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nucleus structure Lecture 2 hcs 113, cell components and function, Golgi…
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Golgi apparatus
Function
- Transports and stores lipids,
- assembles glycoproteins. Further protein processing.
- produces digestive enzymes.
- forms lysosomes and transport vesicles.
Cis-face
- receives transport vesicles from the ER.
Trans-face
- forms new vesicles and lysosomes.
Lysosomes,
- Releases enzymes which destroy worn out organelles.
- Digest phagocytosed material.
- releases enzymes to the out side of the cell via exocytosis.
cell membrane
Functions of the cell membrane. Passive transport. - Channels selective for a particular solute.
Active transport.
- active energy consuming pump for a certain substance.
Enzymatic activity.
- Enzyme embedded in the membrane is expose to a substance and facilitates a reaction.
- A chain of enzymes can be arranged in that way.
Signal transduction.
- A membrane protein can be a receptor for a signalling molecule.
Cell-cell recognition
- Glycoprotein from one cell serves as ID tag for another cell.
Intracellular joining
- membrane protein of different cells can 'hook' together to form junctions.
Attachment
- Elements of the cytoskeleton can bind to proteins in the cell membrane for shape and stability.
Movement across the membrane.
- Semipermeable membrane. - Passive transport (Diffusion and osmosis)
- Active transport (Energy required) sodium. potassium pump, proton pump, coupled transport endo/exocytosis.
Passive transport.
- Diffusion of solutes across a membrane
- Different concentration on both sides of the membrane.
- does not require energy.
Oxygen and carbon dioxide.
Osmosis: Passives transport.
- Water movers from hypotonic to hypertonic solution.
- Osmotic pressure: force of the movement (osmolarity
[osmol/l])
Facilitated diffusion - Carrier protein changes between 2 conformations.
- Transport both directions.
- Direction of transport is dependent on concentration gradient.
Glucose, chloride ions.
Active transport Proton pump create a electrochemical potential across the membrane.
- uses ATP.
- Positive charges are transported outside the cell.
- Stores energy.
Coupled Transport
- 1 pump and 1 cotransporter.
- Only pump uses energy
- Pump creates proton gradient.
- Cotransporters uses stored energy generated by pump.
- Diffusion of H+ drags other molecules with it e.g. Sucrose.
How it all fits together
- the nuclear envelope is connected to the rough ER, which connects to the smooth ER
- Proteins that are produced by the ER move in transport vesicles to Golgi apparatus.
- Lysosomes/transport vesicles split off Golgi.
- Lysosomes fuses with a vesicle for digestion.
- Transport vesicle carries proteins to the plasma membrane for secretion.
Exocytosis -
- the process of moving materials from within a cell to the exterior of the cell. This process requires energy and is therefore a type of active transport.
Endocytosis.
- substances that are external to a cell are brought into the cell.
Ribosomes
Nucleus
- control centre of the cell,
- constant bi-directional flow of information between the nucleus and the rest of the cell.
Ribosomes
- translate this information (
- in the form of messenger RNA from the nucleus. into proteins and/ or enzymes.
Lysosomes
Phagocytosis,
- lysosomes with digest enzymes fuses with food vacuole.
- Hydrolytic enzymes digest food particles.
Autophagy. -
- lysosomes with digestive enzymes fuses with damaged organelle.
- Hydrolytic enzymes digest organelle components.
Tissue Types
Four main categories. Structural:
Excitable:
Epithelial Cell Polarity three distinct surfaces:
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Basal Surface
- Attached to basal lamina
- Site transporter eg Na/K ATPase) and ion channels.
Lateral surface
- Site of cell junction and adhesion molecule.
Apical/luminal Surface.
- Site of main cell activity (eg absorption, secretion, excretion, gas
exchange, transport, protection, etc)
Connective tissue;
- basal lamina is attached to the connective tissues.
Krebs cycle
Glycolysis - occurs in the cytosol of the cell. - Metabolic pathway that creates ATP. - splitting glucose into 2 pyruvate.