Membrane Structures and Functions Flashcards
Phospholipid Bilayer
- Made of a bilayer of phospholipids
- Heads are phoshpates (polar, hydrophilic)
- Tails are lipids (non-polar, hydrophobic)
- Hydrophobic portion acts as a barrier to many molecules
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Integral Proteins
- Span from inner to outer portion of bilayer
- Can act as channel proteins to transport molecules across bilayer
Peripheral Proteins
- Inside - help maintain shape or cell motility
- Can also be enzymes and catalyze reactions in the cytoplasm
Glycoproteins
- Involved in cell recognition (part of immune system)
- Act as receptors in signaling (as with hormones)
Cholesterol
- Reduces fluidity in plasma membrane, thus increasing stability
Carrier Protein
- Specific to molecules
- Changes shape slightly to transport
- Down concentration gradient - facilitated diffusion
- Against concentration gradient - active transport
Receptor Proteins
- Detect hormones to signal changes in cell function
- Involved in other cell and substance recognition (ex. in immune system)
Enzymes
- Catalytic proteins
- End in -ase
- ex. ATP Synthetase, Maltase
Electron Carriers
- Seen in photosynthesis and respiration in oxidation/reduction reactions
Diffusion
- No energy required
- High concentration -> low concentration
- Caused by kinetic energy of particles
- Direction of movement random
Diffusion through a membrane (ex. lungs)
- The location that supplies and maintains the concentration of particles is called the source
- The location where the substance is continually removed (or changed) is called the sink
- Maintaining the concentration gradient between the two areas is a feature of biological systems
Source = blood oxygen in lungs Sink = respiring cell
Osmosis
- Diffusion of water through a membrane
What molecules pass through the membrane with little resistance?
Oxygen, Carbon Dioxide, Water, Lipids (hydrophobic)
Facilitated (passive) Transport Across Membranes
- Chanel proteins - create a tunnel for large molecules
- Carrier proteins
Active Transport Across the Membrane
- Against concentration gradient (low to high cocentration)
- Requires energy (ATP, produced in cell respiration)
- Carrier proteins
- Sodium-potassium pump/Hydrogen-proton pump
- Cells are negatively charged on the inside relative to the outside (creates voltage)
Exocytosis
- The protein is moved through the rER and modified
- A sperical vesicle is formed from the end of the rER with the protein inside
- Vesicle and golgi membranes fuse. The protein is released into the lumen of the golgi apparatus
- The golgi modifies the protein further
- A new vesicle is formed from golgi membrane which then breaks away
- The vesicle migrates to the plasma membrane fuses secretes content. A process called exocytosis.
Endocytosis
a vesicle is formed by the enfolding of the plasma membrane
3 types: phagocytosis (cellular eating) pinocytosis (cellular drinking) and receptor-mediated endocytosis
Membrane Fluidity
- Phospohlipid molecules changing places in horizontal plane caused fluid property of membrane
- Cholesterol reduces fluidity
- Unsaturated hydrocarbon tails - kinks, double bonds, fluid
- Saturated hydrocarbon tails - no kinks, no double bonds, viscous
- No energy required
- High concentration -> low concentration
- Caused by kinetic energy of particles
- Direction of movement random
Diffusion
- The location that supplies and maintains the concentration of particles is called the source
- The location where the substance is continually removed (or changed) is called the sink
- Maintaining the concentration gradient between the two areas is a feature of biological systems
Source = blood oxygen in lungs Sink = respiring cell
Diffusion through a membrane (ex. lungs)
- Diffusion of water through a membrane
Osmosis
- Chanel proteins - create a tunnel for large molecules
- Carrier proteins
Facilitated (passive) Transport Across Membranes
- Against concentration gradient (low to high cocentration)
- Requires energy (ATP, produced in cell respiration)
- Carrier proteins
- Sodium-potassium pump/Hydrogen-proton pump
- Cells are negatively charged on the inside relative to the outside (creates voltage)
Active Transport Across the Membrane
- The protein is moved through the rER and modified
- A sperical vesicle is formed from the end of the rER with the protein inside
- Vesicle and golgi membranes fuse. The protein is released into the lumen of the golgi apparatus
- The golgi modifies the protein further
- A new vesicle is formed from golgi membrane which then breaks away
- The vesicle migrates to the plasma membrane fuses secretes content. A process called exocytosis.
Exocytosis
a vesicle is formed by the enfolding of the plasma membrane
3 types: phagocytosis (cellular eating) pinocytosis (cellular drinking) and receptor-mediated endocytosis
Endocytosis
- Phospohlipid molecules changing places in horizontal plane caused fluid property of membrane
- Cholesterol reduces fluidity
- Unsaturated hydrocarbon tails - kinks, double bonds, fluid
- Saturated hydrocarbon tails - no kinks, no double bonds, viscous
Membrane Fluidity
