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AS Biology > 2 - Cells > Flashcards

2 - Cells Flashcards

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1
Q

Describe the function of the nucleus

A
  • site of DNA replication & transcription
  • contains genetic code for each cell
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2
Q

Describe structure of mitochondrion

A
  • double membrane: inner membrane forms cristae which is site of electron transport chain + has large surface for enzymes needed for oxidative phosphorylation.
  • fluid matrix contains mitochondrial DNA, respiratory enzymes, lipids, proteins
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3
Q

Describe structure and function of Golgi apparatus

A
  • modifies and processes proteins from the rER and combines them with triglycerides
  • packages them into vesicles for release
  • produces lysosomes
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4
Q

Describe structure and function of a lysosome

A

Bags of digestive enzymes

Contain hydrolytic enzymes (lysozymes) which:
- break down pathogens
- digest worn out organelles

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5
Q

Describe structure and function of a ribosome

A

Formed of protein & rRNA, free in cytoplasm or attached to ER

Site of protein synthesis via translation:
- large subunit: joins amino acids
- small subunit: contains mRNA binding site

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6
Q

Describe structure & function of endoplasmic reticulum (ER)

A

Cisternae: folded membranes (rough & smooth ER both have them)

  • rough ER: many ribosomes attached for protein synthesis
  • smooth ER: lipid synthesis
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7
Q

Describe structure of cell wall

A
  • provide structural strength

Plants: made of cellulose
Bacteria: murein
Fungi: chitin
Plasmodesmata join cytoplasms of plant cells + allow molecules to pass between

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8
Q

Describe structure & function of cell vacuole in plants

A
  • has a tonoplast which maintains pressure and rigidity inside the plant cell
  • contains cell sap which can act as a temporary food storage for the cell
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9
Q

What are some common cell adaptations

A
  • folded membrane or microvilli increase surface area eg for diffusion
  • many mitochondria = large amounts of ATP for active transport
  • walls 1 cell thick for short diffusion pathway
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10
Q

What are similarities between prokaryotic & eukaryotic cells?

A

both have:
- cell membrane
- cytoplasm
- ribosomes

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11
Q

Why are viruses “particles” & not cells?

A

They are A-cellular & non living:
- no cytoplasm
- cannot self reproduce
- no metabolism

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12
Q

Describe the structure of a viral particle?

A
  • DNA or RNA & viral enzymes
  • surrounded by capsid
    -no cytoplasm
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13
Q

Describe the structure of an enveloped virus

A
  • simple virus surrounded by matrix protein
  • matrix protein surrounded by envelope derived from cell membrane of host cell
  • attachment proteins on surface
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14
Q

What is the function of mitochondria ?

A
  • site of aerobic respiration
  • site of ATP production
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15
Q

What is structure and function of cell membrane:

A
  • partially permeable, controls the entrance & exit of molecules
  • formed from phospholipid bilayer
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16
Q

Compare the structures that all prokaryotic cells have vs eukaryotic cells

A
  • P have a cytoplasm that lacks membrane bound organelles but E does contain membrane bound organelles
  • P cell has no nucleus so its DNA is loose and circular but E has a nucleus containing linear DNA
  • P cell 70s ribosomes but E cell 80s ribosomes
  • P has a cell wall that contains murein and peptidoglycan but E cell has a cell wall made up of cellulose
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17
Q

What are the structures that some prokaryotic cells have?

A
  • plasmids = small loops of DNA
  • slime capsule
  • flagellum
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18
Q

What is a virus?

A

A cellular and non - living

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19
Q

What is a bacteria’s cell wall made of ?

A

Murein

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20
Q

What structures do bacteria have?

A
  • murein cell wall
  • plasmid dna
  • naked circular dna
  • capsule
  • flagella
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21
Q

How many ribosomes in prokaryotic cells?

A

70s ribosomes

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22
Q

How many ribosomes in eukaryotic cells?

A

80s

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23
Q

How do prokaryotic cells divide?

A

By binary fission NOT mitosis

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24
Q

What are properties of optical/light microscopes?

A
  • quick simple preparation
    -2D image
  • colour image
  • lower resolution
  • larger field of view
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25
Q

What are properties of electron microscopes?

A
  • higher resolution
  • black n white images
  • expensive
  • magnifies objects more
  • 2 types: TEM/SEM
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26
Q

What are properties of SEMs (scanning electrons)?

A
  • high resolution due to short wavelength of electrons but lower resolution than TEM
  • 3D (can see external structures)
  • can see inside cell
  • used on thick specimens
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27
Q

What are properties of TEMs (transmission electrons)?

A
  • electrons have short wavelength so give high resolution
  • denser parts absorb more electrons so appear darker
  • can only be used on dead/thin specimens (bc have to be in vacuum sealed conditions so electrons don’t collide)
  • complex/lengthy preparation
  • can only see in 2D
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28
Q

Before cell fractionation begins what are the tissue conditions?

A

Cold - reduced enzyme activity

Isotonic - same water potential to prevent organelles from damage from osmosis/bursting

buffered - to prevent denaturing of enzyme

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29
Q

What is the method of cell fractionation?

A
  • blend cells and filter
  • In cold, isotonic, pH controlled solution centrifuge and remove cell debris
  • centrifuge again at higher speeds till desired organelle settles out
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30
Q

What are the three stages of the cell cycle?

A
  1. Interphase (G1,S,G2)
  2. Mitosis
  3. Cytokinesis - division of cytoplasm to create the new cells
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31
Q

What happens during prophase in mitosis?

A
  • chromosomes condense
  • chromosomes appear as two sister chromatids joined at the centromere
  • nuclear envelope breaks down
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32
Q

What happens during metaphase in mitosis?

A
  • chromosomes line up on the equator
  • chromosomes are attached to spindle fibres by their centromere
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33
Q

What happens during anaphase in mitosis?

A
  • spindle fibres contract so chromatids are pulled to the opposite ends of the cell
  • centromere divides
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34
Q

What happens during telophase in mitosis?

A
  • chromosomes unwind becoming longer and thinner
  • Nuclear envelope reforms
  • spindle fibres and centrioles break down
  • cytokinesis (cytoplasm splits)
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35
Q

What is simple diffusion?

A
  • a passive process (no ATP needed)
    small lipid soluble/non polar substances going through the cell membrane
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36
Q

How do fatty acids effect the membrane’s fluidity?

A

Saturated: less fluid
Unsaturated: more fluid (can’t pack as close)

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37
Q

What’s the function of glycolipids and glycoproteins in the cell membrane?

A

cell signalling and recognition
Act as antigens

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38
Q

What’s the function of cholesterol in the cell membrane?

A
  • make the membrane less fluid/ more stable by restricting the lateral movement of molecules making up the membrane
  • connect phosplipids
  • add strength to the membrane
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39
Q

What are the two types of intrinsic proteins in the plasma membrane?

A
  1. channel proteins - (facilitated diffusion) allow movement down a conc gradient
  2. carrier proteins - (facilitated diffusion/active transport) allow movement up a conc gradient
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40
Q

Describe active transport and the role of ATP in it

A

active process:
- ATP hydrolysis releases a phosphate group which binds to a carrier protein making it change shape
- the carrier proteins transport molecules from low conc to high

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41
Q

What is the definition of osmosis?

A

The diffusion of water across a partially permeable membrane from an area of high water potential to an area of lower water potential

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42
Q

What is the water potential of pure water?

A

0kPa

43
Q

What is the water potential of solutions?

A

Solutions have a lower water potential than pure water (it is negative)

  • The more solute dissolved in a solution the more negative the water potential 
44
Q

What is hypotonic?

A
  • Less solute in it
  • more water potential
45
Q

What is hypertonic?

A
  • more solute in it
  • less water potential
46
Q

hypo/hypertonic - animal cells

A

hypotonic - swells, expands + bursts
hypertonic - shrivel + die

47
Q

hypo/hypertonic - plant cells

A

hypotonic - turgid
hypertonic - shrinks

48
Q

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

A
  • Folded membrane/microvilli so large surface area for absorption
  • Large number of carrier proteins so fast rate of absorption
49
Q

Describe how the movement of substances across cell membranes is affected by membrane structure. 5m

A
  • Phospholipid bilayer allows movement of lipid soluble substances
  • Phospholipid bilayer prevents movement of lipid-INsoluble substances
  • Carrier proteins allow active transport
  • carrier proteins allow co-transport
  • Cholesterol affects fluidity
50
Q

Describe facilitated diffusion

A
  • also a passive process like simple diffusion

channel/carrier proteins transport large non lipid soluble molecules

51
Q

What is co transport

A

Movement of a 1 substance up a conc gradient at the same time as the movement of another substance going down it

52
Q

Compare + contrast the processes by which water + inorganic ions enter cells

A
  • both move down conc gradient
  • both move through protein channels in membrane
  • ions can move against a conc gradient by active transport
53
Q

Describe binary fission in bacteria

A
  • Replication of DNA
  • replication of plasmids
  • cytoplasm divides to make daughter cells
54
Q

How would you make sure your mitotic index is accurate?

A
  • Examine large number of cells
  • to ensure it is a reliable sample
55
Q

How does chemical stop the growth of roots

A
  • stops mitosis
  • by stopping spindle fibres forming
  • preventing separation of chromatids
56
Q

using a microscope to see cells in mitosis - why are the cells taken from the root tip?

A

It’s the region where mitosis occurs

57
Q

using a microscope to see cells in mitosis - firmly squashing the root tip?

A

Make the tissue layer thin to let light through

58
Q

Compare and contrast membrane structure and the fluid mosaic model

A

S - both have phospholipid bilayer
D- has no carrier proteins but fluid mosaic does
D - no cholesterol but fluid mosaic has it

59
Q

How do you calculate magnification?

A

Image size (what you measure)/actual size

60
Q

nm to ¥m (micrometers)

A

Divide by 1000

61
Q

¥m (micrometers) to nm

A

x 1000

62
Q

¥m (micrometers) to mm

A

Divide by 1000

63
Q

mm to ¥m (micrometers)

A

x 1000

64
Q

mm to cm

A

Divide by 10

65
Q

cm to mm

A

x 10

66
Q

What is an antigen?

A

A foreign protein in the cell surface membrane that stimulates an immune response
- immune system recognises as self or non self

67
Q

Give two differences between specific and nonspecific immune responses

A

Non specific - inflammation & phagocytosis (same for all pathogens)

Specific - B & T lymphocytes (complementary pathogen)

68
Q

Why can you not see certain things with an optical microscope?

A
  • resolution is too low
  • wavelength of light is too long
69
Q

Describe phagocytosis (5m)

A
  • the phagocyte is attracted to chemicals released by the pathogen and moves along a conc gradient
  • cell engulfs the pathogen forming a phagosome
  • forming a vesicle and fusing with lysosome
  • lysozymes are released and hydrolyse the pathogen
  • the cytoplasm absorbs the soluble products of this reaction
70
Q

Give two types of cell other than pathogens that can stimulate an immune response

A
  • cancer cells
  • cells from other organisms
71
Q

Explain how HIV affects the production of antibodies when a person develops AIDS

A
  • no antibody produced
  • because HIV destroys helper T cells
  • so no B cells are stimulated
72
Q

Explain how specific viruses that only infect 1 species are then able to infect other species as well

A

mutation in the viral DNA alters the viral attachment protein

73
Q

How could determining the genome of a virus allow scientists to develop a vaccine

A
  • scientists could identify proteins
  • they could then identify potential antigens to use
74
Q

How do B lymphocytes respond to vaccination

A
  • B cell binds to specific antigen
  • B cell clones
  • plasma cells produce monoclonal antibodies against the virus
  • memory cells are produced
75
Q

What is a monoclonal antibody?

A

Antibodies produced from cloned B cells

76
Q

What’s an example of using Monoclonal antibodies in a medical treatment/drug

A
  • it has a specific tertiary structure
  • so is complementary to the antigen eg on a cancer cell
  • the drug is attached to the antibody
  • the antibody binds to the cell forming an antigen-antibody complex which delivers the drug
77
Q

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

A
  1. First antibody binds to antigen
  2. Second antibody with enzyme attached is added
  3. Second antibody attaches to antigen
  4. Substrate solution is added and colour changes
78
Q

How can antibodies stimulate phagocytosis?

A

They can bind to the antigen and are markers which attract phagocytes

79
Q

How does vaccination work (6m)

A
  • antigen binds to surface receptor on B cell
  • B cell Clones
  • which is stimulated by cytokines/T cells
  • B cells release antibodies
  • B cells become memory cells
  • memory cells produce monoclonal antibodies faster
80
Q

How do antigens present after phagocytosis

A

The antigens from the virus are displayed on the cell membrane by macrophage

81
Q

Describe how an antibody is released against a virus antigen (4m)

A
  • helper T cell binds to the antigen
  • this helper T cell stimulates a specific B cell
  • B cell clones
  • forming plasma cells that release antibodies
82
Q

What is an antibody

A

A protein specific to an antigen that is produced by B cells

83
Q

Give 4 differences between active and passive immunity

A

1) active involves memory cells, passive doesnt

2) active involves production of antibody by plasma cells
- passive involves antibody introduced into body from outside

3) active is long term because antibody is produced in response to antigen
- passive is short term because antibody is broken down

4) active can take time to develop but passive is fast acting

84
Q

Describe how you would determine a reliable mitotic index from tissue observed with an optical microscope

A
  • Count cells in mitosis in field of view
  • repeat many times
  • divide by total number of cells in field of view
85
Q

Describe DNA in Eukaryotic cells

A
  • longer
  • contains introns
  • linear
  • associated with histones
86
Q

Describe DNA in prokaryotic cells

A
  • shorter
  • does not contain introns
  • circular
  • is not associated with histones
87
Q

Describe similarities between DNA in prokaryotic and eukaryotic cells

A
  • nucleotide structure is identical
  • nucleotides joined by phosphodiester bonds
88
Q

How do antigens trigger a specific immune response

A

Lymphocytes have complementary receptors that bind to antigens

89
Q

Describe B cells role in the humoral immune response (the primary response)

A
  • the first time a pathogen enters the body
  • naive B cells have specific receptors that bind to the pathogen.
  • It then processes its antigen and presents it on its surface and the helper T cell binds to it.
  • the helper T cell stimulates the B cells clone
  • each clone can differentiate into either a plasma cell or memory cell
  • is slower
90
Q

Describe B cells role in the humoral immune response (the secondary response)

A
  • the second time the antigen enters the body
  • involves memory cells which form new plasma cells and more memory cells
  • quicker
  • leads to a higher conc of antibodies
91
Q

What are antigen presenting cells

A

Cells which process antigens and present them on their surface

92
Q

What kind of cells can T cells only bind to and why

A

Antigen presenting cells because they can only bind to antigens which have been processed

93
Q

What’s the difference between the humoral immune response and the cellular/cell mediated response

A

Humoral - involves mainly B cells
Cellular - mainly T cells

94
Q

What are the two types of cells that T cells can differentiate into

A
  • T helper cell
  • cytotoxic T cell
95
Q

Describe the 3 ways cloned T cells can carry out the cell mediated/cellular immune response

A
  • by stimulating B cells to clone
  • by stimulating phagocytosis
  • by stimulating cytotoxic T cells which kill infected body cells
96
Q

Describe the effect of antigen variability on disease

A
  • it is when antigens mutate so are no longer complementary to the memory B cell receptors.
  • so memory cells cannot clone so the immune system has to rely on the primary immune response
  • which is a lot slower and less effective against disease
97
Q

Describe how HIV is replicated 7m

A
  • HIV enters bloodstream and circulates
  • attachment proteins bind to CD4 receptor on T helper cell
  • Capsid fuses with cell membrane so enzymes and RNA enter cell
  • Reverse transcriptase converts RNA into DNA
  • DNA is transcribed into HIVmRNA which passes out the nucleus
  • so new HIV particles are made which breakaway from T helper cell
  • lipid envelope is formed
98
Q

How can AIDS effect someone

A
  • with AIDS immune system eventually becomes very weak
  • So it cannot fight off other infections
99
Q

Explain the structure and function of a chloroplast

A
  • thylakoids are flattened sacs which increase surface area for photosynthesis
  • chlorophyll absorbs light for photosynthesis
  • Stoma contains enzymes for photosynthesis
  • DNA and ribosomes for protein synthesis
  • Starch grains for energy storage
100
Q

Why can antibiotics not be used to treat viruses?

A

They do not have a cell wall or a metabolism pathway

101
Q

Describe co transport of glucose and sodium ions

A
  • sodium ions are actively transported out of epithelial cells lining the ileum into the blood by the sodium potassium pump
  • this creates a conc gradient of sodium
  • sodium ions and glucose move by F.D into the epithelial cell from the lumen via a co transporter protein
  • creating a concentration gradient of glucose - higher conc of glucose in epithelial cells than blood
  • glucose moves out of cell into blood by F.D through a protein channel
102
Q

What stages in mitosis will have the highest and lowest distance between centromeres and poles on a graph

A

Metaphase - will have the highest distance
Anaphase - will have the lowest as the distance will drop immediately after

103
Q

What are some similarities between TEM and SEM?

A
  • cannot use live specimens
  • Must be done in a vacuum
  • both have a higher magnification and resolution, then optical microscopes
  • Expensive and complex staining process

AS Biology (6 decks)

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