Cells Flashcards
(120 cards)
1
Q
What is meant by facilitated diffusion?
A
Movement down concentration gradient through a channel/carrier protein
2
Q
What is meant by active transport?
A
Movement against concentration gradient via a carrier protein using ATP/energy (from respiration)
3
Q
What is meant by osmosis?
A
Movement of water from higher to lower water potential/down water potential gradient across a partially/selectively permeable membrane
4
Q
How does resolution affect clarity?
A
Higher resolution, higher clarity
5
Q
Magnification times what equals image size?
A
Actual size
6
Q
Image size divided by actual size equals what?
A
Magnification
7
Q
What is the resolution of a transmission electron microscope?
A
0.1 nm
8
Q
How does a transmission electron microscope work?
A
A beam of electrons is passed through a very thin section of specimen. Some electrons are absorbed, and so show up as dark.
9
Q
What is the resolution of a scanning electron microscope?
A
20nm
10
Q
What are the disadvantages of an electron microscope?
A
The specimen needs to be in a vacuum (therefore must be dead)
The image is black and white (colour can be added)
Prep may be result in artefacts
11
Q
What is an advantage of electron microscopes?
A
They have a short wavelength and so have a high resolving power.
Electrons are charged, and so the microscopes can be focused using electromagnets
12
Q
Describe the process of cell fractionation.
A
Chop up and place in cold, isotonic, buffered solution
Homogenation (blender)
Filter homogenate
Ultracentrifugation (spin)
Look at sediment - low = larger mass organelles, high speed - smaller mass organelles
13
Q
Elijah uses cell fractionation to study the organisms inside a cell. Using this technique, he is able to see the mitochondria. At what speed was the homogenate spun to get this?
A
Medium speed
14
Q
Give an example of an organelle that would be separated from the homogenate if it was spun at a high speed.
A
Lysosomes
Membranes
Ribosomes
15
Q
In cell fractionation, why is the solution isotonic?
A
To prevent osmotic damage
16
Q
In cell fractionation, why is the solution cold?
A
To reduce enzyme activity that could damage organelles
17
Q
In cell fractionation, why is the solution buffered?
A
To maintain a constant pH
18
Q
Describe how you would calibrate the eyepiece graticule
A
Lowest power objective on microscope
Align scale on microscope with graticule scale
Calculate calibration factor
19
Q
What is a key function of the nucleus?
A
Manufacture rRNA and ribosomes
Control cell activity
Contains genetic information
20
Q
What are the key structures of a chloroplast?
A
Grana (made up of thylakoids)
Stroma
Chloroplast envelope
21
Q
What are the key functions of a chloroplast?
A
To harvest sunlight to be converted into chemical energy in photosynthesis
22
Q
What are the key functions of a lysosome?
A
Hydrolysis of ingested materials from phagocyte cell
Digest worn out cells
Break down cells after death
Release enzymes for destruction of material outside cell
23
Q
What are the key functions of a smooth endoplasmic reticulum?
A
Predominantly store, but also synthesis and transport, lipids and carbohydrates
24
Q
What are the key functions of a mitochondria?
A
Site of aerobic respiration (release ATP)
25
What are the key structures found in a mitochondria?
Cristae (the folds), matrix (the space inside)
26
What are the key structures found in a nucleus?
Nuclear envelope, nuclear pores, nucleolus, (chromosomes, nucleoplasm)
27
What are the key functions of a vacuole?
Supports herbaceous plants by making cells turgid
May act as a temporary food store
May contain pigments which colour petals to attract pollinating insects
28
What are the key functions of a rough endoplasmic reticulum?
Pathway for transport of materials
| Increase the SA for protein synthesis
29
What are the key functions of a golgi apparatus?
```
Transport, modify and store lipids
Form lysosomes
Secrete carbs
Produce secretory enzymes
Add carbs to proteins to form glycoproteins
```
30
What are the key functions of a cell wall?
Provide mechanical strength --> prevent cell from bursting from osmotic pressure
Allow water to pass along it
31
What are the key functions of a ribosome?
Site of protein synthesis
32
What are the key differences between eukaryotic and prokaryotic cells?
Pro = smaller, have cytoplasm that lacks membrane-bound organelles, smaller ribosomes, no nucleus (circular, free-floating DNA), a cell wall that contains murein. Many proks also have one or plasmids, a capsule surrounding the cell, one or more flagella
33
Virus are living creatures. True or false?
False
34
What are the key structures of a virus?
A strand of nucleic acid, capsid, attachment protein
35
Which eukaryotic structures are found in plants cells, but not animal cells?
Chloroplasts, cell wall, cell vacuole
36
Chloroplasts are found in what types of cell? (animal, plant etc)
Plant and algae
37
A cell wall is found in what types of cell? (animal, plant etc)
Plant, fungi, algae
38
What is the difference between magnification and resolution?
Magnification is the ability to make small objects seem larger
Resolution is the ability to distinguish between two objects
39
Within multicellular organisms, not all cells retain the ability to divide. True or false?
True
40
At which stage does DNA replication occur?
Interphase
41
What are the stages of the cell cycle?
Interphase, prophase, metaphase, anaphase, telophase
42
What is binary fission?
When the fully grown parent cell splits into two halves to produce two new cells. It is the most common form of reproduction in prokaryotes (e.g. bacteria)
43
What happens during prophase?
Centrioles move to opposite poles
| Nucleolus breaks down
44
What happens during metaphase?
Chromosomes line up at the equator, pulled by the microtubules attached at their centromeres
45
What happens during anaphase?
The attached microtubules shorten, splitting the centromere and chromatids in half and separating them, pulling them to opposite sides of the cell
46
What happens during telophase?
As the chromosomes reach opposite ends of the poles, the spindle fibres disintegrate, and the nucleolus and nuclear membrane begin to reform
47
What happens during cytokinesis?
The cytoplasm divides
| Essentially the cytoplasm 'pinches through' until they separate
48
What happens if cell division is not controlled?
Tumours and cancers may form
49
What are cancer treatments often directed at?
Controlling the rate of cell division
50
Describe the structure of a cell-surface membrane (5)
It is a phospholipid bilayer, whereby the hydrophobic tails point inwards to avoid the surrounding aqueous environment. It is a fluid mosaic, meaning that the individual molecules vary in size, shape and pattern, and can move relative to one another. Proteins, glycoproteins and glycolipids all form part of this selectively permeable membrane. These in turn allow the movement of molecules across the membrane by either diffusion, osmosis or active transport (carrier and channel proteins) or allow other cells to attach (glycolipids/proteins)
51
Describe and explain the key features of a phospholipid bilayer
Fluid - individual molecules can move relative to one another
Mosaic - molecules vary in shape, size and pattern
52
Which type of carrier protein spans the bilayer completely?
Intrinsic
53
How many millimetres are in a micrometer?
1 um = 0.001mm
| 1mm = 1000um
54
How many millimetres are in a nanometer?
1,000,000nm in 1 millimetre
55
Other than as carrier proteins, state two functions of membrane born proteins
Receptors/recognition sites
Help maintain stability of membrane
Structural
56
Through what kind of membrane can osmosis occur?
Semi-permeable
57
Cholesterol may also be present in cell membrane. What is its role?
Add strength to the membranes
| Reduce lateral movement of other molecules inc. phospholipids
58
What are the roles of proteins in the cell-surface membrane?
Provide structural support
Allow transport across membrane (channel, carrier)
Form cell-surface receptors for identifying cells
Act as receptors (e.g. for hormones - 2nd messenger model)
Help cells adhere together
59
In the cell-surface membrane, what are the roles of glycolipids?
Act as recognition sites
Help cells attach to one another and so form tissues
Help maintain stability of the membrane
60
In the cell-surface membrane, what are the roles of glycoproteins?
Act as recognition sites
Helps attach to one another and so form tissues
Allows cells to recognise one another
61
Which types of molecules are NOT able to freely diffuse across the cell-surface membrane?
```
They can't if they are:
too large
polar
same charge as protein channels
not lipid soluble
```
62
State what is meant by 'diffusion'
The net movement of molecules or ions from a region where they are more highly concentrated to one where their concentration is lower, until evenly distributed
63
What is the role of proteins in facilitated diffusion across a cell-membrane?
Molecules bind with a protein causing it to change shape, thus allowing it through (some rotate)
64
Channel proteins allow what types of molecules through?
Water soluble (filled with water)
65
What is water potential measured in?
psi
66
Under standard conditions, what is the water potential of pure water?
0kPa
67
What is an example of passive transport?
Diffusion (simple and facilitated)
| Osmosis
68
How do channel proteins help control entry and exit of ions across the cell-membrane?
Most channel proteins are selective and so will only let certain ions through
69
State what is meant by active transport
The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins
70
How does active transport work?
An ion attaches to the carrier protein
| A Pi from ATP attaches, causing the protein to change shape. This shape change 'pump' the molecule/ion across
71
Describe and explain what happens if the solution outside the cell is hypotonic
Hypotonic - higher water potential outside cell
| Water rushes into the cell to balance the concentrations, causing the cell to swell and burst
72
Describe and explain what happens if the solution outside the cell is hypertonic
Hypertonic - lower water potential outside
| Water rushes from inside the cell to outside to balance the concentrations causing the cell to shrivel/shrink
73
Describe and explain the co-transport of glucose
Na-K actively transports Na+ out of epithelial cells into the blood stream
This therefore lowers the concentration of Na+ in the epithelial cells, increase conc. outside
Na+ reenters the epithelial cell, this time coupled with glucose
They enter via the Na-glucose pump by facilitated diffusion
74
Describe and explain how is the small intestine adapted for the absorption of glucose
Villi and microvilli increase SA
Thin walls means smaller diffusion distance
Good blood supply and movement of villi maintains concentration gradient
75
Which two carrier proteins are involved with the co-transport of glucose?
Na-K and Na-glucose pumps
76
The molecular formula of galactose in C6H12O6. What is the molecular formula of lactose?
C12H22O11
77
What is an example of a non-specific defence mechanism?
Phagocytosis, physical barrier
78
What is an example of a specific immune response?
```
Cell-mediated response (involves T-lympho)
Humoral response (involves B-lympho)
```
79
Define 'antigen'
A protein or glycoprotein found on the surface of cell membranes and foreign material that indicate to the immune system if that cell is self or non-self
80
Describe phagocytosis of pathogens
Phagocyte attracted to the pathogen by chemical products
Phagocyte has several receptors on its cell-surface membrane that attach to chemicals on the pathogen
A phagosome begins to form around the pathogen (engulf). Lysosomes migrate towards this
Lysosome and phagosome fuse. Lysosomes release lysozymes which break the pathogen down by hydrolysis
Debris either displayed on cell surface or released by exocytosis
81
What is the difference between specific and non-specific immunity?
Specific distinguishes between pathogens, non-specific doesn't
82
Describe the humoral response of the immune system
Proteins are released by Th cells which stimulates the rapid production of B cells
These B cells produce plasma cells, which in turn produce antibodies
83
What type of lymphocytes does the humoral response involve?
B lymphocytes
84
Where do T-lymphoctes mature?
Thymus gland
85
Where do B-lymphocytes mature?
Bone marrow
86
Describe the response of T-lymphocytes to a foreign antigen (cell-mediated response)
Receptors on a specific T helper (Th) cell bind to their complementary antigen. They recognise the cell as non self, and are activated to rapidly divide by mitosis. They release proteins which stimulate the rapid production of B cells. Lymphokines stimulate phagocytes to do phagocytosis
Interlukin stimulates cytotoxic T cells (killer/Tc cells)
Tc cells replicate to become effector Tc cells (which identify and secrete proteins to kill infected cells) and Tm cells (which migrate to lymph nodes to be rapidly activated if another invasion)
87
Define what an antibody is
They are specialised protein molecules that bind specifically to antigens
88
Antibodies are able to make it easier for phagocytes by agglutination. What does this mean and how does it make it easier?
Antibodies are able to cause microbes to clump together, thus making it easier for antibodies to engulf them
89
Antibodies assist in the destruction of microbes in 2 ways. What are these two ways?
They act as markers for phagocytes
| Agglutination
90
Describe the structure of an antibody
A double lined Y shaped molecule
Has a light chain and a heavy chain, and constant and variable regions
The antigen binding site is located at the variable regions
Held together by disulphide bridges
91
What is a monoclonal antibody?
A pure antibody, highly specific to one antigen. It comes from a single cell line and consists of identical antibody molecules
92
Describe how monoclonal antibodies are produced
A mouse is injected with some antigen to stimulate production of complementary antibodies
The spleen of this mouse is removed, and from it, the B cells are removed
These cells are fused to myeloma (cancerous) cells. They are grown in culture to produce a hybridoma
These hybridomas multiply and so produce relatively large amounts of antibody molecules
93
How can monoclonal antibodies be used in medication?
They can be produced to target the problem cell
Once attached they can help by:
acting as markers for the immune system
blocking growth signals by attaching to receptors
deliver a radioactive/cytotoxic drug
94
How can monoclonal antibodies be used in medical diagnosis?
Many illnesses affect levels of proteins. Monoclonal antibodies can be produced to interact with these proteins, allowing a level of it to be measured
95
How are monoclonal antibodies used in pregnancy testing?
Pregnant women produce a hormone called human chronic gonadotrophin which can be found in the urine. mABs with coloured compounds attached are complementary specific to hCG. If it is present they bind. The complexes move along the strip until another antibody stops them, causing a coloured line to form
96
What is passive immunity?
Antibodies introduced to individual from an outside source
No direct contact w/ the pathogen/antigen is necessary and immunity is acquired immediately
Antibodies not being produced by self, so antibodies broken down --> no memory cells formed, no lasting immunity
97
Give an example of natural passive immunity
Maternal antibodies
98
Give an example of artificial passive immunity
Anti-venom
99
What is active immunity?
Production of antibodies stimulated by the individual's own immune system
Direct contact w/ pathogen/antigen necessary
Immunity takes time to develop
Generally long-lasting
100
Give an example of natural active immunity
A normal infection
101
Give an example of artificial active immunity
Vaccination
102
What is herd immunity?
When a sufficiently large enough proportion of the population has been vaccinated to make it difficult for a pathogen to spread
103
How do vaccination help prevent disease?
Induce an immune response so memory cells are present. If there is another infection, the memory cells are activated and induce a faster and stronger response
104
What does HIV stand for?
Human immunodeficiency virus
105
What is the structure of a HIV virus?
from inside out:
| RNA, reverse transcriptase, capsid, matrix, lipid envelope, attachment proteins
106
Describe the process of HIV's replication of Th cells
HIV enters bloodstream and circulates
Protein on HIV readily binds to CD4 protein (found on many cells, but mostly binds to Th)
Protein capsid fuses with the cell surface membrane
HIV enzymes and RNA enter the cell
HIV reverse transcriptase converts the rNA to DNA, which is moved into the nucleus of the Th cell. Then inserted into Th DNA
HIV DNA creates mRNA using the cell's enzymes. mRNA contains instructions for making new viral proteins and RNA for new HIV
mRNA exits nucleus and uses cell's protein synthesis mechanisms to make HIV particles
HIV particles break away w/ piece of Th cell surface membrane surrounding (acts as lipid envelope)
107
How does HIV cause AIDs symptoms?
By affecting Th cells and therefore the immune system
108
What does HIV reverse transcriptase do?
Convert the HIV RNA to DNA
109
Once HIV RNA has been converted to DNA, it creates mRNA. What does this mRNA do?
Uses the cell's protein synthesis mechanisms to make HIV particles
110
What does ELISA stand for?
Enzyme linked immunosorbant assay
111
What does the ELISA test do?
Detects the presence of a protein and quantity
112
Describe how you'd carry out the ELISA test
Apply sample to surface to which all desired proteins will attach to
Wash surface several times to remove any unattached
Add complementary specific antibody and leave to bind
Wash to remove all excess antibody
Add 2nd antibody which has an enzyme attached that can bind to first
Add a colourless substrate. The enzyme will act on it, to change it to a coloured product
More intense colour --> more of desired proteins
113
What is one way antibiotics work?
Inhibitng enzymes nec. for the synthesis and assembly of peptide cross linkages in the bacterial cell wall. Weakened wall can't withstand the pressure and so bursts
114
Why are antibiotics ineffective against viruses?
One way antibiotics is by weakening the cell walls. Viruses don't have cells (use hosts to carry out metabolic functions) therefore have no enzymes to inhibit or cell walls to weaken
115
What is an attenuated microorganism?
A weakened microorganism
116
Explain how antigenic variability has caused some people to be infected with the same virus more than once
Memory cells don't recognise
Antibodies previously produced aren't effective
Takes time to produce effective antibodies
117
When a vaccine is given to a person, it leads to the production of antibodies against a
disease-causing organism. Describe how (5) PPQ
1. Vaccine contains antigen from pathogen;
2. Macrophage presents antigen on its surface;
3. T cell with complementary receptor protein binds to antigen;
4. T cell stimulates B cell;
5. (With) complementary antibody on its surface;
6. B cell secretes large amounts of antibody;
7. B cell divides to form clone all secreting/producing same antibody;
118
Describe the difference between active and passive immunity (5) PPQ
1. Active involves memory cells, passive does not;
2. Active involves production of antibody by plasma cells/memory cells;
3. Passive involves antibody introduced into body from outside/named source;
4. Active long term, because antibody produced in response to antigen;
5. Passive short term, because antibody (given) is broken down;
6. Active (can) take time to develop/work, passive fast acting;
119
Give two key features of passive immunity
No direct contact w/ the pathogen/antigen is necessary and immunity is acquired immediately
Antibodies not being produced by self, so antibodies broken down --> no memory cells formed, no lasting immunity
120
Give two key features of active immunity
Direct contact w/ pathogen/antigen necessary
Immunity takes time to develop
Generally long-lasting
