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Biology > Topic 2: Cells > Flashcards

Topic 2: Cells Flashcards

Pack 2, 3, some of 5; 6

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1
Q

What is the cell theory?

A
  • That cells are the most basic form of life
  • All living organisms are made of 1 or more cells
  • Cells arise from pre-existing cells
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2
Q

What is a eukaryotic cell?

A

A cell with a true nucleus with DNA in the form of chromosomes with membranes

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3
Q

What is the function of the plasma membrane?

A

To exchange substances in/out of the cell. (Regulates)

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4
Q

What extra features do plant cells have which animal cells do not?

A
  • Permanent vacuole
  • Chloroplasts
  • Cell wall
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5
Q

What is the average size of nuclei?

A

10-20 µm

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6
Q

What is the function of the nucleus?

A
  • Store DNA (genetic information)
  • Control cell by production of mRNA, tRNA and thus protein synthesis
  • Makesribosomes
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7
Q

Name some sub-structures of the nucleus

A
  • Nuclear envelope
  • Nuclear pores
  • Nucleoplasm
  • Nucleolus
  • Chromosomes
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8
Q

What is the nuclear envelope? What is its function?

A
  • A double membrane surrounding the nucleus, outer membrane continuous with ER
  • Controls what enters/exits nucleus
  • Controls the reactions within the nucleus; DNA, RNA + Ribosomes
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9
Q

What is the function of nuclear pores?

A

Allows passage of very large molecules, inc mRNA

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10
Q

What is the nucleoplasm

A

A granular, jelly-like substance making up the bulk of the nucleus

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11
Q

What are chromosomes?

A

Protein bound, linear DNA

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12
Q

What are ribosomes?

A
  • Small granules found in rough ER or cytoplasm
  • Made from 2 subunits of ribosomal RNA (rRNA) and many proteins
  • NOT enclosed by a membrane
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13
Q

What is the function of ribosomes?

A

The site of protein synthesis

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14
Q

What is the Endoplasmic Reticulum?

A
  • 3D sheet-like membrane system spreading throughout the cytoplasm
  • Continuous with outer nuclear membrane
  • Encloses a network of tubules and flattened sacks called cisternae
  • Cells that make and store carbohydrates, proteins and lipids have an extensive ER
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15
Q

What are the two types of endoplasmic reticulum?

A

Rough ER Smooth ER

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16
Q

What is the rough ER?

A
  • Has ribosomes on outer surface of the membrane - Large SA for protein synthesis
  • Pathway for transport of materials (eg mRNA), especially proteins through the cell
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17
Q

What is the smooth ER?

A
  • No ribosomes, more tubular

- Synthesises, transports + stores lipids or carbohydrates

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18
Q

What types of cells contain a lot of ER?

A

Any cell that produces a lot of proteins (inc enzymes)

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19
Q

How many cisternae will you find in one cell?

A

Just one which has been folded over many times and appears as many depending on angle of cut

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20
Q

What is the golgi apparatus (golgi body)?

A
  • 3D sheet-like membrane system in cytoplasm
  • Similar to smooth ER but compact
  • A cisternae with small vesicles - In secretory cells
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21
Q

What are the functions of the golgi apparatus?

A
  • Adds carbohydrates to proteins to form glycoproteins
  • Produces secretory enzymes (pancreas)
  • Secretes carbohydrates (plant cell walls)
  • Tranports, modifies and stores lipids
  • Forms Lysomers
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22
Q

Which cell organelle stores lipids and proteins made by the golgi apparatus?

A

Vesicles

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23
Q

Which cell organelle processes and packages new lipids and proteins?

A

Golgi body

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24
Q

What are lysosomes?

A

Vesicles produced in the golgi body containing enzymes (proteases and lipases)

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25
Q

What do lysosomes do?

A
  • Help in consume bacteria during phagosytosis
  • Release enzymes to destroy cell material
  • Digest worm out organelles to reuse chemicals
  • Break down cells once they die
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26
Q

In mitochondria, what sub-structure controls the entry and exit of substances?

A

A double membrane, with an inner membrane folded forming a cristae for enzymes involved in respiration

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27
Q

What molecule used for energy in cells is produced in mitochondria?

A

ATP

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28
Q

What is respiration?

A

The oxidization of glucose releasing (not producing) energy

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29
Q

Why do cells that do a lot of active transport require lots of mitochondria?

A
  • Active transport requires energy to go from low to high concentrations
  • Mitochondria are site of respiration
  • produce ATP
  • ATP needed for active transport
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30
Q

Name 3 sub-structures of chloroplasts and their function

A
  1. Chloroplast envelope - Double plasma membrane, v. selective
  2. Thylakoids - Disc structures containing chlorophyll in stacks called grana
  3. Stroma - Matrix containing starch, DNA and ribosomes
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31
Q

What are vacuoles?

A

Fluid-filled sacks bound by a single membrane found in plants containing mineral salts, sugars, amino acids and waste

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32
Q

What is the membrane in vacuoles called?

A

A tonoplast

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33
Q

What is the function of vacuoles?

A
  • To support herbaceous plants (no woody stem)
  • Sugars and amino acids stored as emergency food
  • Pigments colour petals attracting pollenators
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34
Q

What is different about Algae to plant cells?

A

Nothing - same organelles

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35
Q

What do fungal cells have which plant cells do not?

A
  1. Chitin cell walls

2. No chloroplasts (don’t photosynthesize)

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36
Q

What is the function of the cell membrane?

A

Regulates movement of molecules + receptor molecules to detect hormone changes

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37
Q

What are plant cell walls made from?

A

Cellulose

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38
Q

What are fungal cell walls made from?

A

Chitin

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39
Q

How can you study single organelles of cells?

A

With cell fractionation

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40
Q

What are the 2 stages of cell fractionation?

A

Homogenisation and Ultra-centrifugation

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41
Q

What is the first step of cell homogenisation? (most important step)

A
  • Chop up tissues
  • Place in isotonic buffer solution at 2-4 degrees
  • Prevents enzyme action and organelles bursting
  • Buffer solution keeps pH neutral
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42
Q

What is the second step of cell homogenisation?

A
  • Blend the chopped cells

- Releases organelles from the cells

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43
Q

What is the third step of cell homogenisation?

A
  • Filter the blended homogenate
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44
Q

In ultracentrifuation where do heavy organelles fall? What is this layer called?

A
  • Form at bottom

- A SEDIMENT

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45
Q

In ultracentrifuation where do light organelles fall? What is this layer called?

A
  • Forms ontop of sediment

- Called a SUPERNATANT

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46
Q

Summarize ultarcentrifugation.

A
  1. Spin homogenate at low speed for short amout of time
  2. Spin the supernatant from part 1 at a higher speed for longer
  3. Spin the supernatant from part 2 at a higher speed for longer still
    - Pour off supernatant after each step, leaving just the sediment
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47
Q

Where do cells come from?

A

From the division of other cells by mitosis with the same number of genes

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48
Q

Why do cells only do a certain function or role?

A

All cells contain all the genes necessary to develop into any cell but only some genes are switched on or expressed

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49
Q

What is a tissue?

A

A collection of cells that perform a specific function

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50
Q

What is an organ?

A

A combination of tissues that perform one major function

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51
Q

What is an organ system?

A

A number of organs working together. eg digestive system, respiratory system, circulatory system

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52
Q

What is a prokaryotic cell?

A
  • Cells without a nucleus and other membrane-bound organelles
  • Genetic material in circular double-stranded DNA
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53
Q

Name all organelles prokaryotes have that eukaryotes do not

A
  • Flagellum
  • Plasmids
  • Circular DNA (instead of nucleus)
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54
Q

What is the cell wall in prokaryotes made out of?

A

Murein (polymer of polysaccharides and protein)

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55
Q

What is the function of prokaryotic cell walls?

A

A physical barrier, protecting against mechanical damage and turgor pressure (like eukaryotes)

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56
Q

What is the function of prokaryotic cell membranes?

A

Controls entry/exit of chemicals (like in eukaryotes)

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57
Q

What is different about the storage of genetic material in prokaryotes to eukaryotes?

A
  • DNA in circles (plasmids)
  • DNA is not protein bound (no histones)

ALL DNA is double-stranded

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58
Q

What important genes do plasmids in prokaryotes contain?

A

Genes that aid survival by antibiotic resistance

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59
Q

What are plasmids used for in genetic engineering?

A

Used as vectors which can carry genetic info eg insulin

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60
Q

What is the capsule in bacteria?

A
  • A layer of slime found on some bacteria
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61
Q

What is the function of bacterial capules?

A
  • Protection fro other cells

- Helps bacteria stick together for protection

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62
Q

What is the flagellum (prokaryotes) and what is its function?

A
  • A tail, can be more than one

- For locomotion

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63
Q

Are viruses cells?

A

No. They are acellular, non-living particles

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64
Q

How is genetic material stored in viruses?

A
  • Contain nucleic acids like DNA/RNA inside a protein coat or capsid
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65
Q

How do viruses identify and attach to host cells?

A

Attachment proteins line the outside of viruses

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66
Q

Where do viruses reproduce?

A

Inside cells of living organisms, using their DNA and destroying them

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67
Q

What is magnification?

A

How many times bigger the image is than the actual object

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68
Q

What is the formula relating magnification (M), image size (D) and actual size (A)?

A

DAM u!
Image = actualxmagnification
D=AxM

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69
Q

What is resolution?

A
  • How detailed the image is

- Specifically how well a microscope distinguishes between 2 points that are close together

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70
Q

How thin do specimens need to be for a light microscope? Why?

A
  • 2-5 um (micrometres)

- So light can pass through them

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71
Q

How do light microscopes work?

A

Light shines through specimen and through a series of lenses, the resulting image viewed by human eye

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72
Q

Why do light microscope have a poor resolution?

A

Relatively long wavelengths of light cannot pass between very small objects

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73
Q

What is the maximum resolution of light microscopes?

A

0.2 micrometres

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74
Q

What is the difference between a capSULE and a capSID?

A 
Capsule = Bacteria, slime layer
Capsid = Viruses, Protein coat
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75
Q

What is the maximum magnification of light microscopes?

A

1500x

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76
Q

How can you accurately measure objects with a light microscope?

A

With an eyepiece graticule and a stage micrometer

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77
Q

What are the two types of electron microscopes?

A 
SEM = Scanning electron microscope
TEM = Transmission electron microscope
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78
Q

How is an image made using a Scanning electron microscope (SEM)?

A
  • ‘Scans’ the surface to and fro
  • Electrons are scattered depending on contours of specimen
  • Builds a 3D image
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79
Q

What are artifacts?

A

Inaccuracies made during the preparation of specimens for SEMs and TEMs

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80
Q

What is the major difference between light and electron microscopes?

A

One uses a bean of electrons rather than light

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81
Q

Why do electron microscope have a higher resolution?

A

Electrons have a shorter wavelength compared to light

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82
Q

How are electron microscopes focused?

A

Using magnets as electrons are negatively charged

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83
Q

Why does preparation take longer with Transmission electron microscopes (TEMs)?

A

Specimens need to be stained with heavy metals

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84
Q

How does a TEM produce an image?

A
  • Electrons are fired as a beam
  • Electrons which pass through appear bright
  • Absorbed or reflected electrons appear dark
  • 2D image
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85
Q

Why can’t living specimens be observed with a TEM?

A

A near vacuum is required as air molecules interrupt electrons

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86
Q

What is the maximum magnification of scanning electron microscopes (SEMs)?

A

x500,000

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87
Q

What is the resolution of transmission electron microscopes (TEMs)?

A

Up to 0.1nm

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88
Q

What is the resolution of scanning electron microscopes (SEMs)?

A

Up to 20nm

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89
Q

What are the two ways that eukaryotes divide?

A

Mitosis and Meiosis

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90
Q

Can all cells divide?

A

No. Nerve and brain cells cannot

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91
Q

What is the ‘outcome’ of mitosis?

A

MITOSIS

2 genetically identical daughter cells, same number of chromosomes as parent cell (exact copy of DNA)

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92
Q

What is the ‘outcome’ of meiosis?

A

MEIOSIS

4 genetically non-identical daughter cells, half number of chromosomes as parent cell

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93
Q

What do chromosomes do?

A

Carry the genes that control protein synthesis in living organisms. PROTEINS DETERMINE THE CHARACTERISTICS.

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94
Q

Do all organisms have the same numbers of chromosomes?

A

No. Humans have 23 pairs

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95
Q

What are ‘homologous chromosomes’?

A

Pairs of chromosomes (diploid)

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96
Q

What type of cell contains half the dipoid number?

A

Gametes

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97
Q

What are chromatids?

A

Two parts of a chromosome, joined by a centromere

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98
Q

What is a centromere?

A

Joins the two chromatids in a chromosome together

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99
Q

What is the protein found in chromosomes?

A

Histones

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100
Q

What are the 3 main stages of the cell cycle?

A

Interphase, Mitosis, Cytokinesis (can be sub-divided further)

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101
Q

What are the ‘sub-stages’ of interphase?

A

G1 - Growth 1
S -Synthesis
G2 - Growth 2

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102
Q

What occurs in growth 1 (G1) of interphase?

A

Organelles replicate, forms many proteins

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103
Q

What occurs in synthesis (S) of interphase?

A

DNA replication, chromosomes become 2 chromatids joined by a centromere

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104
Q

What occurs in growth 2 (G2) of interphase?

A
  • Organelles continue to replicate
  • Energy store produced
  • Centrioles replicate
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105
Q

What are centrioles?

A

Animal cell organelles which develop spindle fibres

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106
Q

What are the 4 stages of mitosis (in order)?

A 
*PMAT*
Prophase
Metaphase
Anaphase
Telophase
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107
Q

What occurs during cytokinesis in the cell cycle?

A

Organelles are equally distributed into two daughter cells

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108
Q

What happens in prophase (mitosis)?

A
  • Chromosmes become visible, shorten/thicken
  • Centrioles move to opposite poles
  • Spindle fibres form a spindle apparatus
  • Nucleolus disappears + nuclear envelope brakes down
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109
Q

What happens in metaphase (mitosis)?

A
  • Chromosomes clearly seen as two sister chromatids
  • Some spindle fibres attach to centrioles, others pole-to-pole
  • Chromosomes line up along equator
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110
Q

What happens in anaphase (mitosis)?

A
  • Centromeres divide, spindle fibres contract, pulling sister chromatids apart
  • Chromatids move to opposite poles
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111
Q

What happens in telophase (mitosis)?

A
  • Chromosomes reach poles, become long + thin
  • Spindle fibre disintegrates
  • Nuclear membranes and nucleoli reform
  • Followed by cytokinesis
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112
Q

In what stage of the cell cycle does DNA replication occur?

A

Interphase (S - synthesis)

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113
Q

What is the role of the 1/2 spindle fibres in mitosis?

A

Pull chromatids apart from centromeres

114
Q

How would you recognise metaphase (mitosis)?

A

Chromatid pairs line up along the cell equator

115
Q

What the the 3 key roles of mitosis in organisms?

A

GRR!

  1. Growth
  2. Repair
  3. Reproduction
116
Q

What is the mitotic index?

A

The ratio of cells undergoing mitosis to those in interphase. Proportional to time spent in that stage

117
Q

What causes cancer?

A

Mutations to genes that regulate mitosis and cell cycle

118
Q

What is a malignant tumour?

A

A tumour that spreads to surrounding tissues via the blood

119
Q

What is a benign tumour?

A

A tumour that grows slowly and does not spread easily

120
Q

How is cancer controlled?

A

Chemicals are prescribed to block a part of the cell cycle, affects all cells

121
Q

How do prokaryotes divide?

A

By binary fission

122
Q

What are the 4 steps of binary fission?

A
  1. cell elongates, DNA replicated + attaches to membrane
  2. Cell wall + cytoplasm begin to divide
  3. Cross-wall forms
  4. Cells separate with single copy of DNA
123
Q

How do viruses replicate?

A
  • Attach to host cell, inject genetic material (DNA or RNA)

- Host cell produces all components of the virus

124
Q

What is the function of plasma membranes?

A

To control what enters/exits the cell/organelles, forming a boundary between the cell cytoplasm and the surrounding environment

125
Q

What are the 5 main components of plasma membranes?

A 
Phospholipids
Proteins
Cholesterol
Glycoproteins
Gycolipids
126
Q

What 4 molecules make up a phospholipid?

A

Glycerol, 2 fatty acids + phosphate

127
Q

How do phospholipds line up when they form a

membrane?

A

They naturally line up with phosphate head (hydrophyllic) outwards and fatty acid tails inwards - A natural bilayer

128
Q

What is the function of the phospholipid bilayer?

A
  • Allows for lipid soluble substances to enter/exit cell
  • Prevents water soluble substances entering the cell
  • Membrane is flexible and self-sealing
129
Q

Where are proteins found on/in membranes?

A

Can completely span membrane or sit in/on one of the surfaces of the bilayer

130
Q

What are the functions of proteins with plasma membranes?

A
  • Structural support
  • Helps cells attach to each other
  • Channel, carrier proteins
  • Cell surface receptors for hormones / cell recognition
131
Q

What is the function of cholesterol with plasma membranes?

A
  • Adds strength
  • Less fluid at high temperatures
  • Prevents leakage of water and dissolved ions out of cell
132
Q

What are glycolipids?

A

A lipid (In the membrane) convalently bonded to a carbohydrate, extending out the cell

133
Q

What are the functions of glycolipids with plasma membranes?

A
  • Receptors for specific chemicals
  • Maintains membrane stability
  • Help cells attach to each other forming tissues
134
Q

What are extrinsic proteins?

A

Proteins which do not go all through membrane, only one side

135
Q

What are glycoproteins?

A

A extrinsic protein (part of membrane) covalently bonded to a carbohydrate, extending out/away from cell

136
Q

What are the functions of glycoproteins with plasma membranes?

A
  • Recognition sites for chemicals
  • Helps cells attach forming tissues
  • Allow cells to recognize each other, eg lymphocytes recognizing organisms own cells (and don’t eat them…)
137
Q

Why are plasma membranes described as fluid?

A

Molecules inside the membrane can move relative to each other, constantly changes shape

138
Q

Why can’t most substances pass through plasma membranes?

A
  • Not if they are water soluble (only lipid soluble)
  • Not charged particles
  • Not large molecules
139
Q

What substance can cross plasma membranes?

A
  • Lipid soluble substances eg oestrogen

- Small non-polar molecules eg Oxygen +CO2

140
Q

Define diffusion.

A

The net movement of molecules/ions from a region of high concentration to low concentration, until evenly distributed

141
Q

Is diffusion an active process?

A

NO! A passive process

- no metabolic energy required from ATP

142
Q

When does the ‘net flow of molecules’ over a membrane stop?

A

At dynamic equilibrium

143
Q

What factors does the rate of diffusion depend on?

A
  • Temperature
  • Difference in con
  • Distance travelled
  • Area it takes place
  • Nature of structures
  • Size of molecule
144
Q

How does temperature affect the rate of diffusion?

A

Increase in temp = increase in Kinetic energy of molecules, increases rate (collision theory)

145
Q

How does difference in concentration affect the rate of diffusion?

A

A greater difference in concentration will cause a faster rate

146
Q

How does width of membrane (distance) affect the rate of diffusion?

A

A wider membrane means further to travel, so slower. The greater the distance, the slower the rate

147
Q

How does surface area of membranes affect the rate of diffusion?

A

As the area increases, the rate of diffusion increases

148
Q

What is Fick’s law?

A

Diffusion rate = [directly proportional to]

(surface area x conc difference)

/ Diffusion distance

149
Q

What 2 types of protein facilitate diffusion of molecules?

A

Channel and carrier proteins

150
Q

What are 3 key points for facilitated diffusion?

A
  • High to low concentration
  • Carrier or channel proteins
  • No ATP / energy required
151
Q

What do channel proteins do?

A
  • Water filled hydrophillic channels across membrane
  • Specific water-soluble molecules pass through
  • Selective (only open in presence of a specific ion), changes shape of protein
152
Q

How do channel proteins open?

A

A specific ion changes shape of protein to allow a molecule to pass through

153
Q

How do carrier proteins move molecules/ions across plasma membranes?

A

A molecule with a specific, complementary shape binds to carrier protein, causing it to change shape and be released on the other side

154
Q

Why does a large surface area increase the rate of diffusion?

A

The total area is larger, so there are move channel/carrier proteins present

155
Q

Define osmosis.

A

The passive movement of water molecules from a region of high water potential to a region of low water potential through a semi-permeable membrane

156
Q

What is a solute?

A

A substance that dissolves in a solvent to create a solution

157
Q

What is the water potential of pure water under standard temperature and pressure?

A

0 pascals

158
Q

If you add a solute to water how does it affect the water potential?

A

Lowers the water potential (more negative)

159
Q

True or false. Water potential can be positive or negative.

A

FALSE. Always negative

160
Q

What is mean by a protoplast?

A

Everything in plant cells except the cell wall

161
Q

Why do plant cells not burst in a hypERtonic (less negative WP outside cell) solution?

A

Because the cell wall is strong. Cell is turgid

162
Q

If a plant cell is placed in a hypotonic (more negative WP) solution what happens?

A
  • Plant cell has higher (less negative WP)
  • Net movement of water out of cell
  • Protplast shrinks away from cell wall
  • Cell is PLASMOLISED
163
Q

What is ‘incipient plasmolysis’?

A

A cell in an isotonic solution (same WP) - no net movement

164
Q

Define active transport.

A
  • The movement of molecules or ions usually from a region of low concentration to a region of higher conc
  • OR to speed up intake (high-low)
  • Requires respiration, energy from ATP)
  • Involves carrier proteins
165
Q

What is an example of active transport?

A

Sodium/potassium (Na+/K+) pump

166
Q

What other molecule besides Na+ and K+ is required for the sodium/potassium pump to work?

A

ATP, Pi released (by hydrolysis). Pi changes the shape of carrier protein, releasing Na+ out of cell.Pi rejoins ADP (to form ATP) after two K+ ions move into the cell.

167
Q

What do the epithelial cells of the intestine have to maximize absorption (by increasing SA)?

A

Microvilli

168
Q

What role does the circulatory system do to help absorb foods from small intestine into the blood?

A

Blood constantly flows, the concentration gradient is maintained as products of digestion are constantly carried away

169
Q

Over time what will happen to the concentrations of products of digestion in the small intestine and blood?

A

The concentrations will equal out, reach dynamic equilibrium or become higher in the blood

170
Q

What would happen is the products of digestion across the walls of the small intestine moved by diffusion?

A

The products of digestion would have equal concentrations in blood and small intestine, many would pass out of the body (uses co-transport instead)

171
Q

What is co-transport?

A

The facilitated diffusion and active transport of substances from the small intestine into the blood

172
Q

What type of protein moves two molecules through it in co-transport?

A

A co-transport protein or symporter

173
Q

What is used to set up a concentration gradient in co-transport?

A

A sodium/potassium pump, moving Na+ ions into the blood

174
Q

In co-transport does glucose move through the co-transport protein down its own concentration gradient?

A

No. It moves in with Na+ down sodium concentration gradient (glucose is always moving in, regardless of concentrations, glucose moves against it’s own conc gradient

175
Q

Give one method of observing mitosis.

A

Use root tip tissues, squash them and look under a microscope

176
Q

How do you calculate the mitotic index?

A

No. of cells with visible chromosomes / total no. of cells

177
Q

What is the effect of temperature on membrane permeability?

A

Below 0 degrees = Too rigid, proteins deform, freeze thaw, increases permeability
Over 45 degrees = Phospholipids melt and proteins deform, increases permeability

178
Q

What is simple diffusion?

A

When molecules/ions diffuse directly through plasma membrane (not channel proteins)

179
Q

How can you test water potential of plant tissues?

A

Use a serial dilution of different water potentials, add potato cylinders

180
Q

What factors affect the rate of active transport?

A
  1. Speed of individual carrier proteins
  2. Number of carrier proteins present
  3. Rate of respiration of cell + availability of ATP
181
Q

What is a pathogen?

A

Any organism that causes a disease

182
Q

What are the 4 types of pathogen?

A
  • Protozoan (parasites)
  • Fungus
  • Virus
  • Bacteria
183
Q

How do pathogens cause disease?

A

By making you ill in a number of ways. eg. Bacteria secrete toxins, viruses take DNA

184
Q

What is an antigen?

A

Any part of an organism or substance that is recognised as “non-self” - stimulates immune response

185
Q

Do antigens have a specific shape?

A

Yes, a specific, unique structure/shape

186
Q

What do antigens stimulate the production of?

A

Antibodies (complementary to the given antigen)

187
Q

What molecules can antigens be?

A

Proteins and glycoproteins found on the surface of a cell

188
Q

What is the generic shape of an antibody?

A

A Y-shaped protein

189
Q

What part of antibodies bind to the antigen?

A

The binding sites (NOT active), which is specific in shape to a complementary antigen

190
Q

What makes antibodies in an immune response?

A

B lympocytes

191
Q

Why are proteins used for cell identification?

A

There is a wide variety of proteins (20 amino acids in many different orders), creating a specific tertiary structure

192
Q

Why do cancerous cells trigger an immune response?

A

Cancer cells are abnormal, different antigens in surface than normal body cells

193
Q

What is a non-specific immune response?

A

An immediate response, same for all pathogens. Uses physical barriers and phagocytosis

194
Q

What is a specific immune response?

A

A response which is specific to each pathogen (cell mediated/humoral response)
- slower than non-specific

195
Q

Give 6 natural barriers to pathogens.

A
  • Skin
  • Nasal hairs
  • Ear wax
  • Cillia
  • Eyes (containing lysozyme)
  • Stomach acid
196
Q

What causes inflammation?

A

Histamines cause blood vessels to dilate, blood flow increases. Capillaries become more leaky too. Phagocytes move in

197
Q

What is a phagocyte?

A

A white blood cell which carries out phagocytosis, engulfing pathogens

198
Q

What is the 1st stage of phagocytosis?

A

1) Phagocytes move to pathogen in presence of chemicals

199
Q

What is the 2nd stage of phagocytosis?

A

2) Phagocyte attaches to receptor molecules on the surface of the pathogen

200
Q

What is the 3rd stage of phagocytosis?

A

3) Cytoplasm of phagocyte moves around the pathogen, engulfing it. Creates a phagosome

201
Q

What is the 4th stage of phagocytosis?

A

4) Lysosomes in phagocyte fuse with phagosome

202
Q

What is the 5th stage of phagocytosis?

A

5) Lysosomes release lysozyme, digest/hydrolyse the pathogen

203
Q

What is the 6th stage of phagocytosis?

A

6) After the pathogen is digested, products of digestion are absorbed into the cytoplasm or released by exocytosis

204
Q

Where do B lymphocytes originate and mature?

A

In bone marrow

205
Q

Where do T lymphocytes originate?

A

In bone marrow

206
Q

What is clonal selection?

A

The process by which lymphocytes are selected to divide so that sufficient numbers are present to combat infection

207
Q

What is the immune response by T cells called?

A

Cell mediated immunity

208
Q

What is the immune response by B cells called?

A

Humoral immunity

209
Q

What activates T cells?

A

Phagocytes (with presented antigens)

210
Q

What do cloned Th cells do?

A

a) Form Tm cells
b) Stimulate phagocytosis
c) Stimulate B cells to divide and produce antibodies
d) Activate cytotoxic T cells

211
Q

How do ctotoxic T cells kill infected cells?

A

Produce a protein called perforin - makes holes in cell surface membrane (esp important with viruses)

212
Q

How do B cells respond to an infection?

A

Produce antibodies

213
Q

What do B cells develop into?

A
  • Plasma cells (cells which secrete antibodies into blood) primary response
  • B memory cells (increased and more rapid response to second infections) secondary response
214
Q

What type of phagocyte presents antigens?

A

Macrophage

215
Q

What is an antigen joined to an antibody called?

A

Antigen-antibody complex

216
Q

What hierarchy of protein structure are antibodies?

A

A quaternary structure

217
Q

What is the constant region of antibodies?

A

The region which is the same for all antibodies (lower part)

218
Q

What is the variable region of antibodies?

A

Part of antibody with a specific shape to antibody due to amino acid sequence - complementary shape to antigen

219
Q

How do antibodies prevent disease?

A
  • Antibodies bind to antigens at antigen binding site

- The pathogens can be clumped together with agglutination, so can no longer attach to host cells

220
Q

What is the primary response?

A

The first time the immune system encounters a pathogen. Slow as few B cells - takes time for antibodies to be produced, symptoms shown

221
Q

What happens following a primary response?

A

T and B cells produce memory cells to remain in the body in preparation for any future infections (if any)

222
Q

Why is the secondary response quicker than primary?

A

There are B and T memory cells already in the blood, so they can divide more quickly

223
Q

How does the scondary response differ from the primary response?

A
  • More magnitude and speed
224
Q

What is a monoclonal antibody?

A

Antibody produced by a single B cell clone

225
Q

Why is vacination used?

A

It produces immunity to specific diseases by deliberately exposing a person to antigenic material which is harmless.

226
Q

Why do most vaccines not cause symptoms?

A

There are antigens which do not make you ill whilst triggering a primary reponse in prepartaion for a future infection. Causes immunity without symptoms

227
Q

Why might booster vaccines be given?

A

To make sure that memory cells are produced

228
Q

Why are few vaccines taken orally?

A
  • Enzyme breakdown

- Molecules may be too large to be absorbed in gut

229
Q

What is active immunity?

A

Immune system creates its own antibodies after stimulation by an antigen

230
Q

What are the two types of active immunity?

A
  1. Natural (catch the disease ‘normally’)

2. Artificial (a vaccine)

231
Q

What is passive immunity?

A

Given antibodies made by a different organism; babies via placenta/artificial (like antivenom)

232
Q

What is antigenic drift/variation?

A

When antigens on a pathogen change due to genetic mutations

233
Q

What is the issue with antigen variation?

A
  • New pathogens mean secondary response is useless
  • A new primary response is required instead
  • Difficult to develop vaccines
234
Q

Between active and passive immunity which requires exposure to pathogen?

A

Active immunity

235
Q

Between active and passive immunity which results in immediate protection?

A

Passive immunity

236
Q

Are memory cells produced as a result of passive immunity?

A

No. Antigens are given, no B cells stimulated

237
Q

Does passive immunity give long-term protection?

A

No. The given antibodies will break down after infection is tackled

238
Q

Does active immunity give long-term protection?

A

Yes. Stimulates an immune response which causes memory cells to remain in blood for secondary infection

239
Q

Why are many different antibodies produced for one pathogen?

A

Each pathogen has many different antigens on its surface, so antibodies produced for each one in specific immune response

240
Q

What is special about monoclonal antibodies?

A

They have a specific, identical structure which is complementary to only one antigen. Useful fr medical diagnosis

241
Q

What causes an immune response?

A

Antigens (on pathogen)

242
Q

What is the benefit if herd immunity?

A

There are less carriers, so less likely to be passed on

243
Q

What is herd immunity

A

When over 80% of the population are vaccinated/immune to a disease

244
Q

Give some examples of how monoclonal antibodies can be used in medicine.

A
  • Cancer-targeting drugs
  • Medical diagnosis
  • ELISA tests
245
Q

How do cancer-targeting drugs work?

A
  • Tumour markers are antigens only found on cancerous cells
  • Monoclonal antibodies to these antigens have anti-cancer drugs attached or natural killer cells
  • Drugs only affect cancerous cells, so less side effects
246
Q

How can monoclonal antibodies be used to directly target cancers? (no drugs used)

A

Monoclonal antibodies can attach to antigens (with specific, complementary shape) on cancer cell, blocking attachment proteins etc

247
Q

Give an example of use of monoclonal antibodies in medical diagnosis.

A

Pregnancy tests

248
Q

How does a pregnancy test work?

A
  • Urine (containing hormone for pregnancy) applied to the application area
  • Joins a blue bead with antibodies to hormone on it
  • Hormone attached to blue bead moves up strip
  • New antibodies are present on test strip, if hormone is present it binds to antibody
  • Positive if blue, negative clear (as no hormone present)
249
Q

What does an ELISA test show (in layman’s terms)?

A

The presence of an antibody or antigen in a test sample

250
Q

Why are unattached antigens washed off in an ELISA test? (vice-versa for antibodies)

A

To ensure that only the desired antigen is present, and that no unwanted antigens are present

251
Q

Assuming antigens are in the bottom of the well, what do the first antibodies bind onto in an ELISA test?

A

First antibodies bind to the antigens

252
Q

Why must the well be washed out between each step in an ELISA test?

A

So that there are no false positive results

253
Q

What do the second antibodies (attached to enzyme) bind onto in an ELISA test?

A

The first antibody (only complementary to that). Hence why it is needed to wash well of first antibody because second antibody is independent of the original antigen

254
Q

What is added to an ELISA test after the second (and final) antibody (with enzyme) is added?

A
  • Well is washed to remove any unbound second antibodies
  • A substrate is added, which will cause a colour change if enzymes are present
  • ESCs form
255
Q

What organism is commonly used to make monoclonal antibodies? Why is this unethical?

A
  • Mice are used

- They are deliberately given tumour cells, causing suffering

256
Q

What can be done to increase the validity of an investigation?

A
  • Repeats
  • Conduct other tests which come to same conclusion
  • Larger sample sizes
  • Timing of investigation(s)
257
Q

What is accuracy?

A

How close to the real value a result is

258
Q

What is reliability?

A

How “correct” a data is. (i.e is it widely agreed upon?)

259
Q

What does HIV stand for?

A

Human Immunodeficiency Virus

260
Q

How is HIV caught?

A

Transmission of body fluids.

Unprotected sex, blood sharing, pregnancy (but not saliva/sweat/urine)

261
Q

What does AIDS stand for?

A

Acquired Immune Deficiency Syndrome

262
Q

What is AIDS?

A

The final stages of a HIV infection

263
Q

What does HIV do?

A

Infects and kills T helper cells

264
Q

What is the problem with HIV infecting T helper cells?

A

T helper cells send chemical signals that activate phagocytes, Tc cells and B cells. Immune response is greatly reduced - susceptibility to illnesses increases

265
Q

What happens to cause AIDS?

A

T helper cells become critically low so other infections occur

266
Q

What is used to test for HIV?

A

ELISA test

267
Q

What is the core of HIV called?

A

A capsid

268
Q

What is the genetic material of HIV?

A

RNA

269
Q

What is found inside a HIV capsid?

A
  • Genetic material (RNA)

- Enzymes (reverse transpriptase, protease, intergrase)

270
Q

What is the matrix of a HIV made from?

A

Proteins

271
Q

How does HIV fuse with T helper cell membranes?

A

With attachment glycoproteins which stick to receptors on the Th cell membrane

272
Q

What part of HIV is released into T helper cells?

A

The contents of the capsid (RNA and enzymes)

273
Q

What does the enzyme reverse transcriptase (HIV) do?

A

Copies viral RNA into single-stranded DNA, then double-stranded DNA

274
Q

How does viral DNA travel into cell nucleus?

A

Via nuclear pore

275
Q

What HIV enzyme, found in capsid, inserts viral DNA into human DNA?

A

Intergrase

276
Q

In HIV replication, what happens to the human/viral DNA?

A

It is used to make a new copy of HIV RNA which travels to ribosomes to create viral proteins before new HIV particle is made.

277
Q

What is the process called whereby viruses leave cells?

A

Budding

278
Q

How do antibiotics kill bacteria?

A

Antibiotics interfere with metabolic reactions by targeting bacterial enzymes and ribosomes (enzymes and ribosomes in bacterial are different to humans)

279
Q

Why can’t antibiotics be used to kill viruses?

A

Viruses use human ribosomes and enzymes to replicate, so inhibiting these would inhibit vital human reactions

280
Q

What do antiviral drugs do?

A

Inhibit reactions associated only with HIV enzymes, not human enzymes (hence the limited effect)

Biology (10 decks)

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