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A-Level Biology AQA > 2. Cells > Flashcards

2. Cells Flashcards

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1
Q

when drawing a graph, which axis does the independent variable go on?
which axis does the dependent variable go on?

A

independent variable goes on the x axis
dependent variable goes on the y axis

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2
Q

name four examples of eukaryotes

A

plants, animals, algae, fungi

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3
Q

name an example of a prokaryote

A

bacteria

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4
Q

draw and label an animal cell

A
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5
Q

draw and label a plant cell

A
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6
Q

state two differences between fungal cells and plant cells

A
  • fungal cells have no chloroplasts, as they dont photosynthesise
  • fungal cell walls are made of chitin, not cellulose
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7
Q

what is the function of the cell surface membrane?
what does the cell surface membrane contain? + what does this allow it to do?

A
  • the function of the cell membrane is to regulate the movement of substances into and out of the cell
  • the cell membrane contains receptor molecules that allows it to respond to chemicals like hormones
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8
Q

draw and label a nucleus

A
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9
Q
  • what are the gaps in the nuclear envelope called?
  • what do these gaps allow?
A
  • nuclear pores
  • allows substances like mRNA to move between the nucleus and the cytoplasm
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10
Q

what is the function of the nucleolus

A

making rna and ribosomes

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11
Q
  • what is the general function of the nucleus?
  • what reaction is the nucleus involved in?
A
  • to store the cells genetic information
  • protein synthesis
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12
Q

draw and label a mitochondrion

A
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13
Q

what is the function of cristae

A

to provide a large surface area for respiration and the attachment of enzymes

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14
Q

what is the function of the mitochondria?

A
  • the site of aerobic respiration where ATP is produced
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15
Q

provide 3 examples of cells with a high energy requirement and state what they require energy for

A
  • muscle cells require energy for contraction
  • liver cells require energy for metabolism
  • secretary cells require energy for the production of proteins and hormones
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16
Q

draw and label a chloroplast

A
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17
Q
  • what do thylakoid membranes stack up to form?
  • what are the stacked thylakoid membranes linked by? + what are these?
A
  • thylakoid membranes stack up to form grana
  • grana are linked by lamellae, which are thin, flat peices of thylakoid membrane
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18
Q

what is the dna in chloroplasts not attached to?

A

histone proteins

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19
Q
  • what is the function of chloroplasts?
A
  • chloroplasts are the site of photosynthesis
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20
Q
  • what do thylakoid membranes do?
A
  • thylakoid membranes contain chlorophyll to absorb light
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21
Q

what is the function of grana?

A

increase the surface area for light absorption in the chloroplast

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22
Q

draw and label the golgi apparatus

A
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23
Q

what are the functions of the golgi apparatus? [3]

A
  • to process and package lipids
  • to modify simple polypeptides from the RER into functional proteins and package them into vesicles for transportation
  • to make lysosomes
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24
Q

what is the function of golgi vesicles

A

to store lipids and proteins made by the golgi apparatus and transport them out of the cell via the cell membrane - exocytosis

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25
Q

what are lysosomes a type of?

A

golgi vesicle

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26
Q

what is the function of lysosomes?

A

-to bind to phagosomes and release digestive enzymes called lysozymes that digest invading cells and hydrolyse worn out organelles

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27
Q

describe the structure of a ribosome

A

contain one small unit atop one large unit

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28
Q

what are ribosomes made up of?

A

proteins and rRNA

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29
Q

are ribosomes membrane bound?

A

no

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30
Q

what is the function of ribosomes?

A

they are the site of protein synthesis

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31
Q

draw a rough endoplasmic reticulum

A
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32
Q

what is the function of the rough endoplasmic reticulum?

A

to transport simple polypeptides made at the ribosomes

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33
Q

what is the function of the smooth endoplasmic reticulum?

A

to synthesise and transport lipids

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34
Q

what is the cell wall made of in plants and algae?

A

cellulose

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35
Q

what is the cell wall made of in fungi?

A

chitin

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36
Q

what is the function of the cell wall?

A

to support and strengthen the cell, and prevent it from changing shape

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37
Q

what do vacuoles contain? what is this?

A

vacuoles contain cell sap, which is a weak solution of sugar and salt

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38
Q

what is the surrounding membrane of the vacuole called?

A

the tonoplast

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39
Q

what is the function of the vacuole? [2]

A
  • to maintain pressure in the cell and keep it rigid
  • to act as a storage site for the cell
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40
Q

define what is meant by differentiation

A

the process by which cells become speciallised

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41
Q

in what order are speciallised cells organised?

A

cells > tissues > organs > organ systems

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42
Q

what is a tissue?
what is an organ?
what is an organ system?

A
  • a tissue is a group of similar cells working together to perform a particular function
  • an organ in a group of different tissues working together to perform a particular function
  • an organ system is a group of different organs working together to perform a particular function
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43
Q

where are epithelial cells found?

A

the lining of the small intestine

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44
Q

what are epithelial cells speciallised to do?

A

absorb food efficiently

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45
Q

where are villi found? and what do they do?

A

villi are found on the surface of the small intestine, and they increase the surface area for absorption

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46
Q

where are microvilli found and what are they? + what do they do?

A
  • microvilli are found on the surface of villi, and are folds in the cell membranes of epithelial cells
  • microvilli increase the surface area for absorption
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47
Q

why do epithelial cells have lots of mitochondria

A

to provide energy from aerobic respiration and the production of ATP for the active transport of chemicals and digested food molecules into the cell

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48
Q

draw and label a prokaryotic cell

A
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49
Q

what is a prokaryotic cell wall made out of?

A

murein

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50
Q

what is the function of plasmids?

A

the store dna and transfer dna between prokaryotic cells

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51
Q

what is the function of the circular dna molecule in prokaryotic cells

A

to store genetic material

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52
Q

what is the function of the flagellum?

A

to rotate and allow movement in prokaryotic cells

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53
Q

what features do all prokaryotic cells have?

A
  • no membrane bound organelles
  • 70S ribosomes
  • a murein cell wall
  • a cell surface membrane and a circular dna molecule
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54
Q

state six differences between prokaryotes and eukaryotes

A
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55
Q

recall the steps for binary fission

A
  • the circular dna molecule and the plasmids replicate
  • the cell gets bigger and the DNA loops move to opposite ends of the cell
  • the cytoplasm begins to divide and new cell walls begin to form
  • the cytoplasm divides and two new daughter cells are produced.
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56
Q

why are the daughter cells produced during binary fission not identical?

A

because they can have a variable number of copies of plasmids

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57
Q

draw and label a virus

A
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58
Q

state five reasons why viruses are acellular

A
  • they are not made up of cells
  • they have no cell surface membrane
  • they have no organelles
  • they cannot respire
  • they have no metabollic reactions
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59
Q

how do viruses enter living cells?

A

by attaching to host cells by using their attachment proteins

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60
Q

what features do all viruses contain?

A

genetic material
capsid
attachment proteins

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61
Q

what is the function of the genetic material in viruses

A

to code for the viral protein

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62
Q

what is the function of the capsid in viruses

A

to protect the genetic material

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63
Q

what is the function of attachment proteins in viruses

A

to bind to receptors on cells

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64
Q

draw and label a typical hiv virus

A
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65
Q

recall the steps of viral replication

A
  • viruses use their attachment proteins to bind to complementary receptors on the surface of host cells
  • viruses inject their genetic material into the host cell
  • the virus uses the host cells organelles to make more viral particles
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66
Q

define what is meant by magnification

A

how much larger the image is than the specimen

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67
Q

define what is meant by resolution

A

the smallest distance between two points whereby the two points can still be distinguished

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68
Q

what is the formula for calculating magnification

A

magnification = image size / actual size

I
A M

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69
Q

draw a diagram that depicts how you would convert from nm to cm

A
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70
Q

draw a diagram that depicts how you would convert from nm2 to cm2

A
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71
Q

what do light microscopes use to view specimens? + how do they do it?

A

lenses focus a beam of light

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72
Q

why do light microscopes have a lower resolution than electron microscopes?

A

because the wavelength of light is too long

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73
Q

state 3 advantages of using a light microscope instead of an electron microscope

A
  • they can see colour
  • simple staining procedure
  • can view living specimens
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74
Q

how do transmission electron microscopes view specimens?

A

they focus a beam of electrons through the specimen

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75
Q

why are samples non-living when using electron microscopes

A

because they are placed in a vacuum

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76
Q

do transmission electron microscopes produce 2D or 3D images?

A

2D

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77
Q

how do scanning electron microscopes view specimens?

A

they focus a beam of electrons onto the specimen

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78
Q

which type of electron microscope has the higher resolution? transmission or scanning?

A

transmission electron microscopes

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79
Q

do scanning electron microscopes produce 2D or 3D images?

A

3D

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80
Q

compare the use of light microscopes, transmission electron microscopes and scanning electron microscopes [6]

A
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81
Q

state the steps to produce a temporary mount

A
  • pipette a small drop of water onto the microscope slide
  • use tweezers to add a thin layer of cells on top of the water droplet on the microscope slide
  • add a drop of stain (iodine) to the cells
  • lower the coverslip using a mounted needle and push down gently
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82
Q

why is a drop of water added to the microscope slide when producing a temporary mount?

A

to help the specimen stick to the slide

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83
Q

why is a thin layer of cells placed onto the microscope slide?

A

to allow light to pass through

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84
Q

why is a stain added to the specimen when preparing a temporary mount?

A

so that the organelles can be viewed

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85
Q

why is the coverslip lowered using a mounted needle and pushed down gently when producing a temporary mount?

A

to remove air bubbles that will obstruct the view of the specimen
and to avoid breaking the coverslip

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86
Q

what device would we use to work out the scale of an eyepiece graticule?

A

a stage micrometer

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87
Q

usually, what is the value of each stage micrometer unit?

A

0.01mm

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88
Q

what is the process of using a stage micrometer to deduce the scale of an eyepiece graticule called?

A

calibration

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89
Q

what is the purpose of cell fractionation?

A

to separate organelles so they can be viewed

90
Q

state the three steps involved in cells fractionation

A

homogenisation
filtration
ultracentrifugation

91
Q

what is the purpose of homogenisation

A

to break open cell membranes so that organelles can be retrieved

92
Q

what is murein an example of?

A

a glycoprotein

93
Q

why must the solution used during filtration be ice cold?

A

to reduce enzyme activity and prevent enzymes digesting organelles

94
Q

why must the solution used during filtration be isotonic?

A

to prevent water flowing into and out of the cell by osmosis, which would cause the cell to shrink or burst

95
Q

why must the solution used during filtration be buffered?

A

to maintain pH and prevent the denaturing of the tertiary structure of proteins

96
Q

why is the solution filtered after homogenisation?
what is the solution filtered through?

A
  • to separate large cell debris from the organelles
  • the solution is filtered through gauze
97
Q

what is the purpose of ultracentrifugation

A

to separate a particular organelle from the others

98
Q

summarise the process of ultracentrifugation

A

pour the cell solution into a centrifuge tube and place into the centrifuge
spin at low speed and large (heavier) organelles like nuclei settle at the bottom of the tube in a thick sediment called the pellet. the rest of the organelles stay suspended in the fluid above the sediment called the supernatant.
the supernatant is poured into another tube, and spun in the centrifuge again at a higher speed. again, the heavier organelles, this time things like mitochondria and chloroplasts, form a pellet at the bottom of the tube. the supernatant is poured into another tube and spun again at an even higher speed.
this process continues until all the organelles get separated out, the lightest of which being the ribosomes.

99
Q

what are the two ways a eukaryotic cell can divide

A

mitosis
meiosis

100
Q

what type of cells does mitosis produce?

A

genetically identical daughter cells

101
Q

what is mitosis needed for? [2]

A
  • the growth of multicellular organisms
  • the repair of damaged tissues
102
Q

name the different stages of the cell cycle

A

G1, S, G2, Mitosis

103
Q

how long is each stage in the cell cycle?

A

G1 = 10 hours
S = 9 hours
G2 = 4 hours
Mitosis = 1 hour

104
Q

what happens during the G1 phase of the cell cycle?

A

the cell grows and organelles and proteins are made

105
Q

what happens during the G2 phase of the cell cycle?

A

the cell continues to grow and the proteins needed for cell division are made

106
Q

what happens during the S phase of the cell cycle?

A

the cell replicates its DNA in preparation for mitosis

107
Q

what stages of the cell cycle are involved in interphase?

A

G1, S, G2

108
Q

in general, what happens during interphase?

A

the cells dna is replicated to double its genetic content

109
Q

do all cells in multicellular organisms maintain their ability to divide?

A

no

110
Q

does interphase happen before or after mitosis?

A

before

111
Q

what are the four stages of mitosis called?

A

prophase, metaphase, anaphase, telophase

112
Q

what happens during prophase?

A
  • the chromosomes condense from chromatin and become more visible as two chromatids joined at the centromere
  • the centrioles move to opposite poles of the cell and begin to form spindles
  • the nuclear envelope breaks down and the chromosomes lie free in the cytoplasm
113
Q

what happens during metaphase?

A

the chromosomes line up along the equator of the cell attached to spindle fibres by their centromeres

114
Q

what happens during anaphase?

A

the centromeres divide, separating each pair of sister chromatids
- the spindles contract, pulling the chromatids to opposite poles of the cell

115
Q

what happens during telophase

A
  • the chromatids reach opposite poles on the spindle
  • the chromatids uncoil and become long and thin again, they are now referred to as chromosomes again
  • a nuclear envelope forms around each group of chromosomes, so now there are two nuclei
  • cytokinesis (division of the cytoplasm)
116
Q

draw a diagram to depict prophase happening in a cell

A
117
Q

draw a diagram to depict metaphase happening in a cell with four chromosomes

A
118
Q

draw a diagram to depict anaphase happening in a cell

A
119
Q

draw a diagram to depict telophase happening in a cell

A
120
Q

what is the process of mitosis controlled by? + what would happen if these were to mutate?

A
  • genes
  • if the genes were to mutate, uncontrolled cell division would occur
121
Q

what can uncontrolled cell division lead to?

A

the formation of tumours and cancers

122
Q

what is a cancer?

A

a tumour that invades surrounding tissue

123
Q

what is a disadvantage of cancer treatments?

A

they can kill normal healthy body cells too

124
Q

do tumour cells divide more or less frequently than normal body cells?

A

tumour cells divide more frequently than normal body cells

125
Q

what is an advantage of tumour cells dividing more frequently than normal body cells?

A

the cancer treatments are more likely to kill the tumour cells, since there are more of them

126
Q

what part of the cell cycle does chemotherapy affect? + how does it do this?

A
  • chemotherapy affects the G1 phase
    this is because it prevents the synthesis of the enzymes needed for dna replication, so the cell is unable to enter the S phase.
  • as the cell is unable to enter the S phase, it disrupts the cell cycle, thus killing the cell.
127
Q

which part of the cell cycle do radiation drugs affect? + how do they do this?

A
  • radiation drugs affect the S phase of the cell cycle.
  • this is because they damage DNA, so when the cell detects this damage to the DNA it will kill itself, thus preventing tumour growth.
128
Q

how is the mitotic index calculated?

A
129
Q

what kind of substances can pass through cell membranes?

A

small, lipid soluble, non polar substances can travel through cell membranes

130
Q

what substances enable particles that are not small, lipid soluble or non polar to travel through the cell membrane?

A

channel and carrier proteins

131
Q

why are the phospholipids arranged in a bilayer in cell membranes?

A
  • the hydrophillic phosphate heads attract water and the hydrophobic fatty acid tails repel water
  • this means the phosphate heads will face outwards towards the water on the outside of the cell, whereas the fatty acid tails will face inwards as unlike the phosphate heads they repel water
132
Q

why is the phospholipid bilayer described as fluid?
why is the phosphate bilayer described as mosaic?

A
  • the phospholipid bilayer is described as fluid because the phospholipids are constantly moving to allow substances to pass through
  • the phospholipid bilayer is described as mosaic because the membrane contains lots of proteins, making it appear like a mosaic design
133
Q

what is the purpose of carrier proteins?

A

to transport larger substances into and out of the cell

134
Q

what is the purpose of channel proteins?

A

to allow specific ions or molecules to pass through the membrane

135
Q

what is the function of glycoproteins?

A

glycoproteins are involved in cell recognition

136
Q

what is the function of glycolipids

A

glycolipids are involved in maintaining the stability of the cell membrane

137
Q

what do receptor proteins on the cell surface do?

A

allow the cell to detect chemicals released from other cells eg hormones

138
Q

what is the function of cholesterol in cell membranes? [2]

A
  • to restrict the movement of phospholipids to make the cell less fluid and more rigid
  • to maintain the shape of animal cells
139
Q

what does the bilayer allow to be maintained on the other side of the cell?

A

a different environment

140
Q

what does the fluidity of the cell membrane allow it to do?

A

form vesicles and fuse with other membranes

141
Q

what does it mean if a process is passive?

A

no energy is required for it to happen

142
Q

define what is meant by diffusion

A

the net movement of particles from an area of higher concentration to an area of lower concentration down the concentration gradient

143
Q

state and explain 4 factors that can affect the rate of diffusion

A
  • the concentration gradient = the steeper the concentration gradient, the faster the rate of diffusion
  • the diffusion distance = the shorter the diffusion distance, the faster the rate
  • the size of the molecules = smaller molecules diffuse more quickly as they pass through the gaps between the phspholipids easier and have more kinetic energy
  • surface area = the larger the surface area for diffusion to occur, the faster the rate of diffusion
144
Q

how does the number of channel/carrier proteins affect the rate of facilitated diffusion?

A

as the number increases, the rate increases.
however, the rate may become constant, as diffusion cannot happen any faster due to channel/carrier protein availability becoming limiting

145
Q

what structures do molecules travel through the membrane by during facilitated diffusion?

A

channel and carrier proteins

146
Q

what substances do carrier proteins support?

A

large molecules

147
Q

what substances do channel proteins support?

A

water soluble, charged substances

148
Q

how do carrier proteins transport substances across the cell membrane?

A
  • a large molecule attaches to a carrier protein
  • this causes the carrier protein to change shape
  • protein then releases the molecule on the other side of the cell membrane
149
Q

how do channel proteins transport substances across the cell membrane?

A

by forming hydrophillic pores

150
Q

why are kidney dialysis machines kept at 40 degrees celsius?

A
  • to increase the rate of diffusion
  • to prevent increases in the viscosity of blood (blood clotting)
151
Q

why does kidney dialysis fluid flow in the opposite direction to the patients blood flow? + what is this known as?

A
  • to maintain the concentration gradient between the dialysis fluid and the patients blood
  • this is known as counter flow
152
Q

in dialysis machines, what would happen if the dialysis fluid flowed in the same direction as the patients blood? + what would this be called?

A
  • this would result in the concentration gradient between the dialysis fluid and the patients blood not being maintained all the way down the dialysis machine
  • this would be called con-current flow
153
Q

define what is meant by osmosis

A
  • the movement of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential
154
Q

define what is meant by water potential

A

the number of free water molecules in a solution

155
Q

define the term isotonic

A

the solutions are the same water potential
(think isosceles triangle - two sides are the same length)

156
Q

define what is meant by hypertonic

A

a very concentrated solution with a lower water potential
(think hyperactive, giddiness as a result of excess sugar = concentrated solution)

157
Q

define what is meant by hypotonic

A

a dilute solution with a higher water potential
(think hypothermia, you get too cold as a result of too much cold WATER )

158
Q

state and explain three factors that affect the rate of osmosis

A
  • water potential gradient = the higher the water potential gradient, the faster the rate of osmosis
  • thickness of the exchange substance = the thinner the exchange surface, the faster the rate of osmosis
  • the surface area = the larger the surface area, the faster the rate of osmosis
159
Q

what happens when animal cells are placed in a solution with a lower water potential?

A

water will move out of the cell by osmosis, causing the cell to shrivel up

160
Q

what happens when animal cells are placed in a solution with a higher water potential?

A

water will flow into the cell by osmosis, causing the cell to swell and eventually burst

161
Q

what happens when plant cells are placed in a solution with a lower water potential

A
  • water will leave the cell by osmosis, causing the vacuole to decrease in size
  • this causes the cytoplasm to pull away from the cell wall, causing the cell to become plasmolysed, and wilt
162
Q

what happens when plant cells are placed in a solution with a higher water potential?

A
  • water will enter the cell by osmosis, causing the vacuole to increase in size and the cytoplasm to push against the cell wall.
  • this causes the cell to become turgid, allowing it to provide support for the plant
163
Q

when plant cells become turgid, why do they not eventually burst like animal cells?

A

because plant cells have a cell wall that helps them maintain their shape, unlike animal cells that do not have a cell wall

164
Q

define what is meant by active transport

A

the active movement of substances against the concentration gradient, from an area of low concentration to an area of high concentration, requiring energy from respiration

165
Q

why is active transport an active process

A

because energy is required to move substances against a concentration gradient
- this energy comes from the hydrolysis of ATP from respiration

166
Q

what type of proteins are used during active transport

A

carrier proteins

167
Q

what are co-transporters? ? + how do they work?

A

co transporters are a type of carrier protein that binds two molecules at the same time
- the concentration gradient of one molecule is used to move the other molecule against its concentration gradient

168
Q

state three factors that affect the rate of active transport

A
  • the speed of the carrier proteins = the faster they work, the faster the rate
  • the number of carrier proteins present
  • the rate of respiration of the cell/atp availability = if respiration is inhibited, active transport cannot take place.
169
Q

define what is meant by a pathogen

A

a microorganism that causes disease

170
Q

define what is meant by an antigen

A

a foreign protein that generates a specific immune response

171
Q

what types of molecules are the immune system able to identify

A
  • pathogens
  • cells from other organisms
  • abnormal body cells eg cancer cells
  • toxins
  • macrophages
172
Q

what is a phagocyte?

A

a type of white blood cell that carries out phagocytosis

173
Q

describe the process of phagocytosis

A
  • a phagocyte recognises the foreign antigens on a pathogens surface
  • the membrane and cytoplasm of the phagocyte move around the pathogen, engulfing it
  • the pathogen is now contained in a phagocytic vacuole (phagosome) in the phagocyte
  • a lysosome fuses with the phagosome and releases lysozymes to break down and hydrolyse the pathogen
  • the phagocyte then presents the pathogens antigens on its cell surface membrane
174
Q

describe the cell mediated (cellular) response

A
  • receptor proteins on helper T cels bind to complimentary antigens presented to it by phagocytes
  • this binding activates the T cell
  • the T cell then divides by mitosis
  • helper T cells also release chemicals called cytokines
  • cytokines stimulate the differentiation of T cells into cytotoxic T cells and phagocytes
  • cytokines also activate B cells and memory B cells
  • cytotoxic T cells destroy abnormal or infected cells
  • B cells divide by mitosis into plasma cells that can release antibodies
  • antigen-antibody complexes form, and antigens agglutinate so phagocytosis can engulf more antigens at once
175
Q

what chemicals do helper T cells release?

A

cytokines

175
Q

what do cytokines do?

A
  • they activate cytotoxic T cells
  • they form memory B cells
  • they activate phagocytes and B cells
176
Q

what do cytotoxic T cells do?

A

destroy abnormal or infected cells

177
Q

what can B cells do?

A

divide by mitosis into plasma cells that release antibodies

178
Q

what is an antibody?

A

a protein found in the blood that is produced by plasma cells and binds to antigens to form antigen-antibody complexes as part of the immune response

179
Q

describe the humoral response

A
  • when an antibody on the surface of a B cell meets a complementary antigen it binds to it, forming an antigen-antibody complex
  • this binding, along with the release of cytokines, activate the B cell and allow it to divide by mitosis to form plasma cells
  • plasma cells secrete lots of antibodies specific to the antigen called monoclonal antibodies
  • since antibodies have two binding sites, antigens attached to pathogens attach to the binding sites and cause the pathogens to agglutinate
  • this allows phagocytosis to destroy multiple pathogens at once
180
Q

draw and label an antibody

A
181
Q

what happens when an antigen enters the body for the first time? + what is this called?

A
  • it activates the immune system
  • this is called the primary immune response
182
Q

why is the primary immune response slow?

A

because there arent many B cells that can make the complementary antibody needed to bind to the antigen

183
Q

what do helper T cells and B cells produce after being exposed to an antigen? + what do these do?

A
  • they produce memory cells
  • memory cells remain in the body for a long time and remember the specific antibody needed to bind to an antigen
184
Q

describe the primary immune response

A
  • when an antigen enters the body for the first time, it activates the immune system
  • it is slow because there arent many B cells that can make the antibody needed to bind to it
  • eventually, the body will produce enough of the right antibody, but before this the person will show symptoms of the disease
  • after being exposed to the antigen, T and B cells will produce memory cells that remain in the body for a long time and remember the specific antigen and the type of antibody needed to bind to it
185
Q

what happens when an antigen re-enters the body? + what is this known as?

A
  • when an antigen re-enters the body, the immune system produces a quicker and stronger immune response
  • this is known as the secondary immune response
186
Q

why is the secondary immune response faster than the primary immune response?

A

because clonal selection happens faster and memory cells are activated and divide into plasma cells that produce the right antibody for the pathogen

187
Q

describe the secondary immune response

A
  • if the same antigen enters the body again, the immune system will produce a quicker, stronger response
  • clonal selection happens faster, and memory cells are activated and divide into plasma cells that produce the right antibody for the pathogen
  • antigen-antibody complexes can forn much faster
188
Q

what do vaccines contain? + what do these stimulate?

A
  • vaccines contains antigens attached to a dead or attenuated form of a pathogen
  • these stimulate the production of antibodies against a specific antigen, and memory cells that will remember the antigen if infected again (all without the pathogen causing disease)
189
Q

what do vaccines allow?

A

vaccines allow people to become immune without experiencing any symptoms of the disease

190
Q

how may vaccines be taken?

A

they can be injected or taken orally

191
Q

what are the disadvantages of taking vaccines orally?

A
  • they can be broken down by enzymes in the gut
  • the molecules of the vaccine may be too large to be absorbed by the blood
192
Q

how can vaccines reduce the occurence of a disease? + what is this called?

A
  • those not vaccinated are less likely to catch the disease, as there are less people to catch the disease from
193
Q

describe what antigenic variability is and how it affects immunity

A
  • some pathogens can change their surface antigens
  • so the memory cells produced after being exposed to the original antigen wont recognise the different antigen
  • this means the immune system has to carry out the primary response again
194
Q

name 2 pathogens that display antigenic variation

A

hiv virus
influenza virus

195
Q

what can immunity be?

A

passive or active

196
Q

state and explain the two types of active immunity

A

natural = when your body becomes immune after catching a disease
artificial = when you rbody becomes immune after you have been given a vaccination containing the antigen

197
Q

what is passive immunity?

A

the type of immunity you get when you are given antibodies made by a different organism

198
Q

state and explain the two types of passive immunity?

A

natural = when a baby becomes immune due to antibodies it receives from its mother (through the placenta or breast milk)

artificial = when you become immune after being injected with antibodies from someone else

199
Q

state four differences between active and passive immunity

A
200
Q

what are monoclonal antibodies?

A

antibodies with the same tertiary structure, produced by genetically identical B cells

201
Q

what are the antigens found on cancer cells called?

A

tumour markers

202
Q

describe how monoclonal antibodies can be made to treat cancer cells

A
  • cancer cells have antigens on their surface called tumour markers that are not found on normal body cells
  • monoclonal antibodies can be made to bind to tumour markers
  • anti-cancer drugs can then be attached to the antibodies
  • when the antibodies come in contact with the tumour markers, they will bind to the tumour makers and the drug will accumulate where cancer cells are present
203
Q

describe how monoclonal antibodies work in pregnancy tests

A

1 - the application area contains antibodies for hCG bound to a coloured bead (blue)
2 - when urine is applied to the application area, hCG will bind to the antibodies on the coloured beads - forming antigen-antibody complexes
3 - the urine moves up the stick to the test strip, carrying beads with it.
4 - the test strip contains antigens for hCG that are stuck in place (immobilised)
5 - if there is hCG present the stick turns blue, as the immobilised antibody will bind to the hCG, concentrating the hCG antibody complexes with the blue beads attached. if there is no hCG present the beads will pass through the test area without binding anything, so the strip wont go blue.

204
Q

what is the purpose of an elisa test?

A

to allow a patient to see whether they have any antibodies to a certain pathogen or any antigens to a certain antibody - detects pathogenic infections or allergies

204
Q

what hormone do pregnancy tests detect?

A

hCG - found in the urine of pregnant women

205
Q

describe how an indirect elisa test works

A
  1. HIV antigens are attached to the surface of a well.
  2. a sample of the patients blood plasma (that may contain several different antibodies) is added, and the HIV-specific antibodies will bind to the HIV specific antigen stuck at the bottom of the well. the well is then washed out to remove any unbound antibodies.
  3. a secondary antibody, that has an enzyme attached to it, is added to the well. this antibody will bind to the HIV specific antibody (the primary antibody) and the well is washed out again to remove any unbound secondary antibody.
  4. a solution is added to the well that contains a substrate that is able to react to the enzyme attached to the secondary antibody to produce a coloured product. if the solution changes colour it indicates the patient has HIV-specific antibodies in their blood and so has HIV.
206
Q

how does a sandwich elisa test work?

A
207
Q

outline 5 ethical issues regarding vaccination

A
  • theyre expensive which means less money for other treatments
  • theyre tested on animals before humans, so animals may be harmed
  • testing vaccines on humans may also be risky as volunteers may be putting themselves in unnecessary risk.
  • if there was a new disease, difficult decisions would have to be made regarding who got the vaccine first
  • people that dont take the vaccine are protected by herd immunity - some people think this is unfair.
208
Q

what does HIV eventually lead to? + what is this?

A
  • HIV eventually leads to AIDS
  • AIDS is a condition that causes the immune system to deteriorate and eventually fail
208
Q

what does HIV stand for? + what is it?

A

human immunodeficiency virus
- it is a virus that affects the immune system

209
Q

what kind of cells in the immune system does HIV affect

A

HIV infects and kills helper T cells, which act as host cells for the virus

(remember, helper T cells activate cytotoxic t cells, phagocytes, b cells - that divide to form plasma cells and memory cells and antibodies - etc, so theyre very improtant in the immune response)

209
Q

when do people with HIV develop AIDS ?

A

when the number of helper T cells in their body reaches a critically low level

210
Q

draw and label the structure of HIV

A
210
Q

describe the process of HIV replication

A
  • the attachment protein (glycoprotein) attaches to receptor molecules on the cell membrane of the hosts helper T cell.
  • the capsid is released into the cell, where it un-coats and releases genetic material (RNA) into the cells cytoplasm.
  • inside the cell, reverse transcriptase is used to convert RNA to DNA
  • the viral DNA is inserted into the human DNA
  • the host cells enzymes are used to make viral proteins from the viral DNA found within the human DNA
  • the viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells.
210
Q
A
211
Q

what are the initial symptoms of AIDS?

A
  • minor infections of the mucus membranes (nose, ears and genitals)
  • recurring respiratory conditions
211
Q

is there a cure for HIV? + how can HIV be spread?

A
  • no
  • unprotected sexual intercourse, exchange of bodily fluids, from a HIV positive mother to her fetus
211
Q

what infections are patients susceptible to as the immune system becomes more affected as a result of aids?

A

-more serious infections like chronic diarrhoea and tuberculosis arise
- during the late stages of AIDS, patients have a very low number of immune system cells so develop a range of serious infections like toxoplasmosis and candidiasis which can kill.
- its the serious infections that kill the patient, not the HIV itself.

211
Q

what are the factors that can vary the length of time someone can survive with aids?

A

existing conditions
the strain of HIV
access to healthcare
age

211
Q

how do antibiotics kill bacteria?

A
  • antibiotics kill bacteria by interfering with their metabollic reactions
  • they target the bacterial enzymes and ribosomes used in these reactions
212
Q

what substances can be taken to slow down the progression if HIV and AIDS in an infected person

A

antiviral drugs

A-Level Biology AQA (6 decks)

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