topic 2 Flashcards
1
Q
What is the function of the cell membrane?
A
Regulates the movement of substances into and out of the cell.
2
Q
What is the function of the nucleus?
A
Contains the organism’s hereditary material and controls cell activities.
3
Q
What is the function of the mitochondria?
A
Site of aerobic respiration and where ATP is produced.
4
Q
What is the function of chloroplasts?
A
Site of photosynthesis.
5
Q
What is the function of the Golgi Apparatus?
A
Modification and packaging of proteins.
6
Q
What is the function of lysosomes?
A
Break down materials and waste.
7
Q
What is the function of ribosomes?
A
Site of protein synthesis.
8
Q
What is the function of rough endoplasmic reticulum?
A
Synthesis and packaging of proteins.
9
Q
What is the function of the smooth endoplasmic reticulum?
A
Lipid synthesis.
10
Q
What is the function of the cell wall?
A
A rigid, permeable layer that supports the cell and provides mechanical strength against osmotic pressure.
11
Q
What is the function of the cell vacuole?
A
Helps to maintain pressure inside the cell and keep the cell rigid.
12
Q
What is the structure of the nucleus?
A
Nuclear envelope, nuclear pores, chromosomes, nucleolus, nucleoplasm.
13
Q
What is the structure of the cell surface membrane?
A
Phospholipid bilayer with proteins, cholesterol, glycolipids, and glycoproteins.
14
Q
What is the structure of mitochondria?
A
Double membrane with inner membrane folded into cristae and a matrix.
15
Q
What is the structure of chloroplasts?
A
Chloroplast envelope, grana, and stroma.
16
Q
How are chloroplasts adapted to their function?
A
Granal membranes provide a large surface area for attachment of chlorophyll and enzymes.
17
Q
What is the structure of Golgi Apparatus?
A
A stack of membranes forming flattened sacs known as cisternae.
18
Q
What is the function of Golgi Vesicles?
A
Store and transport modified proteins and lipids from the Golgi apparatus.
19
Q
What is the structure of Lysosomes?
A
A membranous sac containing hydrolytic enzymes.
20
Q
What is the structure of a ribosome?
A
Large and small subunit each containing RNA and protein.
21
Q
What is the structure of the Rough Endoplasmic Reticulum?
A
A system of membranes enclosing a fluid filled space covered in ribosomes.
22
Q
What is the structure of the Smooth Endoplasmic Reticulum?
A
A system of membranes enclosing a fluid filled space lacking ribosomes.
23
Q
What is the structure of the cell wall?
A
Consists of cellulose microfibrils embedded in a matrix.
24
Q
Substance for plant and algae cell walls?
A
Cellulose.
25
Substance for bacterial cell walls?
Murein.
26
Substance for fungal cell walls?
Chitin.
27
What is the structure of the cell vacuole?
Contains cell sap and has a surrounding membrane called the tonoplast.
28
What is cell specialization?
The process in which cells develop in different ways to perform particular roles.
29
How does a cell become specialized?
Only some of the genes are expressed in any one cell at any one time.
30
What is a tissue?
A group of similar cells that work together to carry out a particular function.
31
What is an organ?
A group of different tissues that work together to perform a variety of functions.
32
What is an organ system?
A group of organs working together to carry out a particular function.
33
What is a eukaryotic cell?
Cell with a nucleus and membrane bound organelles.
34
What is a prokaryotic cell?
Cell that does not have a nucleus or any membrane bound organelles.
35
Structure of a prokaryotic cell?
Circular strand of DNA, plasmids, 70S ribosomes, surrounded by a plasma membrane.
36
Function of bacterial cell wall?
Physical barrier that excludes certain substances and protects against mechanical damage.
37
Function of bacterial capsule?
Protects cell from other cells and helps groups of bacteria stick together.
38
Function of the circular DNA strand?
Possesses the genetic info for the replication of cells.
39
Function of plasmids?
Possesses genes that may aid survival of bacteria.
40
Differences between prokaryotic cells and eukaryotic cells?
Prokaryotic cells have no true nucleus and no membrane bound organelles.
41
What is a virus?
A tiny, acellular, non-living particle that enters and reproduces inside a living cell.
42
Structure of viruses?
Genetic material, reverse transcriptase enzyme, lipid envelope, attachment proteins, capsid.
43
Why do electron microscopes have higher resolving power than light microscopes?
Electrons have a smaller wavelength than visible light.
44
What is resolution?
The minimum distance apart that two objects can be in order for them to appear as separate items.
45
What is magnification?
How many times larger an image is than when compared to the actual object.
46
What is cell fractionation?
The process where cells are broken up and the different organelles they contain are separated out.
47
What must the conditions be before cell fractionation?
Cold, isotonic, and buffered.
48
What are the 2 stages of cell fractionation?
Homogenisation and ultracentrifugation.
49
What is homogenisation?
Breaking up of cells in a blender to release organelles.
50
What is ultracentrifugation?
The process by which the fragments in the filtered homogenate are separated.
51
How are electron microscopes focussed?
Electromagnets.
52
Limitations of electron microscopes?
Whole system must be in vacuum, complex staining process, extremely thin specimen.
53
Why can't the high resolving power of a TEM always be achieved?
Difficulties preparing specimen limit the resolution.
54
How to measure specimen in light microscopes?
Eyepiece graticule.
55
How to calibrate eyepiece graticule?
Use stage micrometer and count units.
56
What is mitosis?
Cell division in which a eukaryotic cell divides to produce 2 identical daughter cells.
57
What happens in interphase?
G1 - cell growth, S - DNA replication, G2 - preparation for mitosis.
58
What happens in prophase?
Chromosomes shorten and thicken, centrioles move to opposite poles.
59
What happens in metaphase?
Centrioles form spindle across the cell, chromosomes move to equator.
60
What happens in anaphase?
Centromeres divide, spindle fibres pull individual chromatids to opposite poles.
61
What happens in telophase?
Chromosomes reach their poles and become longer and thinner.
62
What is cytokinesis?
The cytoplasmic division of a cell at the end of mitosis.
63
Cell division in prokaryotic cells?
Binary fission.
64
Binary Fission process?
Circular DNA replicates and attaches to cell membrane.
65
Replication of viruses?
Attaching to host cell with attachment proteins.
66
What are 3 stages of cell cycle?
Interphase, Nuclear Division, Cytokinesis.
67
What is cancer?
Uncontrolled cell division by mitosis.
68
Why is mitosis important?
Growth, Repair, Reproduction.
69
How do cancer drugs work?
Preventing DNA from replicating and inhibiting metaphase stage.
70
Functions of phospholipids in cell membranes?
Allow non-polar substances to move in and out of the cell.
71
What is the fluid mosaic model?
Describes the arrangement of the molecules that make up a cell membrane.
72
Function of glycolipids and glycoproteins?
Recognition sites and helps cells attach to each other.
73
Function of cholesterol in plasma membrane?
Reduce lateral movement of phospholipids.
74
Functions of protein in plasma membrane?
Provide structural support and act as channel proteins.
75
Define simple diffusion.
The net movement of particles from high concentration to low concentration.
76
What are limitations to simple diffusion across cell membrane?
Particles that are large and/or polar have difficulty diffusing.
77
Define facilitated diffusion.
The net movement of particles down their concentration gradient with help of proteins.
78
What is a channel protein?
An intrinsic protein that forms a water-filled pore in the membrane.
79
What is a carrier protein?
A protein which changes shape to allow larger molecules to pass through.
80
Define osmosis.
The passage of water from a region of higher water potential to lower water potential.
81
Define active transport.
The movement of molecules from lower concentration to higher concentration using ATP.
82
Describe the active transport of a single molecule/ion.
Carrier proteins bind to molecule and ATP causes shape change.
83
Define co-transport and absorption of glucose in the ileum.
Sodium ions are actively transported out of the epithelial cells.
84
3 ways the rate of movement across membranes can be increased?
Increasing concentration gradient, increasing surface area, increasing density of proteins.
85
Define co-transport.
A method of membrane transport where 2 substances are transported at the same time.
86
What is co-transport?
A method of membrane transport where 2 substances are both transported across a membrane at the same time either in the same or opposite directions.
87
How do sodium ions assist in the transport of glucose or amino acids?
Sodium ions diffuse through a co-transport protein, carrying either amino acid or glucose molecules with them.
88
How can the rate of movement across membranes be increased?
1) Increasing/maintaining concentration gradient
2) Increasing surface area
3) Increasing density of protein channels and carrier proteins.
89
What is immunity?
The ability of an organism to resist infection from invading disease-causing microorganisms, which may involve an immune response through the activation of lymphocytes.
90
What are the types of lymphocytes?
1) T lymphocyte cells
2) B lymphocyte cells.
91
What are T lymphocytes?
Associated with cell-mediated immunity and mature in the thymus gland.
92
What are B lymphocytes?
Associated with humoral immunity and mature in the bone marrow.
93
What is an antigen?
Specific molecules on a cell's surface that identify it; a foreign protein that stimulates an immune response.
94
What do antigens allow the immune system to identify?
- Pathogens
- Cells from other organisms of the same species transplants
- Abnormal body cells
- Toxins.
95
Why does the immune system have a lag between exposure and response?
The specific lymphocyte to the pathogen's antigen is stimulated to divide and build up its numbers to a level where it can be effective in destroying it.
96
What are the two defense mechanisms?
Non-specific and specific.
97
What is a non-specific defense mechanism?
Response is immediate and the same for all pathogens, e.g., stomach acid and skin barrier.
98
What is a specific defense mechanism?
Response is slower and specific to each pathogen, e.g., T and B lymphocytes.
99
What is antigen variability?
The antigens on a pathogen develop variation that can lead to new strains arising in a population.
100
What is the effect of antigen variability on disease and disease prevention?
It is easier to develop vaccines and immunity to pathogens with little or no antigen variability.
101
What is the process of phagocytosis?
1) Chemical products from the pathogen act as attractants for the phagocyte to move towards along a concentration gradient.
2) The phagocyte attaches to the surface of the pathogen.
3) The phagocyte engulfs the pathogen to form a vesicle known as a phagosome.
4) Lysosomes move towards the phagosome and fuse with it, forming a phagolysosome.
5) Enzymes called lysozymes are present within lysosomes and destroy the ingested bacteria by hydrolysis of cell walls.
6) Small soluble products of breakdown are absorbed into the cytoplasm of the phagocyte.
102
What is the T lymphocytes response to foreign antigens?
1) Pathogens invade the body and are ingested by phagocytes.
2) Phagocyte inserts pathogen's antigens into its cell surface membrane to become an antigen-presenting cell.
3) Receptors on a specific helper T cell bind to these antigens.
4) This attachment activates the helper T cell to divide by mitosis rapidly to form clones.
5) These clones:
- Develop into memory cells for faster future response.
- Stimulate phagocytes to engulf more pathogens.
- Stimulate B cells to divide and secrete antibodies.
- Activate cytotoxic T cells.
103
What is the role of antigen-presenting cells in the cellular response?
T lymphocytes will only respond to antigens presented on a body cell.
- Phagocytes presenting pathogen antigens.
- Body cells invaded by virus present virus antigens.
- Transplanted cells have foreign antigens.
- Cancer cells are different from normal body cells and present antigens on the membrane.
104
How do cytotoxic T cells kill infected cells?
By producing a protein called perforin, which makes holes in the cell surface membrane of cells, becoming freely permeable to all substances and killing the cells.
105
What is the B lymphocytes response to foreign antigens?
1) The surface antigens of a pathogen are taken up by a B cell.
2) The B cell processes the antigens and presents them on its surface.
3) Helper T cells attach to processed antigens and activate B cells.
4) B cells divide by mitosis to produce clone plasma cells.
5) Cloned plasma cells secrete specific antibodies.
6) This antibody attaches to antigens and destroys them.
7) Some B cells develop into memory cells which can divide rapidly to form plasma cells if infected again in the future for a quick response.
106
What is clonal selection?
Part of the immune response where specific B cells and helper T cells are chosen to divide by mitosis to produce clones.
107
Why are antibodies in the immune response referred to as monoclonal?
Each clone produces one specific antibody.
108
What is a monoclonal antibody?
Antibodies with the same tertiary structure.
109
What is an antibody?
A globular protein produced by a plasma cell in response to a specific, complementary antigen.
110
What is the structure of an antibody?
- Made from 4 polypeptide chains - 2 heavy and 2 light arranged into a Y shape held together by disulphide bridges.
- Each binding site is different and is therefore known as the variable region formed by unique amino acid sequences to form a specific 3D shape.
- The rest of the antigen is a constant region - contains receptor binding site to attach to other antibodies or lymphocytes, etc.
111
What is an antigen-antibody complex?
When an antibody with a complementary shape to an antigen binds.
112
How do antibodies lead to the destruction of pathogens?
1) Agglutination - clumps of pathogens, easier for phagocytes to locate them and less spread out.
2) Serve as markers which stimulate phagocytes to engulf pathogens attached.
113
What are plasma cells?
- Responsible for the primary immune response.
- Secrete antibodies into the blood plasma.
114
What are memory cells?
- Responsible for secondary immune response (circulate in blood and divide rapidly when the same antigen is encountered again to form plasma cells).
- Produce antibodies faster and in higher quantities.
115
What are the uses of monoclonal antibodies in medicine?
1) They can be used to target specific substances and cells, e.g., cancer cells in direct monoclonal antibody therapy (Herceptin for breast cancer cells).
2) Medical diagnosis (HIV and pregnancy).
3) ELISA tests.
116
What is direct monoclonal antibody therapy?
1) Monoclonal antibodies are produced that are specific to the cancer cells.
2) Antibodies are given to a patient and attach to receptors on their cancer cells.
3) They block the chemical signals that stimulate their uncontrolled growth.
## Footnote
+ Very specific and not toxic, therefore less side effects.
117
What is indirect monoclonal antibody therapy?
A radioactive or cytotoxic drug is attached to the antibody. When the antibody binds to cancer cells, the drug is delivered and it kills the cell.
118
What are the ethical issues with monoclonal antibodies?
1) Involves the use of mice to produce antibodies and tumor cells (purposely inducing cancer into mice).
2) Have been some deaths associated with their use; patients must fully understand risks (informed consent).
3) In March 2006, drug testing for monoclonal antibodies sent patients into multiple organ failure, raising issues.
119
What are the types of immunity?
1) Active (natural and artificial)
2) Passive.
120
What is passive immunity?
The introduction of antibodies into an individual from an outside source - no direct contact with the pathogen or antigen is necessary to induce immunity.
- As antibodies aren't being produced by individuals, antibodies aren't being replaced, so no long-lasting immunity, e.g., antivenoms.
121
What is active immunity?
The immunity that results from the production of antibodies by the individual's own immune system in response to the presence of an antigen.
- Natural (infected with disease)
- Artificial (vaccination).
122
What is a vaccination?
Introduction of a vaccine containing appropriate disease antigens into the body to induce artificial active immunity against a disease (received orally or by injection).
123
What are the features of a successful vaccination program?
Protecting the population via herd immunity.
- Suitable vaccine must be economically available in sufficient quantities.
- Few side effects, if any.
- Means of producing, storing, and transporting must be available.
- Means of administering the vaccine appropriately.
- Must be possible to vaccinate the majority of the population to reach herd immunity.
124
What is herd immunity?
Immunity in most of a population, therefore the transmission is interrupted, preventing infection of unvaccinated individuals.
125
Why is herd immunity important?
- It is never possible to vaccinate everyone in a large population, e.g., babies and young children who cannot get vaccinated as their immune systems are not yet fully functional.
- It could also be dangerous to vaccinate those who are ill or have a compromised immune system.
126
Why vaccination may not eliminate a disease?
- Vaccination fails to induce immunity in those with defective immune systems.
- Individuals may develop the disease immediately after vaccination, before immunity levels are high enough to prevent infection, therefore infecting others.
- Pathogen may mutate frequently (antigenic variability), making vaccines ineffective.
- There may be many varieties of the pathogen (common cold).
- Certain pathogens hide from the immune system, therefore will never be detected by memory cells.
- Individual objections, e.g., religion.
127
What are the ethics of using vaccines?
- Involves the use of animals for testing.
- May have long-term side effects.
- Is it right to make vaccination compulsory?
128
What is the structure of the HIV virus?
- Lipid envelope embedded with attachment proteins.
- Protein layer capsid that encloses two single strands of RNA and enzymes, e.g., reverse transcriptase (catalyzes production of DNA from RNA), therefore called retrovirus.
129
What is the replication process of HIV in helper T cells?
1) Following infection, HIV enters the bloodstream and circulates around the body.
2) A protein on the HIV readily binds to a protein called CD4 on helper T cells.
3) The protein capsid fuses with the cell-surface membrane, and the RNA and enzymes of HIV enter the helper T cell.
4) The HIV reverse transcriptase converts the virus's RNA to DNA, which is moved into the helper T cell's nucleus where it is inserted into the cell's DNA.
5) The HIV DNA in the nucleus creates mRNA using the cell's enzymes, which contains the instructions for making new viral proteins and the RNA to go into the new HIV.
6) The mRNA passes out of the nucleus through a nuclear pore and uses the cell's protein synthesis mechanisms to make HIV particles.
7) The HIV particles break away from the helper T cell with some of its cell-surface membrane surrounding them, which forms their lipid envelope.
130
How does HIV cause symptoms of AIDS?
- HIV specifically attacks helper T cells and causes AIDS by killing and interfering with their normal functioning.
- A person suffering from AIDS has a significantly lower amount of helper T cells in their blood than a healthy person.
- Without a sufficient number of helper T cells, the immune system cannot stimulate B cells to produce antibodies or cytotoxic T cells that kill cells infected by pathogens. Memory cells may also become infected or destroyed. Consequently, the body becomes unable to produce an adequate immune response and becomes susceptible to infections and cancers.
- Many AIDS sufferers develop infections in the lungs, intestines, brain, and eyes, as well as experiencing weight loss and diarrhea. These secondary diseases can ultimately cause death.
131
What is the ELISA test and its procedure?
ELISA stands for enzyme-linked immunosorbent assay. It uses antibodies to detect proteins in a sample.
- Apply sample to a surface for antigens to attach.
- Wash to remove unattached antigens.
- Add specific antibody and leave to bind.
- Wash to remove excess antibody.
- Add second antibody with enzyme that binds to original.
- Add colorless substrate of enzyme - enzyme acts to change it to a colored product.
- Amount of antigen measured by color intensity, therefore can measure quantity - good for allergen and drug tests.
132
Why are antibiotics ineffective against viruses?
- Antibiotics work by disrupting the formation of functional cell walls in bacteria, causing osmotic lysis.
- However, viruses rely on host cells for metabolic processes, therefore lack their own metabolic processes and cell structures to be disrupted.
- Viruses also don't have a cell wall but a protein capsid, so there are no sites for antibiotics to work.
- Viruses can't be reached inside host cells by antibiotics.
133
How to calculate the mitotic index?
Count cells in mitosis in the field of view.
- Divide this by the total number of cells in view.
- Repeat many times.
