Unit 7

Question 1

Describe the fluid mosaic model of the membrane structure

Answer 1

The plasma membrane is described by the fluid mosaic model
Mosaic of protein molecules functioning within a fluid layer of phospholipids
Phospholipids; lipid rafts; cholesterol; glycol, lipids, glycol proteins
Integral (mostly transmembrane) protein; peripheral proteins
Amphipathic components
Selectively permeable

Question 2

Describe how Amphipathic (both hydrophilic and hydrophobic) molecules are important for membrane and function

Answer 2

Amphi (both, dual, around) — pathic (suffering)

Produces a stable boundary between outside/inside
Amphipathic membrane proteins regulate communication and transport across the membrane

Question 3

Explain how the inside and outside of the membrane differ, and the role of carbohydrates

Answer 3

The inner and outer leaflet of the membrane have different phospholipids, carbohydrates, and peripheral proteins

Carbohydrates found only in endomembrane system and on outside surface of the plasma membrane. Those carbohydrates are attached to proteins (making glycolproteins) in the RER; sometimes attached to lipids (making glycolipids). They modify the Golgi apparatus. Their are exported into the surface.

Carbohydrate function;
Cell Dash cell recognition – distinguish cells apart(blood type, immunity, development)
Transport across the membrane – channel proteins and receptors are glycoproteins

Question 4

Describe how freeze fracture technique reveals the mosaic in membranes

Answer 4

1.Freeze cells or tissues.
2. Fracture the tissues with a knife.
Cells fracture between lipid bilayer layer
Transmembrane proteins remain in the membrane
3. Scanning electron microscopy and biochemistry reveals:
1. Membranes have many proteins and lipids.
2. Different membranes have different sets of protein and lipids

Question 5

Describe the fluidity of the components of cell membrane

Answer 5

Phospholipids: spin and move laterally(slipping sides on rare occasion). Hydrophobic contractions keep them together. Self fusion experiments reveal fluidity.

Cholesterol: similar to Phospholipids

Proteins: some are freely mobile. Some restricted to lipid rafts. Some are anchored by cytoplasm proteins.

Question 6

List and explain the four factors that alter membrane fluidity

Answer 6

Unsaturated saturated, fatty acid tails: less saturated = more double bonds = more fluidity

Length of tails: shorter fat ass tails = more fluidity

Temperature:: more fluidity with higher temperatures Less fluid with lower temperatures

Cholesterol: reduces fluidity at elevated temperatures, but increase fluidity at lower temperatures

Question 7

How does cholesterol resist changes in membrane fluidity as temperature changes?

Answer 7

Cholesterol acts as a buffer to membrane fluidity
At Higher temperatures cholesterol restrained, phospholipid movement therefore reduces fluidity

And lower temperatures cholesterol hinders close packing of phospholipids, therefore increases fluidity

Question 8

Why is it important for living organisms to be able to alter their memory fluidity?

Answer 8

Most organisms do not control their temperature so they must control the membrane fluidity by altering composition

Short term, environmental changes (day/night cycle)

Longer environmental changes like the Ice Age

Organisms can regulate their membrane composition
Example– trout and salmon raised in Coldwater of higher omega-3 fatty acids, and those raised in warm farm bonds

Question 9

Distinguish between peripheral and integral membrane proteins

Answer 9

Integral proteins are embedded in the hydrophobic part of the membrane. Most are membrane proteins with stretches of 20 to 30 hydrophobic acids. Trans routines can pass the membrane multiple times (7TM protein)

Peripheral proteins are not imbedded in the membrane and are often reversibly associated with integral proteins

Question 10

List the six major functions of membrane proteins

Answer 10

Transport, enzymatic activity, signal transduction, cell – cell recognition, inter, cellular, joining, attachment to the cytoskeleton and extra cellular matrix

Question 11

Explain the term selectively permeable

Answer 11

The lipid membrane provides a barrier to large molecules and charge molecules/ions

The lipid membrane does not keep out nonpolar molecules, such as lipids, or steroids, or small molecules, like oxygen and CO2

Question 12

Contrast, passive and active transport

Answer 12

Passive transport requires no energy (diffusion, osmosis, filtration, and facilitated diffusion)

Requires energy, usually in the form of ATP(transport, and vesicles)

Question 13

Defined diffusion. Explain why diffusion is a passive and spontaneous process.

Answer 13

Molecules are always in motion
Substances diffuse down concentration gradient (high concentration to low concentration)
Diffusion requires no extra ATP energy

Question 14

Define osmosis and predict the direction of water movement based on differences in solute concentrations

Answer 14

Osmosis is the diffusion of water across a semi permeable membrane

Water moves down the concentration gradient of water, which is opposite of solutes

Question 15

Distinguish between isotonic, hypotonic, hypertonic solutions and their effects on cells

Answer 15

Iso–(same) ; net diffusion both ways as equal. Normal/flacid

Hypo-( less solutes outside than inside the cell’s cytoplasm). Water moves into the cell. Lysed/turgid

Hyper-(more solutes outside than in the cytoplasm) water moves out. Shriveled/plasmolyzed. Died

Question 16

Describe our living cell with and without cell walls, regulate water balance

Answer 16

Cell walls resist plasma membrane swelling (plants, fungi, some bacteria)

Without cell wall
Water pumps( contractile vacuole)
Exist in isotonic solution

Regulation of salutes(Albumin) in our blood, keeps our cells in an is atomic solution. Normal/turgid

Question 17

Define facilitated diffusion. Describe how channel proteins and carrier proteins facilitate diffusion

Answer 17

A channel protein —transmembrane, facilitated diffusion, selective(saw you moves through channel, binding several parts of the channel), no shape change

A Carrier protein— transmembrane, facilitates, diffusion, selective(so you buy a particular site, and shape change, releases), reversible shape change

Question 18

What is facilitated diffusion?

Answer 18

Transport molecules from a region of high concentration to a region of lower concentration with the help of carriers

Question 19

Explain why concentration gradient of a substance across a membrane represents potential energy

Answer 19

Solutes will diffuse down their concentration gradient

If this movement is coupled with another reaction, it can be used to do work
Example: ATP synthase in the electron transport chain in the inner mitochondrial membrane

Question 20

Define active transport. Explain how the sodium potassium bomb maintains sodium/potassium concentrations

Answer 20

Active transport is the movement of ions or molecules across the cell membrane into a region of higher concentration, assisted by enzymes and requiring energy
Active transport allow cells to maintain concentration
gradients. For example, the sodium potassium pump uses ATP to maintain a much higher potassium and lower sodium concentration than surroundings in animal cells

The sodium potassium pump lets three sodium molecules out and takes two potassium molecules in. There is a negative charge inside. The pump regulates the volume of fluid inside cells.

Question 21

Describe the process of cotransport

Answer 21

Cotransport: coupled transport by a membrane protein

Cotransport occurs when active transport of a solute indirectly drives transport of another substance

Symporter— same direction
Antiporter— opposite direction

Question 22

Explain how an electrogenic pump creates voltage across the membrane. name two electrogenic pumps

Answer 22

An electronic pump is a transport protein that generates voltage (charge) across a membrane

The sodium potassium pump is the major electrogenic of animal cells
The electrogenic of plants, fungi, and bacteria is a proton pump

  Mitochondria I have a proton pump used to generate a gradient that helps make ATP

Question 23

Describe the two forces that combine to produce an electro chemical gradient

Answer 23

Two combine forces collectively called the electro, chemical gradient, drive the diffusion of ions across a membrane.
1. Chemical force (the ions concentration gradient.)
2. An electrical force (the effect of the membrane potential on the ions movement)

Question 24

Describe the three types of endocytosis

Answer 24

Endocytosis: brings substances into the cell

Phagocytosis: cell eating
Pinos cytosis: cell drinking
Receptor-mediated endocytosis

Question 25

Describe exocytosis

Answer 25

Exocytosis: expelling substances out of the cell
Transport migrate to the membrane, fuse with it, and release their contents outside the cell