Membranes Flashcards
What is compartmentalisation?
Separation of organelles and areas of cells via membranes
What is the plasma membrane?
A basic structure that separates the cell from its external environment
What is the phospholipid bilayer?
Hydrophilic phosphate group heads and hydrophobic fatty acid tails that form the plasma membrane
What is the fluid mosaic model?
A model presented of plasma membranes that shows proteins incorporated intrinsically and extrinsically
What are membrane proteins?
Proteins in the plasma membrane that are either intrinsic and extrinsic
What are intrinsic proteins?
Proteins that are embedded through both layers of the plasma membrane and come in two types; carrier and channel
What are channel proteins?
Proteins that have a hydrophilic channel and allow passive movement for polar molecules and ions
What are carrier proteins?
Proteins that have a role in passive and active transport and often changes the shape of the protein
What are glycoproteins?
Intrinsic proteins embedded with carbohydrate chains with varying lengths and sizes, they play a role in adhesion and cell signaling (neurotransmitters, peptide hormones (insulin, glucagon))
What is cell signaling?
When a chemical binds and elicits a cascade response inside the cell
What are glycolipids?
Extrinsic lipids with attached carbohydrate chains that act as cell markers and antigens
What are extrinsic proteins?
Proteins that are on one side of the plasma membrane
What are the roles of the plasma membrane?
Environment, transport, cell to cell signaling, detecting changes in the environment, site of chemical changes, pseudopodia, anchorage for the cytoskeleton, cell to cell joining
How does the plasma membrane effect the environment?
Maintains a fixed set of conditions inside the cell
How does the plasma membrane effect transport?
Provides a partially permeable membrane to control which substances enter and exit the cell
How does the plasma membrane effect cell to cell signaling?
Have either glycoproteins or lipoproteins to interact between cells
How does the plasma membrane effect detection of environment changes?
Signal transduction- so having proteins that can act as receptors for hormones
How does the plasma membrane effect chemical reactions?
Proteins in the membranes may act as enzymes
What is pseudopodia?
When plasma membranes are used for feeding and movement in single celled organisms like amobea
How does cholesterol effect the plasma membrane?
Maintains stability and fluidity
What is an amphipathic molecule? Give two examples
A molecule with hydrophilic and hydrophobic regions, phospholipids and cholesterol
How does cholesterol effect the fluidity of the plasma membrane?
It reduces the fluidity by filling the gaps when the fatty acid tail bends more and therefore prevents crystallisation
What are the components in the plasma membrane?
Phospholipids, channel proteins, carrier proteins, glycoproteins, peripheral proteins, cholesterol
What are the structural properties of the phospholipid bilayer?
7.5 nanometres thick, held by weak hydrophobic interactions, have hydrophobic and hydrophilic layers that restrict entry and exit, allow for membrane fluidity,
What are the roles of intrinsic proteins?
Passive and active transport, active transport often includes a change in shape
What are the roles of extrinsic proteins?
Acting as receptors
What are the roles of intrinsic glycoproteins?
Cell signaling
What are the roles of intrinsic channel proteins?
Passive movement and diffusion of polar molecules and ions
What is active transport?
Movement of molecules or ions into our out of a cell from a region of a lower concentration to a region of a higher concentration
What is osmosis?
The diffusion of water across a partially permeable membrane
What is diffusion?
Net movement from a region of a higher concentration to a region with a lower concentration
What is a facilitated diffusion?
Movement down gradient across a membrane through protein channels
What is bulk transport?
Active movement of large molecules
How does temperature affect diffusion rate?
Increases rate due to an increase of kinetic energy
How does concentration gradient affect diffusion rate?
Increases rate due to the increase of substances to be diffused
How does surface area affect diffusion rate?
Increases the rate due to greater area to diffuse across
How does membrane thickness affect diffusion rate?
An increase of membrane thickness decreases the rate of diffusion due to the greater distance to diffuse across
What is facilitated diffusion?
The passive movement of molecules across the cell membrane via the aid of a membrane protein
How does facilitated diffusion work?
Used by molecules that are unable to cross the phospholipid bilayer (large molecules, ions) and is mediated by two types of intrinsic proteins, carrier and channel
How do solvents affect membrane structure?
Solvents dissolve the phospholipids which disrupts the membrane and causes it to be leaky
How does temperature affect the membrane structure?
The increase in temperature increases the kinetic energy, which causes the phospholipid fatty acid tails to vibrate more, which disrupts the membrane
Describe active transport
1 - Molecule or ion binds to receptor
2 - On the inside of the cell, ATP binds to the carrier protein
3 - This causes the protein to change shape
4 - Molecule or ion is transported into the cell
5 - The leftover phosphate molecule reforms ATP from ADP
6 - Carrier protein returns to old shape
What is water potential?
Pressure exerted by water molecules colliding with sides in kPa
