IMED1001 - Cellular Physiology 1

Membranous Organelles

- are membrane bound

- nucleus, mitochondria, lysosomes, endoplasmic reticulum, golgi apparatus, vesicles

Non Membranous Organelles

- not membrane bound

- ribosomes, centrioles, flagella

Plasma Membrane

- phospholipid bilayer

- hydrophillic head

- hydrophobic tails

Nucleus

- stores most of the cells genetic information (DNA)

- Nucleoli is involved in ribosome biogenesis

- few cells are anuclear (no nucleus), some are multinucleate (skeletal muscle cells)

Nuclear Envelope (including things that enter and exit)

- double membrane around nucleus (contains nuclear pores)

- Enter: materials for DNA and RNA synthesis, enzymes/proteins, hormones/chemical messages that activate certain genes

- Exit: RNA

Ribosomes

- Makes proteins (site of protein synthesis)

- produced in nucleoli

LOCATION:

- found free in cytoplasm

- found on membranes (Rough ER, nuclear envelope)

- in other organelles (nucleus, mitochondria)

Endoplasmic Reticulum

- system of channels enclosed by membrane

- continuous with outer membrane of nuclear envelope

- may be rough or smooth

Rough ER

- covered in ribosomes

- synthesises proteins that are packaged in other organelles, secreted from the cell or incorporated into the cell membrane

- produces phospholipids and proteins of the plasma membrane

Smooth ER

- no ribosomes

- Synthesises lipids

- Synthesises steroid hormones

- detoxifies alcohol and other drugs

- stores calcium

Golgi Apparatus

- synthesises carbohydrates

- Receives newly synthesised proteins from rough ER (cis)

- adds carbohydrates/sulfates to some

- packages them into membrane-bound vesicles (trans)

- sorts and targets proteins to their correct destinationa

Vesicle Transport

- Exocytosis: release material from the cell (regulated, needs ATP)

- Endocytosis: brings things into the cell (big things (phagocytosis, cell eating) little things (pinocytosis))

Cytoskeleton (PARTS AND DEFO ONLY, NOT FUNCTION)

- network of protein filaments and cylinders

- Microfilaments: cell shape and movement

- Microtubules: intracellular transport, position of organelles, cell shape and division

- Intermediate Filaments: provide mechanical strength

Function of Cytoskeleton

- Structural Support and organisation of cell: maintain cell shape and organise organelles (all cytoskeleton proteins), provide internal support to plasma membrane (microfilaments), stabilise desmosome cell junctions (intermediate filaments)

- Cell Division: separate chromosomes during cell division (microtubules) and split cell into 2 daughter cells by cytokinesis (microfilaments)

- Movement: facilitate cytoplasmic streaming (microfilaments), serve as a track for movement of organelles and vesicles, participate in muscle contraction, contractile proteins of cilia and flagella

Lysosomes

- membrane bound package of enzymes (produced by Golgi)

- involved in digestion of proteins, nucleic acids, complex carbohydrates, phospholipids

- white blood cells use lysosomes to digest phagocytised bacteria

- digest and dispose of surplus, non-vital organelles (autophagy)

Peroxisomes

- similar to lysosomes, but oxidise organic molecules

- produces hydrogen peroxide (H2O2) which then oxidises other molecules

- detoxify alcohol and other drugs

- break down fatty acids into acetyl groups for mitochondrial use in ATP synthesis

Proteosomes

- clear old/damaged proteins and organelles to provide the cell with building blocks for renewal

- proteosome - digest proteins

- autophagosomes - digest organelles

- they form, then engulf cellular contents, such as damaged proteins and organelles

- fuses with the lysosome, where the contents are degraded into smaller constituents (good image on slides)

Mitochondria

- specialised ATP synthesising organelle

- surrounded by a double membrane (inner membrane has folds called cristae, spaces between cristae contains ribosomes, enzymes used for ATP synthesis, small circular DNA (mtDNA)

- ATP generated by ATP synthase enzymes (membrane proteins that use H+ to add a high energy phosphate to ADP to form ATP)

- energy from organic molecules is extracted and drives protons (H+) across the inner membrane, the "fall" back, powering the ATP synthase