Cells Flashcards
1
Q
What is resolution?
A
The minimum distance two objects have to be in order to be seen as separate items.
Increasing magnification doesn’t always increase resolution.
This basically means his clear the image is.
2
Q
What is cell fractionation?
A
Process where the cells are broken up and the different organelle are separated out.
This takes place in a cold (reduces enzyme activity), same water potential (prevents damage due to osmosis), buffered (pH doesn’t fluctuate) solution.
3
Q
What is homogenation?
A
Cells are broken down by a homogeniser.
This releases organelle from cells.
This resultant fluid known as homogenate is then filtered to remove whole cells and large debris.
4
Q
What is ultracentrifugation?
A
This is the process by which the fragments in the filtered homogenate are separated in a machine called centrifuge.
This spins tubes of homogenate at a very high speed to create a centrifugal force.
Heaviest organelle fall at smaller speeds to force a pellet leaving a supernatant.
The process repeats from the removed supernatant.
5
Q
Advantages of a light microscope?
A
Cheap
Live specimen
Easy staining process
6
Q
Disadvantages of light microscopes?
A
Poor resolution due to long wave length of light. Poor magnification. 2D. Image must be drawn. Artefacts.
7
Q
How does a transmission electron microscope work?
A
Electron gun produces a beam of electrons which is focused onto specimen by a condenser electromagnet.
This is sent through a thin slice of specimen.
Sections of absorbed electrons will appear dark and where they pass will appear bright.
An image is produced on the screen and photographed to produce a photomicrograph.
8
Q
Advantages of a transmission electron microscope?
A
High resolution (0.1nm) as electrons have a short wave length. High magnification.
9
Q
Disadvantages of transmission electron microscope?
A
Vacuum required Complex staining process Black and white Specimen must be extremely thin Artefacts High electron beam may destroy specimen Expensive
10
Q
How does the scanning electron microscope work?
A
SEM directs the beam of electrons above the specimen and onto its surface.
The beam is passed back and forth across the specimen in a regular pattern.
Electrons are scattered by the specimen, this depends on its contours.
A 3D image is built up on the computer.
11
Q
Advantages of a scanning electron microscope?
A
3D image Resolving power of 20nm High magnification Coloured image Specimen not cut thin Unlikely to have artefacts
12
Q
Disadvantages of scanning electron microscope?
A
Vacuum so no live specimen
Complex staining process
Expensive
13
Q
What is a stage micrometer?
A
A slide that had a scale etched onto it.
This is used to calibrate the eyepiece graticule.
Usually the scale is 2mm and the subdivisions are 0.01mm.
14
Q
What is an eyepiece graticule?
A
Glass disc that is placed on the eyepiece and has a scale etched onto it.
This scale is usually 10mm and had 100 subdivisions.
15
Q
How to calibrate the eyepiece graticule?
A
Units on the micrometer must be equal to the units on the graticule scale.
16
Q
Describe nucleus’ structure.
A
10-20um in diameter Nuclear envelope Nuclear pores Nucleoplasm Chromosomes Nucleolus
17
Q
What are the functions of the nucleus?
A
Control centre of the cell.
Retain genetic material.
Manufactures ribosomal RNA and ribosomes.
18
Q
Describe the structure and function of the nuclear envelope.
A
Double membrane that surrounds the nucleus.
The outer membrane is continuous with endoplasmic reticulum of the cell and often had ribosomes on its surface.
It controls the entry and exit of materials in and out of the nucleus.
19
Q
Describe the function and structure of the nuclear pores.
A
Nuclear pores allowed the passage of large molecules such as messenger RNA.
There are typically around 3000 pores in each nucleus each 40-100nm in diameter.
20
Q
What is the nucleoplasm?
A
Nucleoplasm is the granular, jelly like material that makes the bulk of the nucleus.
21
Q
What are chromosomes?
A
They consist of protein bound linear DNA.
22
Q
Describe the structure and function of the nucleolus.
A
Small spherical region within the nucleoplasm.
Manufactures ribosomal RNA and assembles the ribosomes.
There can be more than one within a nucleus.
23
Q
Describe the structure of the mitochondrion.
A
Mitochondria are usually rod shaped and 1-10um in length.
Around the organelle is double membrane that controls the entry and exit of material.
The inner of two membranes are folded to form extensions.
24
Q
What is the Cristae within the mitochondrion?
A
Extension of inner membrane, which in some species extend across the whole length.
These provide high surface area for attachment of enzymes and proteins needed for respiration.
25
What is the matrix within him the mitochondrion?
The matrix makes up the remainder of the mitochondrion.
It contains proteins,lipids, ribosomes and DNA to control the production of their own proteins.
Many enzymes are found here.
26
Describe the structure and function of the chloroplast.
Organelle which carry out photosynthesis.
Typically disc shaped, 2-10um in length.
Made up of chloroplast envelope, the grana and the stroma.
27
What is a chloroplast envelope?
Double plasma membrane that surrounds the organelle.
| It is highly selective in what it allows to enter and leave the chloroplast.
28
What is the grana within the chloroplast?
Stacks of up to 100 disc like structure called thylakoids within these there is the pigment chlorophyll.
This is where the first stage of photosynthesis (light absorption) takes place.
29
What is the stroma within the chloroplast?
Fluid filled matrix where the second stage of photosynthesis (synthesis of sugar) takes place.
There is a number of other structure such as starch grains.
30
Describe the function and structure of the rough endoplasmic reticulum.
Ribosomes present on the outer membrane.
Provides a large surface area for synthesis is of proteins and glycoproteins.
Provide a pathway for the transport of materials, especially proteins through a cell.
31
Describe the structure and function of the smooth endoplasmic reticulum.
Lacks ribosomes on the surface and often looks more tubular.
| It’s function is to synthesise, store and transport lipids and carbohydrates.
32
What’s the structure of Golgi apparatus?
It consists of a stack of membranes that make up flattened sacs or cristernae, with small round hollow structures called vesicles.
33
Functions of the Golgi apparatus.
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Adds carbohydrates to proteins to form glycoproteins.
Produce secretary enzymes.
Secrete carbohydrates.
Transport, modify and store lipids.
Form lysosomes.
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34
What are lysosomes?
Form when vesicles of Golgi apparatus contain enzymes.
These enzymes can hydrolyse the cell walls of a bacteria.
As many as 50 enzymes can be found here.
Release enzymes to the outside of the cell.
Digest worn out organelle.
Completely digest the cell once dead.
35
Describe the structure and function of the ribosome.
Small cytoplasm granule found in all cells in the cytoplasm or associated with the RER.
Have 2 subunits, large and small each containing RNA and protein.
80S are eukaryotic cell 25nm.
70S are prokaryotic, found in both mitochondria and chloroplasts.
36
Describe the function and structure of the cell wall.
Consists of polysaccharide cellulose embedded in the matrix.
Provide mechanical strength in order to prevent the cell from bursting from osmotic pressure.
Allows water to pass along it and contribute to movement.
37
Describe the vacuole.
A fluid filled sac bound by a single membrane (tanoplast).
Contains salts, sugars, amino acids and waste.
Makes cell turgid.
Food store.
38
What is epithelial tissue?
Found in animals and consists of sheets of cells.
| Line surfaces of organs and often have protective or secretory function.
39
What does the digestive system do?
Digests and processes food.
40
What does the respiratory system do?
Used for breathing and gas exchange.
41
What does the circulatory system do?
Pumps and circulates blood.
42
What is a eukaryotic cell?
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Large.
Have nucleus.
Membrane bound organelle.
Ribosomes are 80S.
Cell wall is made up of cellulose.
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43
What’s a prokaryotic cell?
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No nucleus.
Plasmids present.
No membrane bound organelle.
Ribosomes are 70S.
Cell wall made up of murein.
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44
Describe the structure of a bacteria cell.
PROKARYOTIC.
0.1-10um in length.
Simple structure.
Food stored as glycogen granules and oil droplets.
Cell wall made of Murein.
Capsule used for attachment and protection.
Ribosomes are 70S.
Strand of single strand circular DNA and plasmids.
Flagellum for movement.
Cytoplasm.
45
Describe the structure of a virus.
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20-300nm.
Acellular and nonliving.
Attachment protein.
Lipid envelope.
Matrix.
Caspid.
Enzyme and Genetic material.
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46
What is mitosis?
Produces 2 daughter cells that have the same number of chromosomes as the parent cell and eachother.
47
What is meiosis?
Produces 4 daughter cells, each with half the number of chromosomes as the parent cell.
48
What are the stages of mitosis?
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Prophase.
Metaphase.
Anaphase.
Telophase.
Cytokinesis.
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49
What is prophase in mitosis?
Chromosomes shorten and thicken.
Centrioles move to either pole of the cell.
Spindle fibres form.
The nucleolus disappears and the nuclear envelope breaks.
Chromosomes are drawn to the equator by spindle fibres.
50
What is metaphase in mitosis?
DNA is copied and chromatids are joined by centromere.
Some microtubules connected to the centromere.
Chromosomes arrange themselves across the equator of the cell.
51
What is anaphase in mitosis?
Centromeres divide into two and the spindle fibres pull the individual chromatids making up the chromosomes apart.
Chromatids move rapidly to their respective opposite poles.
52
What is telophase in mitosis?
Become longer and thinner and eventually disappear.
| The nuclear envelope and nucleolus reform.
53
What happens during cytokinesis in mitosis?
The cytoplasm divides and 2 cells are now formed.
54
What is binary fission?
Asexual replication carried out by prokaryotic cells.
55
What happens during mitosis?
Circular DNA and plasmids replicate and attach to cell membrane.
The cell membrane grows between the DNA and begins to pinch inward dividing the cytoplasm in two.
A new cells wall forms.
56
How do viruses replicate?
Nonliving so cannot divide.
Replicate using host cell by attaching to it using attachment proteins.
Inject their nucleic acid into host cell.
Host cell then produces more viruses.
57
What is the cell cycle?
Interphase.
Nuclear division.
Cytokinesis.
58
What is cancer?
Group of diseases caused by growth disorder of cells.
It is a result of damage to genes that regulate mitosis and the cell cycle.
This leads to uncontrollably dividing cells called a tumour.
59
What ate the treatments of cancer?
Chemotherapy drugs that prevent DNA from replicating and inhibiting the metaphase stage of mitosis by stopping spindle formations.
60
What is the function of the cell surface membrane?
Forms boundary between cytoplasm and the environment.
Allows different conditions in and out of the cell.
Controls movement of substances in and out of the cell.
61
Function of the phospholipid bilayer in the cell membrane.
Allow lipid soluble substances to enter and leave.
Prevent water soluble substance movement.
Make the membrane flexible and self sealing.
62
Why are phospholipids within the cell surface membrane important?
Hydrophilic head point to the outside of the membrane, attached to the water on both sides.
Hydrophobic tails point inside the membrane, repelled by water on both sides.
63
What can’t diffuse across the phospholipid bilayer?
Not soluble in lipids.
Too large.
Charge is the same as carrier protein.
Polar so repelled by hydrophobic tails.
64
Functions of proteins in the cell membrane.
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Provide structural support.
Act as channels for water-soluble substances.
Act as a cell receptors.
Allow active transport.
Help cells adhere.
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65
What is a glycoprotein?
Cell surface receptors for hormones and neurotransmitters.
Recognition sites.
Helps cells attach to other cells to form tissue.
Allows recognition of other cells.
66
What is a glycolipid?
Carbohydrate covalent bonded with a lipid.
67
Functions of glycolipids in the cell membrane.
Act as a recognition site.
Helps cells attach and form tissue.
Recognise other cells.
68
What is a glycoprotein?
Carbohydrate chains attached to many extrinsic protein.
69
What is an extrinsic protein?
Don’t extend across the entire bilayer.
They act at mechanical support.
Connected to glycolipids and cell receptors.
70
What is an intrinsic protein?
Go completely across the bilayer.
Carrier protein.
Protein channels.
71
What is a protein channel?
Form water filled tubes to allow water soluble substances to pass.
72
What is a carrier protein?
Bind to ions or molecules then change shape to let them cross the membrane.
73
Why is cholesterol important in the cell membrane?
They add strength to the membrane.
They pull together the fatty tails of phospholipids and decrease fluidity.
Very hydrophobic so it prevents loss of water and dissolved ions.
74
Why is it called the fluid mosaic model?
The way in which all the various molecules are combined in the structure of the membrane.
75
Define diffusion.
The net movement of molecules or ions down a concentration gradient from an area of high to low concentration until equilibrium is met.
76
What is facilitated diffusion?
Movement is charged ions and polar molecules by using protein channels and carrier protein.
This is still a passive process and moves down a concentration gradient.
77
Define osmosis.
The passage of water from a region where there is a high to low water potential through a selectively permeable membrane.
Water has water potential 0.
78
Define active transport.
The movement of molecules or ions into of out of the cell from a region of low to high concentration using ATP and carrier protein.
79
In active transport what is ATP used for?
Direct movement of molecules.
| Allows co transport.
80
Describe the process of cotransport?
Sodium ions are actively transported out of the epithelial cells by the sodium potassium, this takes place in a carrier protein.
This maintains a high concentration of sodium ions in the lumen of the intestine rather than inside the cell.
Sodium ions diffuse into epithelial cells through a cotransport protein, as this happens they carry another molecules with them.
The glucose or amino acid pass to the blood plasma by facilitated diffusion by using another type of carrier.
81
How does HIV replicate inside the body?
HIV enters the blood stream and circulates around the body.
A protein on the HIV readily binds to a protein called CD4, this usually happens on the helper T cells.
The protein capsid fuses with the cell membrane, the RNA and enzymes of HIV enter the cell.
The HIV reverse transcriptase converts the RNA into DNA.
DNA the embeds itself into the cell’s DNA.
The HIV DNA then creates messenger RNA using the cell’s enzymes and creates more HIV.
82
How does HIV cause the symptoms of AIDS.
HIV specifically attacks helper T cells.
This means immune response is effected badly.
Memory cells may become inadequate or damaged.
83
What is the ELISA test?
Detect the presence of protein in a sample and the quantity using antibodies.
84
Describe the ALISA test.
Apply the sample to a surface to which all the antigens in the sample will attach to.
Was the surface to remove unattached antigens.
Add antibodies specific to the antigen and leave them to bind.
Wash surface to remove excess antibodies.
Add second antibody to attach to first antibody with an enzyme on it.
Add the colourless substrate of the enzyme this will become coloured as the enzyme acts on it.
The amount of antigen present relates to the intensity of colour.
85
Why are antibiotics ineffective against viruses?
Because they inhibit the ability to create a cell wall cause bacteria to burst as viruses use host cells this would only damage own cells.
86
What is immunity?
Ability of an organism to resist infection.
87
What is passive immunity?
Produced by the introduction of antibodies from an outside source.
No direct contact with the pathogen required.
Immunity is acquired immediately and no memory cells are formed.
88
What is active immunity?
Produced by stimulating the production of antibodies by the individuals own immune system.
Direct contact with the pathogen is required.
This immunity takes time to develop.
89
What is natural active immunity?
Results from an individual becoming infected with a disease under normal circumstances.
90
What is artificial active immunity?
Forms on the basis of vaccination.
| Inducing the pathogen without the suffering the symptoms.
91
What is a vaccine?
This stimulates an immune response against a disease.
This only requires a small amount of weakened or dead pathogens.
Memory cells are produced.
92
Features of a successful vaccination program.
Economically available in large quantities to give to vulnerable population.
Few side effects.
Easy to transport.
Administration done easily.
Must be easy to vaccinate a vast majority creating herd immunity.
93
What is herd immunity?
When a large proportion of the population has been vaccinated making it hard for the pathogen to travel from person to person.
94
Why may a vaccine be unsuccessful?
People have defective immune systems.
Individuals may develop disease straight after vaccinations.
Pathogen may change over time.
Pathogens hide from body’s immune system.
Individuals may object to vaccine due to ethical issues.
95
What is an antibody?
A protein with a specific binding site synthesised by B cells.
Each has 2 identical binding sites.
Each is specific to the antigen on the pathogen.
96
Structure of an antibody.
Made up of 4 polypeptide chains.
Pair of long chains called heavy chains.
A pair of shorter chains called light chains.
The binding site is called the variable region.
97
How do antibodies lead to the destruction of a pathogen.
Prepare the antigen for destruction.
They can cause the agglutination of bacterial cells, this makes it easier for the phagocytes to locate them.
They serve as a markers that stimulate phagocytes to engulf the bacterial cell they are attached to.
98
What is a monoclonal antibody?
Fast multiplying white blood cells specific for a particular purpose.
99
Use of monoclonal antibodies?
Targeting medication.
Medical diagnosis.
Pregnancy tests.
100
What is humoral immunity?
Involves antibodies which as soluble in humours.
101
What is a B cell?
Produce antibodies specific to antigens.
102
What is endocytosis?
Antigen enters the B cell and they are processed and presented on their surface.
103
What is clonal selection?
When T cells attach to B cells stimulating them in to divide through mitosis to produce more antibodies.
104
What is a plasma cell?
Secrets antibodies usually into blood plasma.
Only survive for a couple days.
Make 2000 antibodies every second.
Responsible for immediate defence knows as primary immune response.
105
What’s a memory cell?
Responsible for secondary immune response.
Often live for decades.
When they encounter the same antigen they create plasma cells and more memory cells to fight it off.
106
Describe the process of humoral immunity?
The surface antigens of an invading pathogen are taken up by a B cell.
The B cells presents them on its surface.
The helper T attach to the processed antigens on the B cells activating the B cell.
The B cells now divide by mitosis to give clones of plasma cells.
These produce antibodies which attach to pathogen and destroy them.
Some B cells develop into memory cells which can respond to infections at a later date.
107
What is an antigen?
Any part of an organism or substance that is refocused as non self by the immune system and stimulates an immune response.
108
What is a lymphocyte?
White blood cells responsible for specific long term immune response.
Produced by stem cells in the bone marrow.
109
What is a B lymphocyte?
Mature in bone marrow.
| Associate with humoral immunity.
110
What is a T lymphocyte?
Mature in thymus gland.
| Associated with cell mediated immunity involving body cells.
111
Describe the process of cell mediated immunity.
Pathogen invade body cells or are taken in by pathogens.
The phagocyte places antigens from pathogen on the cell surface membrane.
Receptors on specific helper T cell fit exactly into these antigens.
This attachment activated the T cell to divide rapidly by mitosis and form clone of genetically identical cells.
The clone then:
-develops into a memory cells
-stimulate phagocyte to engulf pathogen by phagocytosis
-stimulate B cell to divide and secrets antibodies.
-activate cytotoxic T cells.
112
How do cytotoxic T cells kill infected cells?
Produce a protein called perforin that makes holes in cell membranes.
This is most effective against viruses.
113
Describe the process of phagocytosis.
Phagocyte is attested to the pathogen by the chemical products of the pathogen moving towards it due to a concentration gradient.
Phagocyte uses receptors to attach to chemicals on the surface of the pathogen.
Lysosome within the phagocyte migrate towards the phagosome formed by engulfing the bacteria.
The lysosome release thief lysozymes into the phagosome where they hydrolyse the bacteria.
The product of this is absorbed by the phagocyte.
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