Biological Membranes Module 2 Flashcards
Structure + uses of cell membrane
mainly made of phospholipids
Keep all components in cell
Controls what enters and leaves
Isolates organelles from cytoplasm
Biochemical reactions
Contains antigens
Enzyme needed in metabolic pathways p
Cell membrane: phospholipids in water
Hydrophobic tail and hydrophilic head
Forms either micelles or bilayer- both hydrophilic head faces water
One fatty acid replaced by phosphate group
Proteins in membrane
Integral (transmembrane) proteins span whole width of membrane, carrier molecule/chanel to help transport bigger substances, square in middle of bilayer
Peripheral protein only in outer or inner surface of membrane, oval on inside or outside
Many protein are glycoprotein (attached to carbohydrate chain) - chain coming of bilayer
Cholesterol in membrane
Type of lipid
C27H46O
controls membrane fluidity - more cholesterol = less fluid = less permeable membrane so more stable
Diffusion
Net movement of particles down conc gradient from high - low
No metabolic energy so passive process - no atp needed
Polarity diffusion
Non polar hydrophobic tail of phospholipid in cell membrane acts as barrier
Small non polar (co2, o2) rapidly diffuse
Small polar (h2o, urea) slowly diffuse
Charged particles (ions) don’t diffuse
Facilitated diffusion
Polar/large molecules can’t pass through bilayer
carrier proteins/ channels allow molecule through
Passive process
Active transport
Requires energy from atp
Cells use carrier proteins to move substance through membrane
Uses of active transport
Uptake of glucose + amino acids in small intestine
Absorbs mineral ions in plant
Excretion of H+ ions
(Lots of active transport = lots of mitochondria)
Types of bulk transport
Endocytosis - bulk transport of materials into cell, 3 processes: phagocytosis, pinocytosis, receptor mediated endocytosis
Exocytosis - bulk transport out of cell, reverse of endo
