Chapter 4 - Transport across cell membranes Flashcards
What do phospholipids do?
Form a bilayer
What is the structure of phospholipids
Hydrophillic head - Points to outside of cell and attracted to water
Hydrophobic Tail - Facing inside the cell
What small non-polar molecules can diffuse through the membrane?
O2 AND CO2 - rapidly diffuse
What small polar molecules can diffuse through the membrane?
H2O + Urea
What is unlikely to diffuse through the membrane?
charged particles (ions)
What is the function of cholesterol?
V.important in controlling membrane fluidity + keeping the membrane in stable normal body temp (without it cells would burst)
More cholesterol = less fluid = less permeable, the membrane
What are integral (Intrinsic or Transmembranes) proteins?
Proteins that span the whole wrath of the membrane
Many are carrier or channel proteins
What are peripheral (extrinsic) proteins?
Proteins are confined to the inner or outer surface of the membrane
May be free on the membrane surface or bound to integral protein
What are glycoproteins?
Proteins with attached carbohydrate chains
What are the functions of (Intrinsic or Transmembranes)
Help transport substances such as ions, sugars, amino acids that can’t diffuse through membrane but are still vital to cells functioning
What are the functions of (extrinsic) proteins?
Act as receptors for hormones or neurotransmitters or involved with cell recognition
Why is the fluid mosaic model described as ‘fluid’?
because individual phospholipid can move relative to each other
Gives a flexible structure
Why is the fluid mosaic model described as ‘mosaic’?
Proteins embedded in phospholipid vary in shape size + pattern
What is simple diffusion?
passive transport (natural, inbuilt motion of particles)
What is the definition of diffusion?
Is the net movement of molecules or ions from a region where they are highly concentrated to one where their conc is lower until evenly distributed down a conc gradient
What is facilitated diffusion?
passive process that relies on inbuilt KE of diffusing molecule
Down a conc gradient
differs
What two proteins are involved in facilitated diffusion?
Protein channels
Carrier proteins
What are protein channels?
Water filled hydrophilic channels across the membrane
What is the function of channel protein?
Selectively slow water-soluble ions to pass through
controls entry + exit
opens one side closes one side
What are carrier protein?
alternative form of FD
involves carrier proteins that span the plasma membrane
What is the function of carrier protein?
molecule specific to protein is present binds with protein causes to change shape molecule released to inside of membrane Molecules move from H to L conc
What is the definition of osmosis?
the passage of water from a region where it has a H water potential to a region of L water potential through selectively permeable membrane
What is water potential?
the pressure created by water molecule under standard temp + pressure
Whats hypertonic?
WP outside is L than inside the cell
H2O moves out of cell
Cell is plasmolyzed (cytoplasm pulled from cell wall)
Whats isotonic?
f
Whats Hypotonic?
WP outside H than inside the cell
H2O enters cell
Cell is Turgid (Cytoplasm pushing against cell wall)
What is the definition of active transport?
The movement of molecules or ions out of a cell from a region of lower conc to a region of higher conc using ATP and carrier proteins
What is ATP used in AT for?
Directly move molecules
Individually move molecules using conc gradient
How does it differs from passive forms of transport?
Uses metabolic energy in form of ATP
substances moved against conc
Carrier proteins acts as pump
Process is selective
Describe the process of direct active transport?
1) Carrier proteins span plasma membrane
What is cotransport?
Indirect active transport (coupled transport)?
What is the role of AT in absorbtion in microvilli?
d
