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Biology > Cell Cycle and Structure > Flashcards

Cell Cycle and Structure Flashcards

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1
Q

Differences between electron microscopes and light microscopes

A
  • LM produce colour images, EM produces black and white images
  • LM the specimen can be alive but in EM the specimen must be unalive
  • EM has a higher resolution and magnification than LM
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2
Q

How do you efficiently mouth a temporary slip

A
  • gather cells by peeling a layer or scraping a sample of the specimen
  • stain (e.g., iodine in potassium iodide)
  • place cover slip on and lightly press down to avoid artefacts
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3
Q

What is prophase

A
  • longest phase of mitosis
  • chromatin condenses and chromosomes become visible
  • nuclear envelope disintegrates and nucleolus disappears
    -Centrioles move to opposite poles and extend the spindle fibres.
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4
Q

How may tumours and cancer develop?

A

Tumours (cancer) develops when cells lose control over the cell cycle and divide in an uncontrollable manner.

Results in a mass of rapidly dividing, abnormal cells.

Cancers result from mutations of key genes that control the cell cycle.

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5
Q

What are the key features of viruses?

A

Acellular, non-living (parasitic)
Contain DNA or RNA nucleic acids (genome)
Enclosed within a protein coat - capsid
Surface attachment proteins
Sometimes enveloped (e.g. HIV)
Require a specific host cell to enter and replicate

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6
Q

Detail the eukaryotic cell cycle.

A

DNA replication occurs in interphase when the chromosome are diffuse.

Mitosis is nuclear division

Cytokinesis is the division of the ‘cell body’.

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7
Q

Describe a prokaryote

A
  • genetic material is circular loop
    flagellum
    ribosomes, smaller than those in eukaryotes
    murein cell wall
    cell surface membrane
    plasmids
    capsule
    cytoplasm
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8
Q

What additional features may some prokaryotic cells have?

A

Cell wall made from muerin - protecting against osmotic lysis
External capsule - protection and helps bacteria to stick together
Plasmids - small circular pieces of DNA which have additional genes e.g. antibiotic resistance
Flagella - motile “tail(s)”
Pili - microscopic tube extensions to allow transfer of plasmid DNA between individual bacteria (transjugation)

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9
Q

How could you calculate the mitotic index for eukaryotic cells going through the cell cycle?

A

cells in mitosis / total number of cells

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10
Q

What are the steps to HIV replication?

A
  • attachment proteins attach to receptors on CSM on T helper cells
  • capsid is released into T cells where it uncoats and releases the genetic material (RNA)
  • reverse transcriptase is used to make a complementry strand of DNA from the RNA template, so double stranded DNA molecule is made
  • this is inserted into the human DNA
  • the host cells enzymes are used to make viral proteins from the viral DNA found in the human DNA.
  • viral proteins are assembled into viruses (which bud off/destroy the host cell and infect new cells)
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11
Q

What is the structure of HIV?

A
  • capsid
  • RNA strands held in capsid
  • reverse transcriptase (enzyme) held in capsid
  • attachemnt proteins
  • envelope (membrane stolen from cell membrane of previous cell host)
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12
Q

Why do we use a sterile pipette/flame the loop, bottle neck and spreader in aseptic techniques?

A

To maintain a pure culture of bacteria

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13
Q

Why do we soak contaminated pipette tips in disinfectant in aseptic techniques?

A

To kill bacteria and prevent spreading outside of the lab

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14
Q

Why do we open the petri dish as little as possible in aseptic techniques?

A

To prevent bacteria in the dish getting out and bacteria in the air getting in and contaminating the plate

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15
Q

Why do we wash hands with soap in aseptic techniques?

A

To prevent contamination from bacteria on hands

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16
Q

Why do we disinfect the surfaces in aseptic techniques?

A

To kill bacteria on surfaces so contamination doesn’t occur

17
Q

Describe and explain osmosis.

A

Movement of water particles from an area of high water potential to low water potential. This is a passive process

18
Q

Describe and explain simple diffusion.

A

Movement of small particles from an area of high concentration to an area of low concentration. This is a passive process.

19
Q

Describe and explain facilitated diffusion

A

The net movement of particles from an area of high concentration to an area of low concentration. This uses carrier and channel proteins to aid the diffusion of large/charged particles across a membrane. This is a passive process.

20
Q

Describe and explain active transport.

A

Movement of molecules from an area of low concentration to high concentration. This uses carrier proteins and co transporters. This is an active process (requires energy)

21
Q

Describe and explain co transport

A

Sodium ions are being actively pumped out of the cuboidal cells by active, ATP driven Na / K exchange pumps.

This sets up a sodium ion concentration gradient., with a higher concentration of sodium ions on the outside.

The co-transporter then facilitates the sodium ions diffusing in down their gradient to “pull in” glucose molecules into the cytoplasm against its gradient (maximum absorption).

The glucose can then passively diffuse out through other carrier proteins onto the other side / passing into the blood capillaries.

22
Q

Outline the Na+/K+ pump model.

A
  • Three sodium ions bind to the pump
  • ATP attaches to the pump and transfers a inorganic phosphate to the pump (phosphorylation) causing it to change shape
  • This results in the pump opening to the outside of the axon
  • The three sodium ions are released
  • Two potassium ions from outside the cell enter and bind to their sites
  • The attached phosphate is released altering the shape of the pump again
  • The change in shape causes the potassium ions to be released inside the cell
23
Q

What are co-transporters?

A
  • a type of carrier protein
  • they bind with 2 molecules at a time
  • where 1 of the molecules is going against the concentration gradient.
24
Q

What is the structure of an antibody?

A
  • 4 disulfide bridges
  • 2 heavy strands
  • 2 light strands
  • variable regions near the tips on the ‘Y’ shape
  • constant regions at the bottom of ‘Y’ shape
  • 2 hinge regions
  • antigen-antibody binding sites
25
Q

How is the immune response split?

A

Into 2 sections:
- cellular
- humoral

26
Q

Outline the CELLULAR section of the immune response

A
  • receptor proteins on T-cells (type of lymphocyte) bind to complementary antigens on APCs
  • T-cell is now activated
  • T-cells either become helper T-cells or remain as memory cells
  • Helper T-cells release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells
  • Cytotoxic cells kill abnormal and foreign cells (cancer cells eg)
27
Q

Outline the HUMORAL section of the immune response

A
  • B-cells become activated by helper t-cells and divide by mitosis
  • They can become memory cells or become plasma cells
  • plasma cells will secrete antibodies complementary to the antigen on ADC
28
Q

Outline phagocytosis

A
  • phagocyte is attracted to chemicals/substances secreted from pathogen
  • phagocyte engulfs pathogen into a phagosome
  • lysosomes in phagocyte fuse with phagosome and release hydrolysis enzymes called lysozymes
  • lysozymes break down pathogen
  • pathogen then displays the pathogens antigen on CSM and acts as an ADC
29
Q

What is an ADC

A
  • an antigen displaying cell
30
Q

Outline an ELISA test

A
  • antigen is bound to bottom of wells in a well plate
  • a sample of blood plasma is added to the wells
  • if there is the antigen-specific antibodies present then they will bind to the antigen
  • the well is then washed out
  • a secondary antibody (that has an enzyme attached to it) is added to the well plate
  • this secondary antibody solution will bind to the antigen specific antibody
  • the well plate is washed again
  • a solution that contains a substrate which will react with the enzyme attached to the secondary antibody is added
  • this will produce a coloured product
  • this indicates that the blood plasma contains antigen-specific antibodies in their immune system.
31
Q

What are some ethical issues surrounding the use of monoclonal antibodies?

A
  • animals are needed in order to make them (suffering)
  • they are expensive to make
  • as successful as they have been, there has been multiple failures
32
Q

Define eukaryotes

A
  • cells with membrane-bound organelles
33
Q

what is the function of ribosomes?

A
  • used to make proteins
  • mostly attached to rough endoplasmic reticulum
  • ribosomes are larger in eukaryotes (80S) than in prokaryotes (70S)
34
Q

What is clonal selection

A

where a specific kind of cell is stimulated to make genetically identical copies of itself by dividing by mitosis

35
Q

what are monoclonal antibodies

A

Antibodies with the same tertiary structure produced by identical plasma cells

36
Q

Why is it sensible to wait a while after recovery of an infectious disease before receiving a vaccine against it?

A

You will be producing antibodies against the antigen
The antibodies in your blood will bind to the antigen in the vaccine, marking it for destruction
So the vaccine won’t work

37
Q

Describe how B lymphocytes would respond to a vaccination against a virus

A

B cell binds to specific antigen
B cell clones and divides by mitosis
These b cell clones turn into plasma cells that release the antibodies
B cells develop into memory cells

Biology (7 decks)

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