Topic 2 - Organisation Flashcards
What does the circulatory system do?
Carries food and oxygen to every cell in the body. It also carries waste products to where they can be removed from the body
What is the circulatory system made up of?
The heart, blood vessels, and blood
What kind of circulatory system do humans have?
Humans have a double circulatory system. Which is 2 circuits joined together
What does the right ventricle do?
It pumps deoxygenated blood to the lungs. Oxygenated blood returns the the heart
What does the left ventricle do?
Pumps oxygenated blood around all the other organs of the body. All the body cells are given oxygen then deoxygenated blood returns to the heart to be pumped out to the lungs again.
What is the heart?
It’s a pumping organ that keeps the blood flowing around the body.
What is the heart made of?
The walls of the heart are mostly made of muscle tissue
Why does the heart have valves?
To make sure that blood flows in the right direction. They prevent it flowing backwards
What are the 4 chambers of the heart?
Right atrium, right ventricle, left atrium, left ventricle
How does the heart use it’s 4 chambers?
Blood flows into the atria via the vena cava and pulmonary vein
They contract pushing blood into ventricles
Ventricles contract forcing blood into pulmonary artery and aorta and out
What happens after the 4 chambers in the circulatory system?
The blood flows to the organs through arteries and returns through veins.
Atria fill again cycle restarts
How does the heart receive it’s own supply of oxygen?
Arteries called coronary arteries branch of the aorta and surround the heart, making sure it gets all the oxygenated blood it needs
cells are…
the basic building blocks that make up all living organisms
what is differentiation?
the process by which cells become specialised for a particular job. it occurs during the development of a multi cellular organism
what do specialised cells form?
cells form tissues, which form organs, which form organ systems
why do large multi cellular organisms have different systems inside them?
for exchanging and transporting materials
what is tissue?
a group of similar cells that work together to carry out a particular function. it can include more than one type of cell
examples of tissues in mammals:
muscular tissue
glandular tissue
epithelial tissue
what does muscular tissue do?
it contracts to move whatever its attached to
what does glandular tissue do?
it makes and secretes chemicals like enzymes and hormones
what does epithelial tissue do?
it covers some parts of the body e.g. the inside of the gut
what is an organ?
a group of different tissues that work together to perform a certain function
what tissues is the stomach made of?
muscular tissue
glandular tissue
epithelial tissue
what does muscular tissue do in the stomach?
it moves the stomach wall to churn up food
what does glandular tissue do in the stomach?
it makes digestive juices to digest food
what does epithelial tissue do in the stomach?
it covers the outside and the inside of the stomach
what is an organ system?
a group of organs working together to perform a particular function. e.g. the digestive system that breaks down and absorbs food. organ systems work together to make entire organisms
what organs make up the digestive system?
glands (pancreas and salivary glands) stomach small intestine liver large intestine
what happens inside of living things constantly?
living things have thousands of chemical reactions going on inside them all the time. these reactions need to be carefully controlled to get the right amount of substances
how can you usually make a reaction happen more quickly?
by raising the temperature
whats the problem with raising the temperature during a reaction?
it speeds up the useful reactions but also the unwanted ones. there’s also a limit to far you can raise the temperature before a living creatures cells are damaged
what can be used to speed up a reaction instead of increasing temperature?
enzymes, which living things produce
what do enzymes do?
they act as biological catalysts. they reduce the need for high temperature, they only speed up useful chemical reactions.
what is a catalyst?
a substance which increases the speed of a reaction, without being changed or used up in the reaction.
what are enzymes?
they are large proteins, which are made up of chains of amino acids. the chain are folded into unique shapes, which enzymes need to do their jobs
what do chemical reactions usually involve?
things being split apart or joined together
what does every enzyme have?
an active site with a unique shape that fits onto the substance involved in a reaction
how are enzymes specific?
they usually only catalyse one specific reaction
why are enzymes specific?
for the enzyme to work the substrate has to fit into its active site. if it doesn’t match the active site, then the reaction wont be catalysed
how is the lock and key theory simpler than how an enzyme actually works?
the active site actually changes shape a little as the substrate binds for a tighter fit. this is called the induced fit model of enzyme reaction
what can change the rate of an enzyme-catalysed reaction?
changing the temperature
how does temperature change the rate of an enzyme catalysed reaction?
higher temperature increases the rate at first but if it gets too high the rate of the reaction will decrease
why will too high a temperature reduce rate of reaction?
if it gets too hot some of the bonds holding the enzyme together break. this changes the shape of the active site so the substrate wont fit. this means the enzyme is denatured
whats the temperature called when the enzyme works best?
the optimum temperature
what also effects rate of reaction other then temperature?
pH
what happens if pH it too high or too low?
it interferes with the bonds holding the enzyme together, which changes the shape of the active site and the enzyme becomes denatured
what is often the optimum pH of an enzyme?
neutral pH 7, but not always. e.g. pepsin breaks down proteins in the stomach with an optimum pH of 2, well suited for acidic conditions
what does amylase do?
it catalyses the breakdown of starch to maltose
what can be used to detect starch?
it is easy to detect starch with iodine solution- if iodine is present it will turn from orange/brown
to blue/black
how to set up an investigation for how pH affects amylase activity:
put a drop of iodine solution in every dimple of a spotting tile
put a Bunsen burner on a heat proof mat and a tripod and gauze over the Bunsen
put a beaker of water on the tripod and heat the water to 35*C
what is needed for an investigation for how pH affects amylase activity:
1cm³ of amylase solution
1cm³ of buffer solution
5cm³ of starch solution
method for an investigation for how pH affects amylase activity:
add amylase and buffer solution to a test tube
put it in beaker of water and leave for 5 mins
add starch solution, mix and start a stop clock
every 30 seconds, add a drop of the solution to spotting tile and continue until iodine stays orange/brown
repeat experiment with buffer solution of different pH values
what precautions must be used when investigating how pH affects amylase activity?
use syringe when adding amylase, buffer and starch
use thermometer to record temperature
use test tube holders when putting test tubes in water
what control variables are there in an investigation for how pH affects amylase activity?
concentration and volume of amylase solution
keep temperature of water in beaker constant
what is it useful to calculate after an experiment for investigating how pH affects amylase activity?
to calculate rate of reaction. rate is measure of how much something changes over time
formula for rate of reaction:
’’’’’’’’’’’’‘<u>1000</u>
Rate = time
what are the units for rate of reaction?
s^-1
how to calculate rate of reaction of something that changes over time:
<u>amount that has changed</u>
time taken
how do digestive enzymes help us to absorb food?
starch proteins and fats are too big to pass through the walls of the digestive system. so digestive enzymes break them down into small molecules like sugars, amino acids, glycerol and fatty acids. small soluble molecules can easily ass through allowing them to be absorbed into the bloodstream
examples of sugars:
glucose and maltose
what do carbohydrases do?
they converts carbohydrates into simple sugars
e.g. amylase breaks down starch into maltose or other sugars like dextrins
where is amylase made?
the salivary glands
the pancreas
the small intestine
what do proteases do?
they converts proteins into amino acids
where is protease made?
the stomach (pepsin) the pancreas the small intestine
what do lipases do?
they convert lipids into glycerol and fatty acids
lipids are fats and oils
where is lipase made?
the pancreas
the small intestine
what does the body do with products of digestion?
they can be used to make new carbohydrates, proteins and lipids. some of the glucose (carbohydrate) thats made is used in respiration
what journey does bile take through the digestive system?
its produced in the liver, stored in the gall bladder, then released into the small intestine
how is bile used in the s,all intestine?
the HCL acid in the stomach is too acidic for enzymes in the small intestine. bile is alkaline and neutralises the stomach acid ad makes conditions alkaline which the enzymes work best in
how does bile speed up digestion?
it emulsifies fat. which means it breaks up fat into tiny droplets, which gives it a larger surface area for lipase to work on
where are digestive enzymes produced?
they’re produced by specialised cells in glands and in the gut lining. different enzymes catalyse the breakdown of different food molecules
organs in the digestive system in order:
salivary glands gullet (oesophagus) stomach liver gall bladder pancreas small intestine large intestine rectum
what do the salivary glands do?
produce amylase enzyme in the saliva
what does the stomach do?
it pummels food with muscular walls
it produces protease enzyme in pepsin
it produces HCL to kill bacteria and to give right pH for protease
what does the liver do?
produces bile, which neutralises stomach acid and emulsifies fat
what does the gall bladder do?
it stores bile before its released into the small intestine
what does the pancreas do?
it produces protease, amylase and lipase enzymes and releases them into the small intestine
what does the small intestine do?
it produces protease, lipase and amylase to complete digestion.
its where the digested food is absorbed out of the digestive system into the blood
what does the large intestine do?
it absorbs excess water from the food
what does the rectum do?
it stores faeces (made of mainly indigestible food) before they leave through the anus
how do you prepare a food sample for identifying what food molecule it has?
break up the food with a pestle and mortar
put it in a beaker with distilled water
stir the mixture with a glass rod to dissolve some of it
filter the solution to get rid of the solid food
what foods can sugars be found in?
biscuits, cereal and bread
what are the 2 types of sugars?
non-reducing and reducing
what does the Benedict’s test test for?
reducing sugars
how to carry out Benedict’s test:
put about 10 drops of Benedict’s solution in 5cm³ of food sample in test tube
put test tube in 75*C water bath for 5 mins
if there’s sugar the solution will turn from blue to green, yellow or brick red
what foods contain lots of starch?
pasta, rice and potatoes
how can you test for starch?
put 5cm³ of prepared food in beaker
add a few drops of iodine solution then gently shake.
if it has starch it will turn from orange/brown to black/blue
which foods contain protein?
meat and cheese
how can you test for protein?
the Biuret test
how to carry out biuret test:
add 2cm³ of prepared food and 2cm³ of biuret solution to a test tube and mix
if it contains protein it will go from blue to purple
what foods are lipids found in?
olive oil, margarine and milk
how to test for lipids:
with Sudan III stain solution
how to carry out Sudan III test:
put 5cm³ of unfiltered prepared food sample in a test tube
add 3 drops of Sudan III stain solution and gently shake
it stains lipids. if there are lipids the mixture will separate into 2 layers and the top will be bright red
what’s the top part of your body called?
the thorax, its separated from the lower part of your body by the diaphragm
what are the lungs like? and how are they protected?
they’re like big pink sponges and are protected by the rib cage. they’re surrounded by the pleural membranes
what passage does air take when we breathe it in?
it goes through the trachea, this goes into 2 tubes called bronchi( singular -bronchus ), which each going to 1 lung. the bronchi split into progressively smaller tubes called bronchioles. these end at small bags called alveoli
the lungs contain millions and millions of…
little air sacs called alveoli, surrounded by a network of capillaries. this is where gas exchange occurs
what does the blood passing next to the alveoli contain?
it has just returned to the lungs from the rest of the body so it has lots of carbon dioxide and very little oxygen.
what happens at gas exchange in the lungs?
oxygen diffuses out of the alveolus into the blood and carbon dioxide diffuses out of the blood into the alveolus to be breathed out
what happens when our blood reaches our body cells ?
oxygen is released from the red blood cells and diffuses into the body. carbon dioxide diffuses out of the body cells into the red blood cells, its then carried back to the lungs
how to work out the breathing rate in breaths per minute?
breaths per minute = number if breaths/number of minutes
name the organs in the trachea:
trachea bronchus bronchiole alveoli diaphragm(underneath) heart (in the middle) pleural membranes(around the lungs) ribs(around membrane) intercostal muscle(between ribs
what is your resting heart rate controlled by?
a group of cells in the right atrium wall that act as a pacemaker.
what do pacemakers do?
these cells produce a small electric impulse which spreads to the surrounding muscle ells, causing them to contract
what happens if the natural pacemaker doesn’t work?
an artificial pacemaker is often used to control heartbeat if the natural pacemaker cells don’t work properly(e.g. irregular heartbeat)
what is an artificial pacemaker?
a little device thats implanted under the sin and has a wire going to the heart. it produces an electric current to keep the heart beating regularly
what are the 3 types of blood vessel?
arteries
capillaries
veins
what do the arteries do?
these carry the blood away from the heart
what do the veins do?
these carry the blood to the heart
what is the purpose of the capillaries?
these are involved in the exchange of materials at the tissues
what are the features of arteries?
strong and elastic walls - heart pumps blood out at high pressure
thick walls compared to the lumen
thick layers of muscle - to make them strong
elastic fibres - to stretch and spring back
what do arteries branch into?
capillaries, that are too small to see
what do the capillaries do?
they carry blood really close to every cell in the body to exchange substances with them.
supply food and oxygen, take away waste like CO2
what are the features of capillaries?
permeable walls - so substances can diffuse in and out
1 cell thick walls - increase the rate of diffusion by decreasing distance over which it occurs
what do capillaries eventually join up to form?
veins
what are the features of veins?
thinner walls than arteries - lower pressure
bigger lumen - help blood flow despite low pressure
valves - help keep blood flowing in the right direction
formula for rate of blood flow:
rate of blood flow = volume of blood / number of minutes
what is the job of the red blood cell?
to carry oxygen from the lungs to all the cells in the body
How are red blood cells well adapted for carrying oxygen?
they are shaped like a biconcave disk, this gives a large surface area for absorbing oxygen
it doesn’t have a nucleus to save space for oxygen
what do red blood cells contain?
a red pigment called haemoglobin
what does haemoglobin do in the lungs?
it binds with oxygen to provide oxyhaemoglobin. in body tissues oxyhaemoglobin releases oxygen and haemoglobin to release oxygen to the cells
what are the 4 main things in the blood?
red blood cells
white blood cells
platelets
plasma
unlike red blood cells, white blood cells contain:
a nucleus
what do different white blood cells do?
some change shape and engulf to kill microorganisms (phagocytosis)
others produce antibodies to fight microorganisms and antitoxins to neutralise toxins
what are platelets?
small fragments of cells. they have no nucleus
what do platelets do?
they help the blood to clot a wound - to stop you bleeding and microorganisms getting in
what can a lack of platelets cause?
excessive bleeding and bruising
what is plasma?
pale - straw coloured liquid which carries lots of stuff
what does plasma carry?
red and white blood cells and platelets
CO2 from organs to the lungs
Urea from the liver to the kidneys
hormones
proteins
antibodies and antitoxins produced by WBC
nutrients like glucose and amino acids(soluble products of digestion absorbed from gut and taken to body cells)
what is cardiovascular disease a term for?
diseases of the heart or blood vessels. (e.g. coronary heart disease)
what is coronary heart disease?
when the coronary arteries that supply blood to the muscle of the heart gets blocked by layers of fatty material building up. this causes arteries to become narrow, so blood flow is restricted and there’s a lack of oxygen to the heart which can lead to a heart attack
what are stents?
tubes that are inserted inside arteries. they keep them open, making sure blood can pass through to the heart muscles. this keeps a persons heart beating
why are stents positive?
they’re a way of lowering the risk of a heart attack in people with coronary heart disease. they’re effective for a long time and recovery from surgery is quick
why are stents negative?
there’s a risk of complications during the operation, and a risk of infection. risk of developing a blood clot near the stent (sometimes called thrombosis)
what is cholesterol?
an essential liquid that your body produces and needs to function properly. too much of a certain cholesterol (bad or LDL cholesterol) can cause health problems
what can having too much LDL cholesterol do?
having too much in the bloodstream can cause fatty deposits to form inside arteries, which can lead to coronary heart disease
what are statins?
drugs that can reduce the amount of bad cholesterol present in the blood stream. this slows down the rate of fatty deposits forming
advantages of statins:
reduce risk of strokes, coronary heart disease and heart attacks
increase amount of good or HDL cholesterol, which removes bad cholesterol
may prevent some other diseases
disadvantages of statins:
long-term, must be taken regularly, someone could forget
can cause negative side effects (headaches), some can be serious(kidney failure, liver damage, memory loss)
its not instant it takes time for effect to kick in
What do doctors do if a patient has heart failure?
Perform a heart transplant using donor organs from people who have recently died. If they’re not available right away they’re not the best option, they may fit an artificial heart
What are artificial hearts?
Mechanical devices that pump blood for a person whose heart has failed.
Artificial hearts are usually only a temporary fix but:
they can keep someone alive until a donor is available or let the heart rest and heal. In some cases they’re used as a permanent fix
What’s the main advantage of artificial hearts?
Less likely to be rejected by immune system then donor. Because they’re made of metals or plastics the body doesn’t recognise them as ‘foreign’
Disadvantages of artificial hearts?
Surgery can lead to bleeding and infection
Doesn’t work as well as natural one - parts of the heart could wear out or the motor could fail
Blood doesn’t flow as smoothly- blood clots and strokes
Patient has to take drugs to thin blood - cause problems with bleeding when heart
How can the valves in the heart be damaged or weakened?
By heart attacks, infection or old age
What can valve damage do?
Stiffen valve tissue so it won’t open properly
Leaky valve allowing back flow of blood - it doesn’t circulate as effectively
What can severe valve damage be treated with?
By replacing the valve.
What are biological valves?
Replacement valves taken from humans or other mammals
What are mechanical valves?
Man made artificial valves
Valve surgery:
Much last drastic then a whole heart transplant. Artificial valves is still major surgery and there can be problems with blood clots
What happens when someone loses lots of blood?
Their heart can still pump the remaining red blood cells around as long as the volume of their blood can be topped up
What is artificial blood?
A blood substitute that is used to replace lost volumes of blood. e.g. a salt solution called saline
Why is artificial blood good?
It’s safe if no air bubbles get into the blood. Can keep people alive even when they lose 2/3 of blood. Gives time to produce new blood cells
What if a patient can’t produce new blood cells?
They will need a blood transfusion . Ideally, artificial blood would replace the function of the lost red blood cells, scientists are working on this
What is health?
It’s the statue of physical and mental wellbeing. Diseases are often responsible for causing ill health
What are communicable diseases?
Diseases that can spread from person or animals to person. Sometimes called contagious or infectious diseases.
What can communicable diseases be caused by?
Bacteria, viruses, parasites and fungi
What are non-communicable diseases?
Those that can’t spread between people or animals and people. They last for a long time and get worse slowly.
Examples of communicable diseases:
Measles and malaria
Examples of non-communicable diseases:
Asthma, cancer and coronary heart disease
who has an increased chance of suffering from communicable diseases?
people who have problems with their immune systems have an increased chance. (e.g. influenza) this is because their body is less likely to be able to defend itself against the pathogen that causes the disease
example of when some types of cancer can be triggered by infection by certain viruses?
some types of hepatitis virus can cause long term infections in the liver where the virus is. this can lead to liver cancer.
HPV can cause cervical cancer
what can immune system reactions caused by infection by a pathogen trigger?
allergic reactions such as skin rashes or worsen the symptoms of asthma
how can mental issues such as depression be triggered?
when someone is suffering from severe physical health problems, especially if they have an effect on everyday activities or affect the persons life expectancy
what factors other than diseases affect your health?
diet
stress
life situation
how can diet affect your health?
whether you have a good and balanced diet that provides your body with everything it needs in the right amounts.
what can a poor diet affect?
your physical and mental health
how can stress affect your health?
being constantly under stress can lead to health issues
how can life situation affect your health?
if you have easy access to medicine to treat illness, or access to things that can prevent you from getting ill. being able to buy healthy food or access condoms to prevent transition of STI’s
what are risk factors?
things that are linked to an increase in the likelihood that a person will develop a certain disease during their lifetime. they don’t guarantee you will get the disease
what can risk factors be?
aspects of a persons lifestyle
presence of certain substances in the environment or in your body(e.g. asbestos)
many non -communicable diseases are caused by…………………….. instead of one
several different risk factors instead of 1
what range can lifestyle factors can have different impacts?
locally, nationally and globally
how can lifestyle factors have different factors nationally?
people from deprived areas are more likely to smoke, have a poor diet and not exercise - cardiovascular disease, obesity, type 2 diabetes
what is the local impacts for lifestyle factors?
your individual choices affect the local incidence of disease
how can lifestyle factors have different factors globally?
in developed countries non-communicable diseases are more common as people generally have a higher income and can buy high fat food
what risk factors are able to directly cause a disease?
smoking
obesity
drinking
radiation
what diseases can smoking directly cause?
cardiovascular disease, lung disease and lung cancer. when pregnant it can cause lots of health problems for the unborn baby
what diseases can obesity directly cause?
type 2 diabetes
what diseases can drinking too much alcohol directly cause?
liver cancer, affects brain function. when pregnant it can cause lots of health problems for the unborn baby
what diseases can exposure to radiation directly cause?
cancer
How can smoking directly cause disease?
it damages the walls of arteries and the cells in the linings of the lungs
How can obesity directly cause disease?
it makes the body less sensitive or resistant to insulin, meaning that it struggles to control the concentration of glucose in the blood
How can drinking to much directly cause disease?
it can damage the nerve cells in the brain, causing the brain to lose volume
How can exposure to radiation directly cause disease?
things that cause cancer are known as carcinogens. ionising radiation is an example of a carcinogen
Why could risk factors not always be as accurate?
Scientists look for correlations in data, which doesn’t always mean it was the cause. Some risk factors aren’t capable of directly causing disease.
Example of how risk factors aren’t capable of directly causing a disease:
Lack of exercise and high fat diet linked to increased chance of cardiovascular disease but don’t cause it directly. It’s the high blood pressure and bad cholesterol levels that actually cause it
What are the 2 costs of non-communicable diseases?
Human cost
Financial cost
What is the human cost of non-communicable diseases?
Tens of millions die from it per year. They have lower quality of life or shorter lifespan. Affects loved ones of sufferers too
What are the financial costs of non-communicable diseases?
NHS for researching and treating them or any other health services
Families who move or adapt their home
If sufferer gives up work or dies, family income reduced
Reduction in people able to work affects country’s economy
how are tumours formed?
changes occur in our cells and result in uncontrolled growth and division which forms a tumor
what are the 2 types of tumour?
malignant and benign
what are benign tumours?
the tumour grows until there is no more room, it stays in one place(usually in a membrane) and doesn’t invade other tissues in the body. its not cancerous and not usually dangerous
what are malignant tumours?
it grows and spreads into neighbouring healthy tissues. the cells can break of and spread to other parts of the body through the bloodstream. they invade healthy tissues elsewhere in the body and form secondary tumours. they are dangerous and can be fatal, they are cancerous
what is a risk factor?
it doesn’t mean you’ll definitely develop factor it just means you have an increased risk of developing the disease
why have cancer survival rates increased?
medical advances like:
improved treatment
being able to diagnose earlier
increased screening for the disease
what life styles are associated with risk factors?
smoking
obesity
UV exposure
Viral infection
how is smoking a risk factor for cancer?
research shows smoking is linked to lung, mouth, bowel, stomach and cervical cancer
how is obesity a risk factor for cancer?
it is linked to many different cancers including bowel, liver and kidney cancer. it is the 2nd biggest preventable cause of cancer after smoking
how is UV expoure a risk factor for cancer?
people who are often exposed to the UV radiation from the sun have an increased chance of skin cancer. people who live in sunny climates or spend lots of time outside are at higher risk of the disease and people who frequently use sun beds put themselves at a higher risk of the cancer
how is viral infection a risk factor for cancer?
infection with some viruses is shown to increase chances of certain types of cancer. e.g hepatitis B and C can increase risk of liver cancer. the likelihood of becoming infected with these viruses sometimes depend on lifestyle, e.g. spreading through unprotected sex or sharing needles
what else can risk factors be associated with other than lifestyle?
genetics
how can risk factors be associated with genetics?
sometimes you can inherit faulty genes which make you more susceptible to cancer. e.g. mutations in the BRCA genes have been linked to an increased likelihood of developing breast and ovarian cancer
plant tissues:
epidermal tissue palisade mesophyll tissue spongy mesophyll tissue xylem and phloem meristem tissue
what is epidermal tissue?
this covers the whole plant
what is palisade mesophyll tissue?
this is the part of the leaf where most photosynthesis happens
what is spongy mesophyll tissue?
its in the leaf, and contains big air spaces to allow gases to diffuse in and out of cells
what is xylem and phloem?
they transport things like water, mineral ions and food around the plant (through the roots, stems and leaves
what is meristem tissue?
this is found at the growing tips of shoots and roots and is able to differentiate (change) into lots of different types of plant cell, allowing the plant to grow
what tissue do leaves contain?
epidermal, mesophyll, xylem and phloem
what is the use of a waxy cuticle?
the epidermal tissues at the top of the leaf are covered with a waxy cuticle which helps reduce water loss through evaporation
how is the upper epidermis adapted?
its transparent so that light can pass through it to the palisade layer
how is the palisade layer adapted?
it has lots of chloroplasts, this means that they’re near the top of the leaf where they can get the most light
how are the xylem and phloem adapted?
they form a network of vascular bundles, which deliver water and other nutrients to the entire leaf and take away the glucose produces by photosynthesis. they also help support the structure
how are the tissue of leaves adapted for efficient gas exchange?
the lower epidermis is full of stomata, which let CO2 diffuse directly into the leaf, the opening and closing of the stomata is controlled by guard cells in response to environmental conditions. the air spaces in the spongy mesophyll tissue increase the rate of diffusion of gases
how are phloem structured?
made of columns of elongated living cells with small pores in the end walls to allow cell sap through
what process do the phloem carry out?
they transport food substances made in the leaves (mainly dissolved sugars) to the rest of the plant for immediate use or for storage. transport goes in both directions. this is called translocation
what is cell sap?
liquid that’s made up of the substances being transported and water
how are xylem structured?
made of dead cells joined end to end with no end walls between them and a hole down the middle. they’re strengthened with a material called lignin
what is the transpiration stream?
the movement of water from the roots, through the xylem and t of the leaves
what do xylem do?
they carry water and mineral ions from the roots to the stem and leaves
what is transpiration caused by?
the evaporation and diffusion of water from a plants surface. most transpiration happens at the leaves
what does transpiration create?
a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem vessels to replace it. more water is drawn up from the roots so there’s a constant transpiration stream of water through the plant
how is transpiration a side effect of the way leaves are adapted for photosynthesis?
they have to have the stomata in them so that gases can be exchange easily. because there is more water inside the plant then in the air outside, the water escapes through the stomata by diffusion
what is transpiration affected by?
light intensity
temperature
air flow
humidity
how does light intensity affect transpiration?
the brighter the light, the greater the transpiration rate. stomata close as it gets darker, photosynthesis can’t happen in the dark, so they don’t need to be open to let CO2 in. when the stomata are closed little water can escape
how does temperature affect transpiration?
the warmer it is, the faster transpiration happens. when it’s warm the water particles have more energy to evaporate and diffuse out of the stomata
how does air flow affect transpiration?
the better the air flow around a leaf the greater the transpiration rate.
how does poor air flow mean low transpiration rate?
water vapour surrounds the leaf and doesn’t move away. it means high concentration of water particles outside the leaf so diffusion doesn’t happen quickly
how does good air flow mean high transpiration rate?
the water vapour is swept away, maintaining a low concentration of water in the air, diffusion happens quickly.
how does humidity affect transpiration?
the drier the air around a leaf, the faster transpiration happens. this works similarly to air flow.
dry = low concentration outside the leaf and fast diffusion
humid = high concentration outside the leaf and less diffusion
how can you estimate the rate of reaction?
by measuring the uptake of water by a plant. this is because we can assume that water uptake is directly linked to transpiration
what is a potometer?
there is a beaker with a plant inside and it is closed off, at the bottom of the test tube is a long tube that connects to a reservoir of water, which is hut off and a beaker of water.
how does the potometer work?
as the plant takes in water an air bubble is created in a tube and a scale is set up along the tube, the distance the bubble travels over a time period can be measured
how do guard cells work?
when the plant has lots of water the guard cells fill up with it and go plump and turgid, which makes the stomata open so gases can be exchanged. when it is short of water the guard cells are flaccid , making the stomata close, so water vapour doesn’t escape
how is the opening and closing of guard cells possible?
thin outer walls and thickened inner walls make the opening and closing work
how do guard cells reduce water loss?
either then closing when there is less water, they are sensitive to light, so close at night, to save water and not lose out on photosynthesis. there are more stomata on the bottom of the leaf because it is more shaded so less water is lost than if it were on the upper surface
