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NSFC A2L3 Edexcell GCSE Biology > Paper 1 > Flashcards

Paper 1 Flashcards

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1
Q

SB1a - How do you calculate Actual Size?

A

Image Size / Magnification

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2
Q

SB1a - How do you calculate total magnification in a light microscope?

A

Objective Lens x Eyepiece Lens

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3
Q

SB1a - List 3 differences between Light and Electron Microscopes

A

Electron microscopes produce a much higher resolution image due to the shorter wavelength of electrons Light Microscopes can show a true colour whereas electron microscopes will show a black and white image since electrons don’t have a colour spectrum Light microscopes can use a live specimen whereas electron microscopes have to use dead specimens due to electrons having to pass through a vacuum

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4
Q

SB1a - Draw SI Units Table

A
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5
Q

SB1a - What 2 things determine how good a microscope is at showing small details?

A

* Magnification: How much it can zoom in * Resolution: The smallest distance between two distinctly different points

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6
Q

SB1a - What has the development of the electron microscope allowed us to do?

A

It has allowed us to see sub-cellular structures as they have a much more powerful resolution and magnifcation

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7
Q

SB1b - How are animal cells different to plant cells?

A

* Animal cells, do not have cell walls, chloroplasts or vacuoles like plants do. * They only have nuclei, ribosomes, mitochondria, cytoplasm and a cell surface membrane.

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8
Q

SB1b - What do the sub-cellular structures in eukaryotic cells do?

A

* Cell membrane: controls what enters and leaves the cell * Nucleus: contains DNA that controls cell activities * Cytoplasm: fills the cell and where reactions occur * Mitochondria: Where respiration takes place * Ribosomes: Where protein synthesis takes place Plant only: * Cell wall: Protects the cell * Chlorplasts: Contain chlorophyll used in photosynthesis * Vacuole: Stores cell sap

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9
Q

SB1b CP - How do you use use a microscope?

A

* Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide * Add a few drops of a suitable stain/dye (e.g. iodine), so that the sample can be seen * Place a coverslip on top of the tissue and place the slide onto the microscope stage. * Use the objective lens with the lowest magnification, and focus on the sample. * Increase the magnification and refocus to see different features of the cell. * If you record the image you see, note down the magnification it was taken at Option 2: You microhope you’re doing it right

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10
Q

SB1c - What are the adaptations of the following cells: * Egg cell * Sperm cell * Cilliated epithelial cell * Cells lining the small intestine

A

Egg cell: Has a haploid nucleus, with a special cell membrane to allow only one sperm cell in and many nutrients in its cytoplasm Sperm cell: Has an acrosome with enzymes to penetrate the egg cell with lots of mitochondria and a tail to swim Ciliated epithelial cell: Lined with cilia and packed with mitochondria this allows the cell to have a ‘wavy’ movement to move an egg along Microvilli: The cells lining the small intestine have small folds called microvilli which increase its surface area making absroption easier

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11
Q

SB1c - What is the function of a gamete?

A

* Gametes are sex cells used in reproduction. * Examples are sperm and egg cells.

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12
Q

SB1d - What are the differences between eukaryotic and prokaryotic cells?

A

A prokaryotic cell will not contain a nucleus, mitochondria or chloroplasts Eukaryotic cells can be up to x1000 times larger than a Prokaryotic Cell

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13
Q

SB1d - What are the functions of structures in bacteria?

A

* Single loop of DNA: Contains chromosomes and genes * Plasmids: Contain additional genes * Flagellum: Used to propel the bacteria * Flexible cell wall: for support * Cytoplasm: Containing prokaryotic ribosomes

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14
Q

SB1e - What are enzymes and what are they made up of made up of?

A

* Enzymes are biological catalysts that speed up reactions. * They break down proteins/substances called substrates. * Enzymes are made up of amino acids and they are proteins. * They are needed to speed up reactions we cannot live without

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15
Q

SB1e - What are the three main nutrient based enzymes? Where are they found and what do they do?

A

* Amylase: Found in saliva. breaks down starch into Sugar * Protease: Found in the stomach, breaks down proteins into amino acids * Lipase: Found in the stomach and pancreas, breaks down lipids into fatty acids and glycerol

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16
Q

SB1e - What is a polymer?

A

* A polymer is a chain of single substances called monomers. * The formation of a polymer is called synthesis. * Enzymes often break down polymers into monomers

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17
Q

SB1f CP - What tests are used to identify main components in food? * Starch * Proteins * Lipids * Sugars

A

* Starch: Iodine will go from yellow to blue-black * Proteins: Biruet’s solution will go from blue to purple * Lipids: Add ethanol and shake - a white emulsion-fatty layer should form if it is present * Sugars: Benedict’s solution while heating which will turn anywhere from green to yellow to red, indicating how much sugar is present This is a semi-quantitative test. It mostly gives non-measurable values

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18
Q

SB1f- How can we use a calorimeter?

A

* Burn a known mass of the food under a boiling tube filled with a known volume of water. * Calculate the change in temperature of the water.

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19
Q

SB1g - How do enzymes work?

A

* Each type of enzyme is in a shape that is specific to their substrate. * They can be re-used as long as they don’t become denatured * The idea that an enzyme bonds with a specific substrate is the lock-and-key mechanism

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20
Q

SB1g - What is the function of the active site of an enzyme?

A

The active site is unique to an enzyme so each enzyme can only work on specific substrates and is where the substrate must be for anything to take place

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21
Q

SB1g - What is the lock and key model?

A

The lock and key model is a model of how enzymes work - it compares enzyme action to a lock and key because of how the substrate and active site fit together When the substrate binds to the active site, it forms the Enzyme-Substrate complex. After the enzyme catalyses the reaction, the products are released because they no longer fits tightly into the active site The enzyme is free to be used again

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22
Q

SB1g- How are enzymes denatured?

A

* Changes in pH and temperature can affect the shape of an enzymes active site. * When the active site can no longer accept any substrates, it is said to have become denatured.

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23
Q

SB1h - Explain how the rate of enzyme reaction is affected by temperature

A

At very low temperatures, the particles do not have enough energy to move, so the enzyme is inactive; the rate of reaction is very low As the temperature increases, particles begin to move more as they gain kinetic energy; the rate of reaction will increase Eventually, the enzyme reachs an optimum temperature where it is working at it’s fastest However, if the temperature increases too far beyond that, the active site will begin to chagne shape and the rate of reaction will decrease Eventually, if high enough temperatures are reached, the shape of the active site is changed to a point where the substrate is no longer able to bind to it. It becomes denatured.

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24
Q

SB1h - How is enzyme activity affected by pH?

A

An enzyme has an optimum pH where it works best. The further away from this, it will get slower till it becomes denatured

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25
Q

SB1h- Explain how the rate of enzyme action is affected by substrate concentration

A

At first, the more substance you use, the higher the rate of reaction as it causes more collisions to occur However, at high concentrations most enzyme active sites conatin substrate molecules therefore there is no benefit to adding more substrate, the rate of reaction won’t increase beyond that point

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26
Q

SB1i - How do cells transport substances against a concentration gradient?

A

* Using active transport which is carried out by transporter proteins on membranes which require energy to run. * They take in the molecule and then change shape to move it through the membrane. * This works against the concentration gradient.

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27
Q

SB1i - What is the difference between diffusion and osmosis?

A

* Diffusion is when particles move from a high concentration to a low concentration. * In osmosis this is the same principal except across a semi permeable membrane where a solvent moves from and area of high concentration to an area of low concentration

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28
Q

SB1i CP - Describe the method you would use to investigate osmosis through potatoes

A

* Cut discs of raw potato, blot them dry, and measure their mass. * Put each disc in a sugar (or salt) solution of different concentrations * After 30 minutes, measure the mass of each disc again. * Subtract the initial mass from the final mass of each disc. * Divide this number by the initial mass and then multiply by 100 to give a percentage change in mass. * The highest change in mass means there was the greatest difference between water concentration as osmosis works with the concentration gradient This can work with any semi-permeable membrane

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29
Q

SB1i CP - Explain why potatoes will gain mass when put into a very dilute solution

A

The concentration of water in the solution will be higher than the concentration of water in the potatoes, so water will move into the potato by osmosis which increases mass

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30
Q

SB1i CP - Explain why potatoes will lose mass when put into a very concentrated solution

A

The water concentration of the potatoes will be higher than that of the solution, so water will move into the solution due to osmosis. Therefore, the potatoes will lose mass.

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31
Q

SB2a - How are tumors formed?

A

* When cells mutate, they can become cancer cells. * This means that they will divide even when they don’t require to divide.

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32
Q

SB2a - How many types of chromosones are in a human cell and what is it called when these are alone or paired up?

A

* 23 types of chromosomes. * When they are paired up to have 46 chromosomes this is a diploid cell and a haploid cell only has 23 chromosomes. * Gametes are haploid cells while all other cells in a human are diploid.

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33
Q

SB2a - What are the products of mitosis called?

A

Daughter Cells

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34
Q

SB2a - What type of organisms do not require mitosis to occur?

A

Unicellular organisms

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35
Q

SB2a - When a regular human body cell divides, what is this process called, and how does it occur?

A

Mitosis Interphase * Copies of the chromosomes are formed in the nucleus Prophase * The nucleus starts to break up and spindle fibres appear. Metaphase * The chromosomes are lined up on the spindle fibre across the middle of the cell Anaphase * The chromosome copies are separated and moved to either side of the cell Telophase * A membrane forms around each set of chromosomes to from a nuclei Cytokeniesis * Cell surface membrane forms separating the two cells (In plants, a cell wall is also formed)

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36
Q

SB2a - Why does asexual reproduction require mitosis?

A

* As asexual reproduction only needs one parent, the offspring will have the same DNA as the parent. * As the offspring are clones and their chromosomes are identical, their cells are formed by mitosis.

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37
Q

SB2b - Define growth.

A

The increase in size as a result of an increase in size of or numbers (due to cell division) of cells.

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38
Q

SB2b - How are red blood cells specialised for their purpose?

A

* Biconcave shape means more surface area for oxygen diffusion. * No nucleus means more space for red haemoglobin molecules and carry more oxygen

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39
Q

SB2b - How is the growth of a baby monitored and how does this work?

A

Using a percentile growth curve: * This graph has many lines showing you how a babies conditions compare to the average. * The healthiest position would be at 50% as half of the population is above or below you. * Being above 98% or below 2% is reason for concern as only 2% of the population is above or below you.

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40
Q

SB2b - What is cell differentiation?

A

When a less specialised cell is changed to become a specialised one.

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41
Q

SB2c - How are root hair cells specialised for their function?

A

large vacuole - stores absorbed water long projection - increases area for absorption thin cell - allows minerals to pass easily into the cell by reducing the area they have to transport

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42
Q

SB2c - How are xylem cells specialised for their function?

A

* They have thick walls containing lignin, giving the xylem a rigid and strong structure * The cells rae dead - so all water carried is transported and not used up by the xylem itself * They have no internal structure at all (nucleus, chloroplasts etc.) this makes it easier to transport water and minerals.

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43
Q

SB2c - What are the meristems?

A

* A group of cells near the end of each shoot that allow plants to continue growing throughout their lives. * They divide rapidly and the cells are elongated and differentiated.

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44
Q

SB2c - What are the zones of differentiation elongation and cell division?

A

* D: Where cells are specialised * E: Where cells are elongated (vertically extended) * CD: Where rapid mitosis occurs (Meristems)

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45
Q

SB2d - How can stem cells be used to treat lukemia?

A

* A patient’s bone marrow is destroyed using radiation * Adult stem cells are inserted into the patient * The stem cells will differentiate specialise and divide to form new blood cells and bone marrow

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46
Q

SB2d - What are the problems with using stem cells in medicine?

A

* If stem cells continue to divide, it can cause a cancerous tumour to form * Stem cells of one person can be rejected by the immune system of another * Embryonic stem cells pose an ethical issue

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47
Q

SB2d - What is an embryonic stem cell?

A

A cell in an early stage embryo that is not specialised and can differentiate to form any type of specialised cell.

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48
Q

SB2d - Where can adult stem cells be found and how are they different to embryonic stem cells?

A

Adult stem cells can be found in most tissues including bone marrow but can only differentiate to cells in the tissue around them .

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49
Q

SB2d - Why don’t plants have adult stem cells?

A

Their cells remain able to differentiate freely throughout their lives.

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50
Q

SB2e - How did Phineas Gage’s accident prove what the cerebral coretex is used for?

A

* Phineas gage had a metal rod stuck inside his brain * It was through his cerebral cortex * He was still able to walk, but his personality changed * This shows that this part of the cerebral cortex controls emotions and personality but not movement or breathing/heart rate

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51
Q

SB2e - The medulla oblongata controls reflexes. What does this mean about its connections?

A

It connects the brain to the rest of the CNS

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52
Q

SB2e - What are the three major structures of the brain, and what are each of their functions?

A

* Cerebral cortex: Main functions and control such as memories language etc. * Cerebellum: Controls balance and movement * Medulla oblongata: Controls heart and breathing rate

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53
Q

SB2e - What type of cells is the brain mostly made up of?

A

Neurones

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54
Q

SB2e - Why may musicians have larger/more developed cerebellums?

A

So can develop and have more control over their fine movements and timing coordination

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55
Q

SB2f - During brain surgery, what may be done to investigate roles of the brain?

A

Probing with electricity (electrodes) means that doctors can control the activity of different parts of the brain

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56
Q

SB2f - How does a CT scan work?

A

* A CT scan involves an x-ray beam moving in a circle around the head. * It produces images that are slices of the brain. * Computers can layer and build these up to produce an image

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57
Q

SB2f - How does a PET scan work?

A

* Radioactive glucose is injected into the body. * More active cells take in more glucose. * The PET scan scans for where the most radioactivity is coming from showing the levels of activity in the brain.

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58
Q

SB2f - Why does chemotherapy not always work for brain tumors?

A

* Chemotherapy involves sending chemical substances through blood to actively kill tumours * The brain has a natural filter called the blood-brain barrier which blocks out foreign substances in the brain * Additionally, chemotherapy can harm healthy cells

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59
Q

SB2f - Why is spinal cord damage so dangerous?

A

* Damage to the spinal cord can sever the connection between your brain and the rest of your body. * This can loose to the loss of control of limbs such as quadripalegia.

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60
Q

SB2g - What are the different types of neurones and their functions?

A

Sensory Neurones - carry impulses from receptor cells to CNS Motor Neurones - carry impulses from the CNS to effector organs Relay Neurones - found in the spinal cords, link motor & sensory

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61
Q

SB2g - How does your body communicate?

A

Using electrical signals called impulses

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62
Q

SB2g - Describe the structures in a sensory neurone Dendrites Cell Body Dendron Axon Myelin Sheath Axon Terminal

A

Dendrites receive the electrical impulses from the receptorThis is passed on through the dendron and the axonAxon terminals at the other end allow the electrical impulse to be passed on The cell body containing the nucleus is between the dendron and axonThe cell is covered in fatty layer called the myelin sheathThis insulates the cell meaning there are no electrical jumps to other cells speeding up neurotransmission

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63
Q

SB2g - What are sense organs?

A

Organs that contain receptor cells which will cause the body to have a response to a stimulus. e.g. eyes, ears etc.

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64
Q

SB2g - What makes up the nervous system?

A

The CNS (Central nervous system): * The brain * The spinal cord * Nerves

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65
Q

SB2h - Describe the structure of the eye.

A

* There is a clear covering called the cornea covering the eye which refracts most of the light * Below this are the iris and the pupil * CIllary muscles alter the shape of the eye (constricting or dialating it) * A lens to fine tune the light refraction * At the back is the retina containing rods (detect light levels) and cones (detect colour. Don’t function well in dim light) * This is passed onto optic nerves which pass electrical impulses to the brain * Refracted light should meet at the retina

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66
Q

SB2h - How does the eye vary with the distance of the object?

A

The ciliary muscles make the lens fatter to focus the light from near objects The ciliary muscles make the lens thinner to focus light from distant objects

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67
Q

SB2h - What is a cataract?

A

* Protein build up in the lens can cause it to become cloudy, clouding your vision. * This can be corrected by replacing the lens with a plastic one

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68
Q

SB2h - What is colour-blindness?

A

* When the cone cells in your eye don’t properly detect colour * The most common form of this is red-green colour blindness * This cannot be corrected

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69
Q

SB2h - What is myopia and hyperopia? * Causes * Treatment

A

Myopia is short sightedness (Can see close): * This is when light focuses too early (before the retina) * The eyeball is too long. * This can be fixed with a diverging lens. Hyperopia is long sightedness (Can see far): * This is when light hasn’t focused by the time it reaches the retina. * The eyeball is too short. * This can be fixed with a converging lens

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70
Q

SB2h - What is the function of the iris?

A

To control the size of the pupil to alter how much light enters the eye

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71
Q

SB2i - Describe the reaction process (not reflex arc).

A

* The receptor cells in your sensory organs respond to a stimulus * They send a neurotransmission which using neurones, travels to your brain * Your brain decides what action to take and sends a neurotransmission using neurones to send a message to an effector e.g. muscle contracting

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72
Q

SB2i - Describe the roles synapses play in the reflex arc. (include the three types of neurones)

A

* The receptor passes on an impulse to the sensory neurone * The sensory neurone reaches a ‘junction’ called a synapse. It contains a tiny gap * Once it reaches here, a chemical (neurotransmitter) is released passing on the impulse to the relay neurone in the spinal cord * The relay neurone reaches another synapse where it releases more neurotransmitters to pass it on to a motor neurone * The motor neurone reaches the effector where it causes a response to take place (e.g. muscle contracting)

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73
Q

SB3a - How may a plant such as a strawberry reproduce asexually?

A

* By using specail stems called runners which grow out from the root of the plant. * These can also provide water and nutrients to the daughter plant until it is well develpoed.

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74
Q

SB3a - In what 3 scenarios would an aphid decide to reproduce asexually rather than sexually?

A

when they couldn’t find a mate when they are very well adapted to a new environment when they needed to reproduce qucikly

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75
Q

SB3a - What are the advantages and disadvantages for asexual reproduction?

A

Pros: * Very quick and takes up very little energy * No need to find a mate * many identical offspring can be produced for well adapted organisms in an unchanging environment Cons: * No variation meaning that if they are vulnerable to a disease there is a high risk of extinciton

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76
Q

SB3a - What are the advantages and disadvantages of sexual reproduction?

A

Pros: * Creates variation meaning that a species is more likely to survive a disaster. * It also allows them to move to different environments Cons: * Time consuming from fertilisation to birth * mate required * smaller number of offspring

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77
Q

SB3a - What is the difference asexual and sexual reproduciton?

A

* Sexual reproduction involves fertilisation of a female gamete by a male gamete (two organisms) * Asexual reproduction only requires one parent anf the offspring is genetically identical to their parent

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78
Q

SB3a - What type of cell divison occurs in each type of reproduction?

A

Sexual Reproduction uses Meiosis to produce gametes which fuse during fertilization Asexual reproduction uses mitosis to produce clones

79
Q

SB3b - Define the term genome

A

The entire genetic material of an organism

80
Q

SB3b - What is the term for a fertilised egg before and after cell division starts to occurs?

A

* Before: A zygote * After: An embryo

81
Q

SB3b - What makes gametes different to regular body cells?

A

They are haploid rather than diploid meaning that they contain 1 set of 23 chromosones.

82
Q

SB3b - What process is used for division of gamete cells, and how does this differ from mitosis?

A

Meiosis: * The gamete ‘making’ cell is diploid. * Once it has divided in the same way as it would in mitosis, it divides once more without replicating the DNA producing haploid daughter cells.

83
Q

SB3c - Describe the hydrogen bonding between Adenine/Thymine and Guanine/Cytosine

A

* A/T form two hydrogen bonds while C/G form three hydrogen bonds. * This explains why each of them have pairs and A can’t bond with C for .

84
Q

SB3c - Describe the lab extraction of a precipitate of peas DNA.

A

* Thoroughly mash up some peas * Make a solution of salt water and detergent without making it soapy * The detergent will break down the cell surface membranes and membranes around the nucleus * Mix the mash into the solution * Place the beaker containing this mixture in a water bath at 60 degrees for 15 minutes * Pour some of the filtrate into a boiling tube and add two drops of the protease enzyme (to break down proteins) * Tilt the tube slightly and let some ice cold ethanol run down the side of the tube slowly * Leave for a few minutes. DNA is insoluble in ethanol, thus the ethanol will cause the DNA to precipitate

85
Q

SB3c - Describe the structure of DNA.

A

* A double helix structure with nuecloetides. * Each nucleuotide contains a phosphate group and a sugar. * This forms a sugar phosphate backbone. * They also have bases which form complementary base pairs and joined together by weak hydrogen bonds. * The bases are adenine guanine thymine and cytosine with A being complimentary to T and C being complimentary to G. * The DNA forms a polymer because it is many nuceuotides joined together.

86
Q

SB3c - How many genes do humans roughly have?

A

20,000

87
Q

SB3c - What are starch, proteins and cellulose polymers of?

A

* P: Polymer of amino acids * S: Polymer of glucose * C: Polymer of glucose

88
Q

SB3c - What causes the hydrogen bonds between DNA bases?

A

Parts of DNA bases have very slight electrical charges, a slightly negatively charged part of one base will attract a slightly positively charged part of another base

89
Q

SB3c - What is a gene and why do genes differ between people?

A

* The order of bases form a gene. * Everyone has a slightly different order of bases (except identical twins) meaning that they all have different genesd. * Since DNA and genes are passed down along family, this information can be used to find out if people are related.

90
Q

SB3c - What is a gene?

A

A section of DNA that contains the code instructions for a protein

91
Q

SB3d - Descibe the process of translation.

A

* Translation is the second stage of protien synthesis and follows transcription * The mRNA attaches to ribocomes in the cytoplasm * The ribosome moves along the mRNA three bases at a time (a triplet of bases is called a codon) * At each codon, a complemantary tRNA molecule, the anticodon, (that codes for a specific amino acid) joins opposite to it. * Eventually, all the amino acids join up to from a polypeptide chain * This chain will then fold up to form a protein

92
Q

SB3d - Describe the process of transcription.

A

* Transcription is the first stage of protien synthesis in which RNA is created inside the nucleus * RNA polymerase attaches to the non-coding binding site of the DNA * This causes the strands of DNA to unzip. One strand acts as a template. * Complemantary neucleotides attach to the template strand EXCEPT Instead of T attaching to A, Uracil attaches to A * The nucleotides join up to form a polymer of mRNA (RNA Polymerase) * The mRNA leaves the nucleus through nuclear pores

93
Q

SB3e - Describe how different bases create different protiens.

A

* A triplet of bases forms a codon. * Each codon codes for a different amino acid. * Different orders and collections of amino acids will form different protiens

94
Q

SB3e - What is a mutation and what are the two types of causes for this?

A

* A mutation is a change in the sequence of bases in a gene. * This can be caused by DNA not being copied properly or by enviromental factors (such as radiation)

95
Q

SB3e - Where along a strand of DNA would a mutation be most harmful?

A

* In the non-coding site. * This is because this site decides when proteins and processes should/should not take place. * A mutation in this could lead to repeated rapid mitosis leading to a cancerous tumor, or a lack of a required protien.

96
Q

SB3f - Describe’s Mendel’s observation and conclusion through his experiment about characteristics of tall and short plants.

A

After breeding tall and short plants together, he noticed that: * In the first generation of offspring, all the plants were tall * Despite having both tall parent plants, the second generation of offspring contained some plants that were short * This meant that characteristics inherited by offspring are not just a blend of parent’s characteristics * Also that there were ‘factors’ (now know as alleles) which affect this outcome and that one was dominant over the other

97
Q

SB3f - What were Mendel’s laws of inheritance?

A

Each gamete receives only one factor for a characteristic The version of a factor that a gamete receives is random and does not depend on the other factors in the gamete Some versions of a factor are more ‘powerful’ than others and always have an effect on the offspring

98
Q

SB3f - Why was Mendel’s work largely ignored?

A

Scientists did not see how ‘factors’ could explain the many variations in characteristics It didn’t fit with Darwin’s theory of evolution

99
Q

SB3g - How is an allele chosen to be visible in the phenotype?

A

* There are dominant alleles (represented by capital letters) and recessive alleles. * In any heterozygous case, the dominant allele will be visible in the phenotype. * The only way a recessive allele can be visible is if both alleles present are recessive.

100
Q

SB3g - What is the difference between heterozygous and homozygous.

A

* Homozygous: Both the allelles are the same * Heterozygous: Both the alleles are different

101
Q

SB3g - What is the phenotype?

A

The physical characteristic

102
Q

SB3g- What is a genotype?

A

The genetic material of an organism, represented by letters

103
Q

SB3g - What is monohybrid inheritance?

A

The inheritance of 1 characteristic

104
Q

SB3h - Explain how the chance of have a boy or girl baby is equal.

A

* Females have XX chromosones; * Males have XY chromosones. * The mother has XX and the father has XY. * The means that if you draw a punnet square: X YX XX XYX XX XY * Thus the chances are 50/50

105
Q

SB3h - What determines the sex of a human?

A

Sex is determined by the sperm the fertilises the egg - whether it carrys an X or a Y chromosome

106
Q

SB3h - What diagram can be used to determine the chance of inheriting a certain characteristics?

A

Punnet squares.

107
Q

SB3i - Define coodominance, using blood as an example.

A

* A pair of alleles inherited that are both dominant alleles. * For example, your blood group can be A, B, o or AB. in this case, o is recessive while A and B are both dominant and so if the AB alleles are inherited, they will both be present in the phenotype giving you AB blood type.

108
Q

SB3i - Explain why a male is more likely to inherit certain genetic disorders.

A

Since males have a Y chromosome which is missing regions, if a recessive allele is present in the X chromosone, but that area isn’t present in the Y chromosome, then the male will get the disease without having to have two recessive alleles.

109
Q

SB3i - How is a Y chromosone different to an X?

A

A Y chromosone is missing regions that are present on an X chromosone.

110
Q

SB3i - What are the different blood types and their possible genotypes?

A

A - IaIa IaIoB- IbIb IbIoAB- IaIbO- IoIo

111
Q

SB3i - Why is a son guarenteed to inherit a recessive sex-linked genetic disorder if his mother has it?

A

* If it is sex-linked, that area isn’t present on the Y chromosone (which he’d inherit from his father) and so only the mother’s genes matter. * Thus if it is a recessive disorder, the mother must have two of this and is guarenteed to pass this on to her son * Meaning her son will inherit the recessive allele and won’t be able to inherit a dominant allele to counter it.

112
Q

SB3j - Explain how variation in height is both envionmental and genetic.

A

* Your capacity to grow is based off the alleles you inherit form your parents and increase the chance of you being tall/short. * However your diet will alsoaffect your growth and so it is affected by genetic and environmental factors.

113
Q

SB3k - If you plot the frequency of a variable with continuous variation in a species on a graph, what will it look like?

A

* It will be a normal distribution (bell-shaped) curve. * The most common value is in the middle of the whole range and the further away from this, the fewer individuals have this value.

114
Q

SB3j -What are the advantages / disadvantages of the Human Genome Project?

A

Advantages Alerting people that they are at risk of certain diseases - people may be able to change their lifestyle to reduce this risk Distinguishing between different forms of diseases Allows doctors to tailor treatment for some diseases to the individual where alleles affect how their respond to the treatment Disadvantages People who are at risk of certain diseases may be discriminated against when applying for work or life insurance It may not be helpful to tell someone they are at risk for a condition which there is no cure.

115
Q

SB3j - What is variation and what is it caused by?

A

The differences in the characteristics of a population - this is caused by mutations.

116
Q

SB3j - What was the Human Genome Project?

A

* The human genome project was a project that was carried out to try to map and identify all of the genes in a human.

117
Q

SB3k - Name the two types of factor affecting variation giving examples of a factor and its variation.

A

* Environmental factors: Effects from your surroundings. e.g. water and light content will affect plant growth * Genetic factors: Effects from your alleles and mutations. e.g, natural hair colour is based off the alleles you inherit form your parents

118
Q

SB3k - What is the difference between discontinuous and continuous variation?

A

* Discontinuous variation is variation in something that has a limited amount of possible values (e.g. number of leaves) * Continuous variation is variation in something that has possible values that could be measured to an infinite degree of accuracy (e.g leaf length)

119
Q

SB4a - How do fossil remains provide evidence for evolution?

A

* Fossil remains of humans can show us the bone structure of previous species * It also shows how the size of (volume) the skulls, increased over time, suggesting that the size of the brain increased aswell * The fossils are dated by the layers under the surface that they are

120
Q

SB4a - How do stone tools provide evidence for evolution?

A

* Stone tools show us what previous species of humans did and what they required tools for * We can see that over time, they become more sophisticated, going from skining animals/cutting up meat to decorations Stone tools are dated by the rock that they are found in.

121
Q

SB4a - Name the species of ‘human’ in order of their evolution, and describe the trend in skull volume.

A

* Adripithecus (Ardi) * Australopithecus (Lucy) * Homo habilis * Homo erectus * Homo sapiens Increasing skull volume over time

122
Q

SB4a - What are the limitations of using fossil remains as evidence for evolution?

A

* Not all organisms are fossilised. * Any organisms made of soft tissue and any soft tissue in organisms are unlikely to fossilise meaning that there are gaps in the records

123
Q

SB4a - What are the two types of evidence for evolution?

A

* Fossil remains * Stone tools

124
Q

SB4b - Describe the process of natural selection.

A

variation - most populations of organisms have individuals who are very slightly different to one another due to mutations over-production - most organisms produce mroe offspring than will survive to childhood struggle for existence - because populations do not generally increases rapidly in size, there therefore must be competition for survival survival - those with advantgeous characteristics are more likely to survive this struggle advantageous characteristics inherited - better adapted organisms are more likely to reproduce successfully passing on the advantageous characteristics to their offspring gradual change - over a period ftime, the proportion of individuals with the advantageous characteristic increase and the poorly adapted characteristic will eventually bel ost

125
Q

SB4b - Using the theory of natural selection, explain why not completing a course of antibiotics is so dangerous.

A

* The population of bacteria have variation in their resistance to antibiotics. * The course of antibiotics kill most of the bacteria * Before the course is finished, the only remaining bacteria are the most resistant * If the course isn’t completed, the remaining (more resistant) bacteria will reproduce, * This will produce another generation of highly resistant bacteria which the antibiotic will be less effective against

126
Q

SB4c - Describe how Darwin’s theories were developed.

A

* After visiting the galapagos islands and seeing differences in the mockingirds of different islands he wondered if spcies changed how they look based on their surroundings * After reading an essay by Thomas Malthus, he came to the conclusion organisms produce more offspring than could survive and so only the best suited survive * Wallace wrote a letter to him saying he came to the same conclusion * They both worked together and Darwin summarised their ideas in a book claled ‘on the origin of species’

127
Q

SB4c - What is the pentadactyl limb and how does this provide evidence for evolution?

A

* The pentadactly limb is a limb that has 5 main bone structures and this is visible in many organisms from humans to bats to dolphins. * As we all have the same 5 bone base structure, this suggests that we all have a common ancestor. * However the layout of these 5 bones changed depending on the surroundings and conditions of a species.

128
Q

SB4d - As you go further down the order of classification, what will happen to the species that are there?

A

They will have increasingly similar characteristics and genes.

129
Q

SB4d- What is the bi-nomial system?

A

* Genus + Species

130
Q

SB4d - What are the 5 kingdoms and the characteristics of each of these?

A

* Animalae: Multicellular. Nuclei are present but no cell walls * Plantae: Multicellular. Nuclei, chloroplasts and (cellulose) cell walls are present * Fungi: Multicellular (apart form yeast). live on dead matter. Nuclei and (chitin) cell walls are present. * Protists: Mostly unicellular. Nuclei and cell walls present * Prokaryotes: Unicellular. No nucleus, flexible cell walls

131
Q

SB4d - What are the three domains and the characteristics of each?

A

* Bacteria: (Cells with no nucleus; containing unused sections of DNA) * Archaea: (Cells with no nucleus or unused sections of genes) * Eukarya: (Cells with a nucleus and no unused sections of genes)

132
Q

SB4d - What is the order of classification?

A

* (Domain) * Kingdom * Phylum * Class * Order * Family * Genus * Species

133
Q

SB4e - Describe the process of selective breeding.

A

* Firstly, out of the population, you pick the two organisms that most strongly present your desired characteristic * Breed these two together * From the offspring choose the two that most strongly show this and repeat * After a couple of generations, almost all of the offspring will display the characteristic * This is selective breeding/artificial selection

134
Q

SB4e - What is genetic engineering?

A

The process of changing the genome of an organism by introducing genes from another to create genetically modified organisms

135
Q

SB4e - What may humans selectively breed an organism for?

A

* Disease resistance * Increased yield * Coping with certain conditions * Fast growth * Flavour

136
Q

SB4f - What are the uses of tissue culture?

A

* Differentiating cells * Producing clones of GMOs * Growing plants of very rare species to stop their extinction * Testing new medical treatment without any affects on life forms * Studying viruses as they require host cells to be alive

137
Q

SB4f - What is tissue culture?

A

* The growing of cells or tissue in a liquid containing nutrients or a solid medium (e.g nutrient agar). * This forms a callus (bunch of unspecialised cells) which can be differentiated and inserte dinto the body

138
Q

SB4f - Describe the steps of plant tissue culture

A

Tissue removed from the tip of the plant Tissue is placed on a medium containing agar jelly containg plant hormones and nutrients Sample grows into hundreds of tiny, identical plants

139
Q

SB4g - Describe the process of genetic engineering of bacteria to produce insulin.

A

DNA from a human cell is cut into pieces using enzymes from restriction enzymes. These make staggered cuts across DNA, leaving a few unpaired bases at each end called sticky ends. Bacteria cells contain small circles of DNA called plasmids. The same restriction enzymes are used to cut plasmids open, leaving sticky ends with matching sets of unpaired bases. The pieces of DNA containing the insulin gene are mixed with the plasmids. The bases in the sticky ends pair up, an enzyme called DNA ligase is then added, linking the DNA back into a continuous circle The plasmids are inserted back into the bacteria. This can be grow in huge fermenters where they can make human insulin

140
Q

SB4g - What are the risks of genetic engineering?

A

* Genes may ‘hop’ onto wild plants, making them resistant * Loose out on genes that may be required in the future * Very expensive * Some people think its bad for your health

141
Q

SB4g - What are the risks of selective breeding?

A

* Animals may loose an allele through this process. * This may be needed later on to help them survive/cope * All the animals become very similar and so any disease that affects one of them, affects all of them * Unethical as some animals live in conditions that aren’t comfortable (e.g chickens with a lot of meat can’t stand up)

142
Q

SB4h - What are the advantages of plants that produce ‘their own insecticide’ such as Bt toxin to famers?

A

* It only affects insects that chew it meaning it targets pests specifically * Higher yield * Less money spent on insecticides

143
Q

SB4h - What are the disadvantages of plants that produce ‘their own insecticide’ such as Bt toxin, to farmers?

A

* Insects such as aphids which suck up sap aren’t affected * Insects can develop resistance to the toxin * GM crops that produce the Bt toxin are expensive

144
Q

SB4i - What is a biological control?

A

When organisms are used to control pests.

145
Q

SB4i - What are the advantages / disadvantages of fertilisers?

A

Advantages Contain nutrients including nitrogen, phosphorus and potassium that helps crops grow well Increase crop yield producing more food Good way to use manure from farms Disadvantages Excess fertiliser can pollute waterways, causing eutrophication Artificial fertilisers can be expensive to make Artificial fertilisers reduce soil biodiversity

146
Q

SB5a - What are the three type of health?

A

* Physical well-being: Being free from disease, getting regular excersize, limiting harmful substance etc. * Mental well-being: How you feel about yourself * Social well-being: How well you get along with others

147
Q

SB5a - What is the difference between communicable and non-communicable diseases?

A

Communicable: * Caused by pathogens (microorganisms athat cause disease) * Can be spread between people * Localised cases Non-communicable: * Caused by problems in the body and by lifestyle choices * Cannot be spread between people * Widely spread cases

148
Q

SB5a - Why may a person be more likely to catch a disease if they’ve already got one?

A

* One disease damages the immune system, making it easier for other pathogens to cause disease * A disease can damage the body’s natural physical and chemical defences making it easier for pathogens to get in * A disease can stop an organ from functioning correctly, meaning other diseases are mroe likely to occur

149
Q

SB5b - Define malnutrition.

A

A lack or excess of a specific nutrient in the body

150
Q

SB5b - Describe the defficiency diseases associated with lack of: * Protien * Vitamin C * Vitamin D and/or Calcium * Iron

A

* Kwashiorkor: enlarged belly, small muscles, failure to grow properly * Scurvy: Swelling/bleeding gums, muscle/ joint pains and tiredness * Rickets/Osteomalacia: Soft bones/cruved leg bones * Anaemia: Less and smaller red blood cells, tiredness

151
Q

SB5b - How do you calculate BMI?

A

mass / height ^2

152
Q

SB5b Why is drinking too much alcohol dangerous?

A

Ethanol is poisonous to cells When absorbed from the gut, it passes to the liver to be broken down. So liver cells are more likely than other cells to be damaged, leading to liver disease e.g cirrhosis

153
Q

SB5b - Why is ethanol (in alcohol) considered a drug and what disease can it lead to?

A

* It’s considered a drug because it changes the way in which the body works * It can lead to liver cirrhosis which is a disease where the liver doesn’t function properly

154
Q

SB5c - What is heart bypass surgery?

A

This is when a new blood vessel is inserted to ‘by-pass’ a blocked artery

155
Q

SB5c - Describe how smoking can lead to blood clots.

A

* Tobacco from smoking will damage artery linings. * Fat (or plaque) can build up in the artery wall making the artery narrow. * This will increase blood pressure * Eventually, the fat will block the whole artery * White blood cells will form a wall around this causing a clot leading to a heart attack or stroke

156
Q

SB5c - Explain how a stent works.

A

* A stent is a small mesh inserted into the artery on a delfated balloon. * Once in place, the balloon is inflated and the stent expands widening the artery * The balloon is taken out but the stent stays in keeping the artery wide

157
Q

SB5c - What is BMI and what are its pros and cons?

A

* A measure of weight relative to height calculated by mass ÷ height². * Its good at being a a measurement and comparison between people helping identify if they’re over/underweight or obese etc. * However it doesn’t take into account varying muscle and bone mass and so isn’t always an accurate way of assesing risk.

158
Q

SB5c - What is CVD?

A

Cardiovascular disease is a result of the circulatory system functioning poorly and can lead to many side effects including high blood pressure, heart pains and even heart attacks

159
Q

SB5c - Why is an obese person at a higher risk of developing CVD?

A

Obese people are more likely to have more body fat. More body fat increases risk of CVD

160
Q

SB5d - Describe and explain the causes, types of baceria, host organisms and symptoms associated with: * Cholera * Tubercolosis(TB) * Chalera dieback

A

Caused by vibrio cholera (bacteria). It’s hosts are animals/humans and it can lead to severe diarrhea and dehydration Caused by mytobacterium tubercolosis (bacteria). It’s hosts are humans/animals. It damages lung tissue leading to coughing fever and tiredness Caused by the fungus chalara and affects trees/plants. Lesions on trunks and leaves die earlier than usual

161
Q

SB5d - Describe and explain the causes, types of baceria, host organisms and symptoms associated with: * Malaria * Typhoid/dysentry * Ulcers

A

Caused by the plasmodium protist, it infects humans using moquitoes as a vector. Leads to fever weakness, sickness and lack of red blood/liver cells Caused by the salmonella typhi bacteria and infecting animals/humans causing severe diarrhea and dehydration Caused by the heliobacter pylori bacteria and infecting humans causing stomach ulcers

162
Q

SB5d - Why are people with HIV likely to develop AIDS?

A

* HIV attacks the white blood cells in your immune system making it weak. * Thus the immune system is inable to defend the body from secondary infections effectively

163
Q

SB5d - Why are viruses not ‘true organisms’?

A

They don’t have a cellular structure and require hosts to survive

164
Q

SB5e - State how the pathogen is spread and 1 way to prevent the spreading of this pathogen cholera tubercolosis malaria stomach ulcers ebola HIV

A

water - boil water to kill bacteria prior to drinking airborne - ventilate buildings to reduce chance of breathing in bacteria in droplets of mucus coughed out by an infected person mosquito vector - prevent mosquitos biting people by keeping them off skin orally - cook food thoroughly to kill bacteria body fluids - quarantine infected people sexual fluids - use condoms

165
Q

SB5f - Describe the lysogenic cycle.

A

* Attachment: The viral particle attaches itself to the host receptor cell * The Viral nuclei acids are incorporated into the DNA * The cell continues to divide - it can stay dormant for a long time * Replication: The virus uses the host’s DNA to replicate and synthesise new viral components * Assembly: The new viral components are assembled into new viruses * Release: Lysis of infected cell leads to release of fully assembled viral particles

166
Q

SB5f - Describe the lytic cycle.

A

* Attachment: The viral particle attache sitself to the host receptor cell * Entry: Nucelic acid of the viruc moves across the membrane into the cell * Replication: The virus uses the host’s DNA to replicate and synthesise new viral components * Assembly: The new viral components are assembled into new viruses * Release: Lysis of infected cell leads to release of fully assembled viral particles

167
Q

SB5g - What are the chemical defences of a plant (giving examples where appropriate)?

A

* Poisons (in foxgloves) * Natural insect repellents/alarm substances (Wild potatoes)

168
Q

SB5g - What are the physical defences of plants?

A

* Waxy layer called the cuticle * Cell walls

169
Q

SB5h - How are keys used to identify plant diseases?

A

Farmers comare visible symptoms on infected plants to pictures to try and deduce which disease the plant has

170
Q

SB5h - How is diagnostic testing used to identify plant diseases?

A

* Farmers will send off a sample of the infected plant to a lab where they will run tests to work out what the pathogen is. * They may also send soil samples to test for nutrients and toxins. * This can be very expensive.

171
Q

SB5h - What is a distribution analysis?

A

This is the study of the pattern of where diseased plants occur to help identify the cause * By using other information such as wind direction, you can deduce how the disease has spread and figure out what the disease is.

172
Q

SB5h - Which two methods may a farmer use to identify plant diseases?

A

* Keys * Distribution analysis * Diagnostic testing

173
Q

SB5i - What are physical and chemical barriers?

A

* Barriers to prevent pathogens from infecting the body. * Physical barriers stop them getting in and chemical barriers stop them from being effective.

174
Q

SB5i - What are the physical and chemical barriers in the body?

A

* Skin * Mucus * Earwax * Cilliated cells * Lysozyme (in saliva and tears) * Hydrochloric acid in the stomach

175
Q

SB5i - What is lysozyme?

A

* Lysozyme is an enzyme screted by skin and in tears and saliva. * It is chemical defence that breaks down the cell walls of types of bacteria.

176
Q

SB5j - Describe and explain the differences in primary and secondary response in terms of lymphocytes.

A

* The primary response takes a long time between infection and rise in antibody numbers * The numbers of antibodies produced isn’t that high * The number of antibodies doesn’t return back to its original value but slightly higher instead * After the second infection, the secondary response is a lot quicker. * It also produces a lot more antibodies * This is because of the already active memory lymphocytes

177
Q

SB5j - How do lymphocytes respond to pathogens?

A

Each pathogen has unique antigens on its surface A lymphocyte with an anti-body that fits the antigen is activated The lymphocyte divides many tiems to produce clones of identical lymphocytes Some of the lymphocytes produce lots of antibodies which stick to the antigen and destroy them Other lymphocytes stay in the blood as memory lymphocytes in case the same antigen returns

178
Q

SB5j - How do phagocytes respond to pathogens?

A

* They detect the pathogen and recognise it as a foreign body. * They then ingest the pathogen and use enzymes to destroy it.

179
Q

SB5j - How does a vaccination work?

A

* A vaccination injects inactive/weak pathogens of a disease. * Lymphocytes with antibodies to tackle these are activated and memory lymphocytes are created * This means that if that pathogen infects the person after, there will be memory lymphocytes to tackle it quiclkly * This increases the person’s immunity to this disease as it reduces the severity of the symptoms and the time taken till the infection is dealt with

180
Q

SB5j - If a child is allergic and cannot be vaccinated, how can they still ba safe from the pathogen?

A

* If around 95% of the people around them are vaccinated there is a very low chance of them getting the disease. * This is because all the others either won’t get it or will get rid of it before coming in contact with them. * This is called herd immunity.

181
Q

SB5j - What are the two main types of white blood cells involved in the immune response?

A

* Phagocytes * Lymphocytes

182
Q

SB5j - Why will memory lymphocytes created after one infection not affect the speed of response for an infection by a different pathogen?

A

The memory lymphocytes created after one infection have antibodies specific to the antigens of that particular pathogen and won’t work on any othe pathogens.

183
Q

SB5k - Describe the stages of the clinical process.

A

Pre-clinical development:Testing on animals and human tissue to look for side effects Clinical development: Phase 1: * Small clinical trial to check for human side effects Phase 2: * Slightly larger sample size looking for the optimum dosage Phase 3: * Large clinical trial to test effectiveness. Placebo (decoy) also used to verify this.

184
Q

SB5k - What are antibiotics?

A

Substances that either kill or bacteria or inhibit their cell processes stopping them from growing/reproducing.

185
Q

SB5k - Why do new antibiotics constantly have to be developed?

A

Because bacteria are constantly evolving and developing resistance to existing antibiotics.

186
Q

SB5k CP - Describe the method you would undertake to investigate the growth of bacteria in relation to anitibiotic concentration.

A

* Using aseptic technique, pour an agar plate, making sure that the bases is covered with a smooth layer of agar * Open a bottle of bacterial culture without putting it down and pass the neck through the flame of a bunsen burner * Take out a sterile pipette and without putting it down, draw some bacterial culture * Slightly open the lid of the petri dish and add some culture. Then place the pipette in disinfectant * Unwrap a steirle spreader, and open the lid of the petri dish slightly, and spread the culture around in a side to side motion. * Using a permanent marker, section out the bottom of the petri dish into four sections * Label one, the control * Using sterilised forceps dip three paper discs each into a different concentration of antibiotic solution, sterilising between * Place each disc ina section of the dish (not near the edge) * Leave for incubation * Measure clear spaces in each section

187
Q

SB5k CP - How do you measure the radius and the area of a clear space?

A

The length from the centre of the area where there hasn’t been bacterial growth to the edge of this section, is the radius of the clear space. The area is πr²

188
Q

SB5k CP - What are methods of aseptic techniques?

A

* Sterilising equipment before use * Lighting a flame nearby * Only opening the petir dish slightly * Using an autoclave * Cleaning down surfaces before use * Wearing gloves

189
Q

SB5k CP - Why do we carry out bacterial cultural in aseptic conditions?

A

To avoid contamination with microroganisms in the air

190
Q

SB5l - Describe how and why monclonal antibodies are made.

A

* First, an antigen is injected into a mouse. * The mouse produces lymphocytes with antibodies to target this antigen * However, once a lymphocyte starts producing antibodies, it can no longer divide, and so a cancer cell is grown in culture medium * The cancer cell is fused with the lymphocyte creating a hybridoma cell whic can both continue to divide and produce lymphocytes

191
Q

SB5l - How are monoclonal antibodies used in cancer diagnosis?

A

* The monoclonal antibodies are made to target cancer cells. * They are also made radioactive. * Once inserted in the body, they will go to where the tumor is. * The radiation given off from the antibodies which help show a PET scanner where the tumors are located.

192
Q

SB5l - How are monoclonal antibodies used in pregnancy tests?

A

In pregnancy tests, to identify is the pregnancy hormone is present in urine. The monoclonal antibody matches the hormone and causes a reaction with the indicator

193
Q

SB5l - Why are monoclonal antibodies effective in treating cancer?

A

* Monoclonal antibodies can be made to specifically target cancer cells. * This means that unlike in many other forms of cancer treatment, healthy cells won’t be harmed.

NSFC A2L3 Edexcell GCSE Biology (20 decks)

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