Cell Cycle and Structure 2 Flashcards
(68 cards)
Differences between electron microscopes and light microscopes
- 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
How do you efficiently mount a temporary slip
- 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
What is prophase
- 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.
How may tumours and cancer develop?
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.
What are the key features of viruses?
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
Detail the eukaryotic cell cycle.
DNA replication occurs in interphase when the chromosome are diffuse.
Mitosis is nuclear division
Cytokinesis is the division of the ‘cell body’.
Describe a prokaryote
- genetic material is circular loop
flagellum
ribosomes, smaller than those in eukaryotes
murein cell wall
cell surface membrane
plasmids
capsule
cytoplasm
What additional features may some prokaryotic cells have?
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)
How could you calculate the mitotic index for eukaryotic cells going through the cell cycle?
cells in mitosis / total number of cells
What are the steps to HIV replication?
- 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)
What is the structure of HIV?
- capsid
- RNA strands held in capsid
- reverse transcriptase (enzyme) held in capsid
- attachemnt proteins
- envelope (membrane stolen from cell membrane of previous cell host)
Why do we use a sterile pipette/flame the loop, bottle neck and spreader in aseptic techniques?
To maintain a pure culture of bacteria
Why do we soak contaminated pipette tips in disinfectant in aseptic techniques?
To kill bacteria and prevent spreading outside of the lab
Why do we open the petri dish as little as possible in aseptic techniques?
To prevent bacteria in the dish getting out and bacteria in the air getting in and contaminating the plate
Why do we wash hands with soap in aseptic techniques?
To prevent contamination from bacteria on hands
Why do we disinfect the surfaces in aseptic techniques?
To kill bacteria on surfaces so contamination doesn’t occur
Describe and explain osmosis.
Movement of water particles from an area of high water potential to low water potential. This is a passive process
Describe and explain simple diffusion.
Movement of small, soluble particles from an area of high concentration to an area of low concentration. This is a passive process.
Describe and explain facilitated diffusion
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.
Describe and explain active transport.
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)
Describe and explain co transport
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.
Outline the Na+/K+ pump model.
- 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
What are co-transporters?
- a type of carrier protein
- they bind with 2 molecules at a time
- where 1 of the molecules is going against the concentration gradient.
What is the structure of an antibody?
- 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
