Cells Flashcards
Describe the structure of the cell membrane
- Arranged in a phospholipid bilayer
- Hydrophillic phosphate heads
- Hydrophobic Fatty Acid tails
- Contains intrinsic and extrinsic proteins
- Contains cholesterol
Describe the function of the cell surface membrane
- Selectively permeable: enables control of passage of substances in and out the cell
- Receptors on the surface: allow cell recognition and signalling
Describe the structure of the nucleus
- Nuclear envelope:
Double membrane, has nuclear pores - Nucleoplasm
- Nucleolus (Dense region)
- Protein (histone) bound, linear DNA:
- Chromatin, condensed
Chromosomes, highly condensed
Describe the structure of the nucleus:
- Stores genetic information which codes for polypeptides
- Site of DNA replication
- Site of transcription, producing mRNA
- Makes ribosomes, rRNA
Describe the structure of a ribosome
- Made of rRNA and proteins (2 subunits)
- Not membrane bound
Describe the function of the ribosome
- Site of protein synthesis (translation)
Describe the structure of rER and sER
- System of membranes
- rER coated with ribosomes
Describe the function of the rER
- Ribosome on surface synthesise proteins
- Proteins processed in rER
- Proteins packaged into vesicles for transport
Describe the structure of the golgi apparatus and golgi vesicles
Golgi apparatus: Flattened membrane sacs
Gogli vesicles: Small membrane sac
Describe the function of the sER
- Synthesises and produces lipids
What is the function of the golgi appartus:
- Modifies proteins (e.g adds carbohydrates to make glycoproteins)
- Modifies lipids (e.g adds carbohydrates to make glycolipids)
- Packages proteins/lipids into golgi vesicles
-Produces lysosomes
What is the function of the golgi vesicles:
- Transports proteins / lipids to their required destination
- Moves to and fuses to cell membrane
Describe the structure of lysosomes
- Membrane
- Hydrolytic enzymes
Describe the function of lysosomes
- Releases hydrolytic enzymes (lysozymes)
- To hydrolyse pathogens or worn out cell components
Describe the structure of mitochondria
- Double membrane, inner membrane (cristae) is folded
- Matrix, which contains small (70S) ribosomes and circular DNA
Describe the function of Mitochondria
- Site of aerobic respiration
- To produce ATP for energy release
- For metabolic reactions e.g protein synthesis
Describe the structure of the chloroplasts
- Double membrane
- Stroma, containing:
- Thylakoid membrane
- 70S Ribosomes
- Circular DNA
- Starch Granules & lipid droplets)
- Lamella - Thylakoid linking grana
- Grana - stacks of thylakoid
Describe the function of chloroplasts
- Absorbs light energy for photosynthesis
- To produce organic substances
Describe the structure of the cell wall in plants/algae and fungi
Composed mainly of cellulose in plants
Composed mainly of chitin in fungi
Describe the function of the cell wall
- Provides mechanical strength to cell
- So prevents cell changing shape or bursting under pressure due to osmosis
Describe the structure of the cell vacuole in plants
- Tonoplast membrane
- Cell sap
Describe the function of the cell vacuole in plants
- Maintains turgor pressure (stopping plant from wilting)
- Contains cell sap: stores sugars, amino acids, pigments and waste chemicals
What are some features of prokaryotic cells
- Cytoplasm lacking membrane-bound organelles
- So genetic material not enclosed in a nucleus
Describe the general structure of prokaryotic cells
ALWAYS CONTAINS:
- Cell Surface membrane
- Cell wall, made of murein
- Cytoplasm
- Small (70S) ribosomes
- Circular DNA, not associated with proteins
SOMETIMES CONTAINS:
- Capsule
- Plasmids (rings of DNA)
- Flagella
Explain why viruses are acellular and non living
- Not made of cells, no cell membrane / cytoplasm / organelles
- Non living: Have no metabolism, so cant independently move
Describe the general structure of a virus particle
- Nucleic acid surrounded by a capsid (protein coat)
- Attachment proteins allow attachment to specific host cells
- No cytoplasm, ribosomes, cell membrane
- Some surrounded by a lipid envelope
Describe how prokaryotic cells replicate
- Replication of circular DNA
- Replication of plasmid
- Division of cytoplasm to produce 2 daughter cells
- Single copy of circular DNA
- Variable number of plasmids
Describe how viruses replicate
- Attachment proteins attach to complimentary receptors on the host cell
- Inject viral nucleic acid into host cell
- Infected host cell replicates virus particles
- Nucleic acid replicates
- Cell produces viral protein/capsid/enzymes
- Virus assembed then released
