3.2.1 Cell structure Flashcards
What happens during Homogenation?
Cells broken open (by a homogeniser/blender) to release organelles
List the 3 heaviest organelles
1) nucleus
2) chloroplasts (plants)
3) mitochondria
Why is homogenate filtered?
To remove complete cells/ large cell debris
How are prokaryotic cells different to eukaryotic cells
- No membrane bound organelles/No endoplasmic reticulum, nucleolus, lysosomes or Golgi apparatus
- Chromosomes are shorter, circular loop of DNA, not associated with proteins
- Smaller 70s ribosomes
- Murein cell wall
- Much smaller
What is the structure and function of the nucleus?
- Contains genetic material - necessary to control cells activities
- Surrounded by double membrane - nuclear envelope. Contains nuclear pores to allow large molecules like mRNA out and into cytoplasm.
- Contains chromosomes with protein-bound, linear DNA
- Filled with nucleoplasm
- Nucleolus makes rRNA which is made into ribosomes
What are lysosomes?
Vesicles/membrane bound organelle that releases hydrolytic (digestive) enzymes like proteases, lipases, carbohydrases.
What are similarities between prokaryotic and eukaryotic cells?
- Both have DNA
- Both have cell-surface membrane
- Both have cytoplasm
- Both have ribosomes
Describe process of ultracentrifugation
- Break open/grind cells/tissue and filter
- In cold, same water potential/concentration, pH
controlled solution - Centrifuge/spin and remove nuclei/cell debris;
- (Centrifuge/spin) at high(er) speed, chloroplasts (e.g.) settle out
In cell fractionation, why is the tissue placed in a cold, buffered, isotonic solution?
Cold: reduce activity of enzymes which may break down organelles (not cells)
Buffered: to maintain constant pH so enzymes aren’t denatured
Isotonic: to stop organelles bursting/shrinking due to osmotic gain/loss of water
What is cell fractionation?
The process where cells are broken up and the organelles they contain are separated out
What are the 2 types of ribosomes?
70s in prokaryotic cells
Larger 80s in eukaryotic cells
What is homogenate?
Fluid containing the organelles, cell membrane and cells
Describe the structure and function of mitochondria
- double membrane
- inner membrane folds into cristae
- fluid inside called matrix
- production of ATP (oxidative phosphorylation)
What is the function of the Golgi apparatus?
Modifies, processes and packages (proteins) into vesicles for transport
Describe the structure and function of the rough and smooth endoplasmic reticulum
- Both have membranes that surround flattened sacs called cristernae
- Rough endoplasmic reticulum has membrane bound ribosomes (site of protein synthesis)
- Transports newly synthesised proteins to Golgi apparatus through vesicles
- Smooth endoplasmic reticulum synthesises, stores and transports lipids
