Cells Flashcards
1
Q
What is the function of the cell surface membrane?
A
Controls exchange between cell and environment. Controls movement in and out of cell.
2
Q
What is the structure of the cell surface membrane?
A
- Selectively permeable.
- Phospholipid bilayer -> to allow endocytosis and exocytosis.
- Receptors -> cell recognition and attachment.
3
Q
What is the function of the nucleus?
A
Contains DNA/chromosomes, the genetic material for the cell.
4
Q
What is the structure of the nucleus?
A
- Contains chromatin -> condenses to form chromosomes.
5
Q
What is the function of the nuclear envelope?
A
Has nuclear pores to let mRNA leave and nucleotides enter.
6
Q
What is the structure of the nuclear envelope?
A
- Nuclear pores.
- Two membranes -> outer one is continuous with RER.
7
Q
What is the function of the nucleolus?
A
Makes rRNA and ribosomes.
8
Q
What is the function of the mitochondria?
A
Site of aerobic respiration using oxygen to make ATP.
9
Q
What is the structure of the mitochondria?
A
- Two membranes -> inner folded to form cristae which surround the matrix.
- Contain circular DNA.
- Contain 70S ribosomes.
10
Q
What is the function of chloroplasts?
A
Site of photosynthesis using light.
11
Q
What is the structure of chloroplasts?
A
- Double outer membrane with stroma inside.
- Grana -> several parallel stacked membrane called thylakoids.
- Contain starch grains in cytoplasm.
- Contain 70S ribosomes.
- Contain circular DNA.
12
Q
What is the function of the golgi apparatus?
A
To package and modify proteins and transport lipids.
13
Q
What is the structure of golgi apparatus?
A
- Stack of flattened cristernae, which form from RER and bud off the form vesicles.
14
Q
What is the function lysosomes?
A
Breakdown unwanted organelles/structures/bacteria in phagocytosis.
15
Q
What is the structure of lysosomes?
A
- Spherical sacs with a single membrane.
- Contain lysozymes.
16
Q
What is the function of ribosomes?
A
Site of protein synthesis.
17
Q
What is the structure of ribosomes?
A
- Made of rRNA and proteins.
- 80S (in eukaryotes).
18
Q
What is the function of RER?
A
Has ribosomes attached which attach to mRNA in protein synthesis, and acts as a transport system.
19
Q
What is the function of SER?
A
Makes lipids, steroids and carbohydrates.
20
Q
What is the structure of SER and RER?
A
- System of membranes continuous with nuclear membrane and golgi body.
- Has flattened sacs called cristernae.
21
Q
What is the function of a cell wall (plants/algae)?
A
Strengthens cell and gives it its structure, and prevents it from bursting.
22
Q
What is the structure of a cell wall (plant/algae)?
A
- Permeable to water and solutes.
- Made of cellulose microfibrils polysaccharide.
23
Q
What is the structure of a cell wall (fungi)?
A
- Made of chitin.
24
Q
What is the function of a vacuole (plant cell)?
A
Act as storage sites.
25
What is the structure of a vacuole (plant cell) ?
1. Large.
2. Surrounded by a tonoplast.
26
What is the function of a vacuole (animal cells)?
Act as contractile vacuoles and may be formed during phagocytosis.
27
What is the structure of a vacuole (animal cells)?
1. Small vesicles.
28
What is a tissue?
Aggregation of similar cells carrying out the same function.
29
What is an organ?
Aggregation of several tissues to perform a particular function for the whole organism.
30
What is an organ system?
Several organs working together.
31
Describes two ways in which epithelial cells in the small intestine are specialised to maximise absorption.
1. Have microvilli -> increase surface area for absorption.
2. Lots of mitochondria -> lots of aerobic respiration to make more ATP for active uptake of molecules.
32
State 7 differences between eukaryotes and prokaryotes?
1. Eukaryotes have DNA enclosed in a nucleus, whereas prokaryotes have their DNA floating in cytoplasm.
2. Eukaryotic DNA is long and linear, whereas prokaryotic DNA is short and circular.
3. Eukaryotic DNA is associated to proteins called histones, whereas prokaryotic DNA is not attached to histones.
4. Eukaryotes have membrane-bound organelles, whereas prokaryotes have no membrane bound organelles.
5. Eukaryotic cell walls contain cellulose (plants) and chitin (fungi), whereas prokaryotic cell wall is made of murein.
6. Ribosomes in eukaryotes are 80S, whereas ribosomes in prokaryotes are 70S.
7. Eukaryotes don't have a smile capsule, whereas most prokaryotes do have a smile capsule.
33
State 5 features of a virus and their function.
1. Acellular -> do not show typical cell structure.
2. Extremely small -> in order to enter living cells.
3. Genetic material -> codes for a viral protein.
4. Capsid -> protects genetic material.
5. Attachment proteins -> binds to receptors on cells.
34
Describe the process of viral replication.
1. Attachment proteins bind to complementary receptors on the surface of its host cells.
2. They inject their genetic material into host cell.
3. Use the host cells organelles to produce more protein capsids and therefore make more viruses.
35
Define magnification.
How many times bigger the imagine is than the specimen.
36
Define resolution.
The ability to see two points as two points.
37
State advantages and disadvantages of an optical microscope.
1. + - Can view live specimen.
2. + - Can see colours.
3. + - Simple staining and slide preparation.
4. x - Lower resolution than electron microscopes -> wavelengths are too long.
38
State advantages and disadvantages of a transmission electron microscope.
1. + - Higher resolution than light -> smaller wavelength of electrons.
2. + -> Can see smaller objects.
3. x - Specimen placed in vacuum ; must be dead.
4. x - Complex staining procedure.
5. x - Black and white only.
39
State advantages and disadvantages of a scanning electron microscopes.
1. + - 3D image produced.
2. x - in vacuum ; must be dead.
3. x - Resolution not as high as TEM.
4. x - Black and white image.
40
What is the equation to find magnification?
Magnification = size of image / size of real object
41
Describe the process of cell fractionation.
1. Place broken open cells in cold, isotonic buffer solution.
2. Filtration -> to filter out large cell debris but organelles pass through.
3. Centrifuge at a slow speed to remove heaviest organelles such as nuclei.
4. Re-spin at an increasing speed to remove pellets of chloroplasts, mitochondria then lysosomes then ribosomes.
5. Ultracentrifugation - spin at a very high speed to separate molecules depending on their mass.
42
What occurs in interphase?
DNA replication.
43
What are the stages within interphase and describe what occurs within each stage?
1. G1 - Cell is metabolically active and duplicates its organelles and cytosylic components.
2. S - DNA is replicated, each chromosome replicates to form two sister chromatids held at a centromere.
3. G2 - Enzyme and protein synthesis occurs, ATP production in large amounts, centrioles replicate.
44
What are the 4 stages of mitosis?
1. Prophase.
2. Metaphase.
3. Anaphase.
4. Telophase.
45
What occurs during prophase?
1. Chromosomes condense from chromatin and become visible as two chromatids joined at a centromere.
2. Nuclear envelope and nucleoli disappears.
46
What occurs during metaphase?
1. Chromosomes line up at the equator of the mitotic spindle.
2. Attached at the spindle by the centromere.
47
What occurs during anaphase?
1. Chromosomes split as centromeres divide as spindle fibres contract.
2. Sister chromatids separate.
3. Pulled in opposite poles of the cell by centromere first.
48
What occurs during telophase?
1. Chromosome elongates and uncoil.
2. Nuclear envelope reforms and nucleoli reappear as two new nuclei are formed.
49
What occurs during cytokinesis?
1. Cytoplasm divides by membrane cleavage.
2. Formation of cell plate then cell wall in plants.
50
What forms from uncontrolled cell division?
Tumours and cancers.
51
How do you calculate the mitotic index?
mitotic index = cells with visible chromosomes / total number of cells visible.
52
Describe the process of binary fission.
1. Circular DNA and plasmids undergo DNA replication.
2. The DNA loop is replicated once, but plasmids are replicated many times.
3. The cell then divides into two cells, each containing roughly half the cytoplasm, one copy of the circular DNA molecule and some of the plasmid copies.
4. Each daughter cell must receive a copy of the single circular DNA molecule.
5. Cell elongates.
5. Cytoplasmic division.
53
What does the 'fluid mosaic model' suggest about cell membranes?
1. Fluid suggests components can move move in the phospholipid bilayer.
2. Mosaic describes how the membrane is made up of lots of small protein components.
54
State the 6 components of a cell surface membrane.
1. Phospholipid bilayer.
2. Carrier protein.
3. Channel protein.
4. Glycoprotein.
5. Glycolipid.
6. Cholesterol.
55
What is the role of the phospholipid bilayer?
1. Forms a barrier.
2. Gives membrane fluidity.
3. Hydrophobic fatty acid tails face inwards, whereas the hydrophilic phosphate head points outwards towards water.
4. Allows passage of non-polar substances, but blocks polar molecules.
56
What is the role of carrier proteins?
1. Act as transport carrier protein.
2. Extrinsic - only in half the membrane.
3. May have hydrophobic areas, which attract the phosphate heads and may have hydrophilic areas, which attracts the fatty acid tails.
57
What is the role of channel proteins?
1. Facilitated diffusion - allow the passage of polar substances.
2. Intrinsic - all the way through the membrane.
3. May be gated (open or closed).
58
What are the roles of glycoproteins and glycolipids?
1. Has a carbohydrate chain on extracellular side - cell/antigen recognition, binding and forms hormones.
2. Binds with water molecules to stabilise membrane.
59
What is the role of cholesterol in the cell membrane?
1. Restricts the movement of other molecules in the membrane.
2. Regulates fluidity.
60
Define diffusion.
The net movement of molecules from a region of a higher concentration to a region of lower concentration down a concentration gradient. It is a passive process.
61
What does the rate of diffusion depend on and how?
1. Concentration gradient - rate is proportional to concentration gradient.
2. Distance of travel - the shorter distance, the faster the rate.
3. Temperature - increase in temperature causes an increase in kinetic energy, so increases rate.
4. Size of molecule - smaller molecules can diffuse more quickly.
62
What does the diffusion of small, non-polar molecules depend on and how?
1. Membrane thickness - thinner membrane means faster rate.
2. Membrane surface area - more surface area, faster rate.
3. Lipid solubility - lipid soluble molecules can diffuse across a membrane as they are soluble in the phospholipid bilayer.
63
Define facilitated diffusion.
The diffusion across the cell surface membrane using protein channel or carries without the use of ATP. It is a passive process.
64
State 3 properties of channel proteins.
1. Hydrophilic - water soluble charged ions can pass through.
2. Each channel protein is specific to one type of ion.
3. Can open and close.
65
How do carrier proteins transport large molecules across a cell membrane?
1. Large molecules attach to carrier protein.
2. Protein changes shape/structure.
3. Molecule is released on opposite side of the membrane.
66
What is active transport?
Where molecules are moved across a membrane against a concentration gradient but ATP is required.
67
When will active transport not occur?
Whenever a respiratory inhibitor is present. This is because they stop aerobic respiration, so no ATP is produced, which is required for active transport.
68
What molecules use active transport across a cell membrane?
Carrier proteins.
69
Explain how co-transport is used through the absorption of glucose with sodium ions and by cell lining the mammalian ileum?
1. Sodium ions pumped out of the epithelial cell into the capillary by active transport using ATP.
2. This creates a lower sodium ion concentration inside the epithelial cell.
3. Sodium ions enter the cell from the intestinal lumen down a concentration gradient through a protein that only allows entry with glucose .
4. Glucose is now high concentration in the cell, and so exits to the capillary by facilitated diffusion down a concentration gradient.
70
Name two ways in which a cell may be adapted to rapid diffusion across their internal and external membranes?
1. Increase in surface area.
2. Increase in number of protein channels and carrier molecules.
71
Define osmosis.
The movement of water molecules from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane.
72
What is meant by an isotonic solution?
A solution of the same water potential.
73
What is meant by a hypertonic solution?
A very concentrated solution with a lower water potential.
74
What is meant by a hypotonic?
A dilute solution with a higher water potential.
75
What is water potential?
The number of free water molecules in a solution (a more concentrated solution will have a lower water potential).
76
What is water potential measured in?
Kilopascals (kPa).
77
What is an antigen?
Any part of an organism/substance/protein that is recognised as foreign and leads to an immune response.
78
What is a phagocyte?
A phagocyte recognises the foreign antigens on a pathogen and engulfs it.
79
What are the three stages of the immune response?
1. (Non specific) Phagocytosis.
2. (Specific) Cellular Response.
3. (Specific) Humoral Response.
80
Describe the process of phagocytosis?
1. Phagocytes recognise antigens pathogens as foreign and engulfs it into a vesicle called a phagosome.
2. A lysosome fuses with the phagosome and releases lysozymes into it.
3. Lysozymes hydrolyse the pathogen.
4. Antigens are displayed on the phagocyte's cell membrane.
81
What are antigen presenting cells?
Any cell that presents a non-self antigen on their surface.
82
Describe the process of the cell mediated response.
1. Pathogen enters the body.
2. Phagocytes 'presents' the antigen and activates specific T-helper cells that has receptor on its surface.
3. The specific helper T cell will divide (by mitosis) and stimulate specific B-cells, release chemicals, stimulate phagocytes and T killer cells.
4. T killer cells perforate pathogens cell membrane so it bursts.
83
Describe the humoral response.
1. T helper cell activates a specific B cell by clonal selection.
2. The B cell divides by mitosis to produce clones.
3. Most B cells differentiate to become plasma cells. Some become memory cells.
4. The plasma cells make antibodies that have a specific tertiary structure that can only bind this antigen.
84
Define an antibodies.
A quaternary proteins made by B cells, they bind to specific antigens to clump them together and aid phagocytosis.
85
Name 3 parts of an antibody.
1. Constant region -> has same sequence of amino acids and is recognised by the phagocytes.
2. Variable region -> a specific tertiary structure which has complimentary to one antigen (antigen binding site).
3. Hinge - antibody can bind more easily with up to 2 antigens forming an antibody-antigen complex.
86
What is antigenic variability?
When a pathogen mutates (change in base sequence in DNA/RNA) so the shape of antigens change and memory cells are unable to recognise them and are no longer complimentary.
87
Describe the primary immune response and explain why?
The primary immune response is the first time that an individual comes into contact with a particular antigen.
It is slower as there aren't as many B cells to produce specific antibodies.
The patient will develop symptoms as the pathogen increases in number and damages cells. B and T cells produce memory cells which remain in the body for a long time.
88
Describe the process of vaccination.
1. A vaccine contains the antigen through a dead/weakened form of a pathogen, which stimulates the production of antigen presenting cells/plasma cells/memory cells.
2. Specific T helper cell detect the antigen and stimulate specific B cells.
3. The B cells divide by mitosis to give plasma cells which produce antibodies and memory cells.
4. A second dose could produce antibodies in a secondary response in higher concentration and quickly.
88
What are 3 differences between active immunity and passive immunity?
1. Active immunity requires exposure to antigen, whereas passive immunity doesn't require contact with antigen.
2. Active immunity takes a long time for protection to develop, whereas passive immunity gives immediate protection.
3. Active immunity is long term as memory cells are produced, whereas passive immunity is short term as memory cells are not produced.
88
Describe the second immune response and explain why?
The second immune response is the next time an individual comes into contact with the antigen.
Clonal selection is much faster, more antibodies are produced in a short space of time.
A rapid response prevents full infection so individual is 'immune'.
88
What is herd immunity?
When a virus is destroyed within a population of vaccinated people, because virus cannot find a vulnerable host, therefore unvaccinated people are more unlikely to come into contact and spread disease.
89
Name 4 components of the HIV structure and explain their purpose?
1. RNA -> The core contains genetic material and some proteins, e.g. the reverse transcriptase enzyme.
2. Capsid -> outer protein coating.
3. Envelope -> made of membrane from previous host cell.
4. Attachment proteins -> Stick out from the envelope and attach to host helper T cells.
90
Describe how HIV is replicated.
1. Attachment proteins attach to receptor molecules on the host T helper cell.
2. Capsid is released into the cell, it un-coats, then releases RNA into the cytoplasm.
3. Reverse transcriptase makes a complimentary strand of DNA from viral RNA template.
4. This makes double stranded DNA which is inserted into the host cell human DNA.
5. Host cell enzymes are used to make viral proteins and RNA which are assembled into new viruses. These new viruses bud from the cell and infect other cells.
91
How does HIV cause symptoms of AIDS?
1. The helper T cell count drops.
2. The immune system deteriorates and eventually fails.
3. The person is then more vulnerable to other infections.
92
Why do antibiotics not work against viral infections?
Antibiotics target cells and viruses aren't cells.
Antibiotics kills bacteria by interfering with their metabolism and enzymes, whereas viruses only use humans metabolism and enzymes.
93
What are monoclonal antibodies?
Antibodies with the same tertiary structure.
94
State two uses of monoclonal antibodies.
1. Medical Treatment -> targeting medication to specific cell types by attaching a therapeutic drug to an antibody.
2. Medical diagnosis.
95
How are monoclonal antibodies used in medical treatment?
Cancer cells have antigens called tumour markers, which are not found on normal, healthy body cells.
Specific monoclonal antibodies can bind to tumour markers.
You can attach anti-cancer drugs to the specific antibodies.
Drugs will only accumulate where there are cancer cells reducing side effects.
96
How are monoclonal antibodies used in medical diagnosis? For example pregnancy tests.
Antigen binds to complementary specific antibodies in result window.
Mobile antibodies also bind to antigen.
Build up of the mobile antibodies, builds up the blue dye and creates a visible line.
Mobile antibodies bind to complementary antibodies in control window. Build up creates visible blue line.
97
Describe the role of antibodies in producing a positive result in an ELISA test.
1. First antibody attaches to complementary antigen.
2. Secondary antigen with enzyme attached is added.
3. Secondary antibody attaches to antigen.
4. Substrate/solution added and colour changes.
98
Describe the process of an indirect ELISA test.
There is an antigen coated wall.
Well is washed.
Specific antibody binds to antigen.
Well is washed.
Enzyme-linked antibody binds to specific antibody.
Well is washed.
Substrate is added and converted by enzyme into coloured product ; the rate of colour formation is proportional to the amount of specific antibody.
99
Describe the process of a direct ELISA test.
There is a monoclonal antibody-coated well.
Well is washed.
Antigen binds to antibody.
Well is washed.
A second monoclonal antibody, linked to enzyme, binds to immobilised antigen.
Well is washed.
Substrate is added and converted by enzymes into coloured product ; the rate of colour formation is proportional to the amount of antigen.
100
Describe the process of how monoclonal antibodies are formed?
1. A mouse is vaccinated to start the formation of antibodies.
2. Spleen cells that form antibodies are collected from the mouse in an operation.
3. These are fused with tumour cells called myeloma cells.
4. This forms hybridoma cells.
5. These are grown in the laboratory and those that produce antibodies are separated.
6. Antibodies are collected.
101
In the formation of monoclonal antibodies, why fuse with cancer cells?
1. Cancer cells divide rapidly.
2. B cells produce antibodies.
102
Evaluate ethical issues for the formation of monoclonal antibodies.
1. Harmful to mouse but not killed.
2. Harmful but only used once.
3. Harmful but stops human suffering.
4. Harmful but produces medicine.
5. Not harmed but injected.
