Cell structure and organisation Flashcards
Define a eukaryotic cell
- A cell with a nucleus and membrane bound organelles.
Describe the structure of a nucleus
- It has a nuclear envelope with a double bilayer and pores to allow RNA and ribosomes to leave.
- It contains a nucleolus which is densely packed with DNA and proteins
- It has a nucleoplasm
Describe the function of the nucleus
- Contains DNA wrapped around histones (Chromatin)
- Co-ordinates cellular activities.
- rRNA (Constituent of ribosomes) is made in the nucleolus.
Describe the structure of a mitochondrion
- Double membrane
- Inner membrane is folded to form cristae
- Matrix contains DNA, enzymes, lipids and protein.
- Has 70s Ribosomes
What is the function of a mitochondrion?
- Site of aerobic respiration to form ATP
- This occurs the inner mitochondrial membrane or the matrix
Describe the structure of the Endoplasmic reticulum
- A system of double membranes making flattened discs
- Two types Rough and Smooth ER
- Rough = Ribosomes
Describe the function of the Smooth Endoplasmic Reticulum
- Synthesis and transport of lipids
Describe the function of the rough endoplasmic reticulum.
- Protein synthesis and transport
Describe the structure of ribosomes
- Made from rRNA and protein.
- Attached to RER or or free in cytoplasm
Describe the function of ribosomes
Translation of proteins
- Large subunit joins amino acids
- Small subunit reads tRNA
Describe the structure of the Golgi body
- Stack of membrane bound flattened sacs.
- Vesicles can be ripped from the Golgi body to transport materials out of the cell.
Describe the function of the Golgi body
- Modifies and packages proteins for transport out the cell
- Synthesises and transports glycoprotein.
- Transport of lipids
- Forms lysosomes
Describe the structure and function of lysosomes
- Fluid-filled vesicles containing enzymes; single membrane
- Phagocytosis; break down and recycle old organelles
Describe the structure of centrioles.
- Cylindrical shape
- Made up of 9 bundles of microtubules = 9 x 3 microtubules.
What is the function of centrioles?
- Moves to opposite poles of the cell to organise the spindle fibres.
Describe the structure of the chloroplast
- Disk shaped surrounded by double membrane
- Thylakoids = flattened discs to form grana
- Lamellae connect thylakoids in adjacent grana
- Stroma = fluid filled area in the chloroplast.
- Starch grains appear dark under microscope
What is the function of the chloroplasts?
- Site of light dependent reactions in photosynthesis
Describe the structure of the vacuole in plants
- Surrounded by the tonoplast; single membrane
- Contains cell sap ( minerals dissolved in water)
Describe the function of the vacuole in plants
- Controls turgor pressure
- maintains PH
- isolates harmful waste products
- water storage
Define plasmodesmata
- Extensions of the cytoplasm which creates channels between plants cells to facilitate symplastic transport.
Define a prokaryotic cell
- A cell WITHOUT a nucleus and membrane bound organelles.
How is genetic information stored in prokaryotes
- In plasmids which are small rings of DNA
- Loop of DNA - Circular DNA stored in the nucleoid section of the cell
Describe the structure and function of flagella
- Long, whip-like tail
- Rotates to propel the organism
Describe the function of the capsule in prokaryotes?
- Protective slimy layer
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