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november mocks Flashcards

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1
Q

what is an enzyme

A

a biological catalyst

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2
Q

how does temperature affect enzyme function

A

as temperature increases the enzyme and substates have more kinetic energy which means they move faster so have more successful collisions

once temperature has got to a certain point the temperature breaks the bonds that hold together the amino acids (which make the proteins) which changes the shape of the enzyme.

this is denaturing

once the enzyme has denatured the substrate can no longer fit in the active site (as it has lost its shape) meaning that the reaction will stop

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3
Q

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

A

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

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4
Q

how is enzyme function affected by changes in pH

A

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

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5
Q

active transport

A

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.

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6
Q

diffusion

A

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

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7
Q

osmosis

A

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

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8
Q

how does surface area to volume ratio affect movement of substances in and out of cells

A

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.

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9
Q

how does distance affect movement of substances in and out of cells

A

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

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10
Q

how does concentration gradient affect movement of substances in and out of cells

A

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.

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11
Q

how does temperature affect movement of substances in and out of cells

A

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

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12
Q

practical - investigate diffusion and osmosis using living systems

A
  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.
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13
Q

practical - investigate diffusion and osmosis using non-living systems

A
  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.
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14
Q

order of organisation

A

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

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15
Q

nucleus

A

controls the cells activity (by making proteins)
contains the chromosomes (strands of DNA which carry genes which code for a protein)

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16
Q

cell membrane

A

boundary between the cytoplasm and the cell’s surrounding.
controls what substances enter and exit the cell.

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17
Q

cytoplasm

A

jelly-like liquid where reactions occur

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18
Q

mitochondria

A

carries out some aerobic respiration, which produces ATP

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19
Q

ribosomes

A

synthesize (assemble) proteins and amino acids

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20
Q

chloroplasts

A

contain chlorophyll, absorb light energy and use it to carry out chemical reactions of photosynthesis making biological molecules for plants.

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21
Q

cell wall

A

helps keep plants in a fixed shape

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22
Q

vacuole

A

filled with a water liquid called cell sap, stores dissolved sugars, mineral ions and other substances.

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23
Q

similarities of plants and animal cells

A

nucleus
cytoplasm
mitochondria
cell membrane
ribosomes

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24
Q

differences of plants and animal cells

A

plants only:
cell wall (cellulose)
vacuole
chloroplasts

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25
Q

what happens in the mouth

A

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

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26
Q

what is chemical digestion

A

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

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27
Q

what is mechanical digestion

A

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

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28
Q

what happens in the oesophagus

A

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

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29
Q

what is peristalsis

A

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

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30
Q

what happens in the stomach

A

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.

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31
Q

what happens in the small intestine

A

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

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32
Q

what happens in the duodenum

A

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

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33
Q

what is bile

A

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
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34
Q

what happens in the ilium

A

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

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35
Q

how is the ilium optimized for diffusion

A

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

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36
Q

what happens in the colon

A

site of all reabsorption of water

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37
Q

what happens the rectum

A

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

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38
Q

what does the pancreas do

A

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

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39
Q

what is the large intestine

A

colon and rectum

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40
Q

how is the small intestine adapted for absorption

A

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

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41
Q

starch ->

A

starch –(amylase)–> maltose

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42
Q

maltose ->

A

maltose –(maltase)–> glucose

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43
Q

protein ->

A

protein –(pepsin)–> peptides

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44
Q

lipid ->

A

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

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45
Q

how do living organisms produce ATP

A

respiration!!

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46
Q

how do cells get energy to carry out their life processes

A

ATP from respiration

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47
Q

peptides ->

A

peptide –(peptidase)–> amino acids

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48
Q

what is the difference between anaerobic and aerobic respiration

A

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

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49
Q

what is cell respiration

A

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

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50
Q

does cell respiration happen in plants

A

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

51
Q

what are carbohydrases

A

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

52
Q

what are proteases

A

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

53
Q

what are lipases

A

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

54
Q

word equation for aerobic respiration

A

oxgyen + glucose —> water + carbon dioxide

55
Q

chemical equation for aerobic respiration

A

C6 H12 O6 + 6O2 → 6CO2 + 6H20

56
Q

why does aerobic respiration produce more ATP than anaerobic respiration

A

aerobic respiration fully oxidizes glucose whereas anaerobic respiration doesn’t

57
Q

word equation for anaerobic respiration in animals

A

glucose —-> lactic acid

58
Q

word equation for anaerobic respiration in plants + fungi + bacteria

A

glucose —-> ethanol + carbon dioxide

59
Q

2.39 practical - investigate the evolution of CO2 and heat for respiring seeds

A
  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

60
Q

structure and function of the thorax

A

ribs - bone structure which protects internal organs
intercostal muscles - muscles between ribs which control the movement of the ribs
diaphragm - sheet of connective tissue and muscle at the bottom of the thorax to allow inhalation and exhalation
trachea - windpipe that connects the mouth 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

61
Q

what is the role of the intercostal muscles and the diaphragm in ventilation

A

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

62
Q

how are alveoli adapted for gas exchange

A

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

63
Q

what is coronary heart disease

A

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

64
Q

what factors make coronary heart disease more likely to happen

A

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

65
Q

chemicals in cigarettes

A

nicotine
tar
carbon monoxide
+ more than 4000 others

66
Q

effects of nicotine

A

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

67
Q

effects of carbon monoxide

A

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

68
Q

effects of tar

A

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

69
Q

how does smoking affect the cilia cells and etc

A

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

70
Q

how does smoke damage the alveoli

A

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

71
Q

2.50 practical - investigate breathing in humans, including the release of CO2 and effect of exercise

A
  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

72
Q

transpiration

A

water lost from the leaves, mainly from the stomata

(water evaporates into the air spaces in the spongy mesophyll then diffuses out of the stomata)

73
Q

how is transpiration rate affected by humidity

A

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.

74
Q

how is transpiration rate affected by wind speed

A

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.

75
Q

how is transpiration rate affected by temperature

A

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

76
Q

how is transpiration rate affected by light intensity

A

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

77
Q

2.58B practical - investigate the role of wind in determining the rate of transpiration for a leafy shoot

A

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.
78
Q

2.58B practical - investigate the role of increased temperature in determining the rate of transpiration for a leafy shoot

A

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.
79
Q

2.58B practical - investigate the role of humidity in determining the rate of transpiration for a leafy shoot

A

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.
80
Q

2.58B practical - investigate the role of light in determining the rate of transpiration for a leafy shoot

A

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.
81
Q

what factors increase the chance of coronary heart disease

A

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

82
Q

structure and function of arteries

A

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

83
Q

structure and function of veins

A

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

84
Q

structure and function of capillaries

A

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

85
Q

what is the acronym of chemical molecules in carbs, lipids and protein

A

CHO CHO CHON

86
Q

carbohydrate structure

A

large molecules made up of smaller basic units.
starch and glycogen from simple sugars (smallest unit of carbs).
complex carbs are made up of 1000s of simple sugars joined together.

87
Q

lipid structure

A

large molecules made up of smaller basic units.
fatty acids and glycerol.
made of 3 fatty acids joined to a glycerol.

88
Q

protein structure

A

large molecules made up of smaller basic units. made of many amino acids joined together.
20 different amino acids can be joined together in any order to create millions of different proteins.
the shape of a protein helps it carry out its job

89
Q

why are starch and glycogen good storage molecules

A

less soluble as simple sugars so have less effect on osmosis

90
Q

what uses starch and glycogen

A

plants store glucose as starch
animals and fungi store glucose as glycogen

91
Q

difference between asexual and sexual reproduction

A

AS only needs 1 parent organim whereas S needs 2
AS uses mitosis whereas S uses meiosis
AS produces genetically identical offspring whereas S produces genetically unique offspring
AS is usually a quick process whereas S takes much longer

92
Q

how do genes exist as alleles

A

Alleles are variations of the same gene
As we have two copies of each chromosome, we have two copies of each gene and therefore two alleles for each gene
One of the alleles is inherited from the mother and the other from the father
This means that the alleles do not have to ‘say’ the same thing
For example, an individual has two copies of the gene for eye colour but one allele could code for brown eyes and one allele could code for blue eyes

93
Q

what does dominant mean

A

a dominant allele is always expressed even if only one copy is present

94
Q

what does recessive mean

A

a recessive allele is only expressed if 2 copies are present (so no dominant)

95
Q

what does homozygous mean

A

when both alleles of a gene is are the same

96
Q

what does heterozygous mean

A

when the 2 alleles of the gene are different

97
Q

what does phenotype mean

A

the observable characteristics of an organism (hair colour)

98
Q

what does genotype mean

A

the combination of alleles that control each characteristic

99
Q

what does codominance mean

A

when both alleles within a genotype are expressed in the phenotype of an individual

eg a red petal flower with a white petal flower becomes a pink petal flower

100
Q

polygenic inheritance

A

Characteristics that are controlled by more than one gene

most phenotypic features are a result of polygenic inheritance

101
Q

structure and function of wind pollinated flowers

A

For wind-pollinated flowers, the process of pollination is more random than it is for insect-pollinated flowers
When ripe, the anthers open and shed their pollen into the open air
The pollen is then either blown by the wind or carried by air currents until it (by chance) lands on the stigma of a plant of the same species, resulting in pollination

petals - small and dull, often green or brown in colour ( as the plant does not need to attract insects)
Scent and nectar - absent as theres no need to waste energy producing these as there is no need to attract insects
number of pollen grains - large amounts as most do not get to another flower to the more produced the higher chance that successfull pollination happens
pollen grains - smooth, small and light so they are easily blown by the wind
anthers - outside the flower, swinging loose on long filaments to release pollen easily
stigma - outside the flower, feathery to catch drifting pollen grains

102
Q

structure and function of insect pollinated flowers

A

Insects often visit these flowers to collect nectar (a sugary substance produced by insect-pollinated flowers and the base of their petals, which provides the insects with energy)
As an insect enters the flowers in search of nectar, it often brushes against the anthers, which deposit sticky pollen onto the insect’s body
When the insect visits another flower, it may brush against the stigma of this second flower and in the process, may deposit some of the pollen from the first flower, resulting in pollination

petals - large and brightly coloured to attract insects
scent and nector - present as it entices insects to visit the flower and push past the stamen to get nectar
number of pollon grains - moderate as insects transfer pollon grains efficiently with a high chance of successful pollination
pollen grains - larger, sticky, and or spiky to attach to insects to be carried away
anthers - inside the flower, stiff and firmly attached to brush against insects
stigma - inside flower, sticky so pollen grains stick to it when an insect brushes past

103
Q

how can plants reproduce asexully

A

plants can reproduce asexually by natural and artificial methods

natural
some plants grow side branches, known as runners, that have small plantlets at their ends
Runners are horizontal stems that grow sideways out of the parent plant
Once they touch the soil, these plantlets will grow roots and the new plantlets will grow and become independent from the parent plant as a genetically identical plant

artificial
A simple method to clone plants (mainly used by gardeners) is by taking cuttings
This is an artificial method of asexual reproduction
The method for taking cuttings is as follows:
Gardeners take cuttings from good parent plants (i.e. those that are healthiest and best-looking)
A section of the parent plant with a new bud is cut off
This cutting can either be placed into water until new roots grow or can sometimes be placed directly into soil
Sometimes, the stem of the cutting may first be dipped into ‘rooting powder’, which contains plant growth regulators (rooting hormones) that encourage new root growth
These cuttings are then planted and eventually grow into adult plants that are genetically identical to the original plant
Plants cloned by taking cuttings can be produced cheaply and quickly

104
Q

when is oestrogen released

A

levels rise from day 1 to peak just before day 14
The peak in oestrogen occurs just before the egg is released

105
Q

what is FSH

A

follicle-stimulating hormone

106
Q

when is progesterone released

A

stays low from day 1 – 14 and starts to rise once ovulation has occurred

107
Q

what is the role of oestrogen in the menstrual cycle

A

This causes the uterine wall to start thickening and the egg to mature

108
Q

what is the role of progesterone in the menstrual cycle

A

inhibits FSH and LH (stops further egg being matured and released)
maintains the thickness of the uterus lining

109
Q

what is the role of LH in the menstrual cycle

A

causes ovulation to occur and also stimulates the ovary to produce progesterone

110
Q

what is the role of FSH in the menstrual cycle

A

causes an egg to start maturing in the ovary
It also stimulates the ovaries to start releasing oestrogen

111
Q

what is LH

A

luteinising hormone

112
Q

what is the role of the placenta in the nutrition of the developing embryo

A

the placenta allows:
- Nutrients (i.e. glucose, amino acids and salts) and oxygen to move from the mother to the embryo
- Metabolic wastes - carbon dioxide and urea - to move from the embryo to the mother

These materials pass from one to the other by diffusion

113
Q

how is the developing embryo is protected by amniotic fluid

A

During pregnancy a membrane called the amnion encloses the developing embryo. The amnion secretes a fluid called amniotic fluid, which protects the developing embryo against jolts and bumps (mechanical shocks), drying out, and temperature fluctuations (due to waters high specific heat capacity)

114
Q

biological consequences of pollution of air by sulfer dioxide

A

acid rain can damage plants and animals and also make rivers + lakes acidic damaging aquatic organisms.
can also cause leaching of toxic minerals into lakes

115
Q

biological consequences of pollution of air by carbon monoxide

A

CO binds irreversibly to hemoglobin in red blood cells forming (carboxyhaemoglobin), preventing them from carrying oxygen to vital organs like the heart and brain

116
Q

what are the greenhouse gases

A

Water vapour
Carbon dioxide
Methane
Nitrous oxides
CFCs - Chlorofluorocarbons

117
Q

how does an increase in greenhouse gases result in an enhanced greenhouse effect

A

The Sun emits rays that enter the Earth’s atmosphere
The heat bounces back from the Earth’s surface
Some heat is reflected back out into space
Some heat is absorbed by greenhouse gases and is trapped within the Earth’s atmosphere – this is normal
However, as the levels of greenhouse gases in the atmosphere rise due to human activities the atmosphere gets thicker and traps more heat causing the earth to heat up more than usual making it the enhanced greenhouse effect

118
Q

how have human activities contributed to greenhouse gases

A

Carbon dioxide is produced during the combustion of fossil fuel
Methane is produced by cattle as they digest grass and released by rice paddy fields
Deforestation: Clearing forests reduces the Earth’s capacity to absorb CO₂ through photosynthesis

119
Q

consequences of global warming

A

Ocean temperatures increasing, causing melting of polar ice caps / rising sea levels / flooding / coral bleaching
Increasing temperatures causing extreme weather like super storms, flooding, droughts
Changes in or loss of habitats due to these extreme weather events
Decreases in biodiversity as food chains are disrupted and extinction rates increase
Increases in migration of species to new places, including increased spread of pests and disease

120
Q

what is the type of bacteria used to create yogurt

A

lactobacillus bulgaricus

121
Q

how does lactobacillus produce yogurt

A

Lactobacillus respires anaerobically producing lactic acid. This lowers the pH, acting as a preservative. The acid also coagulates the milk protein, as the acidic conditions change the shape of the proteins, giving yoghurt its texture and flavour

122
Q

how can selective breeding develop plants with desired characteristics

A

pick 2 best plants with desired characteristics and breed them
pick 2 best offspring and breed again

this reduces the gene pool and increases the chances of getting desired genes

123
Q

how can selective breeding develop animals with desired characteristics

A

pick 2 best animals with desired characteristics and breed them
pick 2 best offspring and breed again

this reduces the gene pool and increases the chances of getting desired genes

124
Q

what are some examples of desired characteristics animals are bred for

A

disease resistance
quicker growing
quicker reproduction
fur coat colour

Biology (7 decks)

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