Unit 2 part 3 Flashcards
Cell Membrane
What is the fluid mosaic model?
The currently accepted model of the cell membrane
What is the “backbone” of the membrane
A bi layer produced from huge numbers of molecules called phospholipids
What happens when the fatty tails aren’t very attracted to each other
membrane tends to be fluid or flexible allowing animal cells to have variable shapes and allows the process of endocytosis
Phospholipid
2 fatty acid chains and a phosphate are bonded to a glycerol molecule
lipid bilayer
phospholipid bilayer of plasma membrane separates cytoplasm and cell contents from environment
What can pass through a bilayer?
Only hydrophobic (uncharged) particles through the centre
Kinetic theory
States that particles are in constant motion
What results in diffusion and osmosis
When particles in gasses, liquids, and solutes move at random in aquas solutions
What is diffusion and osmosis?
Passive process in cells as cells do not provide any energy to make particles
What are integral proteins
permanently attached to plasma membrane and penetrate into centre of phospholipid bilayer
What is simple diffusion?
Passive transport of particles from region of high concentration to a region of low concentration
CO2 and O2 in diffusion
Both are small uncharged molecules and can move between phospholipid molecules of the membrane which makes their diffusion easier
Integral proteins
Permanently attached to plasma membrane + penetrate into centre of phospholipid bilayer
Integral protein features
- Can be trans-membrane or only partially penetrate the bilayer
- Can be glycoprotiens, channels, or protein pumos
Integral protein traits
- 2 hydrophobic sections
- Can be trans-membrane or only partially penetrate the bilayer
- Can be glycoproteins, channels, or protein pumps
Peripheral protein traits
- Charged peripheral protein attached to charged sections of integral proteins + phosphate heads
- Hydrophillic and do not penetrate phospholipid bilayer
- Can be receptors or enzymes
Passive transport?
When a substance goes from an area of high concentration to low along concentration gradient
- Transport that does not require ATP
Active transport?
Substance usually moved against a concentration gradient
Types of passive transports?
- Osmosis
- Diffusion
- Facilitated diffusion
Osmosis?
Water moving from a hypotonic (Lower concentration of solutes, high concentration of water) to hypertonic ( higher concentration of solutes, lower concentration of water) solution
Facilitated diffusion?
Passive transport of molecules from region of high concentration to low thought channel proteins
Requires two types of proteins:
- Channel = Most have gates that open and close in response to chemical signals, don’t change shape, and have pores
- Carrier = Change shape to carry a specific substance, usually ions, from one side of membrane to other and if carrier protein is not working no transport will occur
Types of proteins
- Hormone binding
- Enzymatic
- Cell adhesion
- Cell-to-cell communication
- Channel forming
- Pumps for active transport
aquaporins?
Integral channel proteins that selectively transport water rapidly through membranes
- its presence in plasma increases membrane permeability
Example of facilated diffusion
Osmosis through aquaporins
Channel proteins
Have central pores that allow particles to go though
- Pores are lined w/hydrophilic R groups from amino acids
- Some are gated and only open to let facilated fusion happen
- Cell membrane selectively permeable
Five steps of active transport
- Specific practice binding to a site on a specific protein pump
- ATP bonds to protein pump * hydrolyzes to become ADP
- A phosphate stays attached to protein pump + causes protein pump to change shape
- Particle is moved against concentration gradient and released
- Phosphate is released causing protein pump to return to original shape
Transports and their selectivity
Facilated diffusion
- Selective process b/c only specific particles can pass through protein channel
Active transport
- Selective b/c protein pumps ate specific to particles they can transport
Simple diffusion
- Not selective process because any small or hydrophobic molecule can pass through phospholipid bilayer
Glycosylation
Process that attaches phospholipids and membrane with carbohydrate chains
Glycoproteins?
membrane proteins with carbohydrate chain attached to
Glycolipids?
Phospholipids with carbohydrate chain attached to
Functions of glycolipids and proteins?
- Reception
- Cell to cell communication
- Immune response
- Cell to cell adhesion
Reception
Glycoproteins are receptors for hormones b/c when a hormone bonds to a specific protein receptor it changes metabolism within cell
Cell to cell communication
Neurotransmitters bind to glycoproteins letting cells communicate
Immune response
Glycoproteins act as makers on cell letting immune system distinguish between self and not self cells
Cell to cell adhesion
Glycoproteins interact with each other on neighbouring cells which formulates tissue
Cell recognition
Carbohydrates in glycoproteins and lipids have specific shapes letting immune system recognize cells as self
- If carbohydrate chains are not recognized as self by immune system, glycoproteins and lipids act as antigens
Antigens
Substances that stimulate immune response + production of antibodies
Saturated fatty acids
Single bonds between carbons on hydrocarbon chain
- Linear
- Triglycerides with saturated fatty acids have higher melting point
Unsaturated fatty acids
Have at least one double bond between carbon as hydrocarbon chain
- Bent at position of double bond
- Triglycerides w- unsaturated fatty acids have lower melting point
Fluid phospholipid
Phospholipids in membrane are fluids b/c they are not in a fixed position and move around
- Fluidity is affected by type of fatty acid in phospholipid
Saturated fatty acids + fluidity of membrane
No double carbon bond, straight fatty acid tails that allow close packaging of phospholipids
- Results in phospholipids having higher melting point which increases viscosity
- Saturated fatty acids make membrane stronger at higher temps
Unsaturated Fatty Acids + fluidity of membrane
Have double carbon bond = kinks in fatty acid tails preventing close packaging of phospholipids
- Results in phospholipids having lower temps
- Unsaturated fatty acids make membranes have lower melting points and viscosity
Cholesterol?
A lipid that can be made in the liver and found in blood
- Most are non polar ( hydrophobic)
Where is the cholesterol located?
Between fatty acid tails in membranes of animal cells + helps regulate fluidity of membrane
What forms a hydrogen bond a/ phosphate of phospholipids
Hydroxyl group (-OH) on cholesterol
- Hydrophilic ( non polar)
Cholesterol + membrane fluidity
At higher temps cholesterol reduces fluidity + increases melting point of phospholipid resulting in stable membranes
Cholesterol + membrane fluidity
At higher temps cholesterol reduces fluidity + increases melting point of phospholipid resulting in stable membranes
Vesicles
Small membrane bound structures involved in transporting material w/in cells
- Fluid nature of membranes allows formation of vesicles
Bulk transport ( endo and exocytosis)
Is possible due to fluid nature of plasma membrane allowing formation of vesicles + fusion of beagles w/ the membrane
Steps of protein transport w/in cell
- Proteins are to be secreted from cells are synthesized by ribosomes attached to rough endoplasmic reticulum
- Rough ER forms a vesicle containing protein which is sent to golgi apparatus
- Vesicles fuse w/ golgi apparatus which modifies to protein
- Golgi apparatus packages proteins in secretory vesicles
- Secretory vesicles move towards plasma membrane
- secretory vesicles fuse w/ plasma membrane (exocytosis) releasing protein outside of cell
Exocytosis?
Release of large particles from a cell
- Involves 6
- Active process
Endocytosis?
Process by which large particles enter cell
- Large particles are surrounded by a plasma membrane which buds off inside the cell to form vesicles
- Active process
Gated ion channel
Integral proteins that allow specific ions to pass through by facilitated diffusion
- Pore ion channel = hydrophobic, allowing specific ions to enter
- Play a number of roles in transmission of nerve impulses
Examples of gated ions
- Voltage gated channels –> respond to changes in membrane potential dif
- Ligand gated channels –> respond to a Ligand attaching to channels
Sodium potassium pump
Actively transports sodium ions out of cell and potassium ions into cells
- maintains resting potential in neurons
Process of sodium potassium pump
- 3 Na+ attached to sodium ion binding site on sodium potassium pump protein
- ATP attaches sodium potassium pump
- ATP = hydrolyzed w/ a phosphate remaining attached to a protein pump, ADP is released
- Phosphate causes pump to change shape, moving sodium across axon membrane, releasing Na+ outside axon
- Two K+ attach to potassium ion binding site on sodium potassium pump protein
- Phosphate from the pump
- Pump returns to original shape moving K+ into axon
- process can be repeated
Indirect active transport?
- Glucose transport
- Facilitated diffusion
- Sodium dependent glucose co transporters
Glucose transport?
Transported by 2 mechanisms from small intestine to epithelial cells that line the intestine
Facilitated diffusion?
Glucose is passivley transported through glucose channels from small intestine into epithelial cells
Sodium dependant glucose co transporters
Co-transport links movement of an ion (Na+) down its concentration gradient w/movement of a solute (glucose) against its concentration gradient
Process of indirect transport
- Na+ actively pumped out of epithelial cells by sodium potassium pump = low concentration of Na+ in epithelial
- Na+ and glucose bind to sodium dependent glucose co transporters protein
- Attachment of sodium + glucose causes protein to change shape, moving both glucose and sodium into epithelial cell
