The Plasma Membrane Flashcards
U1L8 (26 cards)
What are the functions of the Plasma Membrane?
Regulate what enters/exits the cell
Transport across the membrane
Catalyse reactions
Cell Recognition
Signal Reception/Transduction
What are the three types of Membrane permeability?
Impermeable: Substances cant pass
Permeable: Substances can pass through
Semi permeable: Substances that pass through are controlled (like a checkpoint).
What does Amphipathic mean?
The phospholipids have a hydrophobic and hydrophilic end.
How is the phospholipid bi-layer arranged?
The polar/non-polar
regions of phospholipids
arrange themselves in a
bilayer.
Vesicles are circular bilayers.
How thick is the plasma membrane?
7-8nm thick.
What is a mosaic in a membrane?
it’s when lots of different substances make up a membrane.
they are in a fluid which means they move around.
What are the two types of proteins in membranes?
Peripheral proteins and Integral proteins.
What about Integral proteins?
When the span the whole membrane, they are called transmembrane proteins. The hydrophobic regions contain nonpolar amino acids.
What are the functions of membrane proteins?
Intercellular joining
Transport
Signal transduction (carried between cells)
Attachment to the cytoskeleton and
extracellular matrix (ECM)
Enzymatic activity
Cell-cell recognition
What are the two carbohydrates found in cell membranes called?
Glycolipids
Glycoproteins
How do cells identify each other?
They bind to surface molecules, often membrane carbohydrates.
Membrane carbs are critical in identifying cells.
Why are plasma membranes selectively permeable?
Because they regulate the cell’s molecular traffic.
What is the role of transport proteins?
They allow the passage of hydrophilic substances across the membrane.
Some transport proteins, called channel proteins,
have a hydrophilic channel that certain molecules
or ions can use as a tunnel.
Channel proteins called aquaporins facilitate the
passage of water.
What are the three categories of passive transport proteins?
Simple Diffusion
Osmosis
Facilitated Diffusion
Passive transport DOES NOT need energy
Molecules move with the concentration gradient
Simple Diffusion and Osmosis?
It’s when hydrophobic and tiny molecules are able to diffuse across the plasma membrane.
These molecules always move from high
concentration to low concentration.
OSMOSIS is the movement of water across a
membrane.
What’s facilitated diffusion?
Its when a protein channel allows a passage way through the cell membrane.
This if often done for larger or polar molecules.
No energy is used, as
molecules travel from
HIGH to LOW
concentration. (diffusion)
What’s Active transport?
Active transport moves moves molecules from
a LOW concentration to a HIGH concentration,
AGAINST the concentration gradient.
This requires ATP.
The energy in the ATP is used to cause a
conformation change (change in shape) in the
transport protein.
What’s membrane assisted transport?
It’s a form of active transport
Its used in the movement of large molecules or
large numbers of molecules/ions in or out of
the cell.
Whats endocytosis?
Its when the movement is into the cell.
What are the types of endocytosis?
bulk-phase (non-specific)
receptor-mediated (specific)
Whats the process of Endocytosis?
1) membrane surrounds material
2) membrane edges meet
3) membranes fuse to form vesicles
e.g. think of when a WBC is ingesting a pathogen.
Whats phagocytosis and pinocytosis?
phagocytosis: cell eats, large molecules
pinocytosis: cell drinks, smaller molecules
whats exocytosis?
the reverse of endocytosis.
its when the cell discharges material.
What’s the process of exocytosis?
1) Vesicle moves to cell surface
2) Membrane of vesicle fuses with membrane
3) Materials are expelled
