Biological Membrane and cell transport Flashcards
What is the main component of a membrane- describe it
- phospholipid (bilayer)
- 2 fatty acid tails; hydrophobic
- polar, phosphate head; hydrophilic
Describe the type of proteins that help particles pass across the membrane.
- channel
- carrier
Factors that affect diffusion?
- size; smaller diffuse quicker
- polarity; non-polar quicker
What are the main roles of the cell surface membrane? (3)
- controls what exists and enters cell
- allows creation of concentration gradient
- contains receptors for cell signalling
Main roles for membranes within cells? (5)
- compartmentalises cell organelles
- allows creation of concentration gradient
- controls what enters and exits the organelle
- provides sites for attachment for ribosomes and enzymes
- isolates metabolic reactions from each other
What model is used to represent the cell surface membrane
- fluid mosaic model
- what are the main components of membranes
- phospholipid (bilayer)
- proteins
- glycoproteins
- glycolipids
- cholesterol
Phospholipids
- phospholipid with chain of sugar attached to it
Describe how cholesterol relates to the membrane
- fatty substance located inbetween the phospholipids
- OH end with hydrophilic phosphate head
- hydrocarbon end with the hydrophobic fatty acid tail
- stabilises the membrane structure by keeping it fluid
What is the width of the plasma membrane
- 7 nm
Glycoproteins + glycolipids
- proteins attached to a sugar
chain - phospholipid attached to sugar chain
- receptors for hormones, drugs and signalling molecules
- stabilises membrane by forming hydrogen bonds with water
- cell signalling;
How does high temperature affect the membrane
At high;
- high kinetic energy means that components move more= more fluidity
- membrane more permeable
- changes structure of protein which disrupts shape of membrane
How do lower temperatures
- lower kinetic energy= less fluidity phospholipid layer
- membrane less permeable
Describe membrane in Mitochondrion
- double membrane
- inner membrane folder to form cristae
- increases surface area for more enzymes and therefore increases rate of reaction
Hypertonic
Water potential of the solution is higher/ less negative than
WP of cell
Hypotonic
WP solution is lower/ more -/ve than that of cell
Water potential
Net movement of water molecules
From high WP/ negation to low WP
Water potential
Relative tendency of water to move from one are to another
Turgid cell
Plant in hypotonic solution
Plant is full of water
Crenated
Shrivelled animal cell
In hypertonic solution
Plasmolysed
Cytoplasm shrinks from cell wall in plants
In hypertonic solution
Cell burst
In hypotonic solution
Animal cells
Diffusion
Passive movement of
Non polar substances
From high concentration to low
Facilitated diffusion
Polar or slight larger substances
Cannot interact with the hydrophobic fatty acid tail
Require Channel or carrier proteins
Transport of large substances
Active transport
Requires energy from ATP
Also uses carrier proteins
Intrinsic proteins
- embedded on both sides of the bilayer
- eg Channel and carrier proteins
Extrinsic proteins
- Embedded on one side of the bilayer.
- Eg glycoproteins and enzymes
Endocytosis (4)
- Bulk transport of material into the cell. Therefore requires ATP
- Either pinocytosis with liquids or phagocytosis with solids
- Cell surface membrane invaginates around material and surrounds it until the membrane fuses to form a vesicle
- The vesicle then pinches off and moves into cytoplasm
Exocytosis
- Bulk transport of material out of the cell. Therefore requires ATP
- Vesicle containing material moves to the plasma membrane and fuses with it.
- Contents in vesicle are then released out of the cell.
When is ATP needed during bulk transport? (3)
- Movement of vesicles using cytoskeleton
- Changing the shape of membrane to engulf material in endocytosis.
- Fusion of cell membranes in both exocytosis and endocytosis
Describe Active transport, including the role of ATP, Phosphate and ADP. (7)
- Using energy in the form of ATP to transport large or charge particles.
1- Ion/ molecule is recognised by protein and binds to receptor to outside the cell.
2- ATP binds to the protein inside the membrane. It is hydrolysed into Phosphate and ADP.
3- Phosphate binds to protein and causes a change in shape which creates opening inside the cell and close outside the cell.
4- Material is released into the cell.
5- Phosphate detaches from protein and combines with ADP to form ATP again
6- The protein returns to its original shape
How does water travel through cell surface membrane (2)
- via phospholipid bilayer
- using aquaporins
