Chapter 7 Flashcards
Ampiphatic
A molecule containing both hydrophilic and hydrophobic areas
What does the fluid mosaic model state?
That the membrane is a fluid structure with various proteins embedded into it
Why can phospholipids move within bilayer?
Hydrophobic interactions are weak
What are the two kinds of phospholipid movements?
Lateral (more often) and flip-flop
Why do phospholipids in membrane move around?
Create heat to prevent solidification
A membrane is fluid in ______ conditions
warmer
Cells in colder climates have more ______ to prevent ________
unsaturated hydrocarbon tails
solidificiation
How is cholesterol a buffer in both high and low temperatures?
High: cholesterol makes bilayer less fluid by restraining phospholipid movement
Low: cholesterol hinders close packing of proteins, lowering temperature required for solidification
What determines the function of the membrane?
Proteins
Integral proteins
Proteins that penetrate through whole bilayer
Peripheral proteins
Proteins loosely binded to membrane surface
Transmembrane proteins
Peripheral proteins that span membrane
What does the hydrophobic region of integral proteins consist of?
1 or more stretches of non polar amino acids coiled into alpha helices
Major functions of membrane proteins
Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to cytoskeleton and extracellular matrix
How do cells recognize eachother?
By binding to surface molecules (often carbs) on membrane
Membrane carbs may be bonded to ______, creating _______, or more commonly bonded to _______, creating ____________
- bonded to lipids, forming glycolipid
- bonded to proteins, forming glycoprotein
Exchange of material with surroundings is controlled by what?
Membrane
______ molecules can pass through membrane easily
Hydrophobic
List hydrophobic molecules that can pass through membrane
Carbon dioxide, oxygen, hydrocarbons
_____ molecules can not cross membrane easily
Polar
List some molecules that cannot pass membrane easily
Sugar, water
What allows passage of hydrophilic substances
Transport proteins
Transport proteins
Allows passage of hydrophilic substances
Channel proteins
Transport protein with hydrophilic channel that certain molecules and ions can use as a tunnel
Aquaporin
Channel protein that facilitates passage of water
Carrier proteins
Transport proteins that bind to molecules and change shape to shuttle across membrane
Transport protein is specific to _______
substance that it moves
Diffusion
Tendency for molecules to spread out evenly into available space
Rule of diffusion
Diffusion of population exhibits net movement in one direction
Dynamic equilibrium
where as many molecules cross one way as the other way
Concentration gradient
Difference in concentration of substance from one area to another
Osmosis
Diffusion of water across selectively permeable membrane
Tonicity
Ability of a solution to cause cell to gain/lose water
What does tonicity depend on?
The concentration of solutes that cannot cross the membrane
Osmoregulation
Control of water balance necessary for adaption to life in hypertonic/hypotonic conditions
What’s special about the Paramecium?
Pond is hypotonic to cell (water moves into cell), so it has contractile vacuole that acts as a pump
Plant cell in hypotonic solution is calledf
Turgid
Plant cell in hypertonic solution causes lethal effect called….
Plasmolysis
Facilitated diffusion
Passive transport quickened by aid of transport proteins
Facilitated diffusion, what do channel proteins do?
- Provide corridors for molecules/ions to move across
- Aquaporins and ion channels
Active transport
Movement of substances against concentration gradient, requiring energy
Active transport is performed by what?
Carrier proteins
What does active transport allow for cell to do?
Maintain concentration gradient different from surroundings
What does the sodium-potassium pump do?
Exchanges sodium for potassium across membrane to maintain steep concentration differences
How do large molecules cross in bulk?
Packaging into vesicles, requiring energy
Exocytosis
Transport vesicles migrate to membrane, fuse, and release contents
In which cells is exocytosis useful?
Secretory cells (to export products)
Endocytosis
Cells take in macromolecules by forming vesicles from plasma membrane
Types of endocytosis
Phagocytosis, pinocytosis, receptor-mediated endocytosis
Phagocytosis
Cell engulfs particle in a vacule
How is the vacuole created in phagocytosis digested?
When fused with lysosomes
Pinocytosis
Cell gulps droplets of extracellular fluid into tiny vesicles
Receptor-mediated endocytosis allows…
Allows human cells to take cholesterol in for use in synthesis of membranes/steroids
Ligands
Any molecule that binds specifically to receptor site of another molecule
Receptor-mediated endocytosis
Binding of ligands to receptor, creating a vesicle
Aquaporins speed up….
Rate at which water reaches water potential equilibrium
