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Chapter 2- Cells Flashcards

1
Q

How do light/optical microscopes work

A

Light microscopes use light wavelengths to view samples. they can resolve images that are 0.2um apart, this is because the wavelength of light is long.

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2
Q

Do light microscopes have a short or long wavelength

A

They have a long wavelength, therefore a lower resolution than electron microscopes

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3
Q

How do you calculate the magnification of an object

A

Size of image/real size of object

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4
Q

How do you calculate the size of image

A

Magnification x real size of object

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5
Q

How do you calculate the real size of object

A

Size of image/magnification

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6
Q

Define resolution

A

It is the minimum distance apart that two objects can be seen as separate objects in an image. The greater the resolution, the more clear the image will be

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7
Q

What are the two types of electron microscopes

A

Transmission electron microscope, scanning electron microscope

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8
Q

How are electron microscopes different to light microscopes

A

Electron microscopes use a beam of electrons rather than light in a vacuumed environment

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9
Q

How do transmission electron microscopes work (TEM)

A

A beam of electrons pass through a thin section of specimen. Areas that absorb the electrons appear darker

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10
Q

How do scanning electron microscopes work (SEM)

A

A beam of electrons are fired down onto the surface of a sample and scatter. The pattern of scattering builds a 3D image

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11
Q

Limitations of electron microscopes

A
  1. Vacuumed sealed, meaning cannot view alive samples.
  2. Specimens have to be very thin so electrons can pass through
  3. SEM has a lower resolving power than TEM, but both have higher resolving power than optical
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12
Q

What is cell fractionation

A

Different parts and organelles of a cell are separated so that they can be studied in detail

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13
Q

Define the method of homogenation

A
  1. The cells are initially blended in a homogeniser to break open the cells.
  2. It is then filtered to remove any cell debris
  3. The tube of the resultant fluid (homogenate) is then placed in a centrifuge and spun at a high speed
  4. The heaviest organelle, the nuclei will settle to the bottom where a thin pellet forms
  5. The fluid at the top (supernatant) is removed and transferred to another tube and spun at a slightly higher speed. The second pellet that forms for an animal cell will be the mitochondria. (FOR PLANTS it will be the chloroplast)
  6. This process is repeated with slightly higher speeds each time to separate the organelles.
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14
Q

Why conditions should the homogenate be held in?

A

A cold, buffered solution, of the same water potential

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15
Q

Why should the homogenate be held in these conditions

A

Cold- To decrease enzyme activity
Buffered- To prevent any damage to enzyme’s tertiary structure
Same water potential- Prevent osmosis and organelles from bursting or shrinking

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16
Q

Describe the nucleus structure and function

A

Nucleus is a double membrane called the nuclear envelope, with nuclear pores embedded (that enables molecules to enter and leave)
-It also contains chromatin and nucleolus which is the site of ribosome production
-Nucleoplasm

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17
Q

Define the structure and function of the rough endoplasmic reticulum

A

-It is a series of flattened sacs with ribosomes on the cell surface membrane.
- The RER folds and processes proteins

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18
Q

Define the structure and function of the smooth endoplasmic reticulum

A

The SER is a system of membrane bound sacs, they produce and process lipids

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19
Q

Define the structure and function of the Golgi apparatus

A

The golgi is a series of fluid filled, flattened and curved sacs with vesicles surrounding the edges.
They process and package proteins and lipids and also produce lysosomes

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20
Q

Define the structure and function of the mitochondria

A

Mitochondria are bound by a double membrane called the envelope. The inner membrane is folded to form projections called cristae with a matrix on the inside

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21
Q

Define the structure and function of the ribosomes

A

Ribosomes are the site of protein production

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22
Q

Define the structure and function of the lysosomes

A

Are vesicles containing lysozymes bound by a single membrane

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23
Q

How does a prokaryotic cell differ from a eukaryotic cell

A

Prokaryotic cells have a plasmid, capsule, and pili, whereas eukaryotic cells do not have that

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24
Q

Are viruses non-living or living

A

Non-living

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25
Define the structure of a virus
They consist a nucleic acid (either RNA or DNA) protected by a capsid. Some viruses have a lipid envelope
26
What does mitosis produce
2 genetically identical diploid daughter cells
27
What happens during prophase
Chromosomes condense, nuclear envelope disappears.
28
What happens during prometaphase
Spindle fibres attach to chromosomes
29
What happens during metaphase
Chromosomes align in the middle of the cell, attached to spindle fibres.
30
What happens during anaphase
Chromosomes centrioles divide and are pulled to opposite ends of the cell as the spindle fibres shorten. (sister chromatids are pulled to opposite poles of the cell)
31
What happens during telophase
Nuclear membrane/envelope reforms Chromosomes decondense and spindle fibres disappear
32
What happens during cytokinesis
The cytoplasm divides and 2 genetically identical diploid daughter cells are produced
33
Why does mitosis happen
For growth and repair
34
Describe binary fission
1. The circular DNA replicates and both copies attach to the cell membrane, plasmids also replicate 2. The cell membrane begins to grow between the two DNA molecules and pinch inwards, cytoplasm is divided into two 3. New cell wall forms between the 2 DNA molecules dividing the original cell 4. The identical daughter cells each have a single copy of the circular DNA and a variable number of plasmids
35
What is the main function of the cell surface membrane
Controlling the movement of substances in and out of the cell/organelles
36
Why is the cell surface membrane described as 'fluid-mosaic'
Fluid- Fluidity of the phospholipids Mosaic- Arrangement of the proteins
37
Function of proteins in the cell surface membrane
Intrinsic proteins- Carrier and channel, which allow substances to cross the membrane Extrinsic- On the surface of the cell surface membrane, used for cell signalling
38
Describe the function of cholesterol
Makes the cell surface membrane more rigid and reduces the lateral movement of phospholipids
39
Describe the function of glycolipids
These extend from the surface of the cell and acts a cell surface receptor
40
Describe the functions of glycoproteins
These attach to extrinsic proteins and act as cell surface receptors and neurotransmitters. These are for cell signalling and recognition
41
What is diffusion
Diffusion is the movement of molecules from an area of high concentration to an area of low concentration across a partially permeable membrane
42
What is facilitated diffusion
Facilitated diffusion requires a channel protein in the cell membrane to transport polar molecules, charged, and water soluble molecules across the membrane
43
What is osmosis
Osmosis is the movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane
44
What is active transport
Active transport is the movement of molecules from an area of low concentration to an area of high concentration with the use of ATP
45
What is co-transport
Co-transport uses ions to move substances in and out of cells. This occurs particularly in epithelial cells of the ileum
46
Describe co-transport in relation to the movement of sodium and potassium ions
Sodium and potassium ions are pumped out of the epithelial cell by active transport into the blood, which leaves a lower concentration in the cell. This causes these ions to move from the lumen into the cell by facilitated diffusion, which at the same time brings glucose and amino acids into the cell. These then diffuse from a high concentration in the epithelial cell to a low concentration in the blood.
47
What affects the rate of gas exchange
Surface area, diffusion gradient, diffusion distance, temperature
48
Do viruses possess cell walls
No
49
What is bacteria's cell wall composed of
Murein
50
What are physical barriers to infection
1. Skin 2. Stomach acid
51
Non-specific immune response
1. Inflammation, histamines released by damaged cells cause blood to flow to the affected area and increase the permeability of blood vessels. 2. Lysozyme action- Lysozymes are found in secretions such as tears and mucus, which kill bacterial cells by damaging their walls
52
Describe phagocytosis
1. The phagocyte is attracted to the pathogen as it releases chemical toxins. 2. The phagocyte moves towards the pathogen 3. The phagocyte attaches to the antigens on the pathogen 4. The phagocyte engulfs the pathogen, forming a phagosome 5. Lysosomes move towards the phagosome 6. Lysosomes release lysozymes that digest and destroy the pathogen (hydrolyse) 7. The products of the pathogen are absorbed by the phagocyte and antigens on the pathogen are presented on the phagocyte's cell surface membrane
53
What is the specific immune response
The specific immune response is antigen specific and produces responses that are only specific to one type of pathogen only
54
What are B cells
B-cells mature in the bone marrow and are involved in the humoral response
55
What are T-cells
T-cells move from the bone marrow into thymus gland where they mature, and are involved in the cell-mediated response
56
What are memory cells
Memory cells are cells which replicate themselves once exposed to a pathogen, they remain in lymph nodes for decades. This results in a much faster immune response if the individual were to have the same pathogen invade again.
57
What are plasma cells
They are anti-body producing cells
58
What are T-helper cells
T-helper cells stimulate B-cells and antibody producing cells
59
What are T-killer cells
T-killer cells destroy pathogens
60
Why is it called the cell-mediated response?
Because T-cells only respond to antigens which are presented on cells
61
Describe the cell-mediated response
1. Once a pathogen has been engulfed and destroyed by a phagocyte, the antigens are presented on its cell surface membrane 2. Helper T-cells have receptors on their cell membrane which attach to the antigens on the APC 3. This activates the helper T-cell to divide my mitosis to make a large number of clones 4. Cloned helper T-cells differentiate into different types of cells, such as; killer T-cells, helper T-cells, suppressor T-cell, and memory T-cell
62
Describe the humoral response
1. B-cells are triggered when it encounters a matching antigen 2. the B-cell engulfs the antigen and digests it 3. The selected B-cell divides by mitosis, some of the daughter cells divide into plasma and memory cells 4. Plasma cells secrete antibodies that specifically combine with the antigen that has entered the body
63
Draw a antibody
Antibody should consist of a heavy chain, light chain, antigen binding sites, receptor binding site, and constant region
64
What is active immunity
Active immunity results in the production of an antibody in response to a foreign antigen
65
What is passive immunity
Passive immunity results of the introduction of antibodies from another person or animal
66
What is natural active immunity
It arises from being exposed to an antigen/getting the disease
67
What is natural passive immunity
Natural passive immunity arises from the mother's antibodies being passed to their offspring through the placenta or breast milk
68
What is active artificial immunity
Active artificial immunity arises through vaccinations, which stimulate the immune system and lead to the production of antibodies
69
What is passive artificial immunity
Passive artificial immunity is when antibodies are injected into the body
70
What is a vaccine
Vaccines are a way of introducing a pathogen into the body in order to produce an immune response
71
What is the success of vaccination programme dependent on
1. Cost of the vaccine 2. Severity of the side effects 3. Ease of production, transportation, and administration 4. Number of people that need to be vaccinated for herd immunity
72
What is the concept of herd immunity
Herd immunity is if you vaccinate enough people in the population, then eventually the pathogen won't be transmitted from different hosts. This therefore means that those who are not vaccinated against the disease are protected by those who are.
73
Ethical considerations of vaccines
-Production and testing may be done on animals -The risk of the vaccine needs to be balanced with the benefits -The vaccine must be tested on humans to determine it's toxicity
74
What is a monoclonal antibody
Monoclonal antibodies are produced from a single clone of plasma cells and are mass produced in a lab.
75
What is direct therapy
Monoclonal antibodies that are specific to antigens found on the surface of cancerous cells can be used to target and destroy the cells as part of an immune response
76
What is indirect therapy
Drugs can be attached to monoclonal antibodies such as cytotoxic drug. The antibody is then used to direct the drug towards the cells displaying a particular antigen rather than towards other cells
77
What is HIV structure
-Lipid envelope with attachment proteins -Capsid with RNA inside and reverse transcriptase
78
How does HIV replicate
In order to replicate, the HIV virus binds to the protein CD4 which is frequently found on T-helper cells 2. The capsid then fuses with the cell surface membrane of the T-helper cell 3. RNA and reverse transcriptase enter the cell, which moves to the nucleus of the cell 4. Reverse transcriptase coverts the RNA to DNA 5. The cell now has instructions to produce HIV components
79
Describe the ELISA test
1. In antigen coated well, wash 2. Then add specific antibody to be measured, then wash 3. Add enzyme conjugated secondary antibody, then wash 4. Add substrate and then measure the colour
80
Are antibiotics effective against HIV and viruses
No, as antibiotics prevent bacteria from making cell walls, and therefore burst
81

Biology (9 decks)

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