Test 2

Front 1

 Separates internal contents of a cell from its external environment
 Some functions include:
 Selective transport of ions and molecules
 Cell compartmentalization (organelles)
 Protein sorting
 Adhesion of cells to each other and to the ECM/cell wall

Back 1

The Plasma or Cell Membrane

Front 2

 Phospholipid bilayer
 Amphipathic molecules
 Hydrophobic (water-fearing) region faces in
 Hydrophilic (water-loving) region faces out
 Proteins and carbohydrates
 Relative amount of each vary

Back 2

Biological Membranes

Front 3

 Mosaic of lipid, protein, and carbohydrate molecules
 Lipids and proteins can move relative to each other within the membrane
 Singer and Nicolson (1972

Back 3

Fluid-mosaic model

Front 4

Integral membrane proteins

Back 4

Proteins bound to membranes

Front 5

Physically embedded in the bilayer hydrophobic

Back 5

Transmembrane proteins

Front 6

Covalent attachment of a lipid to an amino acid side chain within a protein

Back 6

Lipid anchors

Front 7

 Noncovalently bound to:
 Integral membrane proteins
 Polar head groups of phospholipids

Back 7

Peripheral membrane proteins

Front 8

 Individual molecules have the ability to readily move within the membrane
 Semifluid
 Most lipids can rotate freely laterally
 “Flipflop” of lipids does not occur spontaneously
 Flippase requires ATP to transport lipids

Back 8

Membranes are semifluid

Front 9

 Length of tails
 Shorter acyl tails are less likely to interact, which makes the membrane more fluid
 Presence of double bonds in the acyl tails
 Double bond creates a kink in the fatty acyl tail, making it more difficult for neighboring tails to interact and making the bilayer more fluid
 Presence of cholesterol
 Cholesterol tends to stabilize membranes
 Effects depend on temperature

Back 9

Factors affecting fluidity

Front 10

 Integral proteins
 May rotate and move laterally
 Slower rate than lipids movement
 No flip-flops (hydrophilic loops)

Back 10

Movement of membrane proteins

Front 11

 Separates internal contents of a cell from its external environment
 Some functions include:
 Selective transport of ions and molecules
 Cell compartmentalization (organelles)
 Protein sorting
 Adhesion of cells to each other and to the ECM/cell wall

Back 11

The Plasma or Cell Membrane

Front 12

 Phospholipid bilayer
 Amphipathic molecules
 Hydrophobic (water-fearing) region faces in
 Hydrophilic (water-loving) region faces out
 Proteins and carbohydrates
 Relative amount of each vary

Back 12

Biological Membranes

Front 13

 Mosaic of lipid, protein, and carbohydrate molecules
 Lipids and proteins can move relative to each other within the membrane
 Singer and Nicolson (1972

Back 13

Fluid-mosaic model

Front 14

Integral membrane proteins

Back 14

Proteins bound to membranes

Front 15

Physically embedded in the bilayer hydrophobic

Back 15

Transmembrane proteins

Front 16

Covalent attachment of a lipid to an amino acid side chain within a protein

Back 16

Lipid anchors

Front 17

 Noncovalently bound to:
 Integral membrane proteins
 Polar head groups of phospholipids

Back 17

Peripheral membrane proteins

Front 18

 Individual molecules have the ability to readily move within the membrane
 Semifluid
 Most lipids can rotate freely laterally
 “Flipflop” of lipids does not occur spontaneously
 Flippase requires ATP to transport lipids

Back 18

Membranes are semifluid

Front 19

 Length of tails
 Shorter acyl tails are less likely to interact, which makes the membrane more fluid
 Presence of double bonds in the acyl tails
 Double bond creates a kink in the fatty acyl tail, making it more difficult for neighboring tails to interact and making the bilayer more fluid
 Presence of cholesterol
 Cholesterol tends to stabilize membranes
 Effects depend on temperature

Back 19

Factors affecting fluidity

Front 20

 Integral proteins
 May rotate and move laterally
 Slower rate than lipids movement
 No flip-flops (hydrophilic loops)

Back 20

Movement of membrane proteins

Front 21

 May be restricted in their movement
 Restriction by:
 Attachment to cytoskeleton
 Attachment to molecules in ECM

Back 21

Not all integral membrane proteins can move

Front 22

 Glycosylation
 Glycolipid or Glycoprotein
 Recognition signals for other cellular proteins
 Ex. Lysosomes
 Role in cell surface recognition
 Protective effects
 Cell coat or glycocalyx

Back 22

Function of Carbohydrates

Front 23

 Membrane structure ensures that…
 Essential molecules enter
 Metabolic intermediates remain
 Waste products exit
 Use of transport proteins

Back 23

Selective permeability

Front 24

 Hydrophobic core
 Diffusion
 Movement of solute from an area of higher concentration to an area of lower concentration
 Passive diffusion
 Without transport protein
 Solutes vary in their rates of diffusion

Back 24

Phospholipid bilayer is a barrier

Front 25

 Transmembrane concentration gradient
 Concentration of a solute is higher on one side of a membrane than the other
 Ion electrochemical gradient
 Both an electrical gradient and chemical gradient

Back 25

Cells maintain gradients

Front 26

 Does not require an input of energy

Back 26

Passive transport

Front 27

2 types of passive transports

Back 27

 Passive diffusion
 Diffusion without transport protein
 Facilitated diffusion
 Diffusion with the aid of a transport protein

Front 28

– relative solute concentrations

Back 28

Tonicity

Front 29

 Equal water and solute concentrations on either side of the membrane

Back 29

Isotonic

Front 30

 Solute concentration is higher (and water concentration lower) on one side of the membrane

Back 30

Hypertonic

Front 31

Solute concentration is lower (and water concentration higher) on one side of the membrane

Back 31

Hypotonic

Front 32

Water diffuses through a membrane from an area with more water to an area with less water

 If the solutes cannot move, water movement can make the cell shrink or swell as water leaves or enters the cell

Back 32

Osmosis

Front 33

 Tendency for water to move into any cell

Back 33

Osmotic pressure

Front 34

 Must maintain balance between extracellular and intracellular solute concentrations
 Crenation - shrinking of cell in a hypertonic solution
 Osmotic lysis – rupture of cell in a hypotonic solution

Back 34

Animal Cells

Front 35

 A cell wall prevents major changes in cell size
 Turgor pressure - pushes plasma membrane against cell wall (in hypotonic solution)
 Maintains shape and size
 Plasmolysis - plants wilt because water leaves plant cells (in hypertonic solution

Back 35

Plant cells

Front 36

 Enable biological membranes to be selectively permeable
 2 classes:
 Channels
 Transporters

Back 36

Transport protein

Front 37

 Form an open passageway for the direct diffusion of ions or molecules across the membrane
 Aquaporins
 Most are gated
 Open/closed
 Open and close in response to certain stimuli

Back 37

Channels

Front 38

 Also known as carriers
 Conformational change transports solute
 Uptake of sugars, amino acids, and nucleotides
 Key role in export
 Classified according to the number of solutes they bind and the direction of the transport

Back 38

Tranporters

Front 39

 Uniporter
 single molecule or ion


Symporter/ cotransporter
 2 or more ions or molecules transported in same direction


Antiporter
 2 or more ions or molecules transported in opposite directions

Back 39

Transporter types

Front 40

 Couples conformational changes to energy
 ATP-driven pumps
 Binding site for ATP
 ATP hydrolysis
 Active transport

Back 40

Pump (transporter)

Front 41

 Movement of a solute across a membrane against from low concentration to higher concentration
 Requires the input of energy

Back 41

Active transport

Front 42

 Directly use energy (ATP) to transport solute

Back 42

Primary active transport

Front 43

Use pre-existing gradient to drive transport of solute

Back 43

Secondary active transport

Front 44

 Na+/K+-ATPase
 Active transport of Na+ and K+ using ATP
 3 Na+ exported for 2 K+ imported into cell (Antiporter)
 Electrogenic pump - export 1 net positive charge
 Pump that generates an electrical gradient

Back 44

ATP-Driven Ion Pumps Generate Ion Electrochemical Gradients

Front 45

Transport larger molecules such as proteins and polysaccharides, and even very large particles

Back 45

Exocytosis/ Endocytosis

Front 46

Material inside the cell, which is packaged into vesicles, is excreted into the extracellular medium

Back 46

Exocytosis

Front 47

 Plasma membrane invaginates, or folds inward, to form a vesicle that brings substances into the cell
 Receptor-mediated endocytosis – use ligands/receptors

Back 47

Endocytosis

Front 48

cellular drinking

Back 48

Pinocytosis

Front 49

cellular eating

Back 49

Phagocytosis