Cell membranes and cell transport Flashcards
Fluid mosaic model
Used to describe membrane structure
Phospholipid structure
Saturated & unsaturated fatty acid
Double bond leads to bend in structure
Phosphate
Glycerol
Hydrophilic head
Hydrophobic tail
Phospholipid properties w
When compact: too rigid
When straight & bent: fluid & flexible, phospholipids spaced out due to unsaturated tails
Phospholipid bilayer contains
Carbohydrate Glycolipid Glycoproteins Cholesterol Integral protein Protein channel Phosphate
Glycoproteins & glycolipids function
Important in cell recognition and the immune systems ability to differentiate between self and non self in cell adhesion
Cell attachment
Receptors
Integral protein function
Transport/reactions
Protein channel function
Transport of proteins
Hydrophilic core makes
membrane impermeable to most substances, acting as a barrier
Diffusion
Movement of particles from an area of high to low concentration
The process is passive (energy is still required but it’s not from ATP or respiration)
Explain how oxygen enters the cell
Oxygen particles diffuse down the concentration gradient
O2 particles move directly through the phospholipid bilayer due to them being small and non-polar (simple diffusion)
What happens to particles after final picture
Once equilibrium is reached, the particles continue to move although diffusion stops
No net change in concentration
Facilitated diffusion
If particles are large/non-polar, they need the help of protein channels & protein carriers
Passive process
E.g. glucose, amino acids
Describe what will happen to the water in the diagram
Osmosis is the movement of water from an area of high water potential to an area of low water potential
This occurs through a semi permeable membrane
Passive process
Water & simple diffusion
Can move through PLBL through simple diffusion but it’s very slow
So uses protein channel (aquaporin)
Particles in diagram
If particles aren’t made clear, they’re solute
Types of solution
Hypotonic
Isotonic
Hypertonic
Hypotonic
LWP inside cell
Solution has less solute than cell
Isotonic
Solution has the same solute as the cell
WP same on inside and outside
Hypertonic
HWP inside cell
Solution has more solute than cell
Active transport
Movement of particles against the concentration gradient
Requires the help of a protein and energy from the hydrolysis of atp
Often K+, Na+, Ca2+
Energy driven process
Endocytosis
2 types
Phagocytosis - taking in large substances (e.g. pathogens) and enclosing them in a vesicle
Pinnocytosis - taking in liquids and enclosing them in a vesicle
Exocytosis
Giving out (secreting) substances out of the cell by fusing a vesicle with the cell membrane
Co-transport
Process in which two substances are taken into a cell simultaneously by one protein
Co-transport lumen of ileum
Sodium is pumped out into the blood, creating a high Na+ conc in ileum
Sodium ions move down conc gradient from lumen to cells by facilitated diffusion
At same time as sodium, glucose is brought in by sodium-glucose transporter proteins
As conc of glucose inside cell increases, glucose moves down conc gradient through a protein channel from cell to blood
Cell transport adaptations
Increase in surface area of the internal membranes or of the cell surface membrane e.g. microvilli
Increase in the number of protein channels and carrier molecules in their membranes
By mechanisms to set up concentration, water potential or electrochemical gradients across membranes
