Transport 4 Flashcards
(27 cards)
what is a phospholipid?
similar to triglyceride, but one fatty acid is replaced by a phosphate group.
What are fatty acid tails?
Hydrophobic
What are phosphate heads?
Hydrophilic
how do phospholipids make bilayers?
Hydrophobic tails repel water - face inwards
Hydrophilic heads face attract water - face outwards
what is a phospholipid made out of?
2 fatty acids
1 glycerol group
1 phosphate group
what does the plasma membrane do?
Separates cell contents from outside environment.
Regulates passage of substances into and out of cells.
Cell recognition/signalling
What do organelle membranes do?
Divide the cell into sections.
Isolate harmful enzymes, eg lysozymes
Provide surfaces for holding chlorophyll, enzymes and ribosomes.
What are cell membranes usually made of?
Phospholipids
What do phospholipids form?
Bilayers
What is the fluid mosaic model?
Phospholipids move around, proteins are scattered throughout
How is the bilayer partially permeable?
Large lipid-soluble molecules pass through after dissolving
Small molecules can pass through easily.
What molecules cannot pass through the bilayer?
Large water soluble molecules.
How do large water soluble molecules pass through the bilayer?
Alternate methods
What do surface proteins do?
Cell signalling
- hormone receptors
Cell recognition
- antigens for immune system.
What is cholestorol?
A constituent of membranes - source of steroid hormones
What do glycolipids and glycoproteins do?
Cell signalling (hormone receptors)
Cell recognition (immune system - antigens)
3 passive processes of cell membrane transport?
- diffusion
- facilitated diffusion
- osmosis
DONT REQUIRE ENERGY
2 active processes of cell membrane transport?
- Active membrane protein transport
- Membrane transport (endo/exocytosis)
THERE ARE 2 TYPES OF ENDOCYTOSIS : phagocytosis and pinocytosis.
What is diffusion
Diffusion is the net movement of particles from an area of higher conc to a lower conc.
What is diffusion
Diffusion is the net movement of particles from an area of higher conc to a lower conc.
Why does diffusion occur?
Molecules move randomly, using their own kinetic energy.
What is facilitated diffusion
The use of transmembrane proteins to move charged ions or large soluble substances, across a membrane, from a high to low concentration.
What is active transport?
The use of ‘energy’ to move substances across a membrane, from a high to low conc.
- uses ATP
What is Osmosis?
The diffusion of water molecules across a partially permeable membrane - from a region of higher WP to lower WP.
