B2 - cell structure & organelles Flashcards
Nucleus
- has nuclear envelope (double membrane)
- nuclear pores for mRNA to leave through
- houses cell’s genetic material & controls metabolic material
Nucleolus
- In nucleus
- Made of proteins & mRNA
- produces ribosomes
Plasma membrane
- phospholipid bilayer
- controls exchange between cell & environment
Mitochondria
double membrane
cristae = structure
matrix = fluid
aerobic respiration site, stores energy for cell through ATP production.
centriole
- 9 x microtubule triplets
- organise spindle fibres during cell division
- found in flagella and cillia
lysosome
- no internal structure
- has digestive enzymes = breakdown old tissue & foreign material
golgi
- flattened sacs of cisternae
- Add carbs or lipids to protein
- package into vesicles & modify proteins (secretory vesicle leaves cell or lysosome stays in cell)
ribosome
- made of RNA
- small & large subunit
- carries out protein synthesis
RER
- bound to ribosomes
- synthesise & transport proteins
SER
- no ribosomes
- lipid & carbohydrate synthesis
cilia
- parallel microtubules slide over each other = beats & creates a current
- moves fluids adjacent to the cell e.g. moves mucous in the lungs
chloroplast
- chloroplast envelope (double membrane)
- carry out photosynthesis
What are the steps of protein production? (6)
1) protein instruction in DNA
- instruction for hormone = gene = length of DNA on a chromosome
- nucleus makes copy of instruction, called mRNA
2) mRNA leaves through nuclear pore
3) mRNA attach to small subunit of ribosome on the RER, which reads instruction & assembles protein
4) Pinches of RER & transported in a vesicle along microtubule tracks to the golgi
5) golgi fuses with vesicle, then packages & modifies protein
6) moved to cell membrane in vesicle & secreted outside cell.
What are the main differences between prokaryotic and eukaryotic cells? (3)
Prokaryotic:
- Bacteria
- DNA not enclosed in a nucleus
- no membrane-bound organelles
- always unicellular
- smaller ribosomes 70S
Eukaryotic:
- animal & plant cells
- ‘true nucleus’
- membrane-bound organelles
- uni & multicellular
- larger ribosomes 80S for more complex protein formations
What structures would you expect to find in a prokaryotic cell? (5)
- circular chromosome free in cytoplasm
- capsule (protection)
- peptidoglycan cell wall
- mesosome (same role as mitochondria), invaginated/in-folding
- plasmid (small extrachromosomal DNA molecule/extra info that produces enzymes)
- flagella
- ribosomes
- plasma membrane
What structures are in a plant cell that aren’t in an animal cell? (3)
- chloroplasts
- large permanent vacuole (push contents against cell wall to maintain rigid framework)
- cellulose cell wall
What is the difference between chromosomes in eukaryotic & prokaryotic cells?
eukaryotic:
- linear
- DNA wrapped around histones to form chromatin, which condenses into chromosomes
prokaryotic:
- circular
- no histones/chromatin
What structure are found in animal cells that aren’t in plant cells?
- centrioles
- lysosomes
what are the three main fibres of the cytoskeleton?
microfilaments/ actin filaments
microtubules
intermediate filaments
what is the role of microtubules? (3)
- Important structural role: help cell resist compression forces
- grow and shrink by adding & removing tubule proteins.
- use energy from ATP to move.
- have locomotives that run along microtubular tracks. Motor proteins = KINESIN (moves vesicle to cell’s periphery) & DYEIN (moves to interior)
DIKP
What is the structure of microtubules? (2)
- made of tubulin proteins
- hollow tube arrangement
- alpha & beta tubulin
What is the role of intermediate filaments? (2)
- more permanent, structural role
- give mechanical strength to cell to maintain shape
What is the structure of intermediate filaments?
- made of multiple proteins woven together
- e.g. keratin (fibrous protein in hair & nails)
What is the role of microfilaments/ actin filaments?
- responsible for cell movement & contraction during CYTOKINESIS
- contractile protein
What is the structure of actin/microfilaments?
- linked monomers of actin
- 2 strands twisted into a rope structure.
What are centrioles?
- come in pairs called a centrosome
- act as origin for microtubules to extend into cilia or flagella
- organise spindle apparatus for chromosomes to move on during cell division.
How is prokaryotic flagella different to eukaryotic flagella?
- thinner
- no 9+2 arrangement
How do cilia and flagella create movement?
- parallel pairs of microtubules slide over each other in a beating motion
