Cells Flashcards
(115 cards)
1
Q
Role of the cell surface membrane
A
Regulates the movement of substances in and out of the cell. It has receptor molecules which allow it to respond to chemicals like hormones.
2
Q
Role of the nucleus
A
Controls the cells activities through transcription of mRNA, pores in the envelope allow substances to move between the nucleus and cytoplasm.
3
Q
Role of the mitochondrion
A
The site of aerobic respiration, where ATP is produced. Found in large numbers in active cells that require a lot of energy.
4
Q
Role of the chloroplast
A
Absorbs light energy for photosynthesis to produce organic substances
5
Q
Structure of chloroplast
A
Stacked thylakoid membranes make up grana, which are linked together by lamellae. Stroma
6
Q
Golgi apparatus
A
Processes proteins from rEr and packages them into Golgi vesicles, can produce lysosomes.
7
Q
Golgi vesicle
A
Produced by apparatus, transports lipids and proteins made by the Golgi apparatus and transports them out the cells via the membrane.
8
Q
Lysosome
A
Type of vesicle, contains digestive enzyme (lysozyme) . Used to digest invading cells or break down worn out components a cell.
9
Q
Ribosome
A
Where proteins are made.
10
Q
Rough endoplasmic reticulum
A
Surface covered with ribosomes, folds and processes proteins that have been made at the ribosomes. Proteins packaged into vesicles for transport.
11
Q
Smooth endoplasmic reticulum
A
Synthesises and processes lipids.
12
Q
Cell wall
A
Supports cells and prevents them changing shape.
13
Q
Cell vacuole
A
Membrane is called tonoplast. Helps to maintain pressure inside the cell and keeps the cell rigid. Stops plants wilting. Involved in isolation of unwanted chemicals in the cell.
14
Q
Plant cell extra
A
-Plasmodesmata: Channels for exchanging substances with adjacent cells.
-Vacuoles
-Chloroplasts
15
Q
Fungal cells differences
A
-Cells walls made of chitin, not cellulose
-No chloroplasts as they don’t photosynthesise.
16
Q
Tissues are…
A
A group of cells working together to perform a particular function.
17
Q
Prokaryotic v Eukaryotic
A
- Prokarytic no membrane bound organelles, eukaryotic has membrane bound organelles
- Prokaryotic has smaller ribosomes than eukaryotes
- Prokaryotes have no nucleus, DNA floats free in the cytoplasm, not attached to histone proteins, eukaryotes have a nucleus
-Prokaryotes cell wall is made of murein, eukaryotes made of cellulose or chitin
-Prokaryotes have a capsule, helps protect bacteria from attack by cells of the immune system, eukaryotes don’t
-Prokaryotes have plasmids, small loops of DNA and contain genes, eukaryotes don’t
-Eukaryotes are much larger that prokaryotes
18
Q
Viruses
A
Acellular nucleic acids surrounded by protein coat (capsid), which have attachment proteins sticking out.
19
Q
How do prokaryotes replicate
A
-Circular DNA and plasmid replicate
-Main loop is only replicated ONCE
-Cell gets larger and DNA loops move to opposite ends
-Cytoplasm starts to divide and new cell wall forms
-Cytoplasm divides and two daughter cells form.
20
Q
How do viruses replicate within a host
A
-Attachment proteins bind to complementary receptor proteins
21
Q
Magnification formula
A
IAM
22
Q
Magnification is..
A
how much bigger the image is than the specimen
23
Q
Resolution is..
A
how well a microscope distinguishes between two points that are close together
24
Q
Optical V Electron
A
-Optical uses light to form an image, electron uses electrons.
-Optical has a maximum resolution of 0.2 micrometers, electron has a higher resolution.
-Optical’s magnification is much lower than electrons
-Optical microscopes are much cheaper and more accessible
25
TEMs v SEMS
-TEMs can only be used on thin specimen, SEMs can be used on thick ones
-TEMs give high resolution images, SEMs give lower resolution
-SEMs produce 3D images, TEMs only produce 2D images
-On TEMs denser parts of the specimen absorb more electrons, which make them look darker
26
How to prepare specimen on a slide
-Pipette a small drop of water onto the slide
-Use tweezers to place a thin section of specimen top of the water
-Add a drop of a stain to highlight objects in a cell.
-Add cover slip on specimen carefully, avoiding air bubbles.
27
What happens in homogenisation
-Grind cells in a blender which breaks up plasma membrane and releases the organelles into solution
-Ice cold: reduces enzyme activity
-Isotonic: prevent damages to organelles through osmosis
-Buffer: maintains pH
28
Why is the homogenised solution filtered
Separates large cell debris
29
What happens in ultracentrifugation
-Place tube with cell fragments into a centrifuge spin at a low speed
-Heaviest organelles sink to the bottom and form a pellet, the others stay suspended in the fluid (supernatant)
-Supernatant is spun again at a higher speed, for longer times until all the organelles are separated out
30
What is the order of mass of organelles
-Nuclei (heaviest)
-Chloroplasts (plant cells)
-Mitochondria
-Lysosomes
-Endoplasmic Reticulum
-Ribosomes
31
Gap Phase 1?
Number of organelles and volume of cytoplasm increases, protein synthesis and ATP content increases
32
S phase?
Cell replicates its DNA, leading to two sister chromatids
33
Gap Phase 2?
Cell continues to grow and proteins needed for cell division are made
34
What happens in prophase?
Chromosomes condense, getting shorter and thicker. Centrioles move to opposite ends of the cell forming spindle fibres. Nuclear envelope breaks down.
35
What happens in metaphase?
Chromosomes line up along the middle of the cell and becomes attached to the spindle by their centromeres.
36
What happens in anaphase?
Centromeres divide, and the spindles fibres contract pulling chromatids two opposite poles.
37
What happens in telophase?
Chromatids uncoil and become long and thin again, they're now chromosomes. A nuclear envelope forms around each group of chromosomes.
38
What happens in cytokinesis
Cytoplasm divides and there are now two genetically identical daughter cells.
39
Where in plants can cells undergoing mitosis be found
Meristem tissue at shoot root and tips
40
How to prepare a root tip slide
-Warm 1 mol dm-3 of HCl at 60 degrees C in a water bath
-Cut root tip using scalped and add to the HCl, leave for 5 minutes
-Remove from acid and wash with distilled water
-Cut the tip of the root tip and place on a slide
-Add a stain to make chromosomes visible
41
Hazards-RP2
-HCL is corrosive, avoid contact with skin and wear eye protection
-Toluidine Blue stain is an irritant, avoid contact with skin and wear eye protection
-Scalpel is sharp, cut away from fingers
42
How do tumours arise
-Cell cycle is controlled by genes
-If there's a mutation in gene that controls division, cells can grow out of control
-Cells divide to make lots of cells, which forms a tumour
43
Cancer treatments that target cell cycle
G1- Chemical drugs prevent synthesis of enzymes required for DNA replication, if they're not produced cell can't enter s phase and will kill itself.
S- Radiation can damage DNA. Just before and during S phase, DNA is checked for damage and if damage is severe, the cell will kill itself
44
How to observe cells using a microscope
-Clip the slide to a stage
-Select lowest-powered objective lens
-Use course adjustment knob to rise stage
-Look through eyepiece and use the CAK to lower the stage until the image is slightly focused
-Adjust focus with fine adjustment knob until image is clear
-For greater magnification, switch to higher-powered objective lens
45
Describe the stucture of the fluid mosaic model
-Phospholipid molecules form a bilayer, which is fluid as phospholipids move
-Cholesterol is present in the bilayer
-Proteins present in the bilayer
46
Structure of phospholipids
Hydrophilic head
Hydrophobic tail
Centre is hydrophobic, the membrane doesn't allow water soluble substances through it
47
How does cholesterol give the membrane stability
They fit between phospholipids and bind to the tails, causing them to pack close together. Restricts movement of phospholipids, making the membrane less fluid and more rigid.
48
Why are calibration curves used
To determine the conc of an unknown sample by comparing it to a set of standard values with known conc
49
Why are the potato discs left in solution
To allow time for osmosis until the plant tissue reaches equilibrium with surrounding solution
50
Method for investigating osmosis using potato tissue
- Make a dilution of 1 mol dm-3 sucrose to produce 5 concentrations, dilute with distilled water
- Add 5cm3 of each dilution to a test tube
-With a cork borer, cut out 5 potato. chips and cut identically. Dry them with paper towels.
-Weigh them
-Place each chip in a tube and leave for 20 min
-Remove each chip, dry, and weigh
-Calculate % change in mass
51
When the line of best fit touches the x axis..
The solution in isotonic, and the water potential of sucrose is the same as that of the potato tissue, so no net movement of water
52
When the line of best fit touches the x axis..
The solution in isotonic, and the water potential of sucrose is the same as that of the potato tissue, so no net movement of water
53
RP4 Method
-Cut beetroot into 6 identical cubes using scalpel
-Wipe to clean any pigment
-Temperature: Place each cube in an equal volume of water and place each tube in a water bath (30-80 degrees C)
-Concentration of solvents: Create a dilution series of ethanol (0%-100%) using water.
-Leave samples for 20 minutes
-Set colorimeter to blue filter and zero using a cuvette with water
-Filter samples into cuvettes
-Measure the absorbance for each solution
54
Hazards RP4
-Ethanol is an irritant and. flammable keep away from naked flames, wear eye protection
-Keep sharp scalpel away from fingers
-Handle hot water with care
55
How does membrane permeability change with temperature
Below 0°C: Phospholipids don't have a lot of energy, they can't move a lot, packed closely. channel and carrier proteins deform, increasing permeability of the membrane
0°-45°C: Phospholipids move around and aren't packed tightly. Membrane is partially permeable, as temp increases the permeability increases.
Above 45°C: Phospholipid bilayer melts and the membrane becomes permeable. Proteins deform and permeability increases.
56
Osmosis is..
diffusion of water across a partially permeable membrane from an area of high water potential to an area of low water potential
57
Isotonic is when..
two solutions have the same water potential
58
How does osmosis affect plant and animal cells
Into cell:
-Plant: Protoplast swell- cell becomes turgid
-Animal: Lysis
Out of cell
-Plant: Protoplast shrinks- cell becomes flaccid
-Animal: Crenation
59
FD using carrier proteins
-Large molecule attaches to a carrier protein in the membrane
-Protein changes shape
-Molecule is released on opposite side of the membrane
60
FD using channel proteins
-Channel proteins form pores in the membrane for charged particles to diffuse through
61
Active transport v Facilitated diffusion
AT: Solutes move from low to high concentration
AT: Requires energy
AT: Doesn't use channel proteins
62
What are co-transporters
-Type of carrier protein
-Bind two molecules at a time
-Concentration gradient of one molecules is used to move the other against its own conc gradient
63
Factors affecting rate of active transport
-The faster carrier proteins worker, faster the rate
-The more proteins there are, faster the rate
- The rate of respiration and availability of ATP
64
How is glucose absorbed by co transport in the ileum
-Na+ are actively transported out the epithelial ileum cells via sodium-potassium pump, creating a conc gradient as there's a higher conc of glucose in the lumen than inside the cell
-Na+ diffuses from lumen into the cell, via sodium glucose co-transporter proteins
-Co transporter carries glucose into the cell, conc of glucose in cell increases
-Glucose diffuses out of the cell through protein channel
65
What are antigens?
Molecules that can generate an immune response when detected by the body. Used by immune system to identify pathogens, abnormal body cells, toxins, and cells from other individuals of the same species.
66
What happens in phagocytosis
-A phagocyte recognises the foreign antigen on a pathogen.
-The cytoplasm of a phagocyte moves round the pathogen via chemotaxis, engulfing it via endocytosis.
-A lysosome fuses with the phagocytic vesicle, and lysozymes break down the pathogen.
- The phagocyte presents the pathogen's antigens to activate other immune system cells
67
Role of T cells
-Receptor proteins on surface bind to complementary antigens presented to it by phagocytes.
-Helper T cells release chemical signals that activate and stimulate phagocytes, and activate B cells which secrete antibodies.
-Cytotoxic T cells kill abnormal and foreign cells (by producing perforin)
68
Role of B cells
-Covered with antibodies that bind to antigens to form an antigen-antibody complex.
-This activates the B-cell, and is called clonal selection.
-Activated B-cell divides into plasma cells.
69
What is herd immunity
When those not vaccinated are unlikely to catch the disease as vaccines reduce the occurrence of the disease so fewer people pass them on
70
What are the cons of taking a vaccine orally
They may be broken down by the enzymes in the gut or the vaccine may be too large to be absorbed by the blood
71
Why are booster vaccines given
To ensure memory cells are being produced
72
How does antigenic variation affect the production of vaccines to help prevent people catching influenza
-The flu vaccine changes yearly, as the antigens on the surface change, forming new strains of influenza
-Memory cells produced from previous vaccination won'y recognise the antigens on the surface of the new pathogen.
-New vaccines are developed and the most effective one is chosen
73
Differences between active and passive immunity
-Active requires exposure to antigen, passive doesn't
-Active takes time for protection to develop, protection is immediate in passive
-Active produces memory cells, passive doesn't
-Active produces long term protection as the. antibody is produced in response to complimentary antigen present, passive protection is short because antibodies given are broken down.
74
What are monoclonal antibodies
Antibodies produces from a single group of genetically identical B-cells.
75
How can you target drugs to a particular cell (cancer)
-Cancer cells have antigens called tumour markers
-MABs can be made that only bind to the tumour markers
-You can also attach anti-cancer drug to MABs
-MABs will bind to the markers, so the drug will. only accumulate in the body where cancer cells are present
-Risk of using a MAB based drug are lower than other drugs, as they only accumulate to specific cells
76
How can you target a substance for medical diagnosis (pregnancy testing)
-The application area contains antibodies for hCG bound to a coloured (blue) bead
-When urine is applied to the application area and hCG will bind to the antibody on the beads forming an antigen-antibody complex
-Urine moves up the stick, carrying any beads
-The test strip contains antibodies to hCG that are stuck in place
-If hCG is present, test strip will go. blue as the immobilised ABs bind to hCG, concentrating the antigen-antibody complex
77
How to use ELISA as a test for HIV
-HIV antigen is bound to the bottom of a well
-A sample of the patient's blood plasma is added to the well. If there are any HIV specific ABs they will bind to the antigens
-The cell is then washed out to remove unbound antibodies
-Another antibody with a specific enzyme is added to the well. This one can bind to the HIV specific antibody.
-The cell is washed to remove unbound secondary antibody.
-A solution is added to the well, which contains a substrate
-Substrate can react with. the e enzyme to form a coloured product, if solution changes colour it shows that the patient has HIV-specific antibodies and is HIV positive
78
What are some ethical issues surrounding vaccines
-All vaccines are tested on animals before humans-some people disagree with animal testing
-Volunteers may put themselves at unnecessary risk of contracting diseases because they may think they're safe
-Some people don't take vaccines as there could be side effects, but they're still protected due to herd immunity- some people find this unfair
-If there was an epidemic, there would be a rush to receive a vaccine, and it would be difficult to decide who should receive it first
79
What are some ethical issues surrounding MAB therapy
-Animals are used to produce the cells from which MABs are produced
80
How does HIV affect immune response
They infect T-cells, which activate phagocytes, cytotoxic T cells and B cells
81
Structure of HIV
-Core which contains RNA and proteins, including reverse transcriptase, required for virus replication
-Outer coating of protein-capsid
-Envelope made of membrane stolen from the cell membrane of its previous host cell
-Attachment proteins sticking out that help HIV. attach to the host helper T-cell
82
How does HIV replicate
-Attachment protein attaches to a receptor molecule on the host helper T cell
-The capsid is released into the cell, and uncoats and releases the RNA into the cytoplasm
-Reserve transcriptase converts viral RNA two DNA
- Double-stranded DNA is made and inserted into the human DNA
-Host cell enzymes are used to make viral proteins from the viral DNA found within human DNA
-Viral proteins are assembled into new viruses. and released from cell
83
Why don't antibiotics kill viruses
-Antibiotics only kill bacteria by interfering with their metabolic reactions. They target bacterial enzymes and ribosomes used in the metabolic reactions.
-Viruses don't have their own ribosomes and enzymes, they use the host cells
-As human viruses use human enzymes and ribosomes, antibiotics can't help as antibiotics don't target human processes.
84
How are antiviral drugs used
Some enzymes are only used by viruses, such as reverse transcriptase so drugs can be designed to inhibit it without affecting the host cell
85
The process of entering the cell and the breakdown of the antibody to
release the drug is very similar to phagocytosis.
Use your knowledge of phagocytosis to describe how an ADC enters and kills the tumour cell.
Cell engulfs ADC, lysosomes fuse with the vesicles, lysozymes breakdown ADC to release the drug
86
Some of the antigens found on the surface of tumour cells are also found
on the surface of healthy human cells.
Use this information to explain why treatment with an ADC often causes side effects.
ADC will bind to non tumour cell, and cause death of healthy cells
87
Suggest and explain two further investigations that should be done before this ADC is tested on human breast cancer patients
Tested on healthy humans to check for side effects. Investigate different concentrations of ADC to find safe dosage
88
Describe how the human immunodeficiency virus (HIV) is replicated once
inside helper T cells (TH cells).
RNA converts into DNA using reverse transcriptase
DNA inserted into the helper T cells DNA
DNA transcribed into HIV mRNA
HIV mRNA translated into viral proteins, and are assembled into viral particles
89
Give two ways in which pathogens can cause disease.
Releases toxins and kills cells
90
Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar.
Use your knowledge of water potential to suggest how putting honey on a cut kills bacteria.
Water potential in bacterial cells higher than in honey. Water leaves bacteria. Loss of water stops metabolic reactions
91
Describe how a phagocyte destroys a pathogen present in the blood.
-Phagocyte engulfs pathogen
-Forms vesicle and fuses with lysosome
-Lysozymes hydrolyse
92
HIV-1 is the most common type of HIV. HIV-1 binds to a receptor on TH cells called CCR5.
Current treatment for HIV-1 involves the use of daily antiretroviral therapy (ART) to stop the virus being replicated. Only 59% of HIV-positive individuals have access to ART.
Scientists have found that two HIV-1-positive patients (P and Q) have gone into remission (have no detectable HIV-1). This happened after a blood stem cell transplant (BSCT).
* Patient P was given two BSCTs, and patient Q was given one BSCT.
* All BSCTs came from a donor with TH cells without the CCR5 receptor.
* In addition, patient P had radiotherapy, and patient Q had chemotherapy.
Both of these treatments are toxic.
* Both patients (P and Q) stopped receiving ART 16 months after BSCT.
18 months after stopping ART, both patients had no HIV-1 RNA in their plasma, no HIV-1 DNA in their TH cells and no CCR5 on their TH cells.
(b) Use the information given to evaluate the use of BSCT to treat HIV infections.
-There appears to be no HIV, so BSCT could be a cure
-No CCR5 receptor so HIV can't bind to anything
-Only one transplant is necessary as shown by patient Q
-But its unknown if BSCT alone would be effective
-Only worked in two cases
93
Give two types of cell, other than pathogens, that can stimulate an immune
response.
Cancer cells, cells infected by virus
94
What is the role of the disulfide bridge in forming the quaternary structure of an antibody?
Joins two different polypeptides
95
What is the role of the disulfide bridge in forming the quaternary structure of an antibody?
Joins two different polypeptides
96
Explain how HIV affects the production of antibodies when AIDS develops in a person.
No antibodies produced because HIVV destroys helper T cells so fewer B cells stimulated
97
In Europe, viruses have infected a large number of frogs of different species. The viruses are closely related and all belong to the Ranavirus group.
Previously, the viruses infected only one species of frog.
(a) Suggest and explain how the viruses became able to infect other species of frog.
Mutation in the viral genetic material, altered tertiary structure of viral attachment protein, allows it to bind. to receptors of other species
98
Determining the genome of the viruses could allow scientists to develop a vaccine.
The scientists could identify proteins that derive from the genetic code. They could identify antigens to use in the vaccine.
99
Describe how the B lymphocytes of a frog would respond to vaccination against Ranavirus.
B cell binds to complementary antigen. B cell clone. Plasma cells release MABs against the virus. Plasma cells develop memory cells
100
What is a monoclonal antibody
Antibodies with the same tertiary structure, produced from identical B cells
101
Give one example of using monoclonal antibodies in a medical treatment.
Targets drugs to specific cells
102
Describe the role of antibodies in producing a positive result in an ELISA test.
-Antibody binds to complementary antigen
-Antibody with enzyme attached is added
-Antibody attaches to antigen/ to first antibody
-Solution added to the well which contains substrate and colour changes
103
Describe and explain the role of antibodies in stimulating phagocytosis.
Bind to complementary antigens, antibodies cause agglutination.
104
When a person is bitten by a venomous snake, the snake injects a toxin into the person. Antivenom is injected as treatment. Antivenom contains antibodies against the snake toxin. This treatment is an example of passive immunity.
Explain how the treatment with antivenom works and why it is essential to use passive immunity, rather than active immunity.
Antivenom antibodies bind to the venom antigen and causes its destruction, active immunity would be too slow
105
A mixture of venoms from several snakes of the same species is used to make antivenom. Why?
May be different forms of antigens within one species due to mutations. Different antibodies needed in the antivenom
106
During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom.
Use your knowledge of the humoral immune response to explain this vaccination programme.
-B cells specific to the venom reproduce by mitosis
-B cells produce plasma cells and memory cells
-The first dose must be small so the animal doesn't die
-The second dose produces antibodies in higher concentrations and more quickly
107
Suggest and explain why AZT does not destroy HIV in the body but stops or slows the development of AIDS
-The person infected with HIV will still have HIV DNA in their DNA
-AZT inhibits reverse transcriptase
-AZT stops new HIV particles from forming new HIV DNA
-Stops destruction of newly infected helper T cells
-So immune system continues to work and AIDS doesn't develop
108
Suggest and explain two advantages of using HAART
-Slows development of AIDS as HIV resistant AZT is damaged
-No new HIV particles made as antiretroviral particles might interfere with viral protein synthesis .
109
Describe how phagocytosis of a virus leads to presentation of its antigens.
Phagosomes fuses with lysosome. Virus destroyed by lysozymes. Antigens from the virus are displayed on the cell membrane
110
Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen.
Helper T cell binds to the antigen. Stimulates a specific B cell, B cell clones. Forms plasma cells that release antibodies
111
Collagen is a protein produced by cells in joints, such as the knee.
Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease, a person’s immune system attacks their own cells. RA causes pain, swelling and stiffness in the joints.
Scientists have found a virus that produces a protein very similar to human collagen.
Suggest how the immune response to this viral protein can result in the development of RA.
The antibody against the viral antigen will bind to the collagen, resulting in the destruction of the human cells
112
What's an antibody
A protein/ immunoglobin specific to an antigen produced by B cells
113
Bacterial meningitis is a potentially fatal disease affecting the membranes around the brain. Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis.
In the UK, children are vaccinated against this disease. Describe how vaccination can lead to protection against bacterial meningitis.
Antigen on surface of N.meningitidis binds to surface receptor on a specific B cell. B cells divide by mitosis and produces clones. Division stimulated by T cells. Plasma cells release antibodies, B cells become memory cells. Memory cells produce antibodies faster
114
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how.
Vaccines contain antigens against pathogen. Macrophage presents antigen on its surface. T cell with complementary receptor protein binds to antigen. T cell stimulates B cell with complementary antibody on its surface. B cell secretes many antibodies. B cell divides to form clone producing same antibody.
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