Cell structure (Plants and Prokaryotes) Flashcards
(12 cards)
Describe plant cell wall!
- Rigid structure
- Made from cellulose.
- Freely permeable so substances can pass into/out of cell.
- Provides shape.
- Acts as a defence mechanism against invading pathogens.
Describe vacuoles!!
Membrane lined sacs in cytoplasm containing cell sap/sugars + AA
Large permanent vacuole —> maintenance of turgor so that contents of cell push against cell wall and maintain a rigid framework for the cell.
Membrane called tonoplast (selectively permeable)
Describe the chloroplast!!!
- Double membrane structure
- Fluid enclosed in chloroplast = stroma.
- Internal network of membranes ~form flattened sacs called thylakoids.
- Granum = several thylakoids stacked together
- Grana joined by membranes called lamellae.
- Grana contain chlorophyll pigments (where light-dependent reactions occur)
- Starch grains = strach produced by photosynthesis
- Contain DNA + proteins so able to make own proteins.
Functions of the chloroplast
Site of photosynthesis
Internal membranes = large SA –> absorb as much sunlight as possible
What are prokaryotic cells?
Earliest forms of life on Earth.
3.5 billion years ago.
Known as extremophiles (live in salt lakes + hydrothermal vents)
Describe DNA of prokaryotes
Large circular strand of DNA
Extra genes found in plasmids
Genes often grouped into operons.
Describes Ribosomes of prokaryotes.
Smaller than eukaryotes
70S
Necessary for protein synthesis.
Describe the cell wall.
Cell walls made from peptidoglycan (murein)
Describe the flagella of prokaryotes
Thinner and no 9+2 arrangement.
Energy to rotate filament supplied from process of chemiosmosis not from ATP.
The flagellum is attached to cell membrane of a bacterium by a basal body and rotated by a molecular motor.
Molecular motor causes hook to rotate giving the filament a whip-like movement which propels the cell.
Describe role of the capsule
Slimy layer made of proteins.
Prevents bacteria from desiccating (drying out).
Protects bacteria against the hosts immune system.
How are DNA packaged in prokaryotes?
Plasmids —> small loops of DNA which only carry few genes.
Occurs in varying numbers.
What are the differences between eukaryotic cells and prokaryotic cells?
Binary fission vs a/sexual reproduction
70S vs 80S ribosomes
