as much as embryotic ones
if the patient is older the cells are less effective as they may have degenerated
medical uses of stem cells
can be used to repair damaged tissues and grow new organs for transplant and treat diseases
diabetes - stem cells can be differentiated into insulin producing cells which can be put into the patients body so they can produce insulin
difference between antigen and antibody
antigen is a molecule found on the surface of a cell (unique to each cell)
antibody is a protein made by lymphocytes which is complementary to an antigen which attaches to the antigens and clumps the cells together
how does a vaccination work
used to induce immunity to an infectious disease
vaccine contains harmless version of a pathogen (either already killed, only fragments of cells or prevented from dividing)
vaccine in injected
once vaccine is in blood stream then antigens from the vaccine trigger an immune response
some Lymphocytes recognise the antigens in the bloodstream
The activated lymphocytes produce antibodies specific to the antigen encountered
Memory cells are produced from the lymphocytes
Memory cells and antibodies subsequently remain circulating in the blood stream so if the actual pathogen enters the body the lymphocytes produce antibodies much faster
immune response to a pathogen
The pathogen enters the blood stream and multiplies
A release of toxins (in the case of bacteria) and infection of body cells causes symptoms in the patient
Phagocytes that encounter the pathogen recognise that it is an invading pathogen and engulf and digest (non-specific response)
Eventually, the pathogen encounters a lymphocyte which recognises its antigens
The lymphocyte starts to produce specific antibodies to combat that particular pathogen
The lymphocyte also clones itself to produce lots of lymphocytes (all producing the specific antibody required)
Antibodies destroy pathogens
Phagocytes engulf and digest the destroyed pathogens
