2 - Cells Flashcards
1
Q
Describe the function of the nucleus
A
- site of DNA replication & transcription
- contains genetic code for each cell
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
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
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
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
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
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
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
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
10
Q
What are similarities between prokaryotic & eukaryotic cells?
A
both have:
- cell membrane
- cytoplasm
- ribosomes
11
Q
Why are viruses “particles” & not cells?
A
They are A-cellular & non living:
- no cytoplasm
- cannot self reproduce
- no metabolism
12
Q
Describe the structure of a viral particle?
A
- DNA or RNA & viral enzymes
- surrounded by capsid
-no cytoplasm
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
14
Q
What is the function of mitochondria ?
A
- site of aerobic respiration
- site of ATP production
15
Q
What is structure and function of cell membrane:
A
- partially permeable, controls the entrance & exit of molecules
- formed from phospholipid bilayer
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
17
Q
What are the structures that some prokaryotic cells have?
A
- plasmids = small loops of DNA
- slime capsule
- flagellum
18
Q
What is a virus?
A
A cellular and non - living
19
Q
What is a bacteria’s cell wall made of ?
A
Murein
20
Q
What structures do bacteria have?
A
- murein cell wall
- plasmid dna
- naked circular dna
- capsule
- flagella
21
Q
How many ribosomes in prokaryotic cells?
A
70s ribosomes
22
Q
How many ribosomes in eukaryotic cells?
A
80s
23
Q
How do prokaryotic cells divide?
A
By binary fission NOT mitosis
24
Q
What are properties of optical/light microscopes?
A
- quick simple preparation
-2D image - colour image
- lower resolution
- larger field of view
25
What are properties of electron microscopes?
- higher resolution
- black n white images
- expensive
- magnifies objects more
- 2 types: TEM/SEM
26
What are properties of SEMs (scanning electrons)?
- 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
27
What are properties of TEMs (transmission electrons)?
- 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
28
Before cell fractionation begins what are the tissue conditions?
Cold - reduced enzyme activity
Isotonic - same water potential to prevent organelles from damage from osmosis/bursting
buffered - to prevent denaturing of enzyme
29
What is the method of cell fractionation?
- 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
30
What are the three stages of the cell cycle?
1. Interphase (G1,S,G2)
2. Mitosis
3. Cytokinesis - division of cytoplasm to create the new cells
31
What happens during prophase in mitosis?
- chromosomes condense
- chromosomes appear as two sister chromatids joined at the centromere
- nuclear envelope breaks down
32
What happens during metaphase in mitosis?
- chromosomes line up on the equator
- chromosomes are attached to spindle fibres by their centromere
33
What happens during anaphase in mitosis?
- spindle fibres contract so chromatids are pulled to the opposite ends of the cell
- centromere divides
34
What happens during telophase in mitosis?
- chromosomes unwind becoming longer and thinner
- Nuclear envelope reforms
- spindle fibres and centrioles break down
- cytokinesis (cytoplasm splits)
35
What is simple diffusion?
- a passive process (no ATP needed)
small lipid soluble/non polar substances going through the cell membrane
36
How do fatty acids effect the membrane’s fluidity?
Saturated: less fluid
Unsaturated: more fluid (can’t pack as close)
37
What’s the function of glycolipids and glycoproteins in the cell membrane?
cell signalling and recognition
Act as antigens
38
What’s the function of cholesterol in the cell membrane?
- 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
39
What are the two types of intrinsic proteins in the plasma membrane?
1. channel proteins - (facilitated diffusion) allow movement down a conc gradient
2. carrier proteins - (facilitated diffusion/active transport) allow movement up a conc gradient
40
Describe active transport and the role of ATP in it
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
41
What is the definition of osmosis?
The diffusion of water across a partially permeable membrane from an area of high water potential to an area of lower water potential
42
What is the water potential of pure water?
0kPa
43
What is the water potential of solutions?
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
What is hypotonic?
- Less solute in it
- more water potential
45
What is hypertonic?
- more solute in it
- less water potential
46
hypo/hypertonic - animal cells
hypotonic - swells, expands + bursts
hypertonic - shrivel + die
47
hypo/hypertonic - plant cells
hypotonic - turgid
hypertonic - shrinks
48
Describe and explain two features you would expect to find in a cell specialised for absorption
- Folded membrane/microvilli so large surface area for absorption
- Large number of carrier proteins so fast rate of absorption
49
Describe how the movement of substances across cell membranes is affected by membrane structure. 5m
- 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
Describe facilitated diffusion
- also a passive process like simple diffusion
channel/carrier proteins transport large non lipid soluble molecules
51
What is co transport
Movement of a 1 substance up a conc gradient at the same time as the movement of another substance going down it
52
Compare + contrast the processes by which water + inorganic ions enter cells
- both move down conc gradient
- both move through protein channels in membrane
- ions can move against a conc gradient by active transport
53
Describe binary fission in bacteria
- Replication of DNA
- replication of plasmids
- cytoplasm divides to make daughter cells
54
How would you make sure your mitotic index is accurate?
- Examine large number of cells
- to ensure it is a reliable sample
55
How does chemical stop the growth of roots
- stops mitosis
- by stopping spindle fibres forming
- preventing separation of chromatids
56
using a microscope to see cells in mitosis - why are the cells taken from the root tip?
It’s the region where mitosis occurs
57
using a microscope to see cells in mitosis - firmly squashing the root tip?
Make the tissue layer thin to let light through
58
Compare and contrast membrane structure and the fluid mosaic model
S - both have phospholipid bilayer
D- has no carrier proteins but fluid mosaic does
D - no cholesterol but fluid mosaic has it
59
How do you calculate magnification?
Image size (what you measure)/actual size
60
nm to ¥m (micrometers)
Divide by 1000
61
¥m (micrometers) to nm
x 1000
62
¥m (micrometers) to mm
Divide by 1000
63
mm to ¥m (micrometers)
x 1000
64
mm to cm
Divide by 10
65
cm to mm
x 10
66
What is an antigen?
A foreign protein in the cell surface membrane that stimulates an immune response
- immune system recognises as self or non self
67
Give two differences between specific and nonspecific immune responses
Non specific - inflammation & phagocytosis (same for all pathogens)
Specific - B & T lymphocytes (complementary pathogen)
68
Why can you not see certain things with an optical microscope?
- resolution is too low
- wavelength of light is too long
69
Describe phagocytosis (5m)
- 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
Give two types of cell other than pathogens that can stimulate an immune response
- cancer cells
- cells from other organisms
71
Explain how HIV affects the production of antibodies when a person develops AIDS
- no antibody produced
- because HIV destroys helper T cells
- so no B cells are stimulated
72
Explain how specific viruses that only infect 1 species are then able to infect other species as well
mutation in the viral DNA alters the viral attachment protein
73
How could determining the genome of a virus allow scientists to develop a vaccine
- scientists could identify proteins
- they could then identify potential antigens to use
74
How do B lymphocytes respond to vaccination
- B cell binds to specific antigen
- B cell clones
- plasma cells produce monoclonal antibodies against the virus
- memory cells are produced
75
What is a monoclonal antibody?
Antibodies produced from cloned B cells
76
What’s an example of using Monoclonal antibodies in a medical treatment/drug
- 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
Describe the role of antibodies producing a positive result in an ELISA test (4m)
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
How can antibodies stimulate phagocytosis?
They can bind to the antigen and are markers which attract phagocytes
79
How does vaccination work (6m)
- 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
How do antigens present after phagocytosis
The antigens from the virus are displayed on the cell membrane by macrophage
81
Describe how an antibody is released against a virus antigen (4m)
- 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
What is an antibody
A protein specific to an antigen that is produced by B cells
83
Give 4 differences between active and passive immunity
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
Describe how you would determine a reliable mitotic index from tissue observed with an optical microscope
- Count cells in mitosis in field of view
- repeat many times
- divide by total number of cells in field of view
85
Describe DNA in Eukaryotic cells
- longer
- contains introns
- linear
- associated with histones
86
Describe DNA in prokaryotic cells
- shorter
- does not contain introns
- circular
- is not associated with histones
87
Describe similarities between DNA in prokaryotic and eukaryotic cells
- nucleotide structure is identical
- nucleotides joined by phosphodiester bonds
88
How do antigens trigger a specific immune response
Lymphocytes have complementary receptors that bind to antigens
89
Describe B cells role in the humoral immune response (the primary response)
- 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
Describe B cells role in the humoral immune response (the secondary response)
- 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
What are antigen presenting cells
Cells which process antigens and present them on their surface
92
What kind of cells can T cells only bind to and why
Antigen presenting cells because they can only bind to antigens which have been processed
93
What’s the difference between the humoral immune response and the cellular/cell mediated response
Humoral - involves mainly B cells
Cellular - mainly T cells
94
What are the two types of cells that T cells can differentiate into
- T helper cell
- cytotoxic T cell
95
Describe the 3 ways cloned T cells can carry out the cell mediated/cellular immune response
- by stimulating B cells to clone
- by stimulating phagocytosis
- by stimulating cytotoxic T cells which kill infected body cells
96
Describe the effect of antigen variability on disease
- 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
Describe how HIV is replicated 7m
- 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
How can AIDS effect someone
- with AIDS immune system eventually becomes very weak
- So it cannot fight off other infections
99
Explain the structure and function of a chloroplast
- 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
Why can antibiotics not be used to treat viruses?
They do not have a cell wall or a metabolism pathway
101
Describe co transport of glucose and sodium ions
- 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
What stages in mitosis will have the highest and lowest distance between centromeres and poles on a graph
Metaphase - will have the highest distance
Anaphase - will have the lowest as the distance will drop immediately after
103
What are some similarities between TEM and SEM?
- 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
