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AQA Biology > 2 Exam Questions > Flashcards

2 Exam Questions Flashcards

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1
Q

Give two structures found in all prokaryotic cells and in all eukaryotic cells. [2]

A

Cell surface membrane
Ribosomes
Cytoplasm
DNA

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2
Q

Suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration. [2]

A

Amino acids used in protein synthesis
So more enzymes for DNA replication

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3
Q

Describe how a sample of chloroplasts could be isolated from leaves. [4]

A

Breaks open cells and filter
In cold, isotonic, buffer solution
Centrifuge and remove nuclei
Centrifuge at higher speed for chloroplasts to settle out

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4
Q

Give two features of the chloroplast that allows protein to be synthesised inside the chloroplast and describe one difference between these featured in the chloroplast and similar features in the rest of the cell. [4]

A

DNA
Not associated with histones but nuclear DNA is

Ribosomes
Smaller than cytoplasmic ribosomes

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5
Q

Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.

Do not include details of transcription and translation in your answer. [6]

A

DNA in nucleus is code for protein
Ribosomes produce protein
Mitochondria product ATP for protein synthesis
Golgi apparatus package/modify
Vesicles transport
Vesicles fuse with cell surface membrane

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6
Q

Suggest two reasons why a nucleus is not visible in image. [2]

A

A section so nucleus in another part of cell
Nucleus not stained

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7
Q

Give one advantage of viewing a biological specimen using a transmission electron microscope compared with using a scanning electron microscope. [1]

A

Higher resolution

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8
Q

The detail shown in the diagram above would not be seen using an optical microscope.

Explain why. [2]

A

Light has longer wavelngth
So lower resolution

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9
Q

Name an organelle found in both a chloroplast and a prokaryotic cell. [1]

A

Ribosome

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10
Q

A biologist separated cell components to investigate organelle activity. She
prepared a suspension of the organelles in a solution that prevented damage to the organelles.

Describe three properties of this solution and explain how each property prevented damage to the organelles. [3]

A

Ice cold
Prevent/reduce enzyme activity

Buffered
Prevent denaturing enzyme/protein

Isotonic
Prevent lysis/bursting of organelle

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11
Q

Name the process by which prokaryotic cells divide. [1]

A

Binary fission

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12
Q

Contrast how an optical microscope and a transmission electron
microscope work and contrast the limitations of their use when studying cells. [6]

A

TEM use electrons and optical use light
TEM allows greater resolution
So TEM can allow smaller organelles to be observed
TEM view only dead specimens and optical can view live
TEM does not show colour and optical can
TEM requires thinnger specimens and more complex preparation

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13
Q

Before the cell was examined using the electron microscope, it was
stained. This stain caused parts of the structure of the cell-surface
membrane to appear as two dark lines.

Suggest an explanation for the appearance of the cell-surface membrane as two dark lines. [3]

A

Membrane has phospholipid bilayer
Stain binds to phosphate
On inside and outside of membrane

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14
Q

No organelles are visible in the cytoplasm of this red blood cell.

Suggest why. [1]

A

Cytoplasm of red blood cell filled with haemoglobin

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15
Q

Name two structures in a eukaryotic cell that cannot be identified using an optical microscope. [1]

A

Mitochondria
Ribosome
Endoplasmic reticulum
Lysosome
Cell surface membrane

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16
Q

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope. [4]

A

Add drop of water to glass slide
Obtain thin section of plant tissue and place on slide
Stain with iodine in potassium iodide

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17
Q

Describe binary fission in bacteria. [3]

A

Replication of circular DNA
Replication of plasmids
Division of cytoplasm to produce daughter cells

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18
Q

Describe and explain what the student should have done when counting cells to make sure that the mitotic index he obtained for this root tip was accurate. [2]

A

Count only whole cells to standardise counting

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19
Q

Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas. [1]

A

Differences in coiling

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20
Q

What is a homologous pair of chromosomes? [1]

A

Two chromosomes that carry the same genes

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21
Q

Describe three aseptic techniques she would have used when transferring a sample of broth culture on to an agar plate.

Explain why each was important. [6]

A

Keep lip on Petri dish
To prevent unwanted bacteria contaminating the dish

Wash hands
To prevent contamination from bacteria on hands

Flame the neck of the culture container
To maintain a pure culture of bacteria

22
Q

Describe the appearance and behaviour of chromosomes during mitosis. [6]

A

Chromosomes coil/condense/shorten/thicken/become visible
Chromosomes line up on equator of the cell
Chromosomes attached to spindle fibres
The centromere splits
Sister chromosomes are pulled to opposite poles of the cell
Chromosomes uncoil/unwind/become longer/thinner

23
Q

The student prepared a temporary mount of the onion tissue on a glass slide. She covered the tissue with a cover slip. She was then given the following instruction.

“Push down hard on the cover slip, but do not push the cover slip
sideways.”

Explain why she was given this instruction. [2]

A

Push hard spread tissue
Pushing sideways breaks chromosomes

24
Q

Name and describe five ways substances can move across the
cell-surface membrane into a cell. [5]

A

Simple diffusion of small non-polar molecules down a concentration gradient

Facilitated diffusion down a concentration gradient via a channel protein

Osmosis of water down a water potential gradient

Active transport against a concentration gradient via carrier protein using ATP

Co-transport of 2 different substances using a carrier protein

25
Q

Describe and explain two features you would expect to find in a cell
specialised for absorption. [2]

A

Folded membrane so large surface area for absorption
Large number of carrier proteins so faster rate of absorption

26
Q

The movement of substances across cell membranes is affected by membrane structure.

Describe how. [6]

A

Phospholipid bilayer allows movement of non-polar lipid-souble substances
Phospholipid bilayer prevents movements of polar lipid-insoluble substances
Carrier proteins allow active transport
Carry proteins allow facilitated diffusion
Number of carrier proteins determines how much movement
Cholesterol affects permeability

27
Q

Give two similarities in the movement of substances by diffusion and by osmosis. [2]

A

Movement down a gradient from high concentration to low concentration
Passive processes not using energy

28
Q

Describe a method the student could have used to monitor the temperature of the water in each tube. [1]

A

Take regular reading using a thermometer

29
Q

The decrease in the percentage of light passing through the water between 25 °C and 60 °C is caused by the release of the red pigment from cells of the beetroot.

Suggest how the increase in temperature of the water caused the release of the red pigment. [2]

A

Damage to cell surface membrane
Increase fluidity to phospholipid bilayer

30
Q

Suggest and explain two ways the cell-surface membranes of the cells
lining the uterus may be adapted to allow rapid transport of nutrients. [2]

A

Membrane folded so large surface area
Large number of carrier proteins for facilitated diffusion, co-transport, active transport

31
Q

High absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead to a build-up of tissue fluid.

Explain how. [2]

A

Higher salt reduces lower water potential of tissue fluid
Less water returns to capillary by osmosis

32
Q

Compare and contrast the processes by which water and inorganic ions enter cells. [3]

A

Both move down concentration gradient
Both move through protein channels in membrane
Ions can move against a concentration gradient by active transport

33
Q

Contrast the processes of facilitated diffusion and active transport. [3]

A

Facilitated diffusion involves carrier proteins whereas active transport only involves carrier proteins
Facilitated diffusion does not use ATP whereas active transport uses ATP
Facilitated diffusion takes place down a concentration gradient whereas active transport can occur against a concentration gradient

34
Q

Describe how HIV is replicated. [5]

A

Attachment proteins attach to receptors on lymphocyte
RNA enters cell
Reverse transcriptase converts RNA to DNA
Viral protein produced
Virus assembled and released from cell

35
Q

Describe how a phagocyte destroys a pathogen present in the blood. [3]

A

Engulfs pathogen
Forming vesicle and fuses with lysosome
Enzymes hydrolyse

36
Q

Give two types of cell, other than pathogens, that can stimulate an immune response. [2]

A

Abnormal/tumour cells
Cells from other organisms/transplants

37
Q

What is the role of the disulfide bridge in forming the quaternary structure of an antibody? [1]

A

Joins two different polypeptides

38
Q

Explain how HIV affects the production of antibodies when AIDS develops in a person. [3]

A

HIV destroys helper T cells
Less/no antibody produced
So few/no B cells stimulated

39
Q

Determining the genome of the viruses could allow scientists to develop a vaccine.

Explain how. [2]

A

Scientists could identify proteins/proteome
Could identify potential antigens to use in vaccine

40
Q

What is a monoclonal antibody? [1]

A

Antibodies with the same tertiary structure

41
Q

After a disease is diagnosed, monoclonal antibodies are used in some medical treatments.

Give one example of using monoclonal antibodies in a medical treatment. [1]

A

Targets specific cells

42
Q

Describe the role of antibodies in producing a positive result in an ELISA test. [4]

A

First antibody binds to antigen
Second antibody with enzyme attached is added
Second antibody binds to antigen
Solution added and colour changes

43
Q

Describe and explain the role of antibodies in stimulating phagocytosis.

Do not include details about the process of phagocytosis. [2]

A

Bind to antigen
Antibodies cause clumping/agglutination

44
Q

During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom.

Use your knowledge of the humoral immune response to explain this
vaccination programme. [3]

A

B cells specific to venom reproduce by mitosis
B cells produce plasma cells and memory cells
The second dose produces antibodies in secondary immune response in higher concentration quickly

45
Q

Describe how phagocytosis of a virus leads to presentation of its antigens. [3]

A

Phagosome/vesicle fuses with lysosome
Virus destroyed by lysozymes
Antigen from virus are displayed on the cell membrane

46
Q

Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen. [4]

A

Helper T cell binds to antigen on antigen presenting cell
Helper T cell stimulates specific B cell
B cell clones by mitosis
Forms plasma cells that release antibodies

47
Q

What is an antigen? [2]

A

Foreign protein
Stimulates an immune response

48
Q

What is an antibody? [2]

A

A protein specific to an antigen
Produced by B cells

49
Q

When a vaccine is given to a person, it leads to the production of
antibodies against a disease-causing organism.

Describe how. [6]

A

Vaccine contains antigen from pathogen
Macrophage presents antigen on its surface
T cell with complementary receptor protein binds to antigen
T cell stimulates B cell
With complementary antibody on its surface
B cell divides to form clone all secreting same antibody

50
Q

Describe the difference between active and passive immunity. [6]

A

Active involves memory cells, passive does not
Active involves production of antibody by plasma cells
Passive involves antibody introduced into body from outside source
Active long term, because antibody produced in response to antigen
PAss short term because antibody given is broken down
Active can take time to develop, passive fast acting

AQA Biology (43 decks)

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