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biology > past paper Qs > Flashcards

past paper Qs Flashcards

1
Q

`give two types of molecule from which a ribosome is made

A

RNA and amino acids/ribosomal protein

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2
Q

in a eukaryotic cell, the base sequence of the mRNA might be different from the sequence of pre-mRNA - why?

A

introns are found in pre-mRNA only

splicing , sections of pre-mRNA are removed

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3
Q

during pregnancy, cells lining the uterus are an important source of energy for the embryo.

suggest how glycogen acts as a source of energy.

A

glycogen is hydrolysed (into glucose)

this glucose is then used in respiration

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4
Q

how does an enzyme affect a reaction?

(describe a typical enzyme graph)

A

an enzyme increases the rate of reaction , by lowering the activation energy - this increase is often non-linear

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5
Q

explain the importance of DNA replication during the development of a zygote into a blastocyst

A

zygote divides multiple times by mitosis
making identical copies of DNA (all cells will be diploid)
so when mitochondria divides, they will have a copy of the DNA

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6
Q

Describe how macrophages present antigens to t-helper cells.

A

the macrophage engulfs the pathogen
presents antigens on MHC markers
these are complementary to the t-helper cell’s receptors

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7
Q

How much peptidoglycan cell wall does gram negative bacteria have?

A

thin layer

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8
Q

What type of toxins does salmonella produce?

A

endotoxins

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9
Q

outline the differences between endotoxins and exotoxins

A

endotoxins:
produced by gram negative bacteria
lipopolysaccharides
released from dead bacteria

exotoxins:
gram negative and positive bacteria
proteins
released from living bacteria
affect is later

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10
Q

explain the importance of the phosphate group of lipids found in the cell membrane

A

phosphate group is polar
it can interact with aqueous environment
otherwise lipids will not form bilayer

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11
Q

what route does a symplastic / apoplastic pathway take?

A

symplastic - through cell’s cytoplasm

apoplastic- through cell walls

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12
Q

describe the structure of a ribosome

A

made from protein + RNA

made from two subunits

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13
Q

explain why using antibiotics only when needed will reduce antibiotic resistance

A

because antibiotics act as a selection pressure for resistant bacteria

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14
Q

how is tissue fluid formed?

A

high hydrostatic pressure forces plasma/fluid out of the capillaries

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15
Q

describe what happens to the tissue fluid that is not reabsorbed into the blood capillary

A

it enters the lymphatic system (becomes lymph)

lymph is taken to subclavian veins/blood

taken to different parts of the body to be broken down

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16
Q

What organism causes malaria ?

A

Plasmodium falciparum

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17
Q

name methods of controlling malaria and possible implications

A

repellant

insecticide (kill mosquitos)

avoid stagnant water (inconvenient/difficult to get water that’s not stagnant near home/work)

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18
Q

explain the importance of vaccinating as many people as possible against a disease

A

helps create herd immunity
fewer people will become infected, preventing those who can’t get immune through vaccination (e.g due to allergy/intolerance)

19
Q

what classification of virus is ebola?

A

RNA enveloped

20
Q

what classification of virus is lambda phage?

A

DNA non-enveloped

21
Q

what classification of virus is TMV

A

RNA non-enveloped

22
Q

what happens inside cells once they have taken up a virus?

A

the cell reproduces, producing viral RNA
viral protein made
assembly of virus and new virus particles

23
Q

are the following bonds found in carbohydrate, lipid, both or neither:

covalent
ester
hydrogen

A

covalent - carbohydrate and lipid
ester-lipid only
hydrogen-carbohydrate only

24
Q

why can lipids only be respired in aerobic conditions?

A

in anaerobic conditions
pyruvate would be used to reoxidise NADH , so no Krebs cycle
the final electron acceptor oxygen would not be there

25
Q

describe how you could identify different bacteria present in a sample from the body

A

get a sample of (named area)

use selective media to grow bacteria

grow bacteria on media containing different antibiotics

DNA profiling /gram staining/colony shape,size

26
Q

explain how cells that metabolise glycogen to lactic acid can inhibit the growth of pathogenic bacteria

A

lactic acid is toxic to cells and stops bacteria reproducing- lowers pH which denatures enzymes of pathogenic bacteria

grow on skin cells, preventing pathogenic bacteria from doing so

use glycogen so less available for bacteria

27
Q

explain how a blood clot can cause a heart attack

A

blockage due to clot means oxygen can’t reach the cells in the heart

this prevents aerobic respiration , the heart muscle can’t contract, the cells die

28
Q

explain what is meant by ‘myogenic’

A

myogenic means stimulation is generated from within the muscle , resulting in depolarisation

29
Q

explain how and EEG can be used to calculate a person’s heartrate

A

shows electrical activity of the heart

can identify time for one heartbreak using P wave / QRS complex / T wave

count number of peaks in set time

beats/time

30
Q

explain why a carbon dioxide concentration of 5% causes a change in heartrate

A

concentration of carbon dioxide increases in alveoli ( conc gradient increased)

conc of carbon dioxide in blood increases - this is detected by chemoreceptors in medulla
(medulla is a cardiac control centre)
more impulses sent to SAN
SAN rate increases
heart rate will increase

31
Q

explain why someone who has high blood pressure is at a significantly higher risk of developing CVD

A

damage to endothelium
inflammatory response
atheroma
stops blood flow, blood clot forms
this means loss of elasticity and narrowing of lumen

positive feedback- further increase in blood pressure

32
Q

explain why fragments of DNA can be separated by gel electrophoresis

A

there is an electric current

DNA fragments are negatively charged, so move towards the positive anode

smaller fragments move further

33
Q

why would the lag face be longer for bacteria grown in sucrose , compared to if grown in glucose?

A

sucrose is a disaccharide , so it has to be broken down into its monosaccharides first , but once broken down , more energy is released for the bacteria to use for growth.

34
Q

how does stem rust fungus result in a reduction in grain yield?

A

the fungus takes up nutrients and glucose

meaning less amino acids are available to form proteins for the plant

results in damaged vascular tissue

35
Q

state the meaning of the term DNA methylation

A

adding/removing methyl (CH3) groups to bases

36
Q

describe the differences between totipotent , pluripotent and multipotent stem cells during the development of an embryo

A

zygote is totipotent (the stem cells can differentiate into any type of cell)

blastocyst is pluripotent (can differentiate into most types of cells)

cells in developing embryo are multipotent as they become only some cell types

37
Q

explain why properties of lipoproteins enable cholesterol and fatty acids to be transported in the blood stream

A

cholesterol is hydrophobic so can’t be carried in the blood stream

phospholipid tails are hydrophobic so cholesterol can be carried inside lipoprotein

phosphate heads are hydrophilic , enabling transport in blood stream

38
Q

explain why wider stomata would increase the yield of a crop

A

faster photosynthesis, would result in more GALP/glucose produced
would for other organic molecules
transpiration stream would be faster

39
Q

What happens when hydrogen ions are actively transported out of guard cells?

A

ATP is broken down into ADP and phosphate ions by a hydrolysis reaction

40
Q

explain why a change in concentration of amino acids results in the weakening of cardiac muscle

A

decrease in amino acids means certain proteins can’t be made

if these proteins are involved in heart muscle structure, then the cardiac muscle will be weaker

these proteins may affect heart muscle function

41
Q

describe how you could use a plant tissue culture technique to show totipotency.

A

get sample (cutting)
allow to grown on agar (with specific growth substances)
use aseptic technique
cover container to prevent contamination and evaporation
allow sufficient time (name length)
look for roots/leaves forming

42
Q

suggest how a stem cell in the blood can become a differentiated blood cell.

A

a chemical causes some genes to be active and some inactive

only active genes are transcribed (mRNA is only made by the activated genes)

protein that’s made determines the cell structure and function

43
Q

how is the xylem adapted for transport of water and support in plants?

A

water transport:
pores- allow sideways movement of water
hollow tubes - allow vertical movement of water

support:
spirals of lignin provide support

biology (9 decks)

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