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Y1 AQA Biology - Burnley College (2024-25) > Cells 3.2 > Flashcards

Cells 3.2 Flashcards

1
Q

Eukaryotic cells AO1

Eukaryotic cell

A

A cell with a nucleus AND membrane-bound organelles.

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2
Q

Eukaryotic cells AO1

Describe the structure of the nucleus (2 marks).

A

1. Nuclear envelope and pores

OR double membrane and pores;

2. Chromosomes/chromatin

OR DNA wrapped around histones;

3. Nucleolus/nucleoli

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3
Q

Eukaryotic cells AO1

Eukaryotic cells contain linear DNA which is bound / wrapped around which protein?

A

Histones

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4
Q

Eukaryotic cells AO1

Describe the function of the nucleus (2 marks).

A

1. Stores genetic information/material for polypeptides (production)

OR codes for proteins

OR codes for primary structure of polypeptides;

2. Site of (semi-conservative) DNA replication;

3. Production of mRNA/tRNA

OR site of Transcription;

4. Production of rRNA/ribosomes;

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5
Q

Eukaryotic cells AO1

Draw out and label the structure of a mitochondrion

A
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6
Q

Eukaryotic cells AO1

Mitochondrial DNA is linear OR circular?

A

Circular

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7
Q

Eukaryotic cells AO1

Size of mitochondrial ribosomes

A

70S

This is smaller than cytoplasmic ribosomes which are 80S

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8
Q

Eukaryotic cells AO1

Process occuring in mitochondria

A

Aerobic respiration

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9
Q

Eukaryotic cells AO1

Products of aerobic respiration

A

Carbon dioxide, water AND ATP

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10
Q

Eukaryotic cells AO1

The cristae provide a large _________ _________ so more ATP synthase can be embedded into the inner mitochondrial membrane.

A

surface area

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11
Q

Eukaryotic cells AO1

Organelle found on the outer surface membrane of the rough endoplasmic reticulum

A

Ribosome

Size of 80S

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12
Q

Eukaryotic cells AO1

Rough endoplasmic reticulum function

A

Provide a large surface area for the synthesis of proteins via ribosomes on their surface.

Packages proteins into vesicles to be transported to the Golgi apparatus

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13
Q

Eukaryotic cells AO1

Why is the smooth endoplasmic reticulum ‘smooth’?

A

No ribosomes on its surface

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14
Q

Eukaryotic cells AO1

Smooth endoplasmic reticulum function

A
  1. Synthesise lipids and packages them into vesicles.
  2. Synthesise carbohydrates and packages them into vesicles.
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15
Q

Eukaryotic cells AO2

A

1. Less phospholipids in rough
OR
More protein/glycoprotein in rough
OR
Presence of ribosomes in rough;

2. (More protein/glycoprotein/ribosomes)
Rough – production/transport of proteins;

3. (More phospholipid)
Smooth –production / modification / packaging / transport of lipids

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16
Q

Eukaryotic cells AO1

Golgi apparatus function

A

1. Sorts, modifies and packages proteins into vesicles.

E.g. adds a carbohydrate to a protein to form a glycoprotein.

E.g. forms chylomicrons

2. Forms lysosomes

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17
Q

Eukaryotic cells AO1

Name of enzyme contained by lysosomes

A

Hydrolytic enzymes
(aka lysozymes)

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18
Q

Eukaryotic cells AO1

Describe how lysosomes destroy pathogens or damaged organelles
(2 marks).

A
  1. Lysosomes fuse with vesicle
  2. Release its hydrolytic enzymes
  3. Which breakdown pathogens AND/OR damaged and worn out organelles
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19
Q

Eukaryotic cells AO1

Function of ribosomes

A

Synthesise proteins

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20
Q

Eukaryotic cells AO1

Ribosomes are made up of……..

A

ribsomal RNA (rRNA)

Protein sub-units

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21
Q

Eukaryotic cells AO1

Cytoplasmic ribosomes size

A

80S

This is also the size of ribosomes on the rough ER

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22
Q

Eukaryotic cells AO1

Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells (4 marks).

A
  1. DNA in nucleus is code for protein;
  2. Ribosomes/rough endoplasmic reticulum synthesise protein;
  3. Mitochondria produce ATP (for protein synthesis);
  4. Golgi apparatus modifies and packages protein;
  5. Vesicles transport protein

OR

  1. (Vesicles) fuse with cell(-surface) membrane;

Accept exocytosis at cell surface membrane

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23
Q

Eukaryotic cells AO1

Process by which a vesicle fuses with cell surface membrane to release its content

A

Exocytosis

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24
Q

Eukaryotic cells AO1

TRUE or FALSE

The nucleus can contain more than one nucleoli?

A

TRUE

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25
Q

Eukaryotic cells AO1

DNA in the eukaryotic nucleus is linear OR circular?

A

Linear

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26
Q

Eukaryotic cells AO1

The cell-surface membrane consists of a _________________.

A

phospholipid bilayer

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27
Q

Eukaryotic cells AO1

Polymer in plant cell wall

A

Cellulose

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28
Q

Eukaryotic cells AO1

Polymer in fungal cell wall

A

Chitin

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29
Q

Eukaryotic cells AO1

Draw out and label the structure of a chloroplast

A

Chloroplasts also contain circular DNA, 70S ribosomes & starch grains.

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30
Q

Eukaryotic cells AO1

The thylakoid membranes provide a large surface area for more ______________.

A

chlorophyll

this allows MORE light energy to be absorbed during photosynthesis

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31
Q

Eukaryotic cells AO1

The synthesis of glucose as a result of photosynthesis takes place in which part of the chloroplast?

A

Stroma

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32
Q

Eukaryotic cells AO1

Polymer in algal cell wall

A

Cellulose

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33
Q

Eukaryotic cells AO1

Algae are unicellular eukaryotic organisms that can ________________ .

A

Photosynthesise

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34
Q

Eukaryotic cells AO1

Large permanent vacuole function

A

1. Provide support, making cells turgid.

2. Store of sugars and amino acids

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35
Q

Eukaryotic cells AO2

U. marinum cells ingest bacteria and digest them in the cytoplasm.

Describe the role of one named organelle in digesting these bacteria (3 marks).

A

1. Lysosomes;

2. Fuse with vesicle;

3. (Releases) hydrolytic enzymes;

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36
Q

Eukaryotic cells AO1

Give one feature of the chloroplast that allows protein to be synthesised inside the chloroplast and describe one difference between this feature in the chloroplast and similar features in the rest of the cell.

A

Mark in pairs, 1 and 2 OR 3 and 4

1. Ribosomes;

2. Are smaller (70S) than cytoplasmic ribosomes;

OR

3. DNA;

4. Is not associated with protein/histones but nuclear DNA is

OR is circular but nuclear DNA is linear

OR is shorter than nuclear DNA;

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37
Q

Eukaryotic cells AO1

Outline the similarities in the structures of chloroplasts and mitochondria.

A

1. Both double membrane;
2. Both contain (circular) DNA;
3. Both contain ribosomes;

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38
Q

Eukaryotic cells AO1

Outline the differences in the structures of chloroplasts and mitochondria.

A

4. Chloroplasts have thylakoids/grana whereas mitochondria have cristae;
5. Chloroplasts stroma whereas mitochondria matrix;
6. Chloroplasts pigments (chlorophyll) whereas no pigments in mitochondria;
7. Chloroplasts have starch grains whereas mitochondria have no starch grains;

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39
Q

Eukaryotic cells AO1

A

D - Granum/grana/thylakoid(s);

E - starch / lipid;

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40
Q

Eukaryotic cells AO1

A

B;

A;

E;

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41
Q

Eukaryotic cells AO2

Human breast milk is produced and secreted by gland cells. These gland cells have adaptations that include many mitochondria and many Golgi vesicles. The milk contains a high concentration of protein.

Explain the role of these cell adaptations in the production and secretion of breast milk (2 marks).

A
  1. (Many mitochondria) release energy / ATP for movement of vesicles / synthesis of protein / active transport;
  2. (Many Golgi) vesicles transport protein / glycoprotein / milk to cell membrane / out of cell;
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42
Q

Eukaryotic cells AO1

A
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43
Q

Eukaryotic cells AO1

A

B Golgi apparatus / body;

C Mitochondria / mitochondrion;

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44
Q

Eukaryotic cells AO1

Name two structures present in plant cells that are not present in animal cells.

A
  1. Chloroplasts
  2. Cell wall
  3. Cell vacuole
  4. Starch grains
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45
Q

Eukaryotic cells AO1

Chloroplast circular DNA contains nucleotides with which nitrogenous bases

A

Adenine
Thymine
Guanine
Cytosine

It’s DNA, so must contain the classic 4 bases!

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46
Q

Eukaryotic cells AO1

A

A stroma

B granum

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47
Q

Eukaryotic cells AO1

A

W – chloroplast, photosynthesis;

Z – nucleus, contains DNA / chromosomes / holds genetic information of cell.

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48
Q

Eukaryotic cells AO1

Identify X

A

Crista/cristae

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49
Q

Eukaryotic cells AO1

A

L

H

N

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50
Q

Eukaryotic cells AO2

A

Membrane-bound organelle(s)

OR Mitochondrion/mitochondria

OR Vesicle(s)/lysosomes

OR Rough endoplasmic reticulum

OR Nucleus/(double) nuclear membrane/pore(s)/ nuclear envelope;

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51
Q

Eukaryotic cells AO1

Define a tissue

A

Similar specialised cells that perform a specific function

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52
Q

Eukaryotic cells AO1

Define an organ

A

Different tissues that work together to perform a specific / vital function

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53
Q

Eukaryotic cells AO1

Define an organ system

A

Different organs that work together to perform a specific / vital function

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54
Q

Eukaryotic cells AO1

In complex multicellular organisms, eukaryotic cells become _____________ for specific functions.

A

specialised

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55
Q

Eukaryotic cells AO1

Prokaryotic cells are smaller OR larger than eurkaryotic cells

A

Smaller

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56
Q

Prokaryotic cells AO1

Define a prokarytic cell

A

Cells that DO NOT contain a nucleus or membrane-bound organelles

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57
Q

Prokaryotic cells AO1

Describe the structure of DNA in prokaryotic cells

A

no nucleus;

single circular DNA molecule that is free in the cytoplasm;

not associated with proteins/histones;

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58
Q

Prokaryotic cells AO1

Process by which prokarytic cells replicate their DNA

A

Semi-conservative replication

Meselson & Stahl used E.coli (a bacteria) for their experiments

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59
Q

Prokaryotic cells AO1

Glycoprotein that makes up the prokaryote cell wall

A

Murein

(aka peptidoglycan)

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60
Q

Prokaryotic cells AO1

Size of prokaryotic ribosomes

A

70S

This is smaller than cytoplasmic ribosomes in a eukarytic cell

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61
Q

Prokaryotic cells AO1

Extra source of DNA in a prokaryote

A

Plasmid(s)

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62
Q

Prokaryotic cells AO1

Genes typically found in plasmids

A

Genes that benefit prokaryote survival
e.g., antibiotic resistance

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63
Q

Prokaryotic cells AO1

TRUE or FALSE

Prokaryotes can have more than one plasmid

A

TRUE

Prokaryotes have a variable number of plasmids

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64
Q

Prokaryotic cells AO1

Structure that often surrounds the prokaryotic cell

A

Capsule

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65
Q

Prokaryotic cells AO1

Give two structures found in all prokaryotic cells and in all eukaryotic cells.

A
  1. Cell(-surface) membrane;
  2. Ribosomes;
  3. Cytoplasm;
  4. DNA;
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66
Q

Prokaryotic cells AO1

Name two structures found in all bacteria that are not found in plant cells.

A
  1. Circular DNA (molecule in cytoplasm);
  2. Murein cell wall

OR Peptidoglycan cell wall

  1. Smaller/70S ribosomes in cytoplasm;
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67
Q

Prokaryotic cells AO1

TRUE or FALSE:

All prokaryotic cells have one or more flagella.

A

FALSE

Some prokaryotes have NO flagella

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68
Q

Prokaryotic cells AO1

All prokaryotic cells have ___________ ribosomes than eukaryotic cells

A

smaller

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69
Q

Prokaryotic cells AO1

A

Flagellum

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70
Q

Prokaryotic cells AO1

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

A

(70S) Ribosome

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71
Q

Past paper question AO1

A
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72
Q

Prokaryotic cells AO1

A

Second box ticked

B – statements 1, 2 and 4

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73
Q

Prokaryotic cells AO1

A

W – (cell surface) membrane

X – cell wall

Y – capsule

Z – flagellum

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74
Q

Prokaryotic cells AO1

TRUE or FALSE
Prokaryotes can have one or more flagella.

A

TRUE

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75
Q

Eukaryotic cells AO1

Identify organelles S and T

A

S = Vacuole

T = Chloroplast;

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76
Q

Past paper question AO1

Give two features of all prokaryotic cells that are not features of eukaryotic cells.

A

No membrane-bound organelles

Circular DNA OR DNA free in cytoplasm

DNA not associated with proteins/histones

No introns

Murein/peptidoglycan (in) cell wall;

Only have smaller 70S ribosomes

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77
Q

Past paper question AO1

Describe one difference between the structure of DNA in a prokaryotic cell and in a eukaryotic cell.

A

(In prokaryotes)
Circular not linear
OR
Not associated with proteins/histones
OR
No introns;

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78
Q

Structure of viruses (AO1)

Viruses are ________ and non-living.

A

acellular

This means they need a host cell to surivive and reproduce

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79
Q

Structure of viruses (AO1)

Draw out and label the key structures of a virus

A

Structures in red, funtion in black

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80
Q

Structure of viruses (AO1)

Capsid function

A

Protects the viral genome (DNA or RNA)

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81
Q

Structure of viruses (AO1)

Viral genome (DNA or RNA) function

A

Codes for (viral) protein

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82
Q

Structure of viruses (AO1)

RNA viruses (e.g. HIV) contain an enzyme that converts viral RNA into (c)DNA - what is the name of this enzyme?

A

Reverse transcriptase

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83
Q

Structure of viruses (AO1)

Function of viral attachment proteins

A

Binds to receptors (on cell);

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84
Q

Structure of viruses (AO1)

TRUE or FALSE

SOME viruses contain RNA as their genetic material

A

TRUE

These are called retroviruses e.g. HIV

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85
Q

Structure of prokaryotic cells and of viruses (AO1)

A

Capsid and attachment protein

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86
Q

Methods of studying cells (AO1)

Principles of light (aka optical) microscopy

A

A thin specimen is illuminated with light;

This light is focussed using a glass lens;

Magnified and view using the eye piece and objective lenses;

Specimens can be alive or dead;

Cellular structures like the nucleus can be stained with dyes to make them visible;

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87
Q

Methods of studying cells (AO1)

Explain why it is not possible to identify smaller organelles like mitochondria using an optical microscope (2 marks).

A
  1. Wavelength of light is (too) long;
  2. So has a lower resolution
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88
Q

Methods of studying cells (AO1)

A

A section/slice (so nucleus in another part of cell)

OR

(Nucleus) not stained;

A cell is 3D so slicing across the top or bottom may miss the nucleus

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89
Q

Methods of studying cells (AO1)

Give one advantage of viewing a biological specimen using a transmission electron microscope compared with using a scanning electron microscope (1 mark).

A

Higher resolution

OR

View internal structures;

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90
Q

Methods of studying cells (AO1)

Contrast how an optical microscope and a transmission electron microscope work (3 marks).

A
  1. TEM use electrons whereas optical use light;
  2. TEM focuses using magnets whereas optical uses (glass) lenses;
  3. TEM allows a greater resolution;
  4. (So with TEM) smaller organelles / named cell structure (e.g. mitochondria) can be observed
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91
Q

Methods of studying cells (AO1)

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 (3 marks).

A
  1. Add drop of water to (glass) slide;
  2. Obtain thin section (of plant tissue) and place on slide / drop of water;
  3. Stain with / add iodine in potassium iodide.
  4. Lower cover slip using mounted needle.

Allow any appropriate method that avoids trapping air bubbles

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92
Q

Methods of studying cells (AO1)

A student investigated the distribution of stomata on leaves from two species of plant. She removed small pieces from the lower surface of the leaves of each plant species. She mounted these pieces on separate microscope slides. She then counted the number of stomata in several parts of the epidermis on each piece of leaf tissue using an optical microscope.

The pieces of leaf tissue examined were very thin.

Explain why this was important.

A
  1. Single layer(s) of cells;
  2. So light can pass through;
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93
Q

Methods of studying cells (AO1)

A student investigated the distribution of stomata on leaves from two species of plant. She removed small pieces from the lower surface of the leaves of each plant species. She mounted these pieces on separate microscope slides. She then counted the number of stomata in several parts of the epidermis on each piece of leaf tissue using an optical microscope.

Give two reasons why it was important that the student counted the number of stomata in several parts of each piece of leaf tissue.

A
  1. Distribution may not be uniform

OR so it is a representative sample;

  1. To obtain a (reliable) mean;
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94
Q

Methods of studying cells (AO1)

Describe the principles of using a transmission electron microscope to investigate cell structure
(3 marks).

A
  1. Electrons pass through / enter (thin) specimen;
  2. Denser parts absorb more electrons;
  3. (So) denser parts appear darker;
  4. Electrons have short wavelength so give high resolution;
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95
Q

Methods of studying cells (AO1)

Describe the limitations of using a transmission electron microscope to investigate cell structure (3 marks).

A
  1. Cannot look at living material / Must be in a vacuum;
  2. Specimen must be (very) thin;
  3. Artefacts present;
  4. Complex staining method / complex / long preparation time;
  5. Image not in 3D / only 2D images produced.
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96
Q

Methods of studying cells (AO1)

The scientists used a transmission electron microscope to study the structure of the amoeba. Explain why (2 marks).

A
  1. Shorter wavelength of electrons;
  2. So higher resolution;
  3. To see internal structures / organelles / named organelles (e.g. chloroplasts);
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97
Q

Methods of studying cells (AO1)

Give one advantage of using a SEM rather than a TEM.

A

Thin sections do not need to be prepared / shows surface of specimen / can have 3-D images;

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98
Q

Methods of studying cells (AO1)

Describe how the student could use an eyepiece graticule to determine the mean diameter of stomata (3 marks).

A

1. Calibrate eyepiece graticule against stage micrometer;

2. Measure (each stoma) using eyepiece graticule;

3. Take a number of measurements
(to calculate a mean);

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99
Q

Methods of studying cells (AO1)

Define resolution

A

The ability to distinguish between objects that are close together.

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100
Q

Methods of studying cells (AO1)

Define magnification

A

The ability to make an object bigger (when using an optical or electron microscope)

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101
Q

Methods of studying cells (AO1)

Describe the principles of using a scanning electron microscope to investigate cell structure (3 marks).

A
  1. Specimens are NOT sliced
  2. The electrons bounce off the SURFACE of the specimen.
  3. This produces a 3D image / shows the surface of a cell
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102
Q

Methods of studying cells (AO2)

A

1. Nucleus;

2. Nucleolus/nucleoli

OR Nuclear membrane/envelope;

3. Mitochondria/chloroplast contain DNA;

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103
Q

Structure of prokaryotic cells and of viruses (AO1)

Explain why viruses are described as acellular and non-living (2 marks).

A

Mark point 1 (Acellular)
no cell(-surface) membrane;

OR Not made of cells;

Mark point 2 (Non-living)
Cannot (independently) move / respire / replicate /
excrete

OR have no metabolism;

OR have no nutrition;

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104
Q

Methods of studying cells (AO1)

Method for isolating organelles

A

Cell fractionation AND ultracentrifugation

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105
Q

Methods of studying cells (AO1)

Tissues are homogenised to …………

A

break open cells
OR
release organelles

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106
Q

Methods of studying cells (AO1)

The homogenised solution is filtered to…..

A

removes tissue / cells / debris

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107
Q

Methods of studying cells (AO1)

Describe the solution used to isolate organelles

A
  • cold
  • buffered
  • isotonic
    (same water potential)
108
Q

Methods of studying cells (AO1)

Solution is isotonic to…………

A

prevent osmosis
OR
prevent organelles from
shrinking / bursting

109
Q

Methods of studying cells (AO1)

Solution is buffered to…………

A

stop proteins denaturing

110
Q

Methods of studying cells (AO1)

Solution is cold to…………

A

prevent enzyme activity

111
Q

Methods of studying cells (AO1)

Organelle that made up the first pellet after centrifuging at the lowest speed

A

Nucleus / nuclei;

112
Q

Methods of studying cells (AO1)

Describe how a sample of chloroplasts could be isolated from leaves (4 marks).

A

1. Homogenise tissue and filter

2. In cold, isotonic, buffered solution;

3. Centrifuge at low speed AND remove nuclei / cell debris in pellet;

4. Centrifuge at high(er) speed, chloroplasts in the pellet;

113
Q

Methods of studying cells (AO1)

Describe AND explain how you would use cell fractionation and ultracentrifugation to obtain a sample of nuclei from muscle tissue (6 marks).

A

1. Tissues are homogenised to break open cells / release organelles;

2. The solution is filtered to removes tissue / cells / larger debris;

3. Solution is isotonic to prevent osmosis
OR prevent organelles from shrinking / bursting;

4. Solution is buffered to stop proteins denaturing;

5. Solution is cold to prevent enzyme activity;

6. Centrifuge at lower speed to remove nuclei in the pellet

114
Q

Methods of studying cells (AO1)

During cell fractionation explain why biologists use a blender and then filtered the mixture (2 marks).

A

1. Break open cells / release organelles;

2. Remove unbroken tissue / cells / larger debris;

115
Q

Methods of studying cells (AO2)

Explain how ultracentrifugation separates a protein involved in mitosis CENP-W from other molecules (2 marks).

A
  1. Spin (liquid / supernatant) at higher speed;
  2. Molecules / CENP-W separates depending on (molecular) mass / size / density;

Densest molecules/organelles found at bottom of tube.

116
Q

Methods of studying cells (AO2)

Scientists investigated the role of a protein called CENP-W in mitosis. Their method involved cell fractionation and ultracentrifugation.

The scientists began by lysing (breaking open) cells and organelles using a detergent that dissolves lipids in water.

Suggest how the detergent releases CENP-W from cells (2 marks).

A

1. Cell surface membranes made from phospholipid bilyar;

2. Detergent dissolves phospholipid bilayer;

117
Q

Methods of studying cells (AO1)

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 marks).

A
  1. Cold to prevent enzyme activity;
  2. Buffered to prevent denaturing of protein;
  3. Isotonic / same water potential to prevent lysis / bursting (of organelle);
118
Q

Methods of studying cells (AO1)

A
  1. 3D with SEM, but 2D with TEM
    OR
    Only surface visible with SEM, but internal structures visible with TEM;
  2. Electrons bounce off using SEM
    OR
    Electrons pass through using TEM;
119
Q

Methods of studying cells (AO1)

The resolution of an image obtained using an electron microscope is higher than the resolution of an image obtained using an optical microscope.

Explain why.

A

Shorter wavelength between electrons;

OR

Longer wavelength in light rays;

120
Q

Methods of studying cells (AO1)

A student determined the size of a cell structure from a photograph obtained using a microscope.

He used a ruler and a calculator and gave the answer in μm.

Describe how the student determined the size of the structure (2 marks).

A

1. Measure length of structure and divide by magnification;

2. Correct conversion from measured length to µm e.g. ×1000 from mm;

OR

3. Measure (length of structure) and divide by (image) length of scale bar;

4. Multiply by actual length of scale bar;

121
Q

Structure of eukaryotic cells (AO1)

A

1. Magnification show A is bigger than B;
2. A has a nucleus whereas B has free circular DNA;
3. A has mitochondria whereas B does not;
4. A has Golgi body/endoplasmic reticulum whereas B does not;
5. A has no cell wall whereas B has a murein/peptidoglycan cell wall;
6. A has no capsule whereas B has a capsule;
7. A has DNA is bound to histones/proteins whereas B has DNA not associated with histones/proteins
OR
A has linear DNA whereas B has circular DNA;
8. has larger ribosomes;

122
Q

All cells arise from other cells (AO1)

TRUE or FALSE

Within multicellular organisms, all cells retain the ability to divide.

A

FALSE

Stem cells divide by mitosis. Some of these cells then differentiate.

123
Q

All cells arise from other cells (AO1)

Eukaryotic cells that retain the ability to divide show a cell ______________.

A

cycle

124
Q

All cells arise from other cells (AO1)

DNA replication takes place during interphase OR mitosis in the cell cyle?

A

Interphase

During s-phase which stands for semi-conservative replication

125
Q

All cells arise from other cells (AO1)

Draw out and label the cell cycle

A
126
Q

All cells arise from other cells (AO1)

Fill in the missing words:

[1] is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with [2] copies of DNA produced by the parent cell during DNA replication.

A

[1] Mitosis
[2] identical

127
Q

All cells arise from other cells (AO1)

Stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

128
Q

All cells arise from other cells (AO1)

Process where division of the cytoplasm produces two new cells

A

cytokinesis

129
Q

All cells arise from other cells (AO1)

Explain why mitosis is important
(3 marks)

A
  • Growth of multicellular organisms
  • Replacement of cells and repair of tissues
  • Asexual reproduction
130
Q

All cells arise from other cells (AO1)

A

A, D, C, E, B

131
Q

All cells arise from other cells (AO1)

A

Prophase = C
Metaphase = A
Anaphase = D
Telophase = B

132
Q

All cells arise from other cells (AO1)

Homologous chromosomes

A

A pair of chromosomes which contain the same genes but with different alleles

This is what makes cells diploid (2n)

133
Q

All cells arise from other cells (AO1)

Draw out and label a pair of homologous chromosomes after semi-conservative replication.

A

Sister chromatids are held together by the centromere

134
Q

All cells arise from other cells (AO1)

What structure holds sister chromatids together after DNA replication

A

Centromere

135
Q

All cells arise from other cells (AO1)

Describe the structure of a chromosome

A

1. DNA is associated with histones;

2. (During mitosis) chromosome
consists of two sister chromatids joined at a
centromere;

136
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during prophase

A

Chromosomes condense so become visible;

Chromosomes appear as two sister chromatids joined at the centromere;

137
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during metaphase

A

Chromosomes line up on the equator of the cell;

Chromosomes attached to spindle fibres;

By their centromere;

138
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during anaphase

A

The centromere splits / divides;

Sister chromatids / chromosomes are pulled to opposite poles of the cell;

139
Q

All cells arise from other cells (AO1)

Describe the appearance and behaviour of chromosomes during telophase

A

Chromosomes uncoil / become thinner.

140
Q

All cells arise from other cells (AO1)

Organelle that produces spindle fibres

A

centriole

There are two that move to opposite poles during prophase

141
Q

All cells arise from other cells (AO1)

A
  1. Chromosomes (are) becoming visible;
  2. Because (still) condensing;
  3. Chromosomes (arranged) at random/not lined up;
  4. Because no spindle (activity);

OR Because not attached to spindle fibres;

142
Q

All cells arise from other cells (AO1)

A

A

143
Q

All cells arise from other cells (AO1)

Describe what happens to the chromosomes in anaphase (2 marks)

A

Spindle fibres shorten and centromere splits;

Sister chromatids separate;

Sister chromatids pulled to opposite poles of the cell (by spindle fibres);

144
Q

All cells arise from other cells (Maths)

A

1.286

Rate is always DY / DX (time) (read off graph)

DY = 19 - 4 = 15 um
DX = 2500-1800 = 700 secs
min^-1 (per minute), 700 / 60 = 11.67 mins

15 um / 11.67 mins = 1.286 um min^-1

145
Q

All cells arise from other cells (AO1)

A

(D)CBEA.

146
Q

All cells arise from other cells (AO1)

A

1. The (individual) chromosomes are visible because they have condensed;

2. Each chromosome is made up of sister chromatids because DNA has replicated;

3. The chromosomes are not arranged in homologous pairs, which they would be if it was meiosis;

147
Q

All cells arise from other cells (AO1)

What leads to the formation of tumours / cancers.

A

Uncontrolled mitosis

148
Q

All cells arise from other cells (AO1)

What is a tumour?

A
  1. Mass of cells/tissue

OR Abnormal cells/tissue;

  1. (As a result of) uncontrolled mitosis;
149
Q

All cells arise from other cells (AO2)

A

1. 2 nuclei (in cells)

OR Cells (stopped) at telophase;

2. Cytokinesis prevented

OR Stopped cytoplasm dividing;

150
Q

All cells arise from other cells (AO1)

A
151
Q

All cells arise from other cells (AO1)

Process by which prokaryotes divide

A

Binary fission

152
Q

All cells arise from other cells (AO1)

Describe binary fission

A

1. Replication of circular DNA;

2. Replication of plasmids;

3. Division of cytoplasm to produce daughter cells;

153
Q

All cells arise from other cells (AO2)

A

Describe
1. Trend of slowing growth from before birth to 21 days

OR Trend oft decreasing percentage undergoing mitosis from before birth to 21 days

OR (Trend of) decreasing percentage undergoing DNA replication from before birth to 21 days;

Explain
2. DNA replication happens before mitosis

OR Heart growth slowing until (fully) developed

OR These cells lost the ability to divide;

154
Q

All cells arise from other cells (AO2)

A

1. No separation of sister chromatids;

2. Chromatids/chromosomes all go to one pole/end/sides of cell

OR Chromatids/chromosomes not pulled to opposite poles;

3. Doubles chromosome number in cell OR one daughter cell gets no chromosomes or chromatids;

155
Q

Transport across cell membranes (AO1)

Explain the arrangement of phospholipids in a cell-surface membrane (3 marks).

A

1. As a bilayer

2. Phospholipid both hydrophobic and hydrophilic OR Phospholipid polar

3. Triglycerides only hydrophobic
OR Fatty acid/triglyceride is non-polar;

4. Hydrophilic/phosphate group attracts water (to either side of bilayer)

OR Hydrophobic fatty acid tails point away/are repelled from water

156
Q

Transport across cell membranes (AO1)

Explain why the structure of a membrane is described as fluid-mosaic (2 marks).

A

Idea of molecules / named molecules moving (= fluid);

Idea of both proteins and phospholipids (= mosaic);

157
Q

Transport across cell membranes (AO1)

Draw out and label a diagram of the phospholipid bilayer (include different biological molecules)

A
158
Q

Transport across cell membranes (AO1)

Molecule properties to cross cell surface membrane by simple diffusion

A

Lipid-soluble

AND/OR

Non-polar

e.g. hormones, oxygen & carbon dioxide

159
Q

Transport across cell membranes (AO1)

What transport process do channel proteins allow?

A

Facilitated diffusion

160
Q

Transport across cell membranes (AO1)

Receptors are embebbed into the cell surface membrane and have a specific and ___________ shape to only one molecule that binds.

A

complementary

161
Q

Transport across cell membranes (AO1)

Cholesterol role

A

Restricts the movement of other molecules making up the cell surface membrane;

162
Q

Transport across cell membranes (AO1)

A

Q

P

S

163
Q

Transport across cell membranes (AO2)

A

(Similarity)
Both have a phospholipid bilayer OR
Both have protein;

(Differences)
No channel/carrier proteins, whereas fluid mosaic does
OR
Protein layer outside (phospholipids), fluid mosaic is ‘dotted’;
Accept only one type of protein whereas fluid mosaic has many (types)
Cholesterol is not present whereas it is present in fluid mosaic;

164
Q

Transport across cell membranes (AO1)

Channel proteins

A

Specific tertiary structure tertiary;

Allow small polar/charged molecules e.g. ions across the cell surface membrane;

Via faciliated diffusion DOWN a concentration gradient;

165
Q

Transport across cell membranes (AO1)

TRUE or FALSE:
Na+ ions can across the cell surface membrane via calcium ion channels

A

FALSE

166
Q

Transport across cell membranes (AO1)

Carrier proteins

A

Specific tertiary structure tertiary;

Allow polar/charged molecules e.g. glucose across the cell surface membrane;

Via faciliated diffusion AND active transport;

167
Q

Transport across cell membranes (AO1)

TRUE or FALSE

Receptors have active sites

A

FALSE

Receptors have binding sites whereas only enzymes have active sites

168
Q

Transport across cell membranes (AO1)

Diffusion is a ____________ process – it does not require energy from ATP hydrolysis.

A

passive

169
Q

Transport across cell membranes (AO1)

Non-polar, lipid-soluble molecules like oxygen, carbon dioxide and hormones (e.g. oestrogen) can diffuse __________ a concentration gradient and cross the phospholipid bilayer.

A

DOWN

170
Q

Transport across cell membranes (AO1)

Factors that affect simple diffusion

A

Temperature
Surface area
Concentration gradient
Diffusion distance

171
Q

Transport across cell membranes (AO1)

Explain how increasing temperature affects the rate of diffusion.

A

Increase kinetic energy;

So faster movement of molecules;

This leads to a faster rate of diffusion;

172
Q

Transport across cell membranes (AO1)

Explain how increasing surface area affects the rate of diffusion.

A

More cell surface membrane for molecules to pass through;

Therefore a faster rate of diffusion.

173
Q

Transport across cell membranes (AO1)

As a concentration gradient decreases, the rate of diffusion becomes ___________.

A

slower

174
Q

Transport across cell membranes (AO1)

The shorter the diffusion distance, the _______ the rate of diffusion.

A

faster

175
Q

Transport across cell membranes (AO1)

Faciliated diffusion transport proteins

A

Channel proteins
OR
Carrier proteins

176
Q

Transport across cell membranes (AO1)

Facilitated diffusion is a passive process, it does not require ________.

A

ATP

177
Q

Transport across cell membranes (AO1)

Describe how polar substances move across cell-surface membranes by facilitated diffusion (3 marks).

A

1. Via carrier OR channel proteins;

2. Each protein is specific and complementary (to the polar substance being transported);

3. Substance moves down concentration gradient;

178
Q

Transport across cell membranes (AO1)

Factors that affect facilitated diffusion

A

Temperature
Surface area
Concentration gradient
Diffusion distance

179
Q

Transport across cell membranes (AO1)

Explain how an increased surface area affects the rate of faciluated diffusion

A

More cell surface membrane / phospholipid bilayer;

So large number of channel or carrier proteins for faciliated diffusion;

More opportunities for polar molecule to bind to its specific and complemenary receptor;

Faster rate of facilitated diffusion;

180
Q

Transport across cell membranes (AO2)

A

Concentration of sodium ions (outside cell);

As concentration increases so does the rate of (facilitated) diffusion;

181
Q

Transport across cell membranes (AO2)

A

1. Between A and B - Movement through carrier (OR channel proteins);

OR via facilitated diffusion;

2. Between A and B - rate of uptake proportional to external concentration;

3. Between C and D - all channel / carrier proteins in use / saturated / limiting;

182
Q

Transport across cell membranes (AO2)

A

1. Rate of uptake is proportional / does not level off (so diffusion occurring);

Accept as one increases the other increases

2. (Lipid-soluble molecules) diffuse through / are soluble in phospholipid (bilayer);

183
Q

Transport across cell membranes (AO1)

Pure water has the highest water potential and a value of _____ kpa.

A

0

(Zero)

184
Q

Transport across cell membranes (AO1)

Adding a solute (e.g. sucrose) makes the water potential of a solution _________.

A

lower / negative

185
Q

Transport across cell membranes (AO1)

During osmosis, water moves from a [1] water potential to a [2] water potential, [3] a water potential gradient.

A

[1] high

[2] low

[3] DOWN

186
Q

Transport across cell membranes (AO1)

TRUE or FALSE:

Water is a non-polar molecule

A

FALSE

Water is polar so requires aquaporins to cross the cell surface membrane

187
Q

Transport across cell membranes (AO1)

Channel proteins required for osmosis

A

aquaporins

188
Q

Transport across cell membranes (AO1)

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

A

1. Both down a gradient

2. Both passive processes;

OR both do not use energy from ATP;

189
Q

Transport across cell membranes (AO1)

Active transport protein

A

Carrier proteins

190
Q

Transport across cell membranes (AO1)

Active transport only involves [1] proteins.

It involves moving molecules [2] the concentration gradient from low to high.

This requires energy from [3].

A

[1] carrier

[2] AGAINST

[3] ATP hydrolysis

191
Q

Transport across cell membranes (AO1)

TRUE or FALSE:
During active transport, the energy released from ATP hydrolysis changes the tertiary structure of the carrier protein

A

TRUE

192
Q

Transport across cell membranes (AO1)

Name of sites on channel and carrier proteins

A

binding sites

193
Q

Transport across cell membranes (AO1)

Binding sites on channel and carrier proteins are specifc and ________________ to polar molecules

A

complementary

194
Q

Transport across cell membranes (AO1)

Describe the processes of facilitated diffusion AND active transport (3).

A

1. Movement of polar / charged molecues;

2. Faciliated diffusion DOWN a concentration gradient via a channel or carrier protein;

3 Active transport AGAINST a concentration gradient via a carrier protein using energy released from ATP hydrolysis;

195
Q

Transport across cell membranes (AO1)

Cells involved in active transport contain higher numbers of which organelle. Explain why.

A

Mitochondria;

To produce ATP;

Energy from ATP hydrolysis;
(used to change shape of carrier protein)

move molecules against concentration gradient;

196
Q

Cell recognition and the immune system (AO1)

Each type of cell has specific molecules on its surface that identify it. These molecules include proteins and enable the immune system to identify:

A

pathogens;

cells from other organisms of the same species
(e.g. transplants);

abnormal body cells
(e.g. cancer);

toxins;

197
Q

Cell recognition and the immune system (AO1)

Define antigen

A

A foreign molecule / protein;

stimulates an immune response;

results in the production of a specific antibody;

198
Q

Cell recognition and the immune system (AO1)

Is phagocytosis a specific or non-specific immune response?

A

Non-specific

199
Q

Cell recognition and the immune system (AO1)

Which organelle do phagocytes contain many of?

A

Lysosomes

200
Q

Cell recognition and the immune system (AO1)

Describe how a phagocyte destroys a pathogen present in the blood (3 marks).

A

1. Engulfs;

2. Forming vesicle/phagosome and fuses with lysosome;

3. Hydrolytic enzymes hydrolyse the pathogen;

Accept lysozymes for ‘enzymes’

201
Q

Cell recognition and the immune system (AO1)

Which cells stimulate an immune response.

A
  1. Pathogens e.g. bacteria / fungi
  2. Cells from organisms/transplants of the same species;
  3. Abnormal/cancer/tumour (cells);
  4. (Cells) infected by virus;
  5. Antigen-presenting cells
202
Q

Cell recognition and the immune system (AO1)

Describe how phagocytosis of a virus leads to presentation of its antigens (3 marks).

A

1. Phagosome / vesicle fuses with lysosome;

2. (Virus) destroyed by lysozymes / hydrolytic enzymes;

3. Antigens (from virus) are displayed on the cell surface membrane;

203
Q

Cell recognition and the immune system (AO1)

TRUE or FALSE:
The cell-mediated response involves T helper and cytotoxic T cells

A

TRUE

204
Q

Cell recognition and the immune system (AO1)

Which immune cells contain receptors which bind to antigens on antigen-presenting cells during the cellular response?

A

T helper cells

205
Q

Cell recognition and the immune system (AO1)

Roles of T helper cells

A

1) Stimulates B cells to divide by mitosis

2) Stimulates phagocytes

3) Stimulates cytotoxic T cells

206
Q

Cell recognition and the immune system (AO1)

Upon stimulation, what chemicals do T helper cells release?

A

Cytokines

207
Q

Cell recognition and the immune system (AO1)

Which part of the T helper cell is specific and complementary to the shape of the antigen?

A

Receptor

208
Q

Cell recognition and the immune system (AO1)

Cytotoxic T cells destroy which cells?

A

Virally-infected cells;

Cancerous cells;

209
Q

Cell recognition and the immune system (AO1)

Chemical contained by cytotoxic T cells that damages its target cells

A

Perforin

210
Q

Cell recognition and the immune system (AO1)

The humoral response results in the production of ____________ .

A

Monoclonal antibodies

211
Q

Cell recognition and the immune system (AO1)

The humoral response results in the production of ____________ .

A

Monoclonal antibodies

212
Q

Cell recognition and the immune system (AO1)

Upon stimulation, the B cells divide
by _____________ to produce clones.

A

mitosis

213
Q

Cell recognition and the immune system (AO1)

Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen (3 marks).

A

1. Helper T cell cell binds to the antigen (on the antigen-presenting cell / phagocyte);

2. This helper T cell stimulates a specific B cell;

3. B cell divides by mitosis
OR B cell clones;

**4. ** (Forms) plasma cells that release antibodies;

214
Q

Cell recognition and the immune system (AO1)

Primary response

A

B cells differentiate into plasma cells;

which produce and release large quantities of monoclonal antibodies (secreted into the blood);

215
Q

Cell recognition and the immune system (AO1)

Secondary response

A

Some B cells become memory cells;

which persist in the blood;

help to mount a faster immune response upon re-infection;

216
Q

Cell recognition and the immune system (AO1)

Define monoclonal antibody

A

Same tertiary structure produced by identical plasma cells

217
Q

Cell recognition and the immune system (AO1)

Monoclonal antibodies are an example of a ______________ protein

A

quaternary

218
Q

Cell recognition and the immune system (AO1)

The 4 polypeptide chains (2 heavy and 2 light) in an antibody are joined together by _______________.

A

disulphide bridges

219
Q

Cell recognition and the immune system (AO1)

A

‘X’ written at either or both ends of Y shape;

220
Q

Cell recognition and the immune system (AO1)

Describe and explain the role of antibodies in stimulating phagocytosis (2 marks).

A

1. Bind to antigen

OR Accept form (antibody-antigen) complexes/are complementary to antigen

2. (Antibodies) cause clumping/agglutination

OR Attract phagocytes;

221
Q

Cell recognition and the immune system (AO1)

What is formed when an antibody binds to an antigen.

A

Antibody-antigen complex

222
Q

Cell recognition and the immune system (AO2)

NMO is a disease that leads to damage to nerve cells in the spinal cord.

A person with NMO produces anti-AQP4 antibody that attacks only these nerve cells.

Explain why the anti-AQP4 antibody only damages these cells (4 marks).

A
  1. (Anti-AQP4) antibody has a (specific) tertiary structure;
  2. Has binding site that only binds to / complementary to one antigen;
  3. Antigen to this antibody (only) found on these nerve cells;
  4. So, antibody (only) binds to / forms antigen-antibody complex with these nerve cells (causing damage);
223
Q

Cell recognition and the immune system (AO2)

Collagen is a protein produced by cells in joints, such as the knee.

Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease, a person’s immune system attacks their own cells. RA causes pain, swelling and stiffness in the joints.

Scientists have found a virus that produces a protein very similar to human collagen.

Suggest how the immune response to this viral protein can result in the development of RA (2 marks).

A
  1. The antibody against virus (antigen) will bind to collagen;
  2. This results in the destruction of the (human) cells / collagen;
224
Q

Cell recognition and the immune system (AO1)

What does a vaccine contain?

A

A dead / weakened / attenuated form of the pathogen;

Must contain specific antigen or antigens
e.g. an attachment protein on a virus

OFF-SPEC/AO2
mRNA that could be used by ribosomes to produce a specific antigen
e.g. an attachment protein on a virus

225
Q

Cell recognition and the immune system (AO1)

The primary response

After taking a vaccine, stimulation of B cells will lead to mitosis and differentiation into [1] and the production of a small quantity of [2]. [3] cells are also produced.

A

[1] plasma cells

[2] antibodies

[3] Memory

226
Q

Cell recognition and the immune system (AO1)

The secondary response

When a vaccinated person is infected with the actual pathogen, [1] cells will help produce a [2] concentration of antibodies AND [3].

A

[1] memory

[2] higher

[3] faster

227
Q

Cell recognition and the immune system (AO1)

Why do some patient’s receive boosters (a 2nd or 3rd dose of a vaccine)?

A

Produce more memory cells;

So higher concentration of antibodies produced;

At a faster rate;

228
Q

Cell recognition and the immune system (AO1)

Herd immunity

A

When the majority of the population is vaccinated;

Some unvaccinated individuals are also protected;

(this is because) vaccinated individuals are less likely to spread the pathogen to unvaccinated individuals;

229
Q

Cell recognition and the immune system (AO2)

Bacterial meningitis is a potentially fatal disease affecting the membranes around the brain. Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis.

(a) In the UK, children are vaccinated against this disease. Describe how vaccination can lead to protection against bacterial meningitis
(6 marks).

A

1. Antigen on surface of N. meninigitidis / bacterium binds to surface of T helper cell;

2. T helper cell release cytokines / stimulate B cells;

3. (Activated) B cell divides by mitosis;

4. B cells differentiate into plasma cells which release antibodies;

5. (Some) B cells become memory cells;

6. Memory cells produce plasma cells / antibodies faster and at higher concentration;

230
Q

Cell recognition and the immune system (AO1)

What causes antigen variability?

A

random mutations

231
Q

Cell recognition and the immune system (AO1)

What are the consequences of antigen variability on antibody effectiveness?

A

Antigen tertiary structure changes shape;

Antibody binding sites / t cell receptors;

No longer complementary to antigen;

232
Q

Cell recognition and the immune system (AO1)

Vaccines may have negative __________ .

A

side effects

This is a common limitation of AO3 questions involving vaccines

233
Q

Cell recognition and the immune system (AO1)

New vaccines are typically developed and tested using animal models and cell cultures.

Explain why this is a limitation.

A

Even though antibodies may be produced, this does not mean it will have the same positive effect in humans.

234
Q

Cell recognition and the immune system (AO1)

What are the advantages of using animals during vaccine/drug research and development?

A

Stops human suffering through development of useful medicines.

235
Q

Cell recognition and the immune system (AO1)

When testing a new vaccine or drug, a vet closely observes the animals being used. Explain why.

A

A vet could stop the experiment to minimise any suffering;

The experiment may be repeated at lower concentration to reduce side effects

236
Q

Cell recognition and the immune system (AO1)

Give examples of active immunity

A

Natural infection with a pathogen;

Vaccine

237
Q

Cell recognition and the immune system (AO1)

Give examples of passive immunity

A

Maternal antibodies via breast feeding;

Antivenom;
(contains antibodies against a specific pathogen)

238
Q

Cell recognition and the immune system (AO1)

Describe the difference between active and passive immunity (5 marks)

A

1. Active involves memory cells whereas passive does not;

2. Active involves production of antibody by plasma cells / memory cells whereas passive does not;

3. Passive involves antibody introduced into body from outside / named source (e.g. antivenom from horses);

4. Active long term, because antibody produced in response to antigen;

5. Passive short term, because antibody (given) is broken down;

6. Active (can) take time to develop / work whereas passive fast acting.

239
Q

Cell recognition and the immune system (AO2)

When a person is bitten by a venomous snake, the snake injects a toxin into the person. Antivenom is injected as treatment. Antivenom contains antibodies against the snake toxin. This treatment is an example of passive immunity.

Explain how the treatment with antivenom works and why it is essential to use passive immunity, rather than active immunity (2 marks).

A

Antivenom antibodies bind to the toxin / venom / antigen and causes its destruction;

Active immunity would be too slow/slower

OR passive immunity is faster

240
Q

Cell recognition and the immune system (AO2)

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.

A

1. B cells specific to the venom reproduce by mitosis;

2. B cells differentiate into plasma cells and memory cells;

3. The second dose produces antibodies (in secondary immune response) in higher concentration AND faster

241
Q

Cell recognition and the immune system (AO1)

Part of monoclonal antibody that makes it specific

A

Antigen binding site

242
Q

Cell recognition and the immune system (AO1)

What can be attached to a monoclonal antibody?

A

therapeutic drugs (e.g. anti-cancer);

dye / stain / fluorescent marker / enzyme
(e.g. for diagnostics purposes);

243
Q

Cell recognition and the immune system (AO1)

Examples of using monoclonal antibodies for medical treatment

A

Deliver drug by binds to antigens / receptors on specific / cancer cells

OR Block antigens / receptors on cells;

244
Q

Cell recognition and the immune system (AO2)

A

1. Cell engulfs the antibody / ADC

2. Lysosomes fuse with vesicle / phagosome (containing ADC);

3. Hydrolytic enzymes / lysozymes breakdown / digest the antibody / ADC to release the drug;

245
Q

Cell recognition and the immune system (AO2)

The protein ZO-1 is found on the surface of ileum cells.

A scientist used an anti-ZO-1 monoclonal antibody to identify ileum cells in a sample of intestine observed using an optical microscope.

Suggest how the monoclonal antibody helped the scientist to identify ileum cells in the sample of intestine (4 marks).

A

1. ZO-1 is located in cell surface membrane;

2. Antibody is complementary (to ZO-1);

3. Binds to the ZO-1/protein;

Accept ‘forms antigen-antibody complex’

4. (Cells identified with) dye / stain / fluorescent marker linked to antibody;

246
Q

Cell recognition and the immune system (AO1)

Number of monoclonal antibodies required for an ELISA test

A

2

247
Q

Cell recognition and the immune system (AO1)

Describe the role of antibodies in producing a positive result in an ELISA test (4 marks).

A

1. First antibody binds / complementary (in shape) to antigen;

2. Second antibody with enzyme attached is added;

3. Second antibody binds to antigen;

4. Substrate added and colour changes;

248
Q

Cell recognition and the immune system (AO1)

False positive

A

Test is positive but there is NO antigen / pathogen present

249
Q

Cell recognition and the immune system (AO1)

False negative

A

Test is negative but there IS antigen / pathogen present

250
Q

Cell recognition and the immune system (AO2)

A

1. Cancer / fused cells divide / replicate rapidly / uncontrollably;

Accept mitosis

2. B cells produce monoclonal antibody;

251
Q

Cell recognition and the immune system (AO1)

A

A = Attachment protein;

B = Capsid

252
Q

Cell recognition and the immune system (AO1)

Describe the structure of the human immunodeficiency virus (HIV) (4 marks).

A

1.   RNA genome;
2.   Reverse transcriptase;
3.   Capsid;
4.   Phospholipid viral envelope;
5.   Attachment proteins;

253
Q

Cell recognition and the immune system (AO1)

Specific cell that HIV infects

A

T helper cell

254
Q

Cell recognition and the immune system (AO1)

HIV attachment protein binds to a ______________ on the T helper cell

A

receptor

Note: receptors are proteins with a specific tertiary structure

255
Q

Cell recognition and the immune system (AO1)

An individual is ‘HIV positive’ when the viral DNA is ______________ into the T helper cell genome

A

inserted

256
Q

Cell recognition and the immune system (AO1)

Describe how HIV is replicated
(4 marks)

A

1. Attachment proteins bind to receptors on helper T cell;

2. RNA enters cell;

3. Reverse transcriptase converts RNA to viral DNA;

4. DNA inserted into (helper T cell) DNA/chromosome/genome/nucleus;

5. Viral DNA converted to mRNA during transcription

6. New viral protein / capsid / enzymes produced via translation;

7. Virus (particles) assembled and released (from cell);

257
Q

Cell recognition and the immune system (AO1)

TRUE or FALSE:

A virus with a double-stranded DNA genome requires reverse transcriptase

A

FALSE

The virus already has DNA, so no need to convert RNA into DNA

258
Q

Cell recognition and the immune system (AO1)

Describe how the human immunodeficiency virus (HIV) is replicated once inside helper T cells (4 marks).

A

1. Reverse transcriptase converts RNA to viral DNA;

2. DNA inserted into (helper T cell) DNA/chromosome/genome/nucleus;

3. Viral DNA converted to mRNA during transcription

4. New viral protein / capsid / enzymes produced via translation;

5. Virus (particles) assembled and released (from cell);

259
Q

Cell recognition and the immune system (AO1)

What happens to t helper cells infected with HIV?

A

Destroyed;

Number of cells decrease;

260
Q

Cell recognition and the immune system (AO1)

What condition develops when T helper cells falls below a critical threshold?

A

AIDS

Acquired Immunodeficiency Syndrome

261
Q

Cell recognition and the immune system (AO1)

How can AIDS be diagnosed?

A

Lower / decreasing number of T helper cells;

Using ELISAs to measure the concentration of HIV antibodies / antigens;

262
Q

Cell recognition and the immune system (AO1)

Explain how HIV affects the production of antibodies when AIDS develops in a person (3 marks).

A

1. Because HIV destroys / reduces number of helper T cells;

2. Few / no B cells activated / stimulated

OR (So) few/no B cells undergo mitosis / differentiate / form plasma cells;

3. Less antibody produced;

263
Q

Cell recognition and the immune system (AO2)

In Europe, viruses have infected a large number of frogs of different species. The viruses are closely related and all belong to the Ranavirus group.

Previously, the viruses infected only one species of frog.

Suggest and explain how the viruses became able to infect other species of frog (2 marks).

A

1. Mutation in the viral DNA/RNA/genome/genetic material;

2. Altered tertiary structure of viral attachment protein;

Accept causes antigenic variability

3. Allows it/attachment protein/virus to bind to receptors of other species;

264
Q

Cell recognition and the immune system (AO1)

How do antibiotics work?

A

Preventing bacteria from synthesising murein cell walls;

Directly damaging murein cell wall;

(Some) inhibit binary fission by preventing DNA replication and protein synthesis;

265
Q

Cell recognition and the immune system (AO1)

Give one reason why antibiotics are not effective against viruses.

A

Do not have a cell wall/murein;

OR

Do not have bacterial structures/enzymes

OR

Do not have metabolic processes

266
Q

Cell recognition and the immune system (AO2)

Human papilloma virus infects cells that are no longer dividing. The human papilloma virus genome contains genes that code for proteins that cause human cells to restart their cell cycles.

Human papilloma virus infection can cause cancer.

Explain why.

A

Uncontrolled cell cycle / division / mitosis;

Y1 AQA Biology - Burnley College (2024-25) (3 decks)

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