Chapter 5 - Cell Membrane and Signaling

Question 1

Why do phospholipids spontaneously form bilayer structures, while oils form small droplets?

Answer 1

Oils do not have the polar head group that phospholipids have

Question 2

What kind of membrane proteins may be associated with the phospholipid head groups of membrane proteins?

Answer 2

Peripheral membrane proteins

Question 3

In addition to the lipid bilayer and proteins, membranes may contain ____ in the form of _____ and _____

Answer 3

carbohydrates; glycoproteins; glycolipids

Question 4

In animals, cell recognition

Answer 4

involves proteins in plasma membranes

Question 5

Osmosis

Answer 5

is the movement of water across selectively permeable membranes

Question 6

If a suspension of red blood cells in an isotonic NaCl solution was suddenly diluted with pure water, by a factor of 10, the cells would

Answer 6

swell and lyse (burst)

Question 7

In facilitated diffusion

Answer 7

specific integral membrane proteins mediate transport

Question 8

The sodium potassium pump (Na+ - K+ pump)

Answer 8

results in the formation of an Na+concentration gradient across the cell membrane

Question 9

Hormones are chemical signals that

Answer 9

Travel through circulatory systems

Question 10

A universal feature of receptors is that they

Answer 10

undergo structural (shape) changes when the signal molecule is bound

Question 11

T/F

Both receptors and enzymes may be integral membrane proteins

Answer 11

True

Question 12

Chemical signal transduction pathways

Answer 12

involve binding of the signal molecule to receptors

Question 13

Caffeine

Answer 13

binds to receptors in the brain

Question 14

Adenylyl cyclase

Answer 14

makes cAMP from ATP with the liberation of pyrophosphate

Question 15

Which statement about a signal cascade is true?

Answer 15

cAMP is referred to as a “second messenger”

Question 16

The phosphorylation of proteins by ATP

Answer 16

is catalyzed by enzymes know as “protein kinases.”

Question 17

Cholesterol molecule in a membrane

Answer 17

interspersed between the phospholipid tails in the bilayer. Their presence influences the fluidity of the membrane.

Question 18

Carbohydrate associated with membranes

Answer 18

Are attached either to the lipids or to the protein molecules. Located on the outside of the plasma membrane, where they protrude into the extracellular milieu. Crucial in recognizing specific molecules.

Question 19

Non-Transmembrane integral protein

Answer 19

Integral protein that penetrates the phospholipid bilayer but does not extend all the way through it.

Question 20

Transmembrane integral protein

Answer 20

Integral protein is an integral protein that extends all the way through the phospholipid bilayer

Question 21

Cholesterol associated with membranes

Answer 21

They are interspersed between the phospholipid tails in the bilayer. Their presence influences the fluidity of the membrane.

Question 22

3 functions of membrane proteins

Answer 22

some move materials through the membrane, others are involved in intercellular recognition and adhesion, while others receive chemical signals from the cell’s external environment.

Question 23

Peripheral membrane proteins

Answer 23

lack exposed hydrophobic groups and are not embedded in the bilayer. Instead, they have polar or charged regions that interact with exposed parts of the integral membrane proteins, or with the polar heads of phospholipid molecules.
Does not extend into the phospholipid bilayer. Usually attached to integral proteins

Question 24

glycolipid

Answer 24

consists of a carbohydrate covalently bonded to a lipid

Question 25

glycoprotein

Answer 25

consists of one or more short carbohydrate chains covalently bonded to a protein. The bound carbohydrates are oligosaccharides.

Question 26

proteoglycan

Answer 26

a protein with even more carbohydrate molecules attaches to it, and the carbohydrate chains are often longer than glycoproteins

Question 27

selective permeability

Answer 27

allowing certain substances to pass through while other substances are excluded; a characteristic of membranes.

Question 28

passive transport

Answer 28

do not require direct inputs of metabolic energy
substances move from area of high concentration to area of low concentration. Substances moves down the concentration gradient

Question 29

active transport

Answer 29

require the input of metabolic energy because they involve the movement of substances against their concentration gradients. “Acting Against normal flow” (from area of low concentration to area of high concentration)

Question 30

diffusion

Answer 30

the process of random movement toward a state of equilibrium
net movement from regions of greater concentration to regions of lesser concentration

Question 31

how fast something diffuses depends on what

Answer 31

the diameter of the molecules or ions (smaller molecules diffuse faster), the temperature of the solution (higher temperatures lead to faster diffusion because the hear provides more energy for movement), and concentration gradient in the system (the greater the concentration gradient the more rapidly a substance diffuses.

Question 32

simple diffusion

Answer 32

diffusion that doesn’t involve a direct input of energy or assistance by carrier proteins
*the more lipid-soluble the molecule is, the more rapidly it diffuses through the lipid bilayer

Question 33

Hypertonic

Answer 33

solution has a higher solute concentration that the other solution (more outside of the cell than the inside of the cell)

Question 34

Isotonic

Answer 34

solutions have equal solute concentrations

Question 35

Hypotonic

Answer 35

solute has a lower solute concentration than the there solution. (more on inside than outside) Hippo Hypo Swell

Question 36

channel proteins

Answer 36

integral membrane proteins that form channels across the membrane through which certain substances can pass

Question 37

carrier proteins

Answer 37

membrane proteins that bind specific molecules and transport them through the membrane

Question 38

Facilitated diffusion

Answer 38

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

Question 39

ion channels

Answer 39

an integral membrane protein that allows ions to diffuse across the membrane in which it is embedded
all show the same basic structure of a hydrophilic pore that allows a particular ion to move through it

Question 40

Gated channels

Answer 40

a membrane protein that changes its 3D shape and therefore its ion conductance in response to a stimulus. When open, it allows specific ions to move across the membrane.

Question 41

ligand

Answer 41

Any molecule that binds to a receptor site of another (usually larger) molecule
may also be referred to as a chemical signal

Question 42

aquaporins

Answer 42

a transport protein in plant and animal cell membranes through which water passes by osmosis. Also called a water channel protein. Allows large amounts of water to move down its concentration gradient

Question 43

In eukaryotes where is ATP produced?

Answer 43

in the mitochondria and plastids

Question 44

When is ATP energy released

Answer 44

when ATP is converted to adenosine diphosphate (ADP) in a hydrolysis reaction that breaks the bond between the terminal phosphate and the rest of the molecule.

Question 45

primary active transport

Answer 45

direct hydrolysis of ATP, which provides the energy required for transport
The sodium potassium pump

Question 46

Secondary active transport

Answer 46

does not use ATP directly. Instead, its energy is supplied by an ion concentration gradient or an electrical gradient, established by primary active transport. uses the energy of ATP indirectly to set up the gradient

Question 47

Exocytosis

Answer 47

process by which materials packaged in the vesicles are secreted from the cell. Important in the secretion of many types of substances, including digestive enzymes from the pacers, neurotransmitters from neurons, and materials for the construction of the plant cell wall.

Question 48

Endocytosis

Answer 48

processes that bring small molecules, macromolecules, large particles, and even small cells into eukaryotic cells. Often depends on receptors

Question 49

Three types of endocytosis

Answer 49

Phagocytosis

pinocytosis and receptor endocytosis

Question 50

Phagocytosis

Answer 50

receptors in cell membrane recognize a specific ligand on the surface of a large particle or even an entire cell. Binding of the ligand to the receptor causes the phagocytic cell to engulf the particle or other cell.

Question 51

Pinocytosis

Answer 51

vesicles bring fluids and dissolved substances, including proteins, into the cell

Question 52

Receptor endocytosis

Answer 52

mechanism for bringing specific large molecules, recognized by specific receptors, into the cell.

Question 53

signal transduction pathway

Answer 53

the series of biochemical steps whereby a stimulus to a cell (such as a hormone or neurotransmitter binding to a receptor) is translated into a response of the cell.

Question 54

Autocrine signals

Answer 54

affect the same cell that releases them. Ex: many tumor cells reproduce uncontrollably because they self-stimulate cell division by making their own division signals

Question 55

Paracrine signals

Answer 55

diffuse to and affect near by cells. Ex: a neurotransmitter made by a nerve cell that diffuses to an adjacent cell and stimulates it

Question 56

Juxtacrine signaling

Answer 56

requires direct contact between the signaling and the responding cell, usually involves interaction between the signaling molecules bound to the surface of the two cells.

Question 57

hormones

Answer 57

chemical substance produced in minute amounts by endocrine cells and transported in the blood to distant target cells, where it exerts regulatory influences on their function

Question 58

allosteric regulation

Answer 58

regulation of the activity of a protein (usually an enzyme) by the binding of an effector molecule to a site other than the active site.

Question 59

intracellular receptors

Answer 59

located inside the cell. small or non polar ligands can diffuse across the phospholipid biceps. Acetylcholine layer of the cell membrane and enter the cell. Ex: estrogen is a lipid soluble steroid hormone that can easily diffuse across the cell membrane; it binds to receptor inside the cell.

Question 60

membrane receptors

Answer 60

located on the cell surface. Large or polar ligands cannot cross the lipid bilayer. Ex: insulin, is a protein hormone

Question 61

protein kinase receptors

Answer 61

change shape upon ligand binding. modifies specific target proteins in the cell by adding phosphate groups to them.
not all protein kinases are receptors

Question 62

example of a protein kinase receptor

Answer 62

receptor for the hormone insulin

Question 63

G-protein linked receptors

Answer 63

ligand binding on the extracellular domain of the receptor exposes a site on the cytoplasmic side that can bind to a mobile membrane protein called a G protein.
partially inserted in the lipid bilayer and partially exposed on the cytoplasmic surface of the membrane.

Question 64

Glycogen phosphorylase

Answer 64

Activated when an animal faces life-threatening conditions and needs energy fast for the fight-or-flight response. Catalyzes the breakdown of glycogen stored in the liver so that the resulting glucose molecules can be released to the blood.

Question 65

second messengers

Answer 65

do not have enzymatic activity themselves instead they act to regulate target enzymes by binding to them noncovalently. allow a cell to respond to a single event at the cell membrane with many events inside the cell (aka it distributes the initial signal)
Also serve to amplify the signal.

Question 66

inhibition

Answer 66

glcogen synthase, catalyzes the joining of glucose molecules to form the energy-storing molecule glycogen, is inactivated when a phosphate group is added to it by protein kinase A. Thus the epinephrine signal prevents glucose from being stored in glycogen.

Question 67

Activation

Answer 67

Phosphorylase kinase is activated when a phosphate group is added to it. It is part of the cascade of reactions that ultimately leads to the activation of glycogen phosphorylase, another key enzyme in glucose metabolism. This enzyme results in the liberation of glucose molecules from glycogen.