Bio 188: Study Guide Three

Front 1

Describe the Fluid Mosaic Model.

Back 1

The basic structure of membranes in which a variety of proteins and carbohydrates “float” in a lipid “lake” known as the phospholipid bilayer.

Front 2

In the cell membrane, why do the phosphate heads point outward and inward in the phospholipid bilayer?

Back 2

The head groups face outward to come in contact with the aqueous environment and the fatty acid tails face inward to avoid contact with the aqueous environment.

Front 3

What are the functions of the cell membrane?

Back 3

To perform vital role of regulatin what substances enter and leave cells, information processing, energy transformation, organizing chemical reactions, and membrane flow/flux.

Front 4

What is meant by membrane fluidity?

Back 4

viscosity of the lipid bilayer of a cell membrane.

Front 5

What features of the fatty acid tails in the phospholipid bilayer control membrane fluidity?

Back 5

When cholesterol molecules are present in a membrane, they influence the fluidity of fatty acids in the membrane and are commonly situated next to unsaturated fatty acids. The fluidity of the fatty acids in the interior of the bilayer membrane facilitates lateral movement within the plane of the membrane. Short fatty acid chains, unsaturated fatty acids, and higer temperature increase this membrane fluidity.

Front 6

Distinguish between inegral and peripheral membrane proteins.

Back 6

Integral membrane proteins are membrane proteins embedded in the bilayer of the membrane and peripheral membrane proteins are membrane proteins not embedded in the bilayer.

Front 7

What are the functions of membrane carbohydrates?

Back 7

They serve as recognition sites for other cells and molecules. Membrane-associated carbohydrates may be covalently bound to lipids or proteins.

Front 8

Distinguish between glycolipids and glycoproteins.

Back 8

Glycolipids consist of a carbohydrate convalently bound to a lipd. The carbohydrates usually extend outside the membrane, where they serve as recognition signals. The carbohydrates of some glycolipids change when a cell becomes cancerous, allowing white blood cells to target cancer cells fro destruction. Glycoproteins consists of a carbohydrate convalently bound to a protein. Bound carbohydrates are oligosaccharide chains, usually not exceeding 15 monosaccharide units in length. Glycoproteins enable a cell to be recognized by other cells and proteins.

Front 9

Distinguish between diffusion and osmosis.

Back 9

. Diffusion involves movement of any chemical from one place to another; osmosis refers to movement of water across a membrane. Only water can undergo osmosis.

Front 10

What factors control diffusion across the cell membrane?

Back 10

The concentration gradient and the exchange surface (membrane) and diffusing species characteristics (e.g. lipid solubility)

Front 11

Why can’t polar molecules readily diffuse across the cell membrane?

Back 11

The hydrophobic inner core of the membrane allows only nonpolar, lipid-soluble molecules to diffuse.

Front 12

How does diffusion and facilitated diffusion differ? Give an example of each process.

Back 12

Substances which cannot pass through the phospholipid bilayer via simple diffusion may be helped to diffuse in a process called facilitated diffusion through the help of either channel or carrier proteins. Channel proteins are integral membrane proteins with polar amino acids and water on the inside of the channel and nonpolar amino acids on the outside allowing the channel protein to insert itself into the lipid bilayer. Carrier proteins transport polar molecules such as sugars and amino acids across the membrane by binding to them. (ex: glucose transporter)

Front 13

What is active transport?

Back 13

The energy-dependent transport of a substance across a biological membrane against a concentration gradient—that is, from a region of low concentration (of a substance) to a region of high concentration.

Front 14

Distinguish between exocytosis and endocytosis

Back 14

Endocytosis is a process by which liquids or solid particles are taken up by a cell through invagination of the plasma membrane. Exocytosis is a process by which a vesicle within a cell fuses with a plasma membrane and releases its contents to the outside.

Front 15

How does pinocytosis differ from phagocytosis

Back 15

Pinocytosis is endocytosis by a cell of liquid containing dissolved substances. Phagocytosis is endocytosis by a cell of another cell or large particle.

Front 16

What are tight junctions?

Back 16

A junction between epithelial cells, in which there is no gap whatever between the adjacent cells. Materials may pass through a tight junction only by entering the epithelial cells themselves.

Front 17

Define: active transport

Back 17

The energy-dependent transport of a substance across a biological membrane against a concentration gradient—that is, from a region of low concentration (of a substance) to a region of high concentration.

Front 18

Define: Antiport

Back 18

A membrane transport process that carries one substance in one direction and another in the opposite direction.

Front 19

Define: Hydrophobic

Back 19

Having no affinity to water.

Front 20

Define: Integral membrane protein

Back 20

A membrane protein embedded in the bilayer of the membrane.

Front 21

Define: Aquaporin

Back 21

A transport protein in plant and animal cells through which water passes in osmosis.

Front 22

Define: Osmosis

Back 22

The movement of water across a permeable membrane from an area of high concentration to an area of low concentration.

Front 23

Define: Desmosomes

Back 23

An adhering junction between animal cells.

Front 24

Define: Pasive membrane transport

Back 24

Diffusion across a membrane: may or may not require a channel or carrier protein.

Front 25

Define: Diffusion

Back 25

Random movement of molecules or other particles, resulting in even distribution of the particles when no barriers are present.

Front 26

Define: Peripheral membrane protein

Back 26

Membrane protein not embedded in the bilayer.

Front 27

Define: Facilitated Diffusion

Back 27

Passive movement through a membrane involving a specific carrier protein; does not proceed against a concentration gradient.

Front 28

Define: Permeable membrane

Back 28

Membrane that allows all particle to pass through.

Front 29

Define: Fatty Acid

Back 29

A molecule with a long hydrocarbon tail and a carboxyl group at the other end. Found in many lipids.

Front 30

Define: Phagocytosis

Back 30

Endocytosis by a cell of another cell or large particle.

Front 31

Define: Phospholipid bilayer

Back 31

Lipids containing a phosphate group, important constituents of cellular membranes.

Front 32

Define: gap junctions

Back 32

A 2.7-nanometer gap between plasma membranes of two animal cells, spanned by protein chennels. Gap junctions allow chemical substances or electrical signals to pass from cell to cell.

Front 33

Define: Pinocytosis

Back 33

Endocytosis by a cell of liquid containing dissolved substances.

Front 34

Define: Glucose transporter

Back 34

A type of carrier protein that transports polar molecules such as sugars and amino acids across the membrane by binding to them.

Front 35

Define: receptor-mediated endocytosis

Back 35

Endocytosis initiated by macomolecular binding to a specific membrane receptor.

Front 36

Define: Glycerol

Back 36

A three-carbon alcohol with three hydroxyl groups; a component of phospholipids and triglycerides.

Front 37

Define: Semi-permeable membrane

Back 37

A membrane that allows only certain molecules or ions to pass through it by diffusion.

Front 38

Define: Glycolipid

Back 38

a lipid in which sugars are attached.

Front 39

Define: Symport

Back 39

A membrane transport process that carries two substances in the same direction across the membrane.

Front 40

Define: Glycoprotein

Back 40

A protein to which sugars are attached.

Front 41

Define: Tight junctions

Back 41

A junction between epithelial cells, in which there is no gap whatever between the adjacent cells. Materials may pass through a tight junction only by entering the epithelial cells themselves.

Front 42

Define: Hydrophilic

Back 42

Having an affinity for water.

Front 43

Define: Uniport

Back 43

A transporter that mediates the unidirectional movement of a single substrate across the membrane.