Chapter 5

Question 1

What does amphipathic mean?

Example of molecule that is?

Answer 1

Has both hydrophilic and hydrophobic regions

Phospholipids

Question 2

What is the membrane held by?

Answer 2

Hydrophobic interactions

Question 3

In which direction can lipids and proteins in the membrane move

Answer 3

Laterally

Unless protein is attached to cytoskeleton or ECM

Question 4

At what temperatures do membranes remain fluid?

Answer 4

More fluid as temperature increases unless it’s full of unsaturated hydrocarbons. These have kinks that cannot pack close together. So they are more fluid in general

Question 5

What does cholesterol do to membrane fluidity?

Answer 5

Reduced membrane fluidity at moderate temperatures by reducing phospholipid movement, but at lower temperatures it hinders solidification by disrupting the regular packing of phospholipids.

Question 6

What are the two membrane proteins

Answer 6

Integral proteins: protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of membrane.

Peripheral proteins: a protein loosely bound to the surface of a membrane or to part of integral protein and not embedded in the lipid bilayers.

Question 7

What are the 6 functions of membrane proteins?

Answer 7

1. transport-through channel or shuttle
2. Enzymatic activity- enzyme with active site (binding place)
3. Signal transduction- binding site with specific shape that send signals to cell.
4. Cell-cell recognition- so,e glycoproteins have identification tags.
5. Intercellular joining-junctions
6. Attachment to cytoskeleton and ECM- maintain cell shape, coordinate IN and EC changes

Question 8

Describe the role of glycolipids and glycoproteins?

Answer 8

Proteins that recognize other molecules that bind to them by their short carbohydrate chain. This happens in extracellular surface of the plasma membrane.

Ex: blood groups are differentiated by glycoproteins at the surface of RBC

Question 9

What are some things that flow in and out of the cell

What things have a hard time crossing the plasma membranes bilayer?

Answer 9

Oxygen, carbon dioxide, metabolic waste, sugars. Ions, amino acids

Polar molecules and ions have difficulty

Question 10

Transport proteins?

Answer 10

A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.

Ex: channel proteins have hydrophilic channel

Question 11

Aqua porins

Answer 11

Channel proteins that allow passage of water molecules.

Question 12

Carrier proteins

Answer 12

Hold onto their passengers and change shape I’m a way to shuttle them across

Question 13

Passive transport

Answer 13

Diffusion of a substance across a membrane with no energy used

Question 14

Diffusion and osmosis

Answer 14

Movement of a substance from an area of high concentration to an area of low concentration.

Diffusion of free water across a selectively permeable membrane.

Question 15

In a solution with two solutes, both will move ______ their concentration gradient?

Answer 15

Down

Question 16

Tonicity

Answer 16

The ability of a solution surrounding a cell to cause that cell to grow/ lose water

Question 17

Isotonic solution

Answer 17

A solution that when near a surrounding cell causes no net movement of water.

Question 18

Hypertonic solution

Answer 18

A solution that when near a surrounding cell causes the cell to lose water. (More solutes on the outside)

(Crenation if cell)(shrinkage)

Question 19

Hypotonic solution

Answer 19

A solution that when near a surrounding cell causes water to rough into the cell. (Can lyse cell) (burst)

Question 20

Osmoregulation

Answer 20

Regulation of solute concentrations and water balance by a cell or organism

Question 21

Plasmolysis

Answer 21

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell walls, occurs when the cell looses water to hypertonic solution.

Question 22

Facilitated diffusion

Answer 22

Passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific trans membrane transport proteins, requiring no energy.

(Ions)

Question 23

Ions channels are_____ and only open in response to an _____

Answer 23

Gated.

Electrical stimulus

Question 24

Active transport

Answer 24

The movement of substances across a cell membrane against its concentration or electrochemical gradient, mediates by species transport proteins and requiring energy.

• carrier proteins
• ATP

Question 25

Membrane potential

Answer 25

The difference of electrical charge across a cells plasma membrane due to the differential distribution of ions (cytoplasm more negative)

Question 26

Electrochemical gradient

Answer 26

The diffusion gradient of an ion, which is affected by both the concentration difference of the ion across the membrane and the ions tendency to move relative to the membrane potential

• chemical force
• electrical force

Question 27

Electrogenic pump

Example of

Answer 27

An active transport protein that generates voltage across a membrane while pumping ions.

Proton pump: An active transport protein in a cell ,embrace that uses ATP to transport hydrogen ions out of the cell against gradient.

Question 28

Cotransport and example

Answer 28

The coupling where a substance moves against concentration gradient by pairing with a substance that moves with theirs.

Ex: sucrose enters paint cells by coupling to hydrogen

Question 29

Bulk transport

Answer 29

Large molecules such as proteins and polysaccharides generally cross the membrane in bulk, packaged in vesicles.

Question 30

Exocytosis

Answer 30

Cell secretes certain biological molecules by the fusion of vesicles with the membrane.

Question 31

Endocytosis

Answer 31

Cell takes in molecules by forming new vesicles from the plasma membrane.

Question 32

Pinocytosis

Answer 32

Cell continually fills droplets of extracellular fluids into tiny vesicles . It is non specific in what it transports.

Question 33

Receptor mediated endocytosis

Answer 33

Specialized type of pinocytosis that enables cell to acquire bulk quantities of specific substances. In plasma membrane are proteins with receptor sites. Solutes nine to these and receptor proteins cluster into coated pits which form the vesicles.

Question 34

Local signalling

Answer 34

Pacacrine:Cell secretes chemicals to specific target cells.

Synaptic signalling: Specific with nerve cells

Question 35

Long distance signalling

Answer 35

Endocrine: uses hormones that travel through fluids in the body and act on specific cells to change cells functionality.

Question 36

3 stages of cell signalling

Answer 36

1. Reception-target cells detection of a signalling molecule. Chemical signal is detected when the signalling molecule binds to a receptor protein.
2. Transduction- converts signal to a doe, that can bring about cellular response. Uses relay molecules.
3. Response- transducer signal triggers cellular response

Question 37

Ligand

Answer 37

A molecule that bonds specifically to another molecule, usually a larger one.

Question 38

G protein-coupled receptor

Answer 38

A signal receptor protein in the plasma membrane that responds to the binding of a signalling molecule by activating a G Protein. Does this by changing GDP to GTP( like ATP). Activated G protein translocates along cell membrane to an enzyme.

Question 39

Ligand-gated ion channel

Answer 39

A membrane receptor with a region that can act as a “gate” for ions when the receptor assures a certain shape.

Question 40

Intracellular receptor proteins

Answer 40

Proteins in cytoplasm or nucleus of target cells. To reach a signalling molecule they go through the membrane. Molecules do this if they are hydrophobic

Question 41

Protein kinase

Answer 41

An enzyme that transfers phosphate groups ATP to a protein.

-many relay molecules are this.

Question 42

Phosphorylation cascade

Answer 42

A series of chemical reactions during cell signaling mediated by enzymes (kinases), in which each kinase in turn phosphylates and activates another.

(Adding phosphoryl group)

Question 43

Describe the pathway of signal transduction

Answer 43

1. A relay molecule activities protein kinase 1
2. Active protein kinase activates protein kinase 2
3. Active protein kinase 2 phosphorylates a protein that brings about the cells response to the signal.
4. Protein phosphates catalyze the removal of phosphate groups from proteins, making them inactive.

Question 44

Protein phosphatases

Answer 44

Enzymes that can rapidly remove phosphate groups form proteins.

Provide mechanisms for turning off signal

Question 45

Second messengers

Answer 45

A small, non protein, water soluble molecule or ion, such as ca2+ or cyclic AMP that relays a signal to a cells interior in response to a signalling molecule bound by a single receptor protein.