Topic 2A - Cell Structure And Division Flashcards
Identify 3 structure of a eukaryotic cell
Has a nucleus
Has a clear nuclear envelope
DNA is associated with histones
No plasmid
Membrane bound organelles
80s ribosomes
No capsule
Cell wall mostly cellulose (chitin in fungi)
Chloroplasts present in algae and plant cells
Identify 3 structures of a prokaryotic cell
No true nucleus
DNA not associated with histones or proteins
DNA found in plasmids
No membrane bound organelles
70s ribosomes
Cell wall made of murein
Can have a slime layer called a capsule
No chloroplast
Describe and give the functions of a mitochondrian cell
Description:
They’re usually oval shaped. They have a double membrane, the inner membrane folds to from a cristae. Inside the cristae is the matrix, the matrix contains enzymes involved in respiration.
Function:
The site of aerobic respiration aerobic respiration produces ATP - a common energy source.
Describe and give the functions of a chloroplast cell
Description:
A small flattened structure found in plants cells and algal cells. It’s surrounded by a double membrane, and also has membranes inside called thylakoid membranes. These membranes are stacked up is some parts of the chloroplast to form a grana . Grana are linked together by lamella - thin, flat pieces of thylakoid membrane.
Function:
The site where photosynthesis takes place. Some parts of photosynthesis happen in the grana and other parts happen in the stroma (a thick liquid found in chloroplast).
Describe and give the functions of the Golgi apparatus
Description:
A group of fluid-filled membrane-bound flattened sacs. Vesicles are found at the end of the sacs.
Function:
it processes and packages new lipids and proteins. It also makes lysosomes.
Describe and give the function of vesicles
Description:
A small fluid filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus.
Function:
Stores lipids and proteins made by the Golgi apparatus and transports them out of the cell.
Describe and give the function of lysosomes.
Description:
A round organelle surrounded by a membrane, with no clear internal structure. It’s a type of Golgi vesicle.
Function:
Contains digestive enzymes called lysozymes. These are kept separate from the cytoplasm by a surrounding membrane, and can be used to digest invading cells and break down worn out cells.
Describe and give the functions of the rough endoplasmic reticulum
Description:
A system of membranes enclosing a fluid filled space. The surface is covered with ribosomes.
Function:
Folds and processes proteins that have been made at the ribosomes.
Describe and give the functions of the smooth endoplasmic reticulum
Description:
A system of membranes enclosing a fluid filled space.
Functions:
Synthesises and processes lipids.
What happens during homogenisation?
Homogenisation is the breaking up of the cell
Tissue is put in an ice-cold, isotonic, buffered solution
You put the tissue into a blender
This breaks up the cell membrane and release the organelles into the solution
This is called the homogenate
Describe the purpose of an ice-cold, isotonic, buffered solution.
Ice cold - Reduce enzyme activity so it doesn’t damage the cell and organelles
Isotonic - Stop osmotic activity. So water doesn’t move into the cell and damage the organelles by bursting.
Buffered - Keep the pH constant so enzyme activity isn’t increased and it doesn’t damage the cell.
Describe filtration during cell fractionation.
The homogenised solution is passed through a gauze to remove large cell debris, large tissue and unbroken cell
The organelles will pass through the gauze as they are much smaller
What is ultracentrifugation?
The solution which contains the organelles are poured into a test tube.
The test tube is then spun in a centrifuge at a high speed. The most dense organelle (the nucleus) forms a thick sediment at the bottom of the tube - called a pellet.
Above the pellet remains a solution which contains the other organelles - the supernatant.
They supernatant is the removed and poured into another tube. It is then put into a centrifuge where it is spun at a higher speed. The most dense in the solution then forms a pellet at the bottom of the tube (mitochondria).
Remove the supernatant and put into another test tube. Spin at higher and higher speeds until all organelles are separated out.
What are the characteristics of a prokaryotic cell
70s ribosomes
Capsule
No chloroplast
Cell wall made of murein
DNA is in plasmids
No membrane bound organelles
Proteins are not associate with histones
What are the characteristics of a eukaryotic cell
80s ribosomes
No capsule
Has chloroplast
Cell wall made of cellulose (made of chitin in fungi)
DNA contained within nucleus
Has membrane bound organelles
Proteins are associate with histones
Explain the process of binary fission
Step 1 - circular DNA and plasmids replicate. Main DNA loop only replicate once but plasmids replicate as many times as they want
Step 2 - cell gets bigger and the DNA loops move to opposite ‘poles’ of the cell
Step 3 - the cytoplasm begins to divide and new cell walls begin to form
Step 4 - the cytoplasm divides and two daughter cells are produced, each daughter cell has one copy of circular DNA but a variable number of plasmids
What is the structure of viruses?
Genetic material
Attachment protein
Capsid
Explain the process of viral replication? (5)
- Virus attaches to host cell receptor protein
- Genetic material released
- Genetic material replicated using hosts machinery
- Viral components assemble
- Replicated viruses released from host cell
What’s the equation to work out image size?
I = AM
What are the 4 types of microscopes?
Optical
Electron
Scanning
Transmission
Describe the characteristics of the optical microscope?
Uses light
Low res
Low mag
Describe the characteristics of an electron microscope? (3)
Uses electrons
Higher res than light
Higher mag than light
Describe the characteristics of a TEM?
Uses electromagnets to create a beam which goes through the sample
Produces 2d image
Sample must be dead
Black and white image
See internal structure
Describe the characteristics of SEM?
Scans surface using electrons
Can be used on thick specimens
Lower res than TEMs
Can only be used on dead organisms
Can get surface composition
How do you prepare a microscope slide? (4)
- Pipette small drop of water to slide
- Use tweezers to place a thin section of sample on water drop
- Add a drop of a stain
- Add a cover slip. (Stand slip upright on slide, carefully tilt and lower it so it covers the specimen, try not to get any air bubbles between the glass and cover slip)
What are the 3 stages of cell fractionation?
- Homogenisation
- Filtration
- Ultracentrifugation
What is homogenisation?
Break up cells in a blender
- (breaks up plasma membrane and releases organelles into solution)
Put into an ice cold, isotonic, buffered solution
What is filtration?
Filter through a gauze to seperate cell or tissue debris
Organelles much smaller pass straight through
What is ultracentrifugation?
Separating of organelles
- Cell fragments poured in a tube which is put into a centrifuge and is spun at a low speed. Heaviest organelles get flung to the bottom of the tube and form a sediment. The rest of the organelles form a supernatant.
- Supernatant drained of, poured in another tube and spread at a higher speed. Heaviest organelles form a pellet at the bottom. Supernatant removed and process repeated at higher and higher speeds, until all organelles are removed.
What are the stages of the cell cycle? (Not imap)
Mitosis
G1
Synthesis
G2
What occurs during growth phase 1?
Cell grows and new organelles and proteins are made
What occurs during synthesis?
Cell replicates its DNA, ready to divide by mitosis
What occurs during growth phase 2?
Cell keeps growing and proteins needed for cell division are made
What occurs during interphase?
Cells DNA unravels and replicates to double the genetic DNA
What is the structure of a chromosome? (2)
Chromatid
Centromere
What are the 4 stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What occurs during prophase? (3)
Chromosomes condense (getting shorter and fatter) and become visible
Centrioles begin moving to opposite ends
Nuclear envelope breaks and releases chromosomes in cytoplasm
What occurs during metaphase? (2)
Chromosomes align in the middle
Spindles attach to the centromere
What occurs during anaphase? (3)
Centromeres divide separating the chromatids
Spindles pull chromatids to opposite ends
Chromatids appear V shaped
What occurs during telophase? (4)
Chromatids reach opposite poles on spindle
Uncoil and become long and thin again
Nuclear envelope forms around each group of chromosomes again
Cytoplasm divides and there are now 2 identical daughter cells
How do you prepare a root tip cell squash?
- Add 1m HCl to a boiling tube. Put tube in a water bath that is at 60oC
- Use a scalpel to cut 1cm of tip from the growing root
- Carefully transfer root tip into a boiling tube containing acid. Incubate it for about 5 minutes
- Use tweezers to remove the tip from the tube and use a pipette to rinse well with cold water. Pat dry on paper towel
- Place root tip on a microscopic slide and cut 2mm from the tip
- Use a mounted needle to break the tip and spread the cells out thinly
- Add a few drops of stain and leave for a few minutes
- Place a cover slip over the cells and push down firmly
- Now look at all the stages of mitosis under a microscope
Why would a stain be used?
Allow the colourless objects to be seen clearly
Why would we cut from the tip of the sample? (Mitosis)
Where the growth occurs so thats where mitosis takes place
Why do you push down the cover slip firmly?
To squash the organelles making them thinner so light can pass through
