B1 - Cell Biology Flashcards
(18 cards)
What are the benefits of light microscopes?
They are cheap to make
- Allow you to see the outlines of cells
Why are electron microscopes better than light microscopes?
1 - Greater resolving power
2 - Higher resolution
Allow you to visualise finer details - including organelles (sub-cellular structures)
What is the equation for magnification?
Magnification = Image size / actual size
I
A×M
What are eukaryotic cells? Give 2 examples.
Cells that have a nucleus in which their DNA is found
E.g Plant cells and Animal cells
What is a prokaryotic cell? Give an example.
Cells that don’t have a nucleus
- DNA is found in a plasmid (loop of DNA)
E.g Bacteria
What are the 5 main parts of an animal cell and what do they do?
1 - Nucleus: Contains genetic material
2 - Cytoplasm: Liquid that makes up the cell - where most chemical reactions take place
3 - Cell membrane: Semi-permeable (allow certain substances to pass through) - Controls what enters and leaves the cell
4 - Mitochondria: Site of aerobic respiration - releases energy for cell to function
5 - Ribosomes - Where protein synthesis takes place
What extra parts do plant cells have and what do they do?
1 - Cell wall: Made of cellulose - provides a rigid structure
2 - Chloroplasts: Contain chlorophyll - where photosynthesis takes place
3 - Permanent vacuole: Stores sap
How many pairs of chromosomes are there in every nucleus of human cells?
There are 23 pairs (46 individual chromosomes) in every nucleus (diploid cells)
- Gametes (eggs/sperm) only have 23 individual chromosomes
Why are new (diploid) cells made by mitosis?
For growth and repair
Describe the process of mitosis.
- Nucleus dissolves & genetic material is duplicated
- The two sets of chromosomes move to different sides
- Mitochondria, ribosomes & other organelles are duplicated
- The cell divides, producing two identical diploid cells
(New nuclei are formed, or “the nucleus divides”)
What are stem cells?
Cells that haven’t yet specialised to perform specific functions
- Found in animal embryos and plant meristems
- Some are also found in bone marrow but they can only specialise into blood cells
Advantages of cloning?
1 - Embryo clones can be made to harvest stem cells from - can tract conditions without them being rejected by the patient’s body
2 - Can be used to preserve species or produce crops with desired traits
What is diffusion?
The movement of particles from an area of high to low concentration - (DOWN the concentration gradient)
-Passive - requires no energy
Happens across a semi-permeable membrane if the holes are large enough
What is cell differentiation?
When a cell becomes specialised for a specific function
What is osmosis?
The diffusion of water across a semi-permeable membrane to balance the concentrations of solution inside and outside a cell
Water must move because the larger molecules can’t fit through the holes
Water moves in if the concentration is higher outside
How cam you increase the rate of diffusion and osmosis?
Increase:
- The difference in concentrations
- Surface area
- Temperature
Describe the osmosis practical.
- Cut same length cylinders from same vegetable (potato)
- Weigh each of them
- Place them in sugar solutions of varying concentrations
- After set time, remove excess water and reweigh
- Calculate the % change in mass
- Plot on graph
% change in mass = [(final mass - initial mass) / initial mass)] ×100
What is active transport?
The movement of particles through a membrane via carrier proteins
-Requires energy - so can move them AGAINST the concentration gradient
