Chapter 7

Question 1

Plasma membrane

Answer 1

-boundary that separates living cell from surroundings
-controls traffic in and out of cell
-selective permeability-allows some substances to cross easier than others
-choosing what to pass= fundamental to life

Question 2

Phospholipids

Answer 2

-most abundant lipid in plasma membrane
-amphipathic molecules- contain hydrophobic and hydrophilic regions

Question 3

Fluid mosaic model

Answer 3

-membrane is a fluid structure with mosaic of proteins embedded in it
-freeze fracture studies support-splits membrane down middle of phospholipid bilayer

Question 4

Sandwich model

Answer 4

-phospholipid bilayer lies between two layers of proteins
-problems with placement of membrane proteins which has hydrophilic and hydrophobic regions

Question 5

Interactions that hold membrane molecules in place

Answer 5

-relatively weak hydrophobic interactions
-adjacent phospholipids switch positions, large membrane proteins may drift within layer but move slower

Question 6

Fluidity

Answer 6

-influenced by components of membrane
-rich in un saturated fatty acids=more fluid than with saturated fatty acids
-membranes need to be fluid to work properly
-types of lipids determines temp membrane solidifies

Question 7

Cholesterol

Answer 7

-different effects on membrane fluidity at different temps
-warm temps=restrains movement of phospholipids
-cool temps=membranes switch from fluid to solid state

Question 8

Variations in lipid composition

Answer 8

-adaptations to specific environmental conditions
-ability to change lipid composition has evolved in organisms that live where temps vary

Question 9

Membrane

Answer 9

collage of different proteins embedded in fluid matrix of lipid bilayer
-have unique collections of proteins

Question 10

Protein

Answer 10

determine most of membranes specific functions

Question 11

Peripheral proteins

Answer 11

bound to surface of the membrane

Question 12

Integral proteins

Answer 12

penetrate the hydrophobic core
-hydrophobic regions consist of one or more stretches of non polar amino acids coiled into alpha helices

Question 13

Transmembrane proteins

Answer 13

integral proteins that span the membrane

Question 14

Major functions of membrane proteins

Answer 14

-transport
-enzymatic activity
-signal transduction (hormonal messages)
-cell cell recognition (allow proteins ro attach cells together)
-intercellular joining (joining with gap or tight junctions_
-attachment to cytoskeleton and extracellular matrix (maintain shape and stabilize location of proteins)

Question 15

Cell cell recognition

Answer 15

-recognize each other by binding to surface molecules on extracellular surface of plasma membrane
-important in sorting and organizing of cells into tissues and organs
-basis for rejection of foreign cells

Question 16

Glycolipids

Answer 16

membrane carbohydrates covalently bonded to lipids

Question 17

Glyocproteins

Answer 17

membrane carbohydrates covalently bonded to proteins

Question 18

Membrane built by

Answer 18

er and Golgi apparatus
-asymmetrical distribution of proteins, lipids and carbohydrates determined when built

Question 19

What can pass through membrane rapidly

Answer 19

-hydrophobic (non polar) molecules (hydrocarbons, co2, o2) can dissolve in lipid bilayer and pass rapidly

Question 20

What cannot cross membrane easily

Answer 20

polar molecules (sugars) and surrounding shells of water do not cross easily

Question 21

Transport proteins

Answer 21

-allow passage of hydrophilic substances across the membrane
-specific for substance it moves

Question 22

Channel proteins

Answer 22

-transport proteins have a hydrophobic channel that molecules or ion can use as a channel
-aquaporins-channel proteins that facilitate passage of water

Question 23

Carrier proteins

Answer 23

-transport proteins that bind to molecules and change shape to shuttle them across membrane

Question 24

Diffusion

Answer 24

tendency for molecules to spread out evenly into available space
-each molecule is random, diffusion of population of molecules is directional
-diffuse down their concentration gradient
-passive transport because no energy needed to happen

Question 25

Dynamic equilibrium

Answer 25

as many molecules cross the membrane in one direction as in the other

Question 26

Concentration gradient

Answer 26

region along which the density of a chemical substance increases or decreases -no work done, no atp used to move substances down

Question 27

Osmosis

Answer 27

diffusion of water across selectively permeable membrane -water diffuses across membrane from region of lower solute concentration to region of higher solute concentration until concentration is equal on both sides

Question 28

Tonicity

Answer 28

ability of surrounding solution to cause a cell to gain or lose water

Question 29

Isotonic solution

Answer 29

solute concentration is the same as inside the cell, no net water movement across plasma membrane

Question 30

Hypertonic solution

Answer 30

solute concentration is greater than inside the cell, cell loses water

Question 31

Hypotonic solution

Answer 31

solute concentration is less than inside the cell, cell gains water

Question 32

Cell walls

Answer 32

help maintain water balance -in hypotonic solution, wall swells and is now firm -isotonic-no movement of water, wall is limp, wilting -hypertonic- lose water, membrane pulls away from wall-plasmolysis

Question 33

Osmoregulation

Answer 33

control of solute concentrations and water balance -necessary adaptation for life

Question 34

Facilitated diffusion

Answer 34

-transport proteins speed passive movement of molecules across membrane -channel proteins provide corridors that allow specific molecule or ion to move across membrane

Question 35

Ion channels

Answer 35

-channel protein that open or close in response to stimulus

Question 36

Aquaporins

Answer 36

-channel proteins for facilitated diffusion of water

Question 37

Active transport

Answer 37

-moves substances against concentration gradient -requires energy, ate -performed by specific proteins in membranes -allows cells to maintain concentration gradients -sodium potassium pump

Question 38

Sodium potassium pump

Answer 38

-active transport -K+ high inside cells and low outside -Na+ low inside high outside -uses a lot of bodies energy

Question 39

Membrane potential

Answer 39

-voltage difference across membrane -cytoplasm - -extracellular + -created by differences in distribution of positive and negative ions across membrane

Question 40

Electrochemical gradient

Answer 40

-two forces that drive diffusion of ions across membrane -chemical force-ions concentration gradient and -electrical force-effect of membrane potential on ions movement

Question 41

Electrogenic pump

Answer 41

-transport protein that generates voltage across a membrane -ex sodium potassium pump -help store energy that can be used for cellular work

Question 42

Cotransport

Answer 42

-occurs when active transport of solute indirectly drives transport of other solutes

Question 43

Bulk transport

Answer 43

-small molecules enter or leave cell through lipid bilayer or transport proteins -large molecules cross membrane in bulk via vesicles -requires energy -endocytosis and exocytosis

Question 44

Exocytosis

Answer 44

-transport vesicles migrate to membrane, fuse with it and release contents

Question 45

Endocytosis

Answer 45

-cell takes in macromolecules by forming vesicles from plasma membrane -reversal of exocytosis involving different proteins -3 types- phagocytosis, pinocytosis, receptor mediated endocytosis

Question 46

Phagocytosis

Answer 46

-cellular eating -cell engulfs a particle in a vacuole -vacuole fuses with lysosome to digest the particle

Question 47

Pinocytosis

Answer 47

-cellular drinking -molecules taken up when extracellular fluid is gulped into tiny vesicles

Question 48

Receptor mediated endocytosis

Answer 48

-binding of ligands to receptors trigger vesicle formation

Question 49

Ligand

Answer 49

any molecule that binds specifically to a receptor site of another molecule