What do eukaryotic cells contain?
- A distinct nucleus
- Membrane-bounded organelles
What are the functions of a nucleus?
- Contains genetic material in the form of DNA + chromosomes
- Acts as control centre through production of mRNA and tRNA, hence protein synthesis
- Manufactures ribosomal RNA + ribosomes
What is the structure of a nucleus?
- Nuclear envelope - double membrane. Outer membrane is continuous with ER and has ribosomes
- Nuclear pores - allow passage of large molecules eg RNA. 3000 pores
- Nucleoplasm is granular, jelly material that makes up bulk
- Chromosomes have protein-bound, linear DNA
- Nucleolus - small spherical region. Manufactures ribosomal RNA + assembles ribosomes
What are the functions of a mitochondrion?
- Sites of aerobic respiration
- Produce ATP from substrates e.g. glucose
What is the structure of a mitochondrion?
- Double membrane - controls exit/entry of material. Inner membrane is folded to form cristae
- Cristae - extensions of inner membrane, provide large SA for attachment of enzymes/proteins for increased rate of respiration
- Matrix - space containing protein, lipids, ribosomes, DNA, enzymes
Where are many mitochondria found?
- In cells that have a high level of metabolic activity so require lots of ATP
- e.g. muscle cells, epithelial cells -> need lots of ATP in active transport when absorbing substances from intestines
What is the structure of a chloroplast?
- Chloroplast envelope - double plasma membrane that controls exit/entry of materials
- Grana - stacks of thylakoids, containing chlorophyll, where light absorption for PSN takes place
- Stroma - fluid-filled matrix where synthesis of sugars for PSN takes place
What are the functions of a chloroplast?
Carries out PSN by absorbing sunlight
How is a chloroplast adapted to its functions?
- Granal membranes - provide large SA for attachment of substances that carry out PSN
- Fluid of stroma - has enzymes needed to make sugars in 2nd stage of PSN
- Contains DNA = ribosomes - to quickly manufacture proteins needed for PSN
What is the structure of an ER?
- 3D system of sheet-like membranes spreading through cytoplasm
- Membranes enclose network of tubules + flattened sacs called cisternae
What are the functions of an RER?
- Has ribosomes
- Large SA for synthesis of proteins
- Provide pathway for transport of materials through cell
What are the functions of the SER?
- Synthesise, store + transport lipids
- Synthesise, store + transport carbohydrates
Where are extensive ERs found?
- In cells that manufacture + store large quantities of carbohydrates, proteins, lipids
- e.g. liver, secretory cells (epithelial)
What is the structure of a Golgi apparatus?
Stacks of membranes that make up flattened sacs called cisternae, with small rounded hollow structures called vesicles
What are the functions of a Golgi apparatus?
- Modifies + sorts proteins
- They are transported in vesicles which are pinched off from ends of cisternae
What is the structure of a lysosome?
- Formed when vesicles produced by Golgi contain enzymes such as proteases/lipases
- Contain enzymes that hydrolyse some cell walls
What are the functions of a lysosome?
- Hydrolyse material ingested by phagocytic cells
- Release enzymes to outside of cell
- Digest worn out organelles to be reused
- Completely break don cells after they've died
What is the structure of a ribosome?
- Small cytoplasmic granules
- Occur in cytoplasm or with RER
- 80S - eukaryotic
- 70S - prokaryotic (smaller)
- One large unit, one small, containing ribosomal RNA + protein
What is the function of a ribosome?
The site of protein synthesis
What is the structure of a cell wall?
- Has microfibrils made of cellulose embedded in matrix
- Thin layer called middle lamella marking boundary between adjacent cell walls
What are the functions of a cell wall?
- Provide strength to prevent cell bursting from osmotic gain of water
- Provide strength to whole plant
- Allow water to pass along it
What is the structure of a vacuole?
Fluid-filled sac bounded by a single membrane called a tonoplast
What are the functions of vacuoles?
- Support plants by making cells turgid
- Sugars + amino acids act as temporary food store
- Pigments may colour petals to attract insects
What is the structure of a bacterium?
- Cell wall - made of murein
- Capsule - (some bacteria) slime wall for protection
- Cell-surface membrane - with 70S ribsomes
- Circular DNA
- Plasmids - extra loops of DNA
What is a prokaryotic cell?
- No nucleus
- No nuclear envelope
What is a virus?
- Non-living particles
- Smaller than bacteria
- Contain nucleic acids - DNA/RNA - within capsid, a protective protein coat
- Only multiply inside living host cells
- Lipid envelope - (some) if not then attachment proteins to allow virus to attach to host cell
What are the relative sizes of cell types to each other?