Plasma membrane Flashcards
(23 cards)
explain why plasma membrane has a fluid mosaic model
fluid- phospholipid forms a bi-layer in which phospholipid molecules are constantly moving
Mosaic- There are proteins of different sizes and shaped embedded in the phospholipid bi-layer
Key components of cell membrane
Phospholipid bilayer
Proteins
Proteins
Glycoproteins
Glycolipids
Cholesterol
explain phospholipid bi-layer
PHOSPHOLIPID BI-LAYER
each phospholipid molecule is made up of a hydrophilic head and two hydrophobic tail, forms a bi-layer creating a hydrophobic centre so that water soluble substances cannot pass through however lipid soluble substances can dissolve in bi-layer
Explain cholesterol
provides stability to cell membrane consists of hydrophilic and hydrophobic region the hydrophobic region binds to the fatty acid causing them to pack more closely together. This reduces the fluidity of cell membrane
What are the types of proteins and explain them
Intrinsic and Extrinsic proteins
INTRINSIC
They are embedded through both sides of the phospholipid bi-layer
They include channel and carrier proteins which transport large molecules and ions across the membrane
EXTRINSIC
Present on only one side of phospholipid bi-layer
proteins may be involved in cell signalling
Explain glycoprotein and Glycolipids
Glycoproteins consists of INTRINSIC proteins attached to carbohydrates, while Glycoproteins and Glycolipids are involved in the following
They are involved in cell adhesion, cell recognition and cell signalling
Two main types of membrane
CELL SURFACE MEMBRANE: surrounds cell to act as a barrier between the cell and it’s environment controlling which substance enters and leave the cell
MEMBRANE AROUND ORGANELLES: this surrounds organelles e.g mitochondria to act as a barrier between organelle and cytoplasm dividing the cell into different compart COMPARTMENTALIZATION
Factors affecting membrane structure
Temperature
AT LOW TEMP: phospholipids do not have much K.E they are packed closely together to form a rigid cell membrane decreasing the permeability of the membrane
AT MID TEMP: as temp increases phospholipids has more kinetic energy so they move faster and aren’t packed as closely together this increases permeability
AT HIGH TEMP: phospholipid bi-layer breaks down channel and carrier proteins denatures meaning they cannot ctrl what enters and leave the cell. permeability increases
What are solvents and hoe does it affect membrane structure
solvent are liquids that has the ability to dissolve substance.
When cell are placed in a solvent such as ethanol the phospholipids dissolve causing the membrane to become more fluid making it more permeable
INCREASING THE CONCENTRATION OF SOLVENT WILL INVREASE THE PERMEABILITY OF THE CELL
Define diffusion
The net movement of particles from an area of higher concentration to an area of lower concentration
Two types of diffusion
Simple diffusion
Facilitated diffusion
Explain the two types of diffusion
SIMPLE DIFFUSION
O2 and CO2 can diffuse into the cell via simple diffusion because they are small and can pass through the spaces between phospholipids as they are non-polar therefore cannot dissolve in cell membrane
FACILITATED DIFFUSION
large and polar molecules can pass through cell via facilitated diffusion.
Factors affecting rate of diffusion
TEMP- at higher temperature particles have more K.E and diffuse faster
CONC. GRADIENT- The steeper the conc. gradient the faster the rate of diffusion
THICKNESS OF MEMBRANE
SURFACE AREA- large surface area means particles can cross the membrane at once making diffusion faster
No OF CARRIER AND CHANNEL PROTEINS- The more these proteins the faster the rate of facilitated diffusion
What is active transport
This is the movement of PARTICLES from an area of lower concentration to an area of higher concentration
ENERGY IS REQUIRED as particles moves up the concentration gradient
Explain how active transport works
like facilitated diffusion active transport involves the use of carrier protein to transfer molecules or ions across membrane
involves ATP, ADP, and PHOSPHATE
Factors affecting rate of active transport
TEMPRETURE- at higher temp. particles have more K.E and travel faster. High temp. also leads to increased respiration. very high temp. denatures carrier proteins, decreasing the rate of active transport
THICKNESS OF MEMBRANE
NUMBER OF CARRIER PROTEINS
RATE OF RESPIRATION- The more respiration, the more ATP available for active transport
what is bulk transport with examples
large molecules such as hormones or enzymes cannot be transported through channel or carrier proteins so they are moved in through bulk transport
TWO TYPES
Endocytosis- Transport materials into cells [Phagocytosis(uptake of solid materials), Pinocytosis(uptake of liquid materials)]
Exocytosis- Transport materials out of the cell
what is osmosis
it is the DIFFUSION of water molecules from an area of higher water potential across a partially permeable membrane
Explain osmosis in animal cell
HYPOTONIC
Has a higher water potential than the cell
water moves into the cell
cell swells and bursts
ISOTONIC
Has the same water potential as cell
no net movement of water in or out of cell
cell stays the same size
HYPERTONIC
Has lower potential than the cell
water moves out of the cell
The cell shrinks
Explain osmosis in plant cells
HYPOTONIC
cell swells and becomes TURGID
ISOTONIC
cell remains the same size
HYPERTONIC
Cell shrinks and become PLASMOLYSED
Factors affecting osmosis
TEMPRETURE
WATER POTENTIAL GRADIENT- The steeper the gradient the faster the rate of osmosis
THICKNESS OF MEMBRANE
SURFACE AREA
Two types of protein involved in facilitated diffusion
Carrier protein
channel protein
What is water potential
it is the pressure exerted by water molecules on a membrane surrounding a solution
