cells Flashcards
What organelles are present in prokaryotic cells but not eukaryotic cells?
flagellum, DNA loop, centrioles, plasmids
What is the function of the cell surface membrane?
controls what enters and leaves the cell.
What is the function of the nucleus?
controls protein synthesis by mRNA and tRNA. Manufactures RNA and ribosomes.
What is the function of the mitochondrion?
Site of aerobic respiration - production of ATP cells with high levels of metabolic activity.
What is the function of chloroplast?
Site of photosynthesis.
What is the function of golgi apparatus?
Add carbohydrates to proteins, produce secretary enzymes, secrete carbohydrates, transport modify and store lipids, form lysosomes.
What is the function of lysosomes ?
Isolation of enzymes before release to outside of the cell, hydrolyse material ingested by phagocytic cells, release enzymes to destroy material around cell.
What is the function of ribosomes?
protein synthesis
What is the function of rough endoplasmic reticulum?
protein synthesis
What is the function of smooth endoplasmic reticulum?
synthesis and store of lipids and carbohydrates.
What is the function of the cell wall?
mechanical strength to prevent bursting from osmotic pressure, allow water to pass along it.
What is the function of the cell vacuole?
support herbaceous parts of woody plants by making cells turgid, contains sugars and amino acids that may act as a temporary food store.
What is differentiation?
The process by which cells become specialised for different functions.
Define tissue.
A group of similar cells which carry out a specific function.
What are the advantages of a light microscope?
real colours, can use a living sample
What are the disadvantages of a light microscope?
lower resolution, can not see smaller organelles, lower magnification.
what are the advantages of scanning electron microscope?
3D image, thick specimens, false colour
What are the disadvantages of the scanning electron impact microscope?
Sample must be in a vacuum, cant view living samples, lower resolution than T.E.M
What are the advantages of a transmission electron microscope?
higher resolution so can see ultrastructure
What are the disadvantages of the transmission electron microscope?
very thin specimen, black & white image, need a vacuum, image contains artefacts, 2D image.
What is the equation for magnification?
image size = actual size x magnification
Explain how you would prepare a stained temporary mount.
1) use a knife to cut a thin slice of the specimen
2) use forceps to place the specimen on the slide.
3) add iodine
4) use a mounted needle to lower the cover slip onto the slide.
What is cell fractionation used for?
Separating different organelles of a cell so they can be studied in detail.
What is the first stage of cell fractionation?
Tissue is cut up and kept in a cold, isotonic buffered solution.
What is the second stage of cell fractionation?
cut-up tissue is further broken up in homogeniser and filtered to remove large cell debris.
What is the third stage of cell fractionation?
Homogenised tissue is spun in an ultracentrifuge at a low speed for 10 minutes to force the heaviest organelles to the bottom.
What is the fourth stage of cell fractionation?
The supernatent is transferred to another tube and spun at a higher speed. repeated at different speeds,
Order the organelles in order of least to most dense.
ribosomes, endoplasmic reticulum, mitochondria, nucleus
Where is murein used in prokaryotic cells?
cell wall
What occurs in interphase?
cell prepares for division
What happens during prophase?
chromosomes condense to get fatter and smaller. centrioles move to opposite ends of the cell.
What happens during metaphase?
spindle apparatus forms in the cytoplasm, chromosomes align at the centre.
What happens during anaphase?
Spindle fibres attach to chromatids to pull them to each side.
What happens during telophase?
Nuclear envelope and nucleus forms
How do you calculate mitotic index?
number of cells with visible chromosomes/ total number of cells observed
How does a tumour cell develop?
early tumour starts enlarging developing blood vessels and lymphatic vessels. tumour cells squeeze into blood vessels. tumour cells travel in blood and then stick to blood vessels wall.
Define magnification
How many times larger the image is compared to the object
Define resolution
Minimum distance between two objects where they can still be viewed as separate
How do prokaryotic cells divide?
Binary fission
What happens during binary fission?
1) Circular DNA molecule replicates and both copies attach to cell membrane.
2) Plasmids replicates
3) Cell membrane begins to grow between the two DNA molecules and begins to pinch inwards dividing cytoplasm into two.
4) a new cell wall forms between the two molecules of DNA, dividing the original cell into 2 identical daughter cells, each with a single copy of the circular DNA.
Why is the cell membrane described as fluid-mosaic?
Individual phospholipids molecules can move relative to one another giving the membrane a flexible shape. However also mosaic as phospholipids and individual proteins are embedded in the membrane which vary in shape and size.
What is the function of fatty acids in the cell membrane?
Lipids soluble substances can enter.
Prevent water soluble substances entering/leaving.
Membrane flexible & self healing
What is the function of extrinsic/intrinsic proteins in the cell membrane?
Act as channels transporting water soluble substances.
Allow active transport
Cell surface receptors
Help cells adhere
What is the function of cholesterol in the cell membrane?
Reduce lateral movement
Make membranes less fluid at high temperatures
What is the function of glycolipids in the cell membrane?
Recognition site
Cells attach to form tissues
What is the function of glycoproteins in the cell membrane?
Recognition site
Allow cells to recognize
What is the function of the cell membrane?
Separate organelles for specific metabolic reactions.
Provide internal support.
Isolate enzymes that might damage the cell.
What sort of molecules are transferred in simple diffusion?
Lipid soluble, very small molecules
What sort of molecules are transported in facilitated diffusion?
Water & soluble ions
Specific ions
What is the difference between facilitated and simple diffusion?
Simple diffusion the cell cannot control the movement as it depends on the conc gradient. In facilitated diffusion the carrier protein can open and close the channel proteins to allow diffusion.
Define osmosis.
The passage of water from a region of high water potential to a region of lower water potential through a partially permeable membrane.
What are aquaporins?
Integral membrane proteins that serve as channels in transfer of water.
How is the small intestine adapted for efficient diffusion?
Many channels and carrier proteins in the lining of small intestine.
Large surface are from microvilli
Short diffusion distance, one cell thick
Good blood supply so high concentration gradient
Describe active transport.
Molecules bind to a complimentary receptor on the carrier protein.
ATP binds to carrier protein and is hydrolysed into ADP and a phosphate.
Causes carrier protein to change shape and release molecule on other side.
Phosphate ion is released and protein returns to original shape.
Describe the process of co-transport.
1)Sodium ions are actively transported out of epithelial cell into blood. (Reducess concentration of sodium in epithelial cell)
2)Sodium ions diffuse via facilitated diffusion from the illeum into epitheliaal cell to maintain conc gradient.
3) sodium ion has to attach to co-transporter protein so when it binds to a complimentary receptor it allows glucose to bind too.
4) glucose moves by facilitated diffusion into blood from epithelial cell
