Cell Membrane And Transport Flashcards
4 Components in cell membrane
- Phospholipids
- Proteins
- glycoproteins and glycolipids
- Cholesterol
How are Phospholipid arranged in cell membrane
- hydrophobic HC chains arrange around hydrophobic substances
Function of vesicles (bilayer)
BILAYER:
- Hydrophilic head facing inside
- so transports hydrophilic substances
- or secretion vesicles to secrete stuff out of cell
- or vacuole for storage
Micelle function (MONOLAYER)
Hydrophobic side facing inside
- So transports hydrophobic substances
- Helps in transport of fats from gut to liver
2 Types of Proteins in cell membrane
1 - Extrinsic / peripheral
(Includes external extrinsic & internal extrinsic)
2 - Intrinsic / integral
(Includes Transmembrane & unilateral)
Structure & Function of extrinsic / peripheral PROTEINS
- They are Loosely attached to cell surface membrane:
**External extrinsic proteins: **
STRUC - attached to fibres of extracellular matrix (ECM)
F - Keeps the cell in place
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Internal extrinsic:
STRUC - attached to cytoskeleton
F - Maintains shape and motility of the cell
Strict of intrinsic / integral PROTEINS and their BONDS
Embedded in the cell surface membrane.
Intrinsic proteins can be:
1. Transmembrane protein:
- Embedded in the bilayer
-
Unilateral
- Embedded in monolayer
____________________________
Hydrophobic part of intrinsic proteins :
- has hydrophobic interactions w/ hydrophobic HC chains of phospholipids
Hydrophilic part of intrinsic proteins
- Forms H bonds w/ hydrophilic phosphate head phospholipids.
Summary if Function of membrane PROTEINS
- Transport proteins
1a ) Channel proteins
1b) Carrier Proteins
- Enzymes
- Signal transduction
Function of membrane PROTEINS
1. Transport proteins
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Channel Proteins:
- Passive transport (diffusion)
- Have 1 hydrophilic pore
- Hydrophilic molecules can move through membrane
Eg: Polar molecule (glucose), charged molecules (K+)
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Carrier Proteins
- active transport
- Has specific binding sites
- Binds to specific solutes
- Transports them across the membrane
- down a conc gradient, w/ ATP
Function of membrane PROTEINS
- Enzymes proteins in membrane
Eg: ATP synthase in inner mitochondrial membrane
- enzymes carry out metabolic pathway
Function of membrane PROTEINS
- Signal Transduction
- Receptor proteins have sites of attachment for signal molecules to bind
- This allows for cell signalling
GLYCOPROTEINS and GLYCOLIPIDS
Struc:
- Protein / lipids w/ the addition of a short carbohydrate chain
- from GB
- On outer surface of eukaryotic cell membranes
_________\____________________
Func
- Helps in cell-cell recognition
- allow cells to recognise & bind to each other
- Helps in cell-cell adhesion
- Glycoproteins of 2 cells bind tgt
- causes adhesion between cells
- allows for tissue formation
- Act as receptor sites for signal molecules to bind to
- this allows for cell signalling
Cholesterol
Struc + func
Struc
- Has hydrophilic & hydrophobic parts
- Hydrophilic (—OH group)
- Interacts w/ hydrophilic heads in phospholipid bilayer
- Hydrophobic part of cholesterol
- has hydrophobic interactions w hydrophobic HC chains in phospholipid bilayer
- Cholesterol is interspersed throughout bilayer
- Prevents close packing of phospholipids
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Function - Prevents leakage of small polar molecules from cell
- Regulates fluidity
- Maintains mechanical stability of cell membrane
Explain what pinocytosis endocytosis is
-
Pinocytosis
- intake of liquid substances into the cell
- via bulk transport
- w/ use of ATP adenosine triphosphate
- invagination of cell membrane
- non-specific endocytosis
Active transport w/ carrier proteins
- Transport proteins carry out active transport
- against a conc grad, using energy in the form of ATP
- through a partially permeable membrane
What about the phospholipid bilayer supports it being a fluid mosaic model?
Mosaic
- Many diff proteins embedded in the bilayer
Fluid
- Phospholipids move laterally
- phospholipids can but rarely flip flop between layers
Define osmosis
Osmosis is the net movement of water molecules from a less negative water potential to a more negative water potential across a partially permeable membrane
Define active transport
A.T is the movement of substances from a region of lower concentration to a region of higher concentration against a concentration gradient, with the use of energy in the form of ATP
Define facilitated diffusion
Is active transport affect by a concentration gradient?
NO.
- active transport remains constant no matter the conc gradient
- active transport only stops when no more ATP / energy
Explain what phagocytosis endocytosis is
- intake of large solid substances into cell
- by WBCs
- ## extension of pseudopia
