2.5 Biological membranes Flashcards
What does a phospholipid consist of?
-Phosphate head (hydrophilic + Polar)
-Fatty acid tail (Hydrophobic + non-polar)
What sort of substances can pass through the phospholipid bilayer?
-small substances
-lipid soluble substances
what is the role of membranes at the surface of cells?
-seperate cell contents from exterior
-regulate transport of materials
-contains receptors
-contains antigens so organisms immune system doesn’t attack itself
-can release chemicals to signal to other cells
what is the role of membranes within cells?
-site for attachment of enzymes
-provide selective permeability
-creation of concentration gradients
-seperates contents of organelles from the cytoplasm
-controls what substances enter/leave organelles
what is the membrane model called?
fluid mosaic model
what creates the mosaic pattern?
the scattered proteins
what can be found in the membrane?
-phospholipids
-integral protein
-protein channel
-carrier protein
-glycocalyx
-cholesterol
-peripheral protein
what is a peripheral protein?
-can be an enzyme
-dont span the entire phospholipid bilayer
what is an integral protein?
-spans whole bilayer
-receptor
-can be channel/carrier protein
what is a protein channel?
-water filled channel
-inside is lined with hydrophilic amino acids
-outside is lined with hydrophobic amino acids
what sort of molecules does the protein channel allow through?
charged molecules/ ions
what sort of molecules does the carrier protein allow through?
large molecules
what is the glycocalyx?
glycolipids and glycoproteins
They are chains of carbohydrates attached to a lipid/protein
what does the glycocalyx do?
-act as antigens
-cell signalling
-receptors
-bind to other cells for cell adhesion
-attract water with dissolved solutes
what does cholesterol do?
gives mechanical stability and flexibility/fluidity
what is diffusion?
movement of molecules from an area of a high concentration to a low concentration
what is simple diffusion?
when molecules move freely and randomly due to kinetic energy
describe examples of molecules that can pass through simple diffusion
oxygen
carbon dioxide
what are factors which affect the rate of diffusion?
-temperature
-diffusion distance
-surface area
-size of diffusing molecule
-concentration gradient
how can the concentration gradient be maintained?
molecules entering cells pass into organelles and are used for metabolic reactions
Describe examples of molecules entering cells into organelles and being used for metabolic reactions
oxygen in the cytoplasm of respiring cells then into mitochondria from aerobic respiration
what is facilitated diffusion?
movement of molecules from area of a high concentration to a area of low concentration via protein channels or carriers
what is an example of a molecule that passes through a protein channel
glucose
what is a passive process
when molecules only use their kinetic energy and no ATP
