Cells Flashcards
1
Q
What is in the nucleus
A
Nucleolus, chromosome, chromatin, nuclear membrane, nuclear pore, nucleoplasm
2
Q
What does the nuclear pore do
A
Let’s materials in and out of the nucleus
3
Q
What does the nucleolus do
A
Manufactures ribosomal RNA and ribosomes
4
Q
What are the functions of the nucleus
A
To proteinsynthesis (mRNA production)
Retain genetic information (DNA, chromosomes)
Manufacturer ribosomes, ribosomal RNA
5
Q
What is in the mitochondrion
A
Double membrane, matrix, cristae, ribosomes, DNA
6
Q
Why is the cristae in the mitochondrion adapted
A
It is highly folded to provide a large surface area for enzyme attachment for aerobic respiration
7
Q
What is the rough and smooth E.R made of
A
Flat sacs - cisternae
8
Q
What does the rough E.R do
A
It is the site of proteinsynthesis and is the pathway for proteins in the cell
9
Q
What does the smooth E.R do
A
Involved in the synthesis, transport and storage of lipids and carbohydrates
10
Q
What are the functions of the Golgi apparatus
A
Add carbohydrates to proteins to form glycoproteins Make secretory enzymes Secrete carbohydrates Transport, modify and store lipids Form lysosomes
11
Q
What is a lysosome and when are they formed
A
A vesicles containing digestive enzymes
Formed when vesicles pinch off the golgi
12
Q
What are the functions of the lysosome
A
Release digestive enzymes to outside cell
Digest worn out organelles in cell
Digest materials ingested by phagocytic cells
Release digestive enzymes, break cells after they die(autolysis)
13
Q
What are the two types of ribosomes and where are they found
A
70s - prokaryotic cells
80s - eukaryotic cells
14
Q
What is in a chloroplast
A
Chloroplast enevelope, thylakoids, grana, chlorophyll, intergranal lamella, stroma
15
Q
What is the stroma
A
Fluid filled matrix where the second stage of photosynthesis occurs. Inside are a number of structures e.g starch grains
Contains all the enzymes needed to make sugars in second stage of photosynthesis
16
Q
What is the thylakoid
A
Membrane with large surface area for chlorophyll attachment- first stage of photosynthesis
17
Q
Why can chloroplasts photosynthesis quickly
A
They have DNA and ribosomes so can quickly and easily synthesise protein for photosynthesis
18
Q
What is the cell wall made of
A
Microfibrils of the polysaccharide cellulose embedded in the matrix they are strong and add to overall cell strength
19
Q
What are the features of the chloroplast
A
Made of many polysaccharides
Thin layer middle lamella which is a boundary between adjacent cell walls, cements them together
20
Q
What are the functions of the chloroplast
A
Provides strength to stop cell bursting due to osmosis
Mechanical strength to plants as whole
Let’s water pass so adds to water movement throughout plant
21
Q
What are algae cell walls made of
A
Cellulose, glycoproteins of both
22
Q
What are fungi cell walls made out of
A
Mix of chitin, glycan and glycoproteins
23
Q
What surrounds a vacuole
A
The vacuole a fluid filled sac surrounded by a single membrane called the tonoplast
24
Q
What does the solution in the vacuole contain
A
Mineral salts, sugars, amino acids, wastes and sometimes pigments
25
What is the function of a vacuole
Support herbaceous plants, making calls turgid
Sugar and amino acids act as a temporary food store
Pigment may colour petals attracting pollinating insects
26
What does the specimen need to be like when using a light microscope
Doesn't need to be extremely thin
| Can be living
27
What does the light microscope produce
The specimen can be in colour
28
What does the specimen need to be like for a transmission electron microscope
Must all be in a vacuum
A complex staining process must occur
Must be very thin
29
How does a transmission electron microscope work
Electrons are passed through the specimen using a very short wavelength producing a very high resolution 2D image on the screen
30
What is sometimes a problem with using electron transmission microscopes
When cutting the specimen it may contain artefacts - things on the image that aren't part of the specimen
31
How does a scanning electron microscope work
Using a very short wavelength electrons are used to make a very high resolution 3D image
32
How must the specimen be when using a scanning electron microscope
Specimen doesn't need to be extremely thin
| Must be in a vacuum
33
What is the definition of resolution
Minimum distance apart two objects can be for them to appear as separate items
34
What do the letters in the AIM triangle represent
I - image (measurement)
A - actual size (real image)
M - magnification
35
What are the conversions (m, mm, micrometers, nanometers)
1m = 1000mm
1mm = 1000 micrometers
1 micrometer = 1000 nanometers
36
In cell fractionation what conditions is the tissue kept under
Ice cold water - stop autolysis
pH buffer - stop enzyme denaturing
Isotonic - keep constant (sugar, glucose..) concentration
37
What are the stages in cell fractionation
Tissue cut up and kept in certain conditions
Tissue further broken in homogeniser once homogenate filtered (remove debri)
Homogenised tissue spun in ultracentrifuge at low speed for 10 minutes
Then supernatant and sediment are split
38
What would be in sediment 1 and in supernatant 1 in an ultracentrifuge
Sediment 1 - nuclei (as most dense)
| Supernatant 1 - mitochondria, lysosomes..
39
What type of ribosomes are in a prokaryotic cell
70s
40
What is in a prokaryotic cell
70s ribosomes, cytoplasm, plasmid, cell surface membrane, cell wall, capsule, flagellum, circular loop of DNA
41
What does the plasmid in a prokaryotic cell do
It has genes that aid bacteria survival in adverse conditions
42
What does the cell surface membrane in a prokaryotic cell do
It is differentially permeable later it controls the chemicals that go in and out
43
What is the function of the cell wall in a prokaryotic cell
It is a physical barrier that protects against damage and osmotic lysis
44
What does the capsule in a prokaryotic cell do
Protects bacterium from other cells and helps bacteria groups stick together for further protection
45
What is the job of the flagellum in a prokaryotic cell
It moves the cell
| May be more than one for locomotion (only certain species)
46
What does the circular loop of DNA in a prokaryotic cell do
It has genetic information to replicate bacterial cells
47
What does a virus structure contain
Lipid envelope, genetic material RNA, matrix, capsid, reverse transcriptase
48
What does the capsid in the virus cell do
Is a protein layer in the envelope that encloses two single RNA strands and some enzymes
49
What does the reverse transcriptase in a virus cell do
It is an enzyme that catalyses DNA production from RNA
50
What is mitosis
Cell division in eukaryotes that makes two genetically identical daughter cells from one parent cell
51
What is mitosis used for
For growth and tissue repair
52
What occurs at interphase
This is the preparation phase
Chromosomes are not visible
Organelles are replicating
DNA replication
53
What occurs at prophase
DNA condenses to form chromosomes
Each chromosome has 2 arms (chromatids) held by the centromere
Nuclear membrane disappears spindle fibres form (from centrioles)
54
What occurs at metaphase
Chromosomes line along the equator
| Spindle fibres attach to the centromere of each chromosome
55
What occurs at anaphase
Chromosomes separate and identical chromatids are pulled to opposite poles of the cell
Spindle fibres shorten pull chromatids apart
56
What occurs at teleophase
Chromatids now called chromosomes
Nuclear membrane form around 2 groups
Cytoplasm / cell membrane constrict
57
What occurs at cytokinesis
The cell divides and two cells form
| DNA becomes indistinct
58
What is the function of a phospholipid in a cell surface membrane
Stops water soluble substances going in/out of the cell
Let's lipid soluble substances in/out
Makes flexible self-sealing membrane
59
What is the function of a channel protein in the cell surface membrane
They form water-filled tubes that let water soluble substances / non lipid soluble substances diffuse across the membrane
60
What is the function of a glycoprotein in the cell surface membrane
Acts as a recognition site, cells attach to each other to form tissues and this site helps cells recognise
61
What is the function of a receptor protein in the cell surface membrane
Used in intercellular communication
62
What is the function of a carrier protein in the cell surface membrane
Binds to ions/molecules e.g glucose then changes its shape to move it across the membrane
63
What is the function of a glycolipid in the cell surface membrane
Acts as a recognition site, helps maintain the membranes stability and helps cells attach to each other to form tissues
64
What is the function of cholesterol in the cell surface membrane
To reduce lateral movement of molecules including phospholipids
To make the membrane less fluid in high temperatures
Stop water leaking/dissolved ions from cell
65
What is a phospholipid bilayer
Two phospholipids hydrophobic tails facing each others and hydrophobic heads away from each other
66
What can uncontrollable cell division lead to
Formation of tumours and cancers
67
How may cancer be treated
By controlling the rate of cell division
68
What is a pathogen
A disease-causing microorganism
69
How do pathogens cause harm
Produce toxins
| Cause damage to host cells/tissues
70
What is non specific immunity
Doesn't distinguish between pathogens but fast acting
Phagocytosis
Pathogen barrier
71
What is specific immunity
Distinguishes between different pathogens
Less rapid response but long term immunity
Involves white blood cell - lymphocyte (T and B)
72
Why doesn't our immune system attack own cells
Lymphocytes must be able to distinguish body's own cells and chemicals (self) from foreign (non-self) if couldn't do this would destroy own tissues
Each cell has specific molecules on surface identify it, variety of types, proteins that are most important as have enormous variety and high specific tertiary structure, distinguishes cells
73
What do the proteins allow the immune system to identify
Pathogens
Non-self materials e.g. cells from other organism of same species
Abnormal body cells e.g. cancer
Toxins including those produced by pathogens e.g. cholera pathogen
74
How does the correct lymphocyte replicate
Out of the 10million different lymphocytes a protein on lymphocyte surface will be complementary to the protein on pathogen surface, this lymphocyte recognises the pathogen and replicates
75
Why is there a time lag between exposure to the pathogen and body's defences bringing it under control
As so many types of lymphocyte, not many of each type. Complementary lymphocyte must replicate and build numbers to level where can be effective in destroying it
76
Why must organ transplants have a close tissue match
The immune system recognises the donor tissue as non-self attempts to destroy transplant, minimise effect organs with close tissue matches used and immunosuppressant drugs of en used
77
How does immune system ensure that none of the 10 million lymphocytes match own cell when a foetus
In foetus lymphocytes constantly colliding in other cells
Infection in foetus rare as protected from outside by placenta
Lymphocytes collide with body's own material (self)
Die or be suppressed
Some lymphocytes have receptors that fits body's own cells
Remaining lymphocytes might fit foreign material (non-self)
78
How does immune system ensure that none of the 10 million lymphocytes match own cell when an adult
In adults, lymphocytes produced in bone marrow only initially encounter self-antigens
Any lymphocytes that show immune response to self-antigens undergo programmed death - apoptosis before mature lymphocytes
No anti-lymphocytes clones will appear in blood only leaving those that might respond to non-self antigens
79
What are the two main types of white blood cells
Phagocytes - engulf and destroy pathogen by process phagocytosis before can cause harm.
Lymphocytes - involved in specific immune response
80
How does phagocytosis occur
Phagocyte attracted to pathogen by a chemoattractant of pathogen, moves towards pathogen along concentration gradient
Receptors on phagocyte surface membrane attach to surface of pathogen
Lysosomes in phagosome migrate to pathogen formed by engulfing bacterium
Lysosomes release lysozymes into phagosome, hydrolyse bacterium - now soluble molecules absorbed into phagocyte cytoplasm
80
What is an antigen
Usually a protein that is on the cell surface membrane of a pathogen that induces an immune response in the cell e.g. antibody production
80
What do B-lymphocytes do and where are they made
Mature in bone marrow
| Associated with immunity involving antibodies present in body fluids ("humour") - humour also immunity
81
What do T-lymphocytes do and where are they made
Mature in the thymus gland
| Associated with cell-mediated immunity - involving body cells
82
What do T-lymphocytes respond to
Organisms own body cells invaded by non-self material e.g. virus
83
How do T-cells know when cells are genetically non-self
Respond to cells from individuals of same species as they're genetically different so different antigens on cell surface membrane
84
How do T-cells recognise forgein cells
Phagocytes which engulfed, digested/hydrolysed pathogen and body cells infected by a virus, present some of pathogens antigen on cell membrane
Transplanted cells different antigens on membranes
Cancer cells different from normal body cells, display antigens on membrane
85
What are the four stages in cell-mediated immunity and which lymphocyte is involved (in order they occur)
Antigen presentation
T-helper cell activation
T-helper cells divide by mitosis
Cytotoxic T-Cells, memory cells, activates B-lymphocytes, stimulates phagocytosis
86
What occurs at the antigen presentation stage
Pathogen broken down, protein from pathogen presented in surface of affected cell
Body cell 'shows' antigen to all T-cells
87
What occurs at T-helper cell activation
Millions of different T-helper cells (still T-lymphocyte) in blood all with different shaped receptors
One with receptor which fits antigen binds and T-helper cell activated
88
What happens once the T-her cells are activated
Divide by mitosis form T-helper cell clones
These:
Stimulate cytotoxic Tc cells
Develop into memory cells enable rapid response to future infection by same pathogen
Activates B lymphocytes divide, secrete antibody
Stimulates phagocytosis
89
How do cytotoxic T-cells work
Kill body cells infected by pathogens
Produce protein - perforin that makes holes in infected cell membrane, freely permeable to all substances, dies
Most effective as viruses replicate inside cells
90
Why are there so many different B-cells
Around 10million different B-cells produce a different type of antibody respond to specific antigen
Antigen enter blood one B-cell that has antibody on surface that's complementary to the antigen
Antibody attaches to antigen (antigen-antibody complex)
Antigen enters B-cell by endocytosis is presented on surface
Th cell bind to processed antigens stimulate B-cell replicate by mitosis, clones produce same specific antibody - clonal selection
91
What are the two B-lymphocytes
Plasma cells
| Memory cells
92
What is a plasma cell how long does it last and what does it do
Secrete antibodies directly
Only survive few days
Make 2000 antibodies every second
Antibodies destroy pathogen and toxins it produces
Responsible for immediate defence against infections
Primary immune response
93
How long to memory cells live and what do they do
Longer than plasma cells sometimes decades
Don't produce antibodies directly but circulate in blood and tissue fluid
If encounter same antigen at later date divide rapidly develop into plasma cells produce antibodies kill pathogen
Provide long term immunity against original antigen - secondary immune response
Produced far larger antibody amount more rapidly, pathogens destroyed before symptoms develop
94
What occurs at humoral immunity
Surface antigens of invading pathogen taken up by B-cell (endocytosis)
B-cell processes antigens, presents in its surface
Helper T-cells (activated in process) attach to processed antigens in B-cell, activating them
B-cell now activated, divide by mitosis give clone of plasma cells
Clone produce, secrete specific antibodies fit antigen on pathogen surface
Antibody attaches to antigen on pathogen, destroys it
Some B-cells develop into memory cells, can respond to future infection by same pathogen by dividing rapidly into plasma cells
95
What is the primary immune response
Initial exposure to antigen, immune response
| Not many antibodies made
96
What is the secondary immune response
Second exposure to same antigen, more antibodies produced rapidly kill pathogen before symptoms
97
Why does each pathogen lead to numerous different antibodies
Typical pathogen has many different proteins on surface all act as different antigens
Some pathogens produce toxins
Each protein/toxin acts as antigen so many different B-cells make clones, produce own antibodies
98
What is another name for an antibody
Immunoglobulin
99
Describe the structure of an antibody
All have similar structure composed of 4 polypeptide chains (2 heavy and 2 light) joined by strong disulphide bonds to form a Y-shape
Stem of Y is the constant region, all have same amino acid sequence
Ends of Y arms are variable regions as all have different amino acid sequence and so different structures. These 2 sites are called antigen-binding sites
Variable regions where antigens bind to form antigen-antibody complexes
100
How do bacterial cells destroy antigens
Cause agglutination of bacterial cells so clumps of bacteria are formed, easier for phagocytes to locate them
Serve as markers that stimulate phagocytes to engulf the bacterial cells to which they're attached
101
What chemical bind joins the amino acids in an antibody
Peptide bond
102
How is passive immunity achieved
Introducing antibodies into individuals from outside source
| No direct contact needed with antigen or pathogen
103
Why isn't passive immunity long lasting
Antibodies not being produced by individuals the antibodies aren't replaced when broken down, no memory cells are formed
104
What are some examples of passive immunity
Anti-venom given to victims of snake bites
| Immunity acquired by foetus when antibodies pass across placenta from mother
105
How is active immunity achieved
Stimulating the production of antibodies by the individuals own immune system
Direct contact with the pathogen is necessary
Immunity takes time to develop usually long lasting
106
What is natural active immunity
Results from individual becoming infected with disease under normal circumstances
Body produces own antibodies and memory cells
107
What is artificial active immunity
Forms basis of vaccination (immunisation)
| Inducing immune response in individual (antibodies, memory cells produced) no disease symptoms
108
What is a vaccination
Introducing appropriate disease antigen into body, injection or mouth
Contain dead or attenuated version of pathogen or usually one or more antigens from pathogen
Stimulates immune response, memory cells produced
109
How does a vaccination work
Antigens in vaccination stimulate immune response to particular disease, producing antibodies and importantly memory cells
Memory cells remain in blood if individual comes into contact with same antigen/pathogen again there is rapid production of large amount of antibodies (secondary response) so that the pathogen is killed before any symptoms develop
When carried out on large scale provides protection against disease for whole populations
110
What factors affect the success of a vaccination programme
Must be possible to vaccinate vast majority of vulnerable population to produce herd immunity
Administering vaccine properly at appropriate time, must train staff with right skills at different centres throughout population
Must be able to produce, store, transport vaccine usually involves technology advanced equipment, hygienic conditions, refrigerated
Suitable vaccine economically available in sufficient quantities to immunise most of vulnerable population
Few if any side effects
111
What is herd immunity
When a large proportion of the population has been vaccinated make it difficult for the disease to spread within population
Concept based in idea disease passed from person to person in close contact
Vast majority of people vaccinated, unlikely susceptible person contact with infected one.
112
Why is herd immunity important
Not possible to vaccinate everyone
Babies/young cant be as immune systems not fully functional
Dangerous if ill or have compromised immune systems
Vaccination percentage varies to achieve herd immunity for different diseases
Vaccination best carried out at one time, certain period very few infected, disease transmission interrupted
113
Why might vaccination not eliminate disease
May fail to induce immunity in some
Many varieties of pathogen may exist, impossible develop vaccine that's effective against all
Pathogen may mutate frequently, antigens change and vaccines ineffective, immune system no longer recognises them no antibodies made
Individuals may have objections to vaccines e.g. religious, ethics, medical
Certain pathogens 'hide' from immune system concealing in cells or living in places out of reach e.g. cholera in intestines
114
What are some ethical questions raised due to vaccines
Production of vaccines often involves animals
Side-effects may cause long-term harm, how is side-effect risk balanced with risk of developing disease causing more harm
Who are they tested on
Is it ok to trial new vaccine with unknown health risks only in country where targeted disease is common on basis population has most to gain
How can any individual health risks from vaccination be balanced against advantages of controlling disease
115
What is a monoclonal antibody
Antibodies produced from a single clone of B-plasma cell so they will only recognise one particular antigen
116
Why can monoclonal antibodies be used in research and medicine
They're specific to certain antigen so can be used to target specific substances/cells
117
How are monoclonal antibodies used in cancer treatment
Produce specific monoclonal antibodies that are complementary to the antigens on the cancer cell
Given to patient, attach themselves to receptors on cell
Attach into surface blocking chemical signals that stimulate uncontrolled growth
118
What are the advantages of using monoclonal antibodies to treat cancer
Antibodies aren't toxic and are highly specific
| Lead to fewer side effects than other therapy forms
119
What is indirect monoclonal antibody therapy
Involves attaching radioactive/cytotoxic drug to monoclonal antibody
When antibody attaches to cancer cell, kills them
120
What is the advantage of using indirect monoclonal antibody therapy over conventional
Referred to as 'magic bullets' can be used in smaller doses as they're targeted on specific sites
Cheaper, reduces drug side effects
121
How does a pregnancy test work
Urine sample applied to bottom of stick
Any hCG present binds to first anti-hCG antibody (complementary)
In test region is immobilised anti-hCG antibodies, bind alternative sites on hCG , trapping at the site, enzyme attached to first antibody changes colour of coating in stick, evidence of positive test
Control region has unbound antibodies, progress up stick here where bound by third type of antibody. Again attached enzyme causes colour change, proof only antibodies behaving properly
122
Arguments for the use of monoclonal antibodies
Successfully treated diseases such as cancer, diabetes - saved lives
Used to indicate pregnancy
Diagnosis of influenza, hepatitis, chlamydia
123
Arguments against the use of monoclonal antibodies
Mice induced with antibodies, to make antibodies needed in pregnancy test, but they may get cancer
Use of treatment caused deaths associated with MS
124
What does the ELIZA test do and what is it used for
Uses antibodies to detect protein presence in sample, and quantity. Very sensitive, only detect very small amounts of a molecule in sample being tested. Used to detect HIV, TB, hepatitis and do particular drugs and allergens
125
What would occur when trying to see if particular protein, in this case an antigen is present in a sample
1. Apply sample to surface where all antigens in sample will attach
2. Wash surface several times to remove any unattached antigens
3. Add antibody (sample being tested) that's specific to antigen we're trying to detect, they bind
4. Wash surface to remove excess
5. Add secondary antibody, bind with first one. Secondary has enzyme attached
6. Re-wash remove enzyme, add colourless substrate. Enzyme reacts change the colour. Amount of antigen present relative to intensity of colour
126
What is HIV
Human immunodeficiency virus
127
What is AIDS
Acquired immune deficiency syndrome
128
What does HIV cause
AIDS
129
What is the structure of HIV
Same as a virus cell
130
How does HIV cause the symptoms of AIDS
1. HIV virus specifically attracts T-helper cells, which are killed
2. Uninflected person normally has 800-1200 helper T-cells in each mm^3 of blood. If have AIDS can be as low as 200mm^-3
3. Not enough T-helper cells immune system can't stimulate B cells to make antibodies
4. Body can't make immune response, becomes susceptible to infection
131
Why do many AIDS suffers develop infections
Body can't produce and immune response so susceptible to other infections
132
Does HIV cause death
Not directly, but infecting immune system prevents functioning causing infections
133
What occurs in the replication of HIV
1. HIV enters the blood stream, circulates round body
2. Protein on HIV readily binds to protein CD4, while protein occurs on cells, HIV most frequently attacks T-helper cells
3. Protein capsid fuses with cell surface membrane, RNA and enzymes from HIV enter helper-T cell
4. HIV reverse transcriptase converts virus RNA to DNA
5. Newly made DNA moved into helper-T cell nucleus where incorporated into DNA cells
6. HIV DNA in nucleus makes mRNA using cells enzymes, mRNA contains new viral protein/RNA to go into new HIV instructions
7. mRNA passes out nuclear pores into cytoplasm, uses cells proteinsythesis mechanism crate HIV particles
8. HIV breaks away from helper-T cell with piece of cell surface membrane surrounding which makes lipid envelope
