cell structure

Question 1

the process of cell fractionation

Answer 1

1) sample of cells we are interested in

2) we homogenise (blend) using homogeniser its in
-buffer pH constant (stop denaturing
- WP same as cells WP (stop osmosis)
- ice (slows destructive enzymes from damaging)

ultracentrifugation
3) cell homogenate spun in centrifuge. heavy organelles experience greater forces so they sink (nucleus)

4) Pellet removed from supernatant (liquid), centrifuged at higher speed ( mitochondria

5) repeat until desired organelle to study separates

Question 2

why can we not study endoplasmic reticulum

Answer 2

it tends to get blended up by homogeniser

Question 3

advantages and limitations of light microscopes

Answer 3

advantages
- small
- inexpensive
- can view original colour
- can view living cells ( we can see processes like mitosis

limitations
- stain can kill living cells
- low in resolution ( long wavelength of light) 0.2 um

Question 4

limitations and advantages of SEM

Answer 4

advantages
- higher resolution
- 3D
- visualise enzymes and see their movement , activity

disadvantages
- expensive
- difficult to operate
- requires coating of gold - causes artefact

Question 5

limitations and advantages of TEM

Answer 5

advantages
- high resolution - make major discoveries in Biology

limitations
-black and white
- vacuum cannot view living organisms
- vary careful staining
-specimen must be thin
- artefacts

TEM is 2d vs SEM id 3D

Question 6

prokaryotes vs eukaryotes

Answer 6

• euks are small vs pros that are small
• pro have plasmid euk do not
• no histone vs histones
• 70s vs 80s ribosomes
• no membranes pro , vs membranes
• DNA in double membrane vs DNA in cytoplasm
• pro - slime capsule ( protection from phagocytosis, MUREIN cell wall ( strength)

Question 7

viruses

Answer 7

cannot reproduce independently, they need host cells to reproduce

attach to host cells by their attachment proteins

genetic material in capsid

Question 8

the structure and functions of the nuleus

Answer 8

structure
- nucleoplasm (contains nucleotides and enzymes for DNA/ RNA replication

• double membrane
• nuclear pores (allows mRNA to leave to cytoplasm)
• Nucleolus contains chromatin
• continuous with RER

function
- DNA replication

• contains instructions for encoding amino acid sequence of proteins by transcription + translation

Question 9

RER structures + functions

Answer 9

structure
- flattened sacs CISTERNAE

function
- transports proteins that have diff destinations

• cisternae covered in ribosomes that translate protein to be secreted by cell.
  passes through lumen of cisternae where its folded into tertiary structure
  packages into vesicle to Golgi for further modification
  then exported from cell

Question 10

lysosymes functions and structure

Answer 10

lysozymes digest foreign substances and damaged cells
they fuse with phagosome and release hydrolytic enzymes

which have optimal pH of acidic

Question 11

mitochondria functions and structure

Answer 11

function
aerobic respiration of glucose to water transferred to ATP for ENERGY
1) krebs cycle
2) oxidative phosphorylation

structure
- enzymes for kerbs cycle are found in matrix

• cristae folds add surface area for enzymes needed for oxidative phosphorylation
• mitochondrial RNA + ribosomes for its own synthesis for enzymes for aerobic

found in cells with high energy consumption (muscle cells)

Question 12

chloroplasts function and structure

Answer 12

function
- photosynthesis, light + water make oxygen + glucose

structure
- double membrane - controls what enters + leaves

• thylakoid - contain chlorophyll + enzymes needed for light
• grana - stacking of thylakoid SA for absorbing light
• lamellae allow chemicals to pass through grana
• stroma - light independent enzymes contained
• glucose - starch - starch granules
• contain loop of DNA + ribosomes = encodes proteins needed for photosynthesis

Question 13

cell wall structure and functions

Answer 13

functions
- mechanical strength - for withstanding the hydrostatic pressure of the protoplast + allows cell to be RIGID (stops wilting)

structure
- permeable to water molecules

• microfibrils - contribute strong mechanical strength
• lamella - acts as a glue in between plant cells

fungi (chitin)

Question 14

vacuole function and structure

Answer 14

functions
e.g phagosome where they are contained

• removal of waste materials
• contains poisons, waste chemicals
• allow osmosis, water enters

structure
- tonoplast (vacuole membrane, controls what leaves + enters
cell sap contains nutrients, or poisonous chemicals. waste chemicals

• contains dissolved chemicals - low water potential, water enters in through osmosis, hydrostatic pressure makes cell TURGID