things idk from the spec Flashcards
(174 cards)
1
Q
what is a pathogenic example of a Protoctista
A
plasmodium and it is responsible for causing malaria
2
Q
what are 2 examples of a bacteria
A
- lactobacillus bulgaricus -> a rod shaped bacterium used in the production of yogurt from milk
- pneumococcus -> a spherical bacterium that acts as the pathogen causing pneumonia
3
Q
what are some examples of viruses
A
- tobacco mosaic virus which causes the discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts
- the influenza virus which causes the flu
- the HIV virus which causes AIDS
4
Q
describe what tissue is
A
a group of similar cells that work together to carry out a particular function
5
Q
describe what an organ is
A
a group of different tissues that work together to perform a function
6
Q
describe what an organ system is
A
organs work together to perform an organ system, each system does a different job
7
Q
describe what an organelle is
A
a subcellular structure that has one or more specific jobs to perform in the cell
8
Q
describe what a cell is
A
the fundamental unit that makes up living things
9
Q
what is the function of the nucleus
A
an organelle which contains the genetic material that controls the cells activities, it is surrounded by its own membrane
10
Q
what is the function of the cytoplasm
A
a gel like substance where most of the cells chemical reactions happen, it contains enzymes
11
Q
what is the function of the cell wall in a plant
A
a rigid structure made of cellulose which surrounds the cell membrane, it supports and strengthens it
12
Q
what is the function of mitochondria
A
- small organelles where most of the reaction for aerobic respiration take place, respirations transfers energy that the cell needs to work
13
Q
what is the function of chloroplasts
A
- photosynthesis which makes food for the plant happens here, chloroplasts contain a green substance called chlorophyll which is used in photosynthesis
14
Q
what is the function of ribosomes
A
- small organelles where proteins are made in the cell
15
Q
what is the function of the vacuole
A
a large organelle that contains cell sap, it helps support the cell
16
Q
what is the difference between a plant and animal cell
A
- plant cells have everything that animals have plus chloroplasts, cell wall and a vacuole
17
Q
what are the chemical elements present in carbohydrates
A
- carbohydrate molecules contain the elements carbon, hydrogen and oxygen
- starch and glycogen are large, complex carbohydrates, which are made up of many smaller units such as glucose and maltose which are joined together by a long chain
18
Q
what are the chemical elements present in proteins
A
- proteins are made up of long chains of amino acids
- they all contain carbon, nitrogen, hydrogen and oxygen atoms
19
Q
what are the chemical elements present in lipids
A
- lipids are built from fatty acids and glycerol
- lipids contain carbon, hydrogen and oxygen atoms
20
Q
how do you make a food sample
A
- get a piece of food and break it up using a pestle and mortar
- transfer the ground up food to a beaker and add some distilled water
- give the mixture a good stir with a glass rod to dissolve some of the food
- filter the solution using a funnel lined with filter paper to get rid of the solid bits of food
21
Q
describe the benedict’s test
A
- test for glucose
- prepare a food sample and transfer 5cm3 to a test tube
- prepare a water bath so that its set to 75 deg
- add 10 drops of benedict’s solution to the test tube using a pipette
- place the test tube in the water bath using a test tube holder and leave it in there for 5 mins, make sure the tube is pointing away from you
- if glucose is present it will turn from blue to brick red
22
Q
describe the iodine test
A
- test for starch
- make food sample and transfer 5cm3 of your sample to a test tube
- add a few drops of iodine solution and gently shake the tube to mix the contents
- if starch is present it will turn from orange to blue black
23
Q
describe the biuret test
A
- test for protein
- prepare a food sample and transfer 2cm3 of your sample to a test tube
- add 2cm3 of biuret solution to the sample and mix the contents by shaking it gently
- if the food sample contains protein the solution will change from blue to purple
24
Q
describe the emulsion test
A
- test for lipids
- place food sample in a test tube
- add a small volume of absolute ethanol and shake to dissolve any lipid in the alcohol
- add an equal volume of water
- a cloudy white colour caused by an emulsion forming indicated the presence of lipids
25
what is the definition of active transport
- the movement of particles against a concentration gradient, from an area of low concentration to an area of high concentration using energy released from respiration
26
describe the practical for how to investigate osmosis using a living system
- cut up a potato into identical cylinders and get some beakers with different sugar solutions in them
- one should be pure water and the other a very concentrated sugar solution
- then you have others with concentrations in-between
- measure the length of the cylinders then leave a few in each beaker for an hour
- take them out and measure them again
- if the cylinders have drawn in water via osmosis they will be longer, if water has been drawn out they will have shrunk a bit
27
describe the practical for how to investigate osmosis using a non-living system
- fix some Visking tubing over the end of the thistle funnel, then pour some sucrose solution down the glass tube and into the thistle funnel
- put the thistle funnel into a beaker of pure water- measure where the sucrose solution comes up to on the glass tube
- leave the apparatus overnight, then measure where the solution is in the glass tube. water should be drawn through the Visking tubing via osmosis and this will force the solution up the glass tube
28
what is the balanced symbol and word equation for photosynthesis
- carbon dioxide + water ---> glucose + oxygen
- 6co2 + 6h20 ---> c6h12o6 + 6o2
29
how can varying co2 concentrations affect the rate of photosynthesis
- increasing the concentration of co2 will only increase the rate of photosynthesis up to a certain point
- after this the graph will flatten out showing that co2 is no longer the limiting factor
- it will either be light intensity or temperature which is the limiting factor
30
how can varying light intensity affect the rate of photosynthesis
- if the light intensity is increased then the rate o photosynthesis will increase steadily, but only up to a certain point
- beyond that it wont make any difference because it will either be co2 concentration or temperature which is the limiting factor
31
how can varying temperature affect the rate of photosynthesis
- as the temperature increases, so does the rate of photosynthesis, up to a point
- if the temp is to high then the plants enzymes will denature so the substrate will no longer be complimentary, so the rate of photosynthesis decreases rapidly
- usually though, if temperature is the limiting factor it is because it is too low
32
describe the 6 ways that the structure of a leaf is adapted for photosynthesis
- leaves are broad so there's a large surface area exposed to light
- most of the chloroplasts are found in the palisade layer, this is so that they are near the top of the leaf where they get the most light
- upper epidermis is transparent so light can pass through to the palisade layer
- leaves have networks of vascular bundles- these are the transparent xylem and phloem, they deliver water and other nutrients to every part of the leaf and take away the glucose produced by photosynthesis
- the waxy cuticle helps reduce water loss via evaporation
- the adaptations of leaves for efficient gas exchange also make photosynthesis more efficient, the lower surface is full of stomata which allow co2 to diffuse directly into the leaf
33
why do plants require nitrates
- contain nitrogen for making amino acids and proteins
- these are needed for cell growth
- if a plant cant get enough nitrates it will be stunted and older leaves will turn yellow
34
why do plants require phosphates
- contain phosphorous for making DNA and cell membranes and their needed for respiration and growth
- plats without enough phosphate have poor root growth and their older leaves are purple
35
why do plants require potassium
- it helps the enzymes needed for photosynthesis and respiration
- if there's not enough potassium in the soil, plants have poor flower and fruit growth and discoloured leaves
36
why do plants require magnesium in small amounts
- magnesium is one of the most significant because its needed for making chlorophyll which is needed for photosynthesis
- plants without enough magnesium have yellow leaves
37
how can you test for starch to investigate photosynthesis
- start by duking the leaf in boiling water ( hold with forceps) this stops any chemical reactions happening in the leaf
- put the leaf in a boiling tube with some ethanol and heat it in an electronic water bath until it boils - this gets rid of any chlorophyll and makes the leaf a white ish colour
- rinse the leaf in cold water and add a few drops of iodine solution- if starch is present the leaf will turn blue black
38
how can you show that chlorophyll is needed for photosynthesis
- take a variegated leaf from a plant that has been exposed to light for a bit, make sure you record which bits are green and which are not
- test the leaf for starch, you will see that only the bits that were green turn blue black
- this suggests that only the parts of the leaf that contained chlorophyll are able to photosynthesize and produce starch
39
how can you show that co2 is needed for photosynthesis
- you will need a sealed bell jar, soda lime, a light and a plant
- the soda lime will absorb co2 out of the air in the jar
- if you leave the plant in the jar for a while and then test a leaf for starch, it wont turn blue black
- this shows that no starch has been made in the leaf, which means that co2 is needed for photosynthesis
40
how can you show that light is required for photosynthesis
- you need a plant that's been grown without any light, e.g in a cupboard for 48 hrs, this will mean that its used up its starch stores
- cut a leaf from the plant and test it for starch using iodine solution, the leaf wont turn blue black
- this shows that light is needed for photosynthesis, as no starch has been made
41
describe the practical of oxygen production showing the rate of photosynthesis
- set up the apparatus, including a ruler, light source, syringe, 2nd ruler, clamp, clamp stand, capillary tube,gas syringe
- gas syringe should be empty to start of with, sodium hydrogen carbonate may be added to the water to ensure the plant has enough co2
- a source of white light is placed at a specific distance from the pondweed
- the pondweed is left to photosynthesise for a specific amount of time, as it photosynthesises the oxygen released will collect in the capillary tube
- at the end of the experiment, the syringe is used to draw the gas bubble in the tube up along side a ruler and the length of the gas bubble is measured, this is proportional to the amount of o2 produced
42
what is vitamin A found in and what is its function
- found in liver/ organ meats
- helps prevent night blindness and keep your skin and hair healthy
43
what is vitamin d found in and what is its function
- eggs
- calcium absorption
44
what is vitamin c found in and what is its function
- found in fruit
- need to prevent scurvy
45
where are mineral irons like iron found and what is its function
- found in red meat
- needed to make haemoglobin for healthy blood
46
where is dietary fibre found and what's its function
- found in wholemeal bread
- aids the movement of food through the gut
47
describe how food is moved through the gut via peristalsis
- there's muscular tissue all the way down the alimentary canal
- its job is to squeeze balls of food ( called boluses) through your gut, otherwise it would get clogged up with old food
- this squeezing action, which is waves of circular contractions is called peristalsis
48
what is the function of the mouth in the human alimentary canal
- salivary glands in the mouth produce amylase enzyme in the saliva
- teeth break down food
49
what is the function of the oesophagus in the human alimentary canal
- the muscular tube that connects the mouth ad stomach
50
what is the function of the liver in the human alimentary canal
where bile is produced
51
what is the function of the gall bladder in the human alimentary canal
where bile is stored
52
what is the function of the large intestine in the human alimentary canal
- also called the colon
- where excess water is absorbed from the food
53
what is the function of the rectum in the human alimentary canal
- the last part of the large intestine
- where the faeces ( made up of mainly indigestible food) are stored
54
what is the function of the stomach in the human alimentary canal
- it pummels the food with its muscular walls
- it produces the protease enzyme, pepsin
- it produces hydrochloric acid for 2 reasons
. to kill bacteria
. to give the optimum PH for the protease enzyme to work
55
what is the function of the pancreas in the human alimentary canal
- produces protease, amylase and lipase enzymes
- it releases these into the small intestine
56
what is the function of the small intestine in the human alimentary canal
- produces protease, amylase and lipase enzymes to complete digestion
- this is also where the nutrients are absorbed out of the alimentary canal into the body
- the first part is the duodenum and the last part is the ileum
57
how do villi in the small intestine help with absorption
- the small intestine is adapted for absorption of food
- its very long so there is time to break down and absorb all the food before it reaches the end
- there's a really big surface area for absorption, because the walls of the small intestine are covered in millions of tiny projections called villi
- each cell on the surface of a villus also has its own microvilli -> little projections that increase the surface area even more
- villi have a single permeable layer of surface cells and a very good blood supply to assist quick absorption
58
what is the role of bile
- produced in the liver and stored in the gall bladder before its released into the small intestine
- the hydrochloric acid in the stomach makes the PH too acidic for the enzymes in the small intestine to work properly.
- bile is alkaline- it neutralises the acid and makes conditions alkaline, the enzymes in the small intestine work best in these alkaline conditions
- bile also emulsifies fats, which breaks the fat into tiny droplets, this gives a much bigger surface area of fat for the enzyme lipase to work on - which makes digestion faster
59
what digestive enzyme converts starch to maltose
amylase enzyme
60
what digestive enzyme converts maltose to glucose
maltase enzyme
61
what digestive enzyme converts proteins to amino acids
protease enzyme
62
what digestive enzyme converts lipids into glycerol and 3 fatty acids
lipase enzyme
63
how does the process of respiration produce ATP in living organisms
- respiration is the process of transferring energy from glucose
- some of the energy is transferred by heat
- the energy is transferred by respiration cant be used directly in cells- so its used to make a substance called ATP. ATP stores the energy needed for many cell processes
- when a cell needs energy, ATP molecules are broken down and energy is released
- there are two types of respiration aerobic and anaerobic
64
give the work equation and balanced symbol equation for aerobic respiration
glucose + oxygen --> carbon dioxide + water (+ energy)
c6h12o6 + 6o2 --> 6co2 + 6h2o
65
give the work equation for anaerobic respiration
glucose --> lactic acid (+ energy)
66
what is the word equation for anaerobic respiration in plants
glucose -->ethanol + carbon dioxide (+ energy)
67
what happens when breathing in
- intercostal muscles and diaphragm contract
- thorax volume increases
- this decreases the pressure, drawing air in
68
what happens when breathing out
- intercostal muscles and diaphragm relax
- thorax volume relaxes
- air is forced out
69
describe the experiment to investigate the release of co2 in your breath
- set up 2 boiling tubes, put the same amount of limewater in each
- put your mouth around the mouthpiece and breath in and out several times
- as you breath in air is drawn in through the opposite boiling tube, this contains very little co2 so the limewater will remain colourless
- when you breath out, the air you exhale bubbles through the limewater in the boiling tube, this air contains co2 produced during respiration so the limewater turns cloudy
70
what are the biological consequences of smoking
- smoking damages the walls inside the alveoli, reducing the surface area for gas exchange and leading to diseases like emphysema
- the tar is cigarettes damages the cilia in your lungs and trachea, the cilia along with mucus catch a load of dust and bacteria before they reach the lungs , the cilia also help to keep the trachea clear by sweeping mucus back towards the mouth
- tar also irritates the bronchi and bronchioles, encouraging mucus to be produced which cant be cleared by damaged cilia, this causes bronchitis and smokers cough
- carbon monoxide reduces the amount of oxygen the blood can carry, to make up for this the heart rate increases which leads to an increased blood pressure, high BP damages artery walls, making blood clots more likely, increases risk of CHD
- tobacco also contains carcinogens that lead to cancer
71
what are the 5 reasons that alveoli are specialised for gas exchange
- huge number of alveoli gives an enormous surface area
- there's a moist lining for gases to dissolve in
- the alveoli have very thin walls - 1 cell thick, so a short diffusion distance
- they have a great blood supply to maintain a high concentration gradient
- the walls are permeable so gases can diffuse across easily
72
describe the structure of the phloem
- made of living cells
- have pore in its end walls
- contains cytoplasm
- doesn't contain lignin
- tubular
- made from cells
73
describe the structure of the xylem
- made from dead cells
- do not have pores in their end walls
- hollow
- contains lignin
- tubular
- made of cells
74
describe the role of the xylem
- transports mineral salts and water from the root to the shoot of the leaves in the transpiration stream
75
describe the role of the phloem
- transports sugars like sucrose and amino acids from where there made in the leaves to other parts of the plant
- the movement of food substances around the plant is known as translocation
76
what is plasma
- pale yellow liquid which carries everything around the body including:
- red and white blood cells and platelets
- digested food products from the gut to all body cells
- carbon dioxide from body cells to the lungs
- urea from the liver to kidneys
- hormones which act as chemical messengers
- heat energy
77
what are platelets
- when you damage a blood vessel, platelets clump together to plug the damaged area
- the is known as blood clotting, blood clots stop you losing to much blood and prevent microorganisms from entering your wound
- in a clot, platelets are held together by a mesh of protein called fibrin
78
what is the structure of a red blood cell
- small and have a biconcave shape to give a large surface area for absorbing and releasing oxygen
- don't have a nucleus which frees up space for more haemoglobin, so they can carry more oxygen
79
how does the hormonal system help to control heart rate
- when an organism is threatened, the adrenal glands release adrenaline
- adrenaline binds to specific receptors in the heart, this causes the cardiac muscles to contract more frequently and with more force, so heart rate increases and the heart pumps more blood
- this increases oxygen supply to the tissues, getting the body ready for action
80
describe how exercise increases the heart rate
- when you exercise your muscles need more energy, so you respire more
- you need to get more oxygen into the cells and remove more carbon dioxide, for this to happen the blood has to flow faster, so your heart rate increases
- exercise increases the amount of co2 in the blood
- high levels of blood co2 are detected by receptors in the aorta and the carotid artery
- these receptors send signals to the brain
- the brain sends signals to the hear causing it to contract more frequently with more force
81
what does pulmonary mean
to do with the lungs
82
what does renal mean
to do the the kidneys
83
what does hepatic mean
to do with the liver
84
describe the ole of phagocytes
- phagocytes recognise pathogen
- phagocyte engulfs pathogen in a process called phagocytosis
- the lysozymes containing enzymes move towards the pathogen
- enzymes break down pathogen
- useful materials are absorbed
- waste products are removed from the phagocyte
85
describe what auxins are
- auxins are plant hormones which control growth at the tips of shoots and roots, they move through the plant in solution
- auxins are produced in the tips and diffuse backwards to stimulate the cell elongation process
- promotes growth in the shoot but inhibits growth in the root
86
what is the role of synapses
- the connection between 2 neurones is called a synapse
- the nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap
- these chemicals then set of a new electrical signal in the next neurone
87
describe what happens in the eye when adjusting for bright and dim light
- very bright light triggers a reflex that makes the pupil smaller and the circular muscles contact, allowing les light in
- the opposite happens in dim light a the radial muscles contract which makes the pupil bigger, it dilates
88
describe what happens in the eye when focussing on a distant object ( accommodation)
- the ciliary muscles relax which allows the suspensory ligaments to pull tight
- this makes the lens go thin ( less curved )
- so it refracts less light
89
describe what happens in the eye when focussing on a near object ( accommodation)
- the ciliary muscles contract, which slackens the suspensory ligaments
- the lens becomes more curved
- this increases how much light it refracts
90
where is insulin produced and what's its role and effect
- produced in the pancreas
- helps control blood sugar level
- stimulates the liver to turn glucose into glycogen for storage
91
where is progesterone produced and what's its role and effect
- produced in the ovaries
- supports pregnancy
- maintains the lining of the uterus
92
describe the steps of mitosis
- the cell grows
- prophase: the DNA replicates to form two copies of each chromosome, these chromatids are joined together at the centromere
- metaphase: the nuclear membrane breaks down, the chromosomes line up across the centre of the cell, attached to spindle fibres
- anaphase: the chromatids are pulled apart and move to opposite ends of the cell
- telophase: the cytoplasm and cell membrane divides to form two identical cells
93
describe the steps of meiosis
- the parent cell grows
- the DNA replicates to form 2 copies of each chromosome, these chromatids are joined together at the centromere
- the nuclear membrane breaks down, the homologous pairs of chromosomes join together
- the homologous pairs of chromosomes exchange sections of DNA, they then attach to the spindle fibres in pairs, at the centre of the cell
- the homologous pairs of chromosomes are pulled apart and moved to opposite ends of the cell, the cell divides
- the chromosomes line up along the centre of the cell, attached to the spindle fibres. the chromatids separate and move to opposite ends of the cell, each cell divides again
94
describe the 7 stages of sexual reproduction
- 1) sexual reproduction is where genetic information from 2 organisms is combined to produce genetically different offspring
- in sexual reproduction the mother and father produce gametes
- gametes are haploid so 23 chromosomes each
- at fertilisation the male gamete fuses with the female gamete to form a zygote , the zygote has all 46 chromosomes
- the zygote then undergoes mitosis and develops into an embryo
- the embryo inherits features from both parents, mixture of chromosomes
- the fertilisation of gametes is randoms, this produces genetic variation in offspring
95
how are some plants adapted for insect pollination
- they have brightly coloured petals to attract insects
- they have scented flowers and nectaries to attract insects
- they make big, sticky pollen grains- the grains stick to insects as they go from plant to plant
- the stigma is sticky so that any pollen picked up by insects on other plants will stick to the stigma
96
describe how some plants are adapted for wind polination
- small, dull petals on the flower as they don't need to attract insects
- no nectaries or strong scents
- a lot of pollen grains - they're small and light so that they can easily be carried by the wind
- long filaments that hang the anthers outside the flowers, so that a lot of pollen gets blown away by the wind
- large and feathery stigma to catch pollen as its carried past by the wind, the stigma often hangs outside of the flower to
97
describe the process of fertilisation in plants
- a pollen grain lands on the stigma of a flower, usually with help from insects and the wind
- a pollen tube grows out of the pollen grain and down through the style to the ovary and ovule
- a nucleus from the male gamete moves down the tube to join with the female gamete in the ovule. fertilisation is when 2 nuclei fuse together and form a zygote, this divides by mitosis to form an embryo
- each fertilised female gamete forms a seed, the ovary develops into a fruit around the seed
98
describe what germination is
- a seed will lie dormant until the conditions are right for germination
- they need water and oxygen and temperature
- water is needed to activate the enzymes that break down the food reserved in the seed
- oxygen is needed for respiration which transfers the energy from food for growth
- a suitable temp is needed for the enzymes inside the seed to work
99
describe how germinating seeds get energy from food stores
- a developed seed contains an embryo and a store of food reserved, wrapped in a hard seed coat
- when a seed starts to germinate, it gets glucose for respiration from its own food store, this transfers the energy it needs to grow
- once the plant has grown enough to produce green leaves it can get its own energy from photosynthesis
100
what is the stamen in a plant
- the male reproductive part
- consists of the anther and the filament
- the anther contains the pollen grains, these produce the male gamete (sperm)
- the filament is the stalk that supports the anther
101
what is the carpel in the plant
- the female reproductive part
- the carpel consists of the ovary, style and stigma
- the stigma is the end bit that the pollen grains attach to
- the style is the rod like section that supports the stigma
- the ovary contains the female gametes (eggs) inside ovules
102
describe what pollination is
- the transfer of pollen from the anther to the stigma, so that the male gametes can fertilise the female gametes in sexual reproduction
103
describe the practical to investigate the conditions needed for germination
- take 4 boiling tubes and put cotton wool at the bottom of each one
- put 10 seeds on top of the cotton wool in each boiling tube
- set up one tube as a control with all conditions, another tube with all the conditions apart from water, another with all the conditions but is in the fridge, another has a layer of oil to prevent oxygen entering
- leave the tubes for 7 days and then observe what has happened
104
how do you interpret your observations for the conditions needed for germination in plants
- you should only see germination happening in tube 1
- this is because all of the conditions needed for germination are present
- the seeds in the other boiling tubes wont germinate, this shows that water, oxygen and a suitable temp is needed for germination
105
describe how plants can reproduce asexually using natural methods like runners
- the parent plant sends out runners which are fast growing stems that grow out sideways, just above the ground
- the runners take root at various points a short distance away and new plants start to grow
- the new plants are clones of the parent plant, so there is no genetic variation between them
106
describe how plants can reproduce asexually using artificial methods such as cuttings
- gardeners can take cuttings from good parent plants and then plant them to produce clones of the parent plant
- these plants can be produced quickly and cheaply
107
describe how the male reproductive system creates sperm
- sperm are male gametes, they're made in the testes all the time after puberty
- sperm mix with a liquid to make semen, which is ejaculated from the penis into the vagina during sexual intercourse
108
describe how the female reproductive system makes ova (eggs)
- ova are female gametes, an ovum is produced every 28 days from 1 of the 2 ovaries
- it then passes through the fallopian tube, this is where it would meet sperm
- if it isn't fertilised by sperm, the ovum will break up and pass out of the vagina
- if it is fertilised, the ovum starts to divide, the new cells will travel down the fallopian tube to the uterus and attach to the endometrium, a fertilised ovum develops into an embryo
109
describe the role of oestrogen
- produced in the ovaries
- causes the uterus lining to grow
- stimulates the release of LH
110
describe the role of progesterone
- produced in the ovaries
- maintains the lining of the uterus during the 2nd half of the cycle, when the level of progesterone drops the lining breaks down
- inhibits the release of LH and FSH
111
describe the role of placenta in the nutrition of the developing embryo
- once the embryo has implanted, the placenta develops
- this lets the blood of the embryo and mother get very close to allow the exchange of food, oxygen and waste, short diffusion distance
- villi provide a large surface area for diffusion/active transport
- blood supply/cappilaries brings nutrients and removes waste
112
how is the developing embryo protected by amniotic fluid
- an amnion membrane forms
- this surrounds the embryo and is full of amniotic fluid
- amniotic fluid protects the embryo against knocks and bumps as it provides a cushion between the foetus and umbilical cord
113
what are the chromosomes in females
xx female
114
what are the chromosomes in males
xy male
115
how many cells does mitosis produce
2 identical sets of chromosomes
116
what is the role of mitosis
growth and repair, cloning and asexual reproduction
117
what is the definition of an ecosytsem
all the organisms living in a particular area
118
why is only 10% of energy transferred from one trophic level to another
- plants use energy from the sun to make food via photosynthesis, tis energy makes its way through the food chain as animals eat the plants and each other
- some parts of food e.g roots and bones aren't eaten so the energy isn't taken in, some parts of the food are indigestible like fibre, so pass through organisms and come out as waste
- a lot of the energy is used for staying alive like in respiration
- most of this energy is eventually transferred to the surroundings as heat
- only 10% of the total energy available becomes biomass
119
describe what eutrophication is
- fertilisers enter the water, adding extra nutrients
- the extra nutrients cause algae to grow fast and block out the light (algal bloom)
- plants cant photosynthesise due to lack of light and start to die
- with more food available microorganisms that feed on dead plants increases in number and deplete the oxygen levels in water
- organisms that need water (fish) die
120
how do glasshouses/polythene tunnels increases crop yield
- keeping plants enclosed helps to keep them free from pests and diseases
- it also helps the farmers to control the water supplied to their crops
- commercial farmers use artificial light after the sun goes down to give their plants more time to photosynthesise
- glasshouses trap the suns heat to keep the plants warm, in the winter the farmer might use a heater to maintain an optimum temp
121
what is the effect of increases in co2 and temperature in glasshouses on crop yield
- glasshouses trap the suns heat to keep the plants warm, in winter a farmer might use a heater to keep the temp ideal
- farmers also increase the level of co2 in glasshouses by using paraffin heaters to heat the place, as it burns it makes co2 as a bi product
- by increasing the co2 and temperature concentrations, a farmer can increase the rate of photosynthesis for their plants
122
how do fertilisers ensure the crops have enough minerals and increase crop yield
- plants need certain minerals like nitrogen, potassium and phosphorus so they can make important compounds like proteins
- if plants don't get enough of these minerals their growth and life process is affected
- sometimes these minerals are missing from the soil because they've been used up by a previous crop
- farmers use fertilisers to replace these missing minerals or provide more of them
123
how can pest control stop pests from eating crops
- pesticides are a form of chemical pest control, often poisonous to humans so must be used in consideration
- biological control is an alternative to using pesticides, it means using other organisms to reduce the numbers of pests, by encouraging wild organisms or adding new ones
- the helpful organisms be predators, parasites or disease causing
- biological control can have longer lasting effect than spraying on pesticides and can be less harmful to wildlife , they can cause problems however as they can become a pest themselves
124
how is yeast used when making bread
- a bread dough is made by mixing yeast with flower, water and a bit of sugar
- the dough is left in a warm place to rise
- enzymes break down the carbohydrates in the flour into sugars
- yeast then uses these sugars in aerobic respiration producing co2
- when the oxygen runs out the yeast uses anaerobic respiration, this is known as fermentation and produces co2 and ethanol
- the co2 produced is trapped in bubbles in the dough
- these pockets of gas expand and the dough begins to rise
- the dough is then baked in the oven where the yeast continues to ferment until the temp of the dough rises enough to kill the yeast, any alcohol is bubbled away
- as the yeast dies, the bread stops rising but the pockets are left in the bread where the co2 was trapped
125
how is bacteria used to make yogurt
- the equipment is sterilised to kill of any unwanted organisms
- the milk is pasteurised ( heated to 72 c for 15s) again to kill any harmful microorganisms, then the milk is cooled
- lactobacillus bacteria are added, and the mixture is incubated in a fermenter
- the bacteria ferment the lactose sugar in the milk anaerobically to form lactic acid
- lactic acid causes the milk to clot and solidify into yoghurt
126
describe the practical to investigate the respiration rate of yeast depending on its conditions
- mix together some sugar, yeast and distilled water, then add the mixture to a test tube
- attach a bung with a tube leading to the next test tube of water
- sealing the 2 tubes with bungs stops oxygen from entering, so the yeast has to start respiring anaerobically
- place the test tube containing the yeast mixture in a water bath at a certain temp
- leave the tube to warm up a bit and then count how many bubbles are produced per minute
- calculate the rate of co2 produced, this gives an indication of respiration rate
- repeat this with the water bath at different temperatures
- respiration is controlled by enzymes, so as temp increases so should rate of respiration
127
how can selective breeding create animals with desired characteristics
- cows can be selectively bred to produce offspring with a high meet yield
- first, the animals with characteristics that will increase meet yield are selected and bred together
- next the offspring with the best characteristics are selected and bred together
- if this is continued over several generations, cows with very large meet yields can be produced
- mating cows and bulls naturally can be difficult, so artificial insemination is often used. its safer for the cow, and its much quicker and cheaper to transport semen than bulls, the semen can also be used to inseminate multiple cows and be stored after the bull has died
128
how can selective breeding develop plants with desired characteristics
- selective breeding can be used to combine two different desirable characteristics
- tall wheat plants have a good grain yield but are easily damaged by wind and rain. dwarf wheat plants can resist wind and rain but have a lower grain yield
- these two types of wheat plant cab be cross-bred, and the best resulting wheat plants were cross-bred again
- this resulted in a new variety of wheat combining the good characteristics- dwarf wheat plants which could resist bad weather and had a high grain yield
129
how can enzymes be used to cut DNA or join DNA pieces together
- restriction enzymes recognise specific sequences of DNA and cur the DNA at these points
- ligase enzymes are used to join two pieces of DNA together
- two different bits of DNA stuck together are known as recombinant DNA
130
what is a vector
something that's used to transfer DNA into a cell, there are 2 sorts , plasmids and viruses
131
what are plasmids that act as vectors
small circular molecules of DNA that can be transferred between bacteria
132
what are viruses that act as vectors
- viruses insert DNA into the organisms they infect
133
what does transgenic mean
- the transfer of genetic material from one species to a different species
134
how does genetic engineering work
- the DNA that you want to insert ( the gene for human insulin) is cut out with a restriction enzyme, the vector DNA is then cut open using the same restriction enzyme
- the vector DNA and the DNA your inserting are mixed together with ligase enzymes
- the ligases join the 2 pieces of DNA together to produce recombinant DNA
- the recombinant DNA is inserted into other cells e.g bacteria
- these cells can now use the gene you inserted to make the protein you want e.g bacteria for human insulin can be grown in huge numbers in a fermenter to produce insulin for people with diabetes
- bacteria that contain the gene for human insulin are transgenic -this mean they contain genes transferred from another species
135
how can genetically modified plants improve food production
- crops can be genetically modified to increase food production, e.g making them resistant
tant to insects or resistant to herbicides
- making crops insect resistant means farmers don't have to spray as many pesticides, so wildlife that don't eat the crop isn't harmed, also increases crop yield producing more food
- making crops herbicide resistant means farmers can spray their crops to kill weeds, without affecting the crop itself, this will increase crop yield
- there are concerns about growing GM crops, transplanted genes may get into the environment, for example a herbicide resistance gene may be picked up by weeds, another concern is that GM crops wood adversely affect food chains, or even human health
- some people are against genetic engineering altogether, they worry that changing an organisms genes might create unforeseen problems, which could get passed to future generations
136
what effect does temperature have on transpiration
- on a hot day, water will evaporate quickly from the leaves of a plant as the water molecules have more kinetic energy
- transpiration therefore increases as temperature increases
137
what effect does light intensity have on transpiration
- light itself does not affect evaporation, but in daylight the stomata of leaves are open to supply co2 for photosynthesis
- this allows more water to diffuse out of the leaves and into the atmosphere
138
what effect does humidity have on transpiration
- 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 as humidity decreases
139
what effect does wind speed have on transpiration
- in still air, the region around a transpiring leaf will become saturated with water vapour so that no more can escape 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
140
what effect does water supply have on transpiration
- if water supply is in short supply, and the plant is losing water by transpiration faster than its being taken up by roots
- the plant may start to wilt
- before this happens the guard cells will become flaccid and stomata start to close, therefore reducing transpiration and delaying wilting
141
describe the potometer experiment to find transpiration rates
- the potometer must be set up under water - this prevents any air bubbles from entering the system and blocking the xylem
- cut the stem of a shoot
- put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents water loss and air entry
- put the bung into the potometer
- make sure the tap is closed and it is full of water (no bubbles), then lift the potometer out of the water
- leave the end of the capillary tube out of the water until an air bubble forms then put the end into a beaker of water
- you can measure the transpiration rate as distance the bubble travels in 5 minutes, take a number of readings to find a mean rate
142
definition of active transport
the movement of molecules from an area of low concentration to an area of high concentration using ATP
143
definition of osmosis
net diffusion of free water molecules from an area of high wate concentration to an areas of low water concentration across a partially permeable membrane
144
definition of diffusion
random movement of molecules from an area of high concentration to an area of low concentration
145
what is the name of the type of genetic control where many genes control 1 phenotype
polygenetic
146
describe an experiment to show how different concentrations of sodium chloride solution affect the appearance of plant cells
- immerse onion epidermis in sodium chloride
solution
- have a control variable wit just water and take a photo
- use the same volume of solutions
- 3 of more concentrations of sodium chloride solution
- leaf cells for 2 hours
- observe using a microscope and take a photo
147
what enzyme converts protein to peptide
pepsin or trypsin
148
what enzyme converts peptide to amino acids
peptidase
149
why do plants not gain 100% of the energy from the sun
- some light is reflected
- not all of the plant has chloroplasts
150
define specialised cells and give an example
- specialised to carry out a particular function so their structures vary
- in humans red blood cells are specialised for oxygen and white blood cells are specialised for defending the body against disease
151
explain the importance of cell differentiation in the development of specialised cells
- cell differentiation is the process by which a cell changes to become specialised for its job
- as cells change they develop different organelles and turn into different types of cells, this allows them to carry out different functions
- undifferentiated cells, called stem cells, can divide to produce lots more undifferentiated cells, they can differentiate into different types of cell, depending on what instructions they are given
- stem cells are found in early human embryos, they have the potential to tune into any kind of cell
- adults also have stem cells, but there only found in certain places, like bone marrow, unlike embryonic stem cells they cant turn into any kind of cell, only certain ones like blood cells
- stem cells from embryos and bone marrow can be grown in a lab to produce clones and made to differentiate into specialised cells to use in medicine or research
152
advantages of stem cells in medicine
- medicine already uses adult stem cells to cure disease, for example stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells
- embryonic stem cells can also be used to replace faulty cells in sick people, you could make insulin producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries
- however there are some risks involved in using stem cells in medicine, for example, stem cells grown in a lab may become contaminated with a virus which could be passed on to the patient making them sicker
153
give reasons why people are against stem cell research
- they feel that human embryos should not be used for experiments as each one is a potential human life
- others think that curing existing patients who are suffering is more important than the rights of embryos
- an argument is that embryos used in research are usually unwanted ones from fertility clinics which, if they weren't used for research, would be destroyed, however campaigners for the rights of embryos are against this too
- these campaigners feel that scientists should concentrate more on finding and developing other sources of stem cells, so people could be helped without having to use embryos
154
how do you find the energy content of food
- use dried banana chips
- weigh a small amount of food then skewer it on a mounted needle
- add a set volume of water to a boiling tube (held with a clamp)
- measure the temp of the water, then set fire to the food using a Bunsen flame , make sure the Bunsen isn't near the water
- hold the burning food under the test tube of water until it goes out
- relight the food and hold it under again, repeat this until the chip wont light again
- measure the temp of water and use Q=mcΔt
155
how do plants exchange gases by diffusion via respiration and photosynthesis
- when plants photosynthesise they use up co2 from the atmosphere and provide o2 as a waste product. when plants respire they use up o2 and produce co2 as a waste product. these waste products are lost through the stomata
- when a plant is photosynthesising it uses up lots of co2, so there's hardly any left inside the leaf. this makes more co2 move into the leave through diffusion
- at the same time lots of o2 is being made as a waste products of photosynthesis, some is used in respiration and the rest diffuses out through the stomata
156
how does the net exchange of gases depend on light intensity
- photosynthesis only happens during the day, but plants must respire all the time to get the energy they need
- during the day when light intensity is high plants make more oxygen by photosynthesis than they use in respiration, so in daylight they release oxygen, they also use up more co2 than they produce so they take in co2
- at night when light intensity is low plants only respire- there's not enough light for photosynthesis. this means they take in oxygen and release co2
157
how are leaves adapted for gas exchange
- leaves are broad so there's a large surface area for diffusion
- they are thin so gases only have to travel a short distance to reach the cells where they are needed
- there are air pockets inside the leaf, this lets gases like co2 and o2 move easily between cells, it also increases the SA for gas exchange
- the lower epidermis is full of stomata, they let gases out like co2 and o2 by diffusion, they also allow water to escape via transpiration
- stomata close as it gets dark, photosynthesis cant happen in the dark so they don't need to be open to let co2 in, when the stomata are closed water cant escape, this stops the plant drying out
- stomata also close when supplies of water from the roots start to dry up, this stops the plant from photosynthesising but prevents the plant from drying out and dying
- guard cells increase their volume to open stomata and decrease in volume to close stomata
158
what colour does hydrogen carbonate indicator go when levels of co2 fluctuate
- when co2 is high - yellow
- when co2 is low - purple
159
describe the practical to investigate the effect of light on net gas exchange from a leaf using hydrogen carbonate indicator
- add the same volume of hydrogen carbonate indicator to 4 boiling tubes
- put similar sized healthy looking leaves into 3 of the tubes and seal with a rubber bung, trap the leaf stem with the bung to stop it falling down into the solution
- keep the 4th tube empty as a control
- completely wrap one tube in aluminium foil and a 2nd tube in gauze
- place all tubes in bright light
- leave the tubes for an hour then check the colour of the indicator
160
how do root hair cells take in water
- the cells on plant roots grow into long 'hairs' which stick out into the soil
- each branch of a root will be covered in millions of these microscopic hairs
- this gives the plant a big SA for absorbing water from the soil
161
describe ultrafiltration in the kidneys
- blood from the renal artery flows through the glomerulus - a bundle of capillaries at the start of a nephron
- a high pressure is built up which squeezes water, urea, ions and glucose out of the blood and into the bowman's capsule
- the membranes between the blood vessels in the glomerulus and the bowman's capsule act as filters so large molecules like proteins and blood cells are not squeezed out , the filtered liquid is known as the glomerular filtrate
162
describe reabsorption in the kidneys
- as the filtrate flows along the nephron, useful substances are selectively reabsorbed back into the blood
- all the glucose is reabsorbed from the PCT so that it can be used in respiration, the reabsorption of glucose involves the process of active transport against the conc gradient
- sufficient ions are reabsorbed, excess ions aren't
- sufficient water is reabsorbed from the collecting duct into the blood stream by osmosis
163
describe the release of waste from the kidneys
- the remaining substances after selective reabsorption including water, ions and urea form urine, this continues out of the nephron through the ureter and down to the bladder, where it is stored before being released via the urethra
164
how do the kidneys adjust the bodys water content
- water is taken into the body as food and drink and is lost by sweating, breathing and weeing
- the body has to constantly balance the
water coming in against the water going out, this is osmoregulation
- one way it can do this is by adjusting the amount of water that is excreted from the kidneys in the urine, e.g more water is reabsorbed if a person is sweating a lot, maintaining the water balance
- when the kidneys reabsorb more water the urine has a smaller volume and is more concentrated
165
how does ADH help to control water content
- the amount of water reabsorbed in the kidney nephrons is controlled by a hormone called ADH, it makes the collecting ducts more permeable so more water is reabsorbed back into the blood
- the brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed
- the whole process of osmoregulation is controlled by a mechanism called negative feedback. this means that if the water content gets too high or too low a mechanism will be triggered that brings it back to normal
166
what is the source role and effect of FSH
source- pituitary gland
role- female sex hormone
effect- causes egg to mature and stimulates production of oestrogen which then inhibits the release of LH
167
what is the source role and effect of LH
- source - pituitary gland
- role- female sex hormone
- effect- stimulates the release of an egg from an ovary
168
describe the differences between the process of transcription and translation
- transcription occurs in the nucleus
- transcription uses DNA to make RNA
- DNA unzips/ one strand is copied
- transcription makes/produces mRNA
- translation takes place at ribosomes in cytoplasm
- translation involves mRNA and tRNA
- anticodons bind to codons
-translation produces amino acid chain/protein/polypeptid
169
what does co-dominance mean
- a monohybrid cross
- when neither allele is recessive so you show characteristics from both alleles e,g not group A or B but AB
170
describe fish farming in cages at sea (salmon farming in Scotland)
- the fish are kept in cages in the sea to stop them using as much energy swimming about
- the cage also protects them from interspecific predation
- they are fed a diet of food pellets that's carefully controlled to maximise the amount of energy they get, the better the quality of food is, the quicker and bigger the fish will grow
- young fish are reared in special tanks to ensure as many survive as possible
- its important to keep younger fish separate from bigger fish, and to provide regular food- this makes sure that the big fish don't eat the little ones. this is intraspecific predation, where organisms eat individuals of the same species
- fish kept in cages are more prone to disease and parasites, one pest is sea lice which can be treated with pesticides that kill them, to avoid pollution from chemical pesticides, biological pest control can be used instead e.g small fish called wrasse eat the lice
- the fish can be selectively bred to produce less aggressive, faster growing fish
171
describe fish farming in tanks and the factors that need to be monitored
- the water can be monitored to check the temperature and PH and oxygen levels
- its easy to control how much food is supplied and give exactly the right sort of food
- the water can be removed and filtered to get rid of waste food and fish poo, this keeps the water clean for the fish and avoids pollution wherever the water ends up
172
how is micropropagation used to clone plants
- a plant with desirable characteristics is selected to be clones, explants are taken from the tips of the stems and the side shoots of this plant
- the explants are sterilised to kill any microorganisms
- the explants are then grown in vitro - they are placed in a petri dish containing a nutrient medium, the medium has all the nutrients the explant needs to grow, it also contains growth hormones, the meristem is used for fast mitosis
- the cells in the explants divide and grow into a small plant. if large quantities of plants are required, further explants can be taken from these small plants, until enough small plants are produced
- the small plants are taken out of the medium, planted in soil and put into glasshouses - they'll develop into plants that are genetically identical to the original plant - so they share the same characteristic's
173
describe how cloning an adult mammal is done by transplanting a cell nucleus
- the nucleus of the sheep's egg cell was removed creating an enucleated cell
- a diploid nucleus is inserted in its place, this is a nucleus from a mature udder cell of a different sheep
- the cell was stimulated by an electric shock so that it starts dividing by mitosis, as if it were a normal fertilised egg
- the dividing cell was implanted into the uterus of another sheep to develop until it was ready to be born
174
how can cloned transgenic animals be used to produce human proteins
- cows and sheep make a protein naturally in their milk, by transferring human genes into the cells of these animals, researchers have managed to get them to produce useful proteins in their milk
- for example, they can produce human antibodies that can be used in therapy for illness like arthritis, some types of cancer and multiple sclerosis
- transgenic chickens have also been engineered to produce human proteins in egg white
- these transgenic animals can then be cloned so that the useful genetic characteristic is passed on, this doesn't always happen with breeding
