Structure and functions in living organisms Flashcards
What is an enzyme?
a biological catalyst which speed up reactions. They are made of proteins. They lower the activation energy of a reaction.
What is a catalyst?
a substance which increases the speed of a reaction, without being changed or used up in the reaction.
What are the chemical reactions in the body that enzymes speed up called?
metabolic reactions
How do enzymes catalyse a specific reaction?
They catalyse a specific reaction due to the shape of the active site. The substrate has to fit into the active site of the enzyme in order for the reaction to take place. This is called the ‘lock and key’ model.
What conditions speed up enzyme reactions?
- Temperature
- Concentration of enzymes
- Optimum pH
- Concentration of substrates
How does temperature change the rate of an enzyme-catalysed reaction?
high temps increase the rate at first
the enzymes have more kinetic energy
they move more and more likely to collide and form enzyme-substrate complexes.
if too hot, violent collisions break bonds in active site changing its shape so substrate cant fit. Enzyme is denatured
How does pH affect the rate of an enzyme-catalysed reaction?
If pH is too high or low, it interferes with bonds holding enzymes together. Changes shape of the active site and denatures the enzyme. All enzymes have an optimum pH they work best at. Optimum pH is often neutral 7 pH.
Explain the investigation of how temperature affects enzyme activity.
The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen.
Can collect the oxygen and measure how much is produced in a set time.
Use pipette to add a set amount of hydrogen peroxide to a boiling tube. Put tube into water bath at 10ºC
Set up measuring cylinder so its underwater with delivery tube going into it.
Add source of catalase (eg 1 cm³ of potato)to hydrogen peroxide and quickly attach bung
record how much oxygen is produced in first minute
repeat 3 times an calculate mean
repeat at 20ºC, 30ºC, 40ºC
Control variable = pH, potato used, size of potato pieces
Describe investigation of temperature affecting enzymes when measuring how fast a substrate disappears
Enzyme amylase catalyses breakdown of starch to maltose
Easy to detect starch using iodine solution - if starch present iodine will turn from browny-orange to blue-black
Put starch solution and amylase enzyme into boiling tube and heat in waterbath at correct temperature
Put a drop of iodine solution into each well on spotting tile
Every ten seconds drop a sample of mixture into a well using a pipette
when iodine solution remains browny-orange record total time taken
repeat with water bath at different temperatures to see how it affects time taken for starch to be broken down.
Explain investigation of how pH affects enzyme activity.
use enzyme catalase
set up same apparatus but no water bath
add buffer solution with different pH level to a series of different tubes containing hydrogen peroxide
record how much oxygen is produced in first minute
repeat three times, calculate mean
repeat at different pH
control variables = same temp, volumes, concentration
What is diffusion?
the net movement of particles from an area of high concentration to low concentration, down a concentration gradient
Explain the diffusion of oxygen from cell to cell.
Oxygen particles are moving from an area of high to low concentration, down a concentration gradient. This means particles will spread out more by moving through the cell membrane, particles will move faster if the cell membrane is thin
Why does diffusion happen in liquids and gases?
particles are free to move about randomly
What is Osmosis?
The net diffusion of water molecules across a selectively permeable membrane, from a region of higher water potential to lower water potential
What is water potential?
the ability of water molecules to move freely
How does solute concentration affect water potential?
solutes (eg glucose or salt) bond with water molecules. Thus meaning there are less free water molecules that could move.
the more solute present, the fewer water molecules can move freely and the lower the water potential
What is a solution with a low solute concentration known as?
hypotonic - weak solution
What is a solution with a high solute concentration known as?
hypertonic - strong solution
Why is a barrier needed during osmosis
(selectively permeable) to measure movement of water
Why does increasing temperature increase diffusion?
Increasing temperature, increases kinetic energy
particles move around faster and spread out faster
diffusion therefore takes place faster at high temperatures
Use CORMS to outline investigation of Osmosis in living systems.
(Potato Cylinders)
Change - salt concentration
Organism - same species of swede
Repeat - Do each concentration 10x
Measure - change in mass
Same - temp, time, SA of potato
What is active transport?
The movement of particles against a concentration gradient using energy released in respiration
How is active transport used in the digestive system?
If lower concentration of nutrients in gut than blood, active transport allows nutrients to be taken into the blood, despite concentration gradient being wrong way. Essential to stop us starving. Needs energy from respiration to happen.
How does SA:Volume affect movement of substances?
Rate of diffusion, osmosis, active transport is higher in cells with larger SA:Volume. Substances move into and out of smaller cube faster.
How does Distance affect movement of substances?
Short distances increases rate
as substances can move in and out of cells quicker
eg thin cell membrane
How does Temperature affect movement of substances?
Increasing temperature, increases rate
particles have more kinetic energy
so they move faster
so move in and out of cells faster
How does Concentration Gradient affect movement of substances?
Doesn’t affect rate of active transport
Bigger difference in concentration increases rate of diffusion and osmosis
If lots more particles on one side, more to move across so substances move in and out faster
Outline investigation of Diffusion in non-living systems.
Independent - amount of jelly/ size of cell (SA:Volume)
Dependent - Time taken to change colour (pink - colourless as acid diffuses into jelly and neutralises sodium hydroxide)
Control - Same volume of hydrochloric acid, temperature of acid, concentration of acid
Risks - getting acid in someones eye
Do multiple repeats
Equipment:
Measuring cylinder
Stop watch
Teaspoon to handle agar cube
100cm³ glass beaker
Hydrochloric acid
Agar cubes containing alkali and cresol red indicator
What is respiration?
the process of transferring energy from glucose, which happens constantly in every living cell
How is energy transferred by respiration?
Used to make ATP which stores the energy needed for many cell processes
What is ATP?
adenosine triphosphate, releases energy quickly
How is ATP used?
ATP molecules are broken down and energy is released.
What is the word and chemical equation for aerobic respiration?
glucose + oxygen -> carbon dioxide + water ( + energy)
C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O
How many molecules of ATP are produced during aerobic respiration?
32 molecules per molecule of glucose
(most efficient way to transfer energy from glucose)
What is the word equation for anaerobic respiration in animals?
glucose -> lactic acid (+energy)
Why do we anaerobically respire?
doing vigorous exercise means your body can’t supply enough oxygen to working muscles for aerobic respiration. Instead muscles respire without oxygen
How many molecules of ATP are produced during anaerobic respiration?
2 molecules per glucose molecule
What happens when lactic acid is produced?
glucose is only partially broken down and lactic acid is produced which builds up in muscles - painful and leads to cramp
How is lactic acid removed?
by blood flowing through muscles
What is the word equation for anaerobic respiration in plants?
glucose -> ethanol + carbon dioxide (+ energy)
What is the role of diffusion in gas exchange?
Blood passing next to the alveoli has returned from lungs and rest of body so contains carbon dioxide and very little oxygen. Oxygen diffuses out of the alveoli and into the blood which is a lower concentration. Carbon dioxide is diffused out of the blood and into the alveoli which is a lower concentration so it can be breathed out. Oxygen released from red blood cells once it reaches body cells via diffusion. Carbon dioxide diffuses out of body cells and into blood at same time to be carried back to lungs.
What is the structure of a leaf?
Waxy cuticle - reduces water loss
Upper epidermis - contain no chloroplasts and are transparent to allow light in
Palisade mesophyll - cells tightly packed near top of leaf to get lots of sunlight, contain many chloroplasts, most photosynthesis happens
Spongy Mesophyll - contain air spaces to allow movement of gases throughout leaf
Lower epidermis - cells contain no chloroplasts apart from guard cells
Guard cells - help regulate movement of gases in and out of leaf, help control water vapour loss.
How are leaves adapted for gas exchange?
Leaves are broad - large SA for diffusion
Thin - gases travel a short distance
Air spaces inside leaf - lets gases move easily between cells. Increases SA for gas exchange
What is the role of the stomata in gas exchange?
Stomata close as it gets dark. Photosynthesis cant happen in dark, so don’t need to be open to let in CO₂
water can’t escape when closed, stops plant drying out
Opening and closing is controlled by guard cells. do this by changing their shape and volume (increase in volume to open up, decrease to close)
What is the role of diffusion in photosynthesis?
When plant is photosynthesising it uses up lots of CO₂, so hardly any left inside plant, This makes more CO₂ move into the leaf via diffusion.
At sane time lots of O₂ is being made as a waste product of photosynthesis. Some used in respiration, rest diffuses out through stomata
What does the xylem do?
transports water (and minerals) to the leaf
How do the xylem transport water and mineral ions from root to leaf?
Water molecules move through the plant upwards in a transpiration stream
How is water absorbed by root hair cells?
Root hair cells are elongated cells which give the plants a big surface area for absorbing water from the soil.
Water is taken in via osmosis
What is transpiration?
The evaporation of water from the stomata
What factors affect the rate of transpiration?
Light intensity
Temperature
Wind speed
Humidity
How does light intensity affect the rate of transpiration?
brighter light, greater transpiration rate
stomata close as it gets darker as photosynthesis can’t happen. When stomata are closed, little water can escape
How does temperature affect the rate of transpiration?
warmer = faster transpiration
particles have more energy to evaporate and diffuse out of the stomata
How does wind speed affect the rate of transpiration?
higher wind speed around leaf, greater transpiration rate
water vapour is swept away, maintaining a low concentration of water in air around leaf. Diffusion happens quickly, from area of high to low concentration
How does humidity affect the rate of transpiration?
drier air, faster transpiration
if air is humid, there is lots of water surrounding plant so little difference between inside and outside of plant. Diffusion happens slowly/not at all
Use CORMS to describe an investigation of the role of environmental factors in determining the rate of transpiration from a leafy shoot.
Potometers measure the uptake of water and estimate transpiration
Change - conditions ( vaseline, no vaseline, wind, no wind )
Organism - plant (cut shoot at slant to increase SA and underwater to prevent air from entering xylem )
Repeat - 3 times
Measure - distance bubble moves
Same - species (laurel)
What is excretion?
the removal of waste products
What are the excretory products of the lungs?
Carbon dioxide made from aerobic respiration
What are the excretory products of the kidneys?
Urea made from excess protein
removed as urine
Water made from aerobic respiration removed as urine
Ions (salt)
What are the excretory products of the skin?
Water made from aerobic respiration removed as sweat
How does the kidney carry out excretion?
Ultrafiltration, Reabsorption and Releasing waste into bladder where it is stored before being released via the urethra
How does the kidney carry out osmoregulation?
Water is excreted by the kidneys in the urine.
What is part of the urinary system?
aorta
vena cava
renal artery
renal vein
kidneys
ureter
bladder
sphincter
urethra
What is part of the nephron?
bowman’s capsule
glomerulus
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting duct
What is ultrafiltration?
renal artery flows through glomerulus
glomerulus filters out large molecules like proteins and blood cells so they stay in blood and don’t go in nephron
high pressure built up which squeezes small molecules (water, urea, ions, glucose) out of blood and into bowman’s capsule
this is called filtrate
What is the composition of glomerular filtrate?
water
salts/ions
glucose
amino acids
urea
renal ____ enters the kidney and renal ____ leaves the kidney
renal artery enters the kidney and the renal vein leaves the kidney
How is water reabsorbed into the blood from the collecting duct?
Water is reabsorbed into blood via osmosis
Collecting duct is affected by ADH which makes the collecting duct more permeable so more water is reabsorbed into the blood
This is called osmoregulation
What gland releases ADH?
pituitary gland
What is osmoregulation controlled by?
negative feedback. If water gets too high or low, mechanism triggered that brings it back to normal
What is selective reabsorption?
Glucose is reabsorbed from proximal convoluted tubule via active transport so it can be used in respiration
Sufficient ions are reabsorbed but excess ions aren’t
What does urine contain?
Urea
Ions/salts
Water
How are organisms able to respond to changes in their environment?
external environment: eg avoiding places to hot/cold
internal environment: make sure conditions are always right for their metabolism
Receptors detect stimuli and effectors produce a response
what is negative feedback
a corrective mechanism which responds to a change in conditions from ideal or set point and returns conditions back to set point
Define homeostasis
maintenance of a stable internal environment in the body
What are some examples of homeostasis?
body water content
body temperature
define hormones
A chemical messenger which is made by an endocrine gland. Released in blood and affects target organs
define ADH
hormone produced by the pituitary gland that increases the re absorption of water in the collecting duct of the kidney
define CNS
the brain and spinal cord which coordinates the response of effectors
What type of signals do the endocrine and nervous system use?
endocrine: chemical
nervous: electrical
How do signals move in the endocrine and nervous system?
endocrine: plasma
nervous: neurons
What are the effectors in the endocrine and nervous system?
endocrine: all cells
nervous: muscle/gland
What is the speed of response in the endocrine and nervous system?
endocrine: slower
nervous: fast
What is the duration of the response in the endocrine and nervous system?
endocrine: longer
nervous: very short
what does sensory neurone do
Impulses from receptors pass along sensory neurones until they reach the brain and spinal cord
what does relay neurone do
impulses pass to relay neurons in the CNS
what does the motor neurone do
Impulse passes to effectors along motor neurone which causes the effector to contract
define neurotransmitters
chemicals that are released at synapses
define receptors
cells that detect a stimulus
what is the reflex arc
a rapid and automatic response to a stimulus
What is the pathway of neurones
stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response
What is the pathway of neurones
stimulus, receptor, sensory neurone, relay neurone, motor neurone, effector, response
what is a stimulus
a change in an organism internal or external environment that can be detected by receptors
what is the junction between two nerve cells
synapse, neurotransmitters released to diffuse across
compare a reflex action to a voluntary action
reflex is faster and doesn’t use the brain. Automatic
What is the eye made up of?
Suspensory ligament
cornea
iris
pupil
lens
ciliary muscle
sclera
retina
fovea
optic nerve (sensory neurone)
what are the two photoreceptors in retina and what do they do
rods: measure light intensity and send messages along sensory neurone
cones: measure colour and send messages along sensory neurone
what happens in eye in dark light
radial muscles in iris contracts. circular relax. iris causes pupil to dilate to let more light in
what happens in eye in bright light
radial muscles in iris relax. circular contract. iris causes pupil to get smaller to let less light in
what happens in eye when focussing on far away object
suspensory ligaments contract
ciliary muscle relax
lens become long and thin
light focused on retina
what does the axon do
electrical impulse travels down it
what does the myelin sheath do
insulates the axon
what is the myelin sheath made out of
fatty substance
what neurones have a myelin sheath
sensory and motor
what neurones have cell body at end
relay and motor
How does the skin regulate temperature?
sweating
vasoconstriction
vasodilation
what does sweat do
evaporation of water in sweat removes heat energy from the skin, cooling the body down by removing that heat
define vasoconstriction
constriction of blood vessels near the surface of the skin to reduce blood flow near the surface of the skin and therefore reducing the amount of heat that is radiated from the skin
define vasodilation
the dilation of blood vessels near the surface of the skin and increasing the amount of blood flowing near the surface of the skin and so increasing the amount of heat that is radiated from the skin
define adrenaline
a hormone produced by the adrenal glands in response to fear or stress. Increase heart rate and boosts the delivery of blood to the muscles, fight or flight response.
define insulin
hormone secreted by the pancreas when blood glucose concentration is too high, reducing blood glucose concentration by increasing the uptake of glucose from the blood into liver
define testosterone
the main male reproductive hormone, produced by the testes, stimulating sperm production and secondary sexual characteristics
define progesterone
a hormone produced in the ovaries, specifically by the corpus luteum and the placenta that maintains the interim lining and inhibits the release of FSH and LH
define oestrogen
a female sex hormone release by the ovaries and stimulate the growth of the uterus lining whilst inhibiting the release of FSH
