Structure and Functions in living organisms Flashcards

Question

practical - investigate how enzyme activity can be effected by changes in temperature

Answer 1

amylase digests starch 1. mix 10cm of 10% starch solution with 5cm of 5% amylase in a boiling tube. 2. heat in a water bath 3. every minute add 1 drop of this solution to 1 drop of iodine in a spotting tile 4. repeat using different temps of water baths when the starch has been fully digested (so none is present) iodine will stay orange

Answer 2

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

Answer 3

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.

Answer 4

the movement of water molecules from a high potential to a lower potential across a partially permeable membrane

Answer 5

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.

Answer 6

Diffusion takes longer if the molecules have to travel further. Therefore cells are small (smaller volume reduces distance).

Answer 7

At higher temperatures, molecules have more kinetic energy and so move faster.

Answer 8

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.

Answer 9

1. Make a 5 different concentration of sucrose solutions 2. Measure 5cm3 of each dilution into separate test tubes. 3. 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. 4. Weigh each before the start of the experiment. 5. Place a potato chip in each test tube (one per sucrose concentration) and leave for 20 minutes. 6. Remove each potato chip, dry gently using paper towel, and weigh them in turn. 7. Calculate the percentage change in mass for each sucrose solution.

Answer 10

1. Add sucrose solution to a section of Visking tubing – a selectively permeable substance used to model a cell membrane. 2. Weigh the Visking tubing and its contents. 3. Add the Visking tubing to a beaker of water. 4. Leave for 1 hour. 5. Pat the Visking tubing dry to remove excess water. 6. Reweigh the Visking tubing and its contents.

Answer 11

plants produce glucose from simple inorganic molecules – carbon dioxide and water – using light energy

Answer 12

water + carbon dioxide -> (light energy) oxygen + glucose

Answer 13

6CO2 + 6H2O → C6H12O6 + 6O2

Answer 14

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

Answer 15

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

Answer 16

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

Answer 17

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

Answer 18

upper epidermis is transparent which allows light to pass through to the mesophyll

Answer 19

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

Answer 20

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)

Answer 21

xylem transports the water into the leaves. this provides a short distance for the water to diffuse into the photosynthesis cells

Answer 22

for chlorophyll

Answer 23

for amino acids

Answer 24

1. Take a bundle of shoots of a pondweed 2. Submerge them in a beaker of water 3. Use a light a set distance from the plant (measure with a ruler) As oxygen is produced, the bubbles of gas will appear 4. count the number of bubbles over a set time, eg 60 secs Repeat steps for different distances of the light and calculate mean

Answer 25

carbohydrates, proteins, lipid, vitamins, minerals, water, dietary fiber

Answer 26

bread, potatoes, pasta, rice, cereals, fruit

Answer 27

meat, eggs, fish, quinoa, quorn

Answer 28

butter, cooking oils, cream, avocados

Answer 29

fuel for respiration

Answer 30

growth and repair of cells and tissues fuel for respiration

Answer 31

store of energy fuel for respiration insulation for (thermal and electrical)

Answer 32

red meat, liver, spinach

Answer 33

fish liver oil, liver, butter, carrots

Answer 34

milk and dairy products

Answer 35

fresh fruit and vegetables

Answer 36

forms part of hemoglobin which binds to oxygen

Answer 37

dairy products, oily fish

Answer 38

needed to form bones and teeth

Answer 39

making a chemical retina and also protects the surface of the eye

Answer 40

needed for cells and tissues to stick together

Answer 41

needed to absorb calcium and phosphate ions from food

Answer 42

night blindness and damaged corena

Answer 43

rickets caused from weak bones

Answer 44

water is an essential solvent and is used to transport the components of blood and is crucial for temperature regulation by sweating

Answer 45

fiber helps the movement of food through the intestine, preventing constipation and bowel cancer.

Answer 46

Young people need more energy requirements as it is used for growth and muscle development

Answer 47

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

Answer 48

Energy requirements increase as energy is needed to support fetus, and the larger mass the mother needs to carry

Answer 49

taking food in through the mouth and swallowing

Answer 50

breaking down large insoluble molecules into smaller pieces (physical digestion) and smaller soluble molecules

Answer 51

movement of small soluble molecules out of the gut and into the blood by diffusion and active transport

Answer 52

passing out undigested food out through the anus

Answer 53

building larger biomolecules from the small soluble molecules in all cells

Answer 54

mouth + oesophogus

Answer 55

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

Answer 56

food broken down into smaller soluble molecules by enzymes, bile and acids

Answer 57

food broken down via physical methods such as churning, grinding and chewing

Answer 58

long tube that connects the mouth and the stomach. the bolus is pushed down/through by peristalsis

Answer 59

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

Answer 60

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.

Answer 61

both digestion and absorption happen in the small intestine made up of duodenum and ileum

Answer 62

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

Answer 63

bile is produced by the liver and stored in the gall bladder 1. neutralizes the stomach acid because the duodenum enzymes work best at 7-8 pH 2. emulsifies lipids - breaks down the large droplets into smaller droplets, increasing SA for lipase to digest the fat

Answer 64

absorption begins. the small soluble molecules are absorbed. some by diffusion but some such as glucose by active transport.

Answer 65

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

Answer 66

site of all reabsorption of water

Answer 67

the faeces are stored in the rectum and egested from the anus

Answer 68

the removal of waste products by chemical reactions eg urea removed by the kidneys and sweating

Answer 69

produces and secretes amylase, trypsin, lipase into the duodenum secretes an alkaline fluid into the duodenum to neutralize the acidity of the stomach

Answer 70

1. 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) 2. Turn off the bunsen burner 3. 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 4. Rinse the leaf in cold water This is done to soften the leaf tissue after being in ethanol 5. 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

Answer 71

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 1. 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) 2. Turn off the bunsen burner 3. 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 4. Rinse the leaf in cold water This is done to soften the leaf tissue after being in ethanol 5. 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

Answer 72

place one leaf into a conical flask containing soda lime (which absorbs CO2) place another leaf into a conical flask without anything in 1. 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) 2. Turn off the bunsen burner 3. 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 4. Rinse the leaf in cold water This is done to soften the leaf tissue after being in ethanol 5. 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

Answer 73

villi and micro villi very long which increase SA and time for diffusion and active transport peristalsis mixes food together and keeps things moving

Answer 74

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

Answer 75

starch --(amylase)--> maltose

Answer 76

maltose --(maltase)--> glucose

Answer 77

protein --(pepsin)--> peptides

Answer 78

peptides --(trypsin)--> amino acids

Answer 79

lipid --(lipase)--> glycerol and 3 fatty acids

Answer 80

BANANA CHIP 1. attach a boiling tube to a clamp stand 2. Use the measuring cylinder to measure out 25cm3 of water and pour it into the boiling tube 3. Record the starting temperature of the water using the thermometer 3. Weigh the initial mass of the food sample 4. 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 5. Record the final temperature of the water 6. (Once cooled) weigh the mass of any remaining food and record 7. 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))

Answer 81

respiration!!

Answer 82

ATP from respiration

Answer 83

cells constantly break down food molecules to produce ATP this happens continuously because without it the cell would have no energy and die

Answer 84

yes it is part of the process as they photosynthesis to create glucose and then respire the glucose to create energy

Answer 85

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

Answer 86

they are enzymes that break down carbohydrates into simple sugars amylase and maltase

Answer 87

they are enzymes that break down protein into amino acids pepsin, trypsin, proteases

Answer 88

they are enzymes that break down lipids into glycerol and fatty acids lipase

Answer 89

oxgyen + glucose ---> water + carbon dioxide

Answer 90

C6 H12 O6 + 6O2 → 6CO2 + 6H20

Answer 91

aerobic respiration fully oxidizes glucose whereas anaerobic respiration doesn't

Answer 92

glucose ----> lactic acid

Answer 93

glucose ----> ethanol + carbon dioxide

Answer 94

1. place some alive seeds soaked in Milton solution (bleach which kills any bacteria present which would also respire affects results) in a thermos flask 2. place some dead seeds (boiled to denature enzymes) soaked in Milton solution in another thermos flask 3. Make sure the cotton wool is plugging the top of each flask 4. place a thermometer and the flasks 5. place a delivery tube into the flasks and collect the gas produced 6. Record the initial temperature 7. 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

Answer 95

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

Answer 96

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

Answer 97

nicotine tar carbon monoxide + more than 4000 others

Answer 98

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

Answer 99

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

Answer 100

tar is a carcinogen carcinogens are chemicals that can alter the DNA and increase the risk of cancer (rapid, uncontrolled cell growth)

Answer 101

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

Answer 102

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

Answer 103

1. get 2 or more students 2. Work out student A's breathing rate at rest 3. Count their number breaths for 15 seconds and multiply by 4 4. Repeat several times to calculate an average 5. Student A should then exercise for a set time (at least 4 minutes) 6. Immediately after exercising, count the breaths taken in 15 seconds and multiply by 4 to obtain the breathing rate per minute 7. Compare the result to the breathing rate at rest in order to work out the change in breathing rate as a result of exercise 8. 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

Answer 104

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.

Answer 105

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)

Answer 106

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.

Answer 107

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.

Answer 108

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

Answer 109

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

Answer 110

potometer!! 1. The potometer must be set up under water - this prevents any air bubbles from entering the system and blocking the xylem.. 2. Cut the stem of a shoot whilst submerging the shoot 3. Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents water loss and air entry 4. Put the bung into the potometer. 5. Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the water. 6. 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. 7. place a hairdryer so its blowing on the plant to recreate wind 8. 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.

Answer 111

potometer!! 1. The potometer must be set up under water - this prevents any air bubbles from entering the system and blocking the xylem.. 2. Cut the stem of a shoot whilst submerging the shoot 3. Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents water loss and air entry 4. Put the bung into the potometer. 5. Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the water. 6. 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. 7. make the room hot 8. 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.

Answer 112

potometer!! 1. The potometer must be set up under water - this prevents any air bubbles from entering the system and blocking the xylem.. 2. Cut the stem of a shoot whilst submerging the shoot 3. Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents water loss and air entry 4. Put the bung into the potometer. 5. Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the water. 6. 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. 7. surround the plant in a clear plastic bag 8. 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.

Answer 113

potometer!! 1. The potometer must be set up under water - this prevents any air bubbles from entering the system and blocking the xylem.. 2. Cut the stem of a shoot whilst submerging the shoot 3. Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents water loss and air entry 4. Put the bung into the potometer. 5. Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the water. 6. 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. 7. make the room dark 8. 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.

Answer 114

the removal of toxic waste products that have been made by cells

Answer 115

skin, lungs, kidneys

Answer 116

excrete toxic waste products and substances in excess osmoregulation

Answer 117

the process of maintaining water and salt concentrations across membranes in the body example of homeostasis

Answer 118

cortex - the outmost region Medulla - the inner section of the kidney Renal pelvis - the tube linking the kidney to the ureter

Answer 119

in the kidney Nephrons start in the cortex of the kidney, loop down into the medulla and back up to the cortex

Answer 120

drain into the renal pelvis and the urine collects there before it flows into the ureter to be carried to the bladder for storage

Answer 121

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

Answer 122

section of nephron after the bowmans capsule and before the loop of henle

Answer 123

section of nephron after the loop of henle and before the collecting duct

Answer 124

Ultrafiltration Selective reabsorption of glucose Reabsorption of water and salts

Answer 125

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

Answer 126

glucose, water, urea, salts

Answer 127

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

Answer 128

water, urea, ions

Answer 129

Salts are reabsorbed by diffusion and active transport as well as water by osmosis also makes the medulla salty which makes osmosis more efficient

Answer 130

The distal convoluted tubule (DCT) assists in the regulation of potassium, sodium, calcium, and pH levels in the body.

Answer 131

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

Answer 132

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

Answer 133

amylase digests starch 1. mix 10cm of 10% starch solution with 5cm of 5% amylase in a boiling tube. 2. add in a few drops of a solution with a specific pH 3. every 10s add 1 drop of this solution to 1 drop of iodine in a spotting tile 4. 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.

Answer 134

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

Answer 135

the exchange of gases from an organism to the enviroment or vice versa

Answer 136

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

Answer 137

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

Answer 138

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

Answer 139

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.

Answer 140

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

Answer 141

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

Answer 142

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

Answer 143

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

Answer 144

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

Answer 145

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

Answer 146

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

Answer 147

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

Answer 148

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

Answer 149

the zylem and phloem in a plant (they are always arranged together in the root, stem and leaves)

Answer 150

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

Answer 151

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

Answer 152

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

Answer 153

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

Answer 154

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

Answer 155

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

Answer 156

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

Answer 157

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

Answer 158

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

Answer 159

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

Answer 160

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

Answer 161

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

Answer 162

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

Answer 163

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

Answer 164

heart - vena cava + aorta lungs - pulmonary artery + vein liver - hepatic artery + vein kidney - renal artery + vein

Answer 165

heart -> lungs -> heart -> liver -> (gut -> liver) -> kidneys -> other organs -> heart

Answer 166

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

Answer 167

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

Answer 168

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

Answer 169

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

Answer 170

colon and rectum

Answer 171

homeostasis

Answer 172

the maintenance of a constant internal environment examples of homeostasis: body water content body temperature

Answer 173

stimulus, receptor and effector

Answer 174

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

Answer 175

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

Answer 176

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

Answer 177

the brain and spinal cord which are linked to sense organs by nerves

Answer 178

stimulation of receptors in the sense organs which send electrical impulses along nerves into and out of the CNS

Answer 179

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

Answer 180

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

Answer 181

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)

Answer 182

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

Answer 183

the pathway of a reflex response (specifically, the pathway taken by electrical impulses as they travel along neurones)

Answer 184

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

Answer 185

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)

Answer 186

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

Answer 187

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

Answer 188

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

Answer 189

produced in pancreas targets the liver effect - causes glucose to convert to glycogen for storage (glycogen is less soluble so does not effect osmosis)

Answer 190

produced in testes targets the testes effect - sperm production (and causes secondary sexual characteristics)

Answer 191

produced corpus luteum in ovaries targets the ovaries effect - maintains the uterus lining and inhibits LH and FSH production

Answer 192

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

Answer 193

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

Answer 194

produced in pituitary gland (brain) targets the ovaries causes the egg to mature and stimulates oestrogen production

Answer 195

produced in the pituitary gland (brain) targets the ovaries triggers ovulation and the release of progesterone

Answer 196

light + gravity

Answer 197

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)

Answer 198

a response to light shoots grow up towards light (positively phototropic - grows to light) (negatively geotropic - grows away from gravity)

Answer 199

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)

Answer 200

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

Answer 201

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

Answer 202

transparent lens that refracts light as it enters the eye

Answer 203

controls how much light enters the pupil

Answer 204

transparent disc that can change shape to focus light onto the retina

Answer 205

contains light receptor cells – rods (detect light intensity) and cones (detect colour)

Answer 206

sensory neuron that carries impulses between the eye and the brain

Answer 207

hole that allows light to enter the eye

Answer 208

a ring of muscle that contracts and relaxes to change the shape of the lens

Answer 209

ligaments that connect the ciliary muscle to the lens

Answer 210

centered point where light is focused onto retina

Answer 211

spot where there are no photoreceptor cells

Answer 212

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

Answer 213

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)

Answer 214

(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

Answer 215

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

Answer 216

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

Answer 217

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

Answer 218

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

Answer 219

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

Answer 220

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

Answer 221

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

Structure and Functions in living organisms Flashcards

pass gcse (253 cards)