slide 7

Question 1

Cell membranes are selectively

permeable

Answer 1

– they allow some
substances to cross more easily
than other substances.

Question 2

Although only two phospholipid

molecules thick the cell membrane

Answer 2

regulates all differences between
the internal and external
environments.

Question 3

Relative to the size of other macromolecule

Answer 3

structures of critical

importance, the thickness of the phospholipid bilayer is very small.

Question 4

An amphipathic

Answer 4

molecule is one that has both

a hydrophilic region and a hydrophobic region

Question 5

fluid mosaic

Answer 5

The phospholipids and
proteins comprise a
fluid mosaic

Question 6

Freeze-fracture preparation of cell plasma

Answer 6

membranes for electron microscopy confirms that

the proteins are imbedded in the membrane

Question 7

A membrane is a complex collage

Answer 7

of different proteins
embedded in the lipid bilayer and connected to both the
cytoplasm and extracellular matrix

Question 8

The membrane is held together primarily by hydrophobic

interactions

Answer 8

• phospholipid molecules can move within it

Question 9

Proteins can

Answer 9

also move within the phospholipid bilayer

Question 10

Tracking of proteins in the cell membranes

Answer 10

of a mouse cell
and a human cell after experimental fusion of these cells
demonstrates the movement of proteins in the membranes.

Question 11

The fluidity of membranes changes with:

Answer 11

• Temperature
• Structure of phospholipid tails
• Cholesterol

Question 12

Phospholipids form the main
structure of the cell membrane
but the proteins determine
most of its functions.

Answer 12

Peripheral proteins are those
that are bound only to one
surface of the membrane

Question 13

(a) Transport

Answer 13

Proteins that span the
membrane can provide
passage for hydrophilic
molecules.
Some proteins actively pump
substances from one side of
the membrane to the other.

Question 14

Water is critical for cells -

Answer 14

• but water does not pass easily

through biological membranes.

Question 15

Aquaporins are transmembrane proteins

Answer 15

through which

water can pass the hydrophobic region of the membrane

Question 16

(b) Enzymatic Activity

Answer 16

Enzymes can exist embedded
in the membrane where they
act upon substances in the
adjacent solution.

Question 17

(c) Signal Transduction

Answer 17

Some transmembrane
proteins change shape when
they bind specific substances
such as hormones.
This change in shape can
relay a chemical message to
the inside of the cell by
binding to a cytoplasmic
protein.

Question 18

(d) Cell Recognition

Answer 18

Some glycoproteins serve a
identification tags that are
specifically recognized by
membrane proteins of other
cells.

Question 19

(e) Intercellular Joining

Answer 19

Membrane proteins play a
role in forming connections
between cells. Gap junctions
and tight junctions are
established through proteins.

Question 20

Attachment to ECM

Answer 20

Elements of the cytoskeleton
can be bound to membrane
proteins to stabilize their
position.
Membrane proteins can bind
to the extracellular matrix to
stabilize the position of cells
and coordinate cellular
changes.

Question 21

An emergent property derived

Answer 21

from the organization of
molecules in the endomembrane system is the ability to
regulate transport into, within, and out of the cell.

Question 22

How do substances cross

the plasma membrane?

Answer 22

It depends on the
chemistry of the
molecules.

Question 23

Hydrophobic molecules are lipid soluble and

pass through the phospholipid bilayer rapidly.

Answer 23

Polar molecules do not pass through the

phosholipid bilayer rapidly.

Question 24

Passive transport is

Answer 24

movement of a substance

across a membrane with no energy investment

Question 25

Active transport

Answer 25

uses energy to move | substances across a membrane

Question 26

Cell membranes use both methods

Answer 26

passive transport | active transport

Question 27

Cell membranes use both methods

Answer 27

passive transport | active transport

Question 28

diffusion.

Answer 28

The passive movement of molecules from where they are more concentrated to where they are less concentrated is called diffusion.

Question 29

concentration gradient

Answer 29

This is movement down a concentration gradient

Question 30

In the process of osmosis

Answer 30

``` water moves across a membrane from where it is more concentrated (relative to hydrophilic solutes) to where it is less concentrated. ```

Question 31

In the process of osmosis

Answer 31

``` water moves across a membrane from where it is more concentrated (relative to hydrophilic solutes) to where it is less concentrated. ```

Question 32

Hypotonic solution:

Answer 32

solutes are less concentrated in the solution than in cell

Question 33

Isotonic solution

Answer 33

solutes have the same concentration inside and outside cell

Question 34

Hypertonic solution:

Answer 34

solutes are more concentrated in the solution than in cell

Question 35

facilitated diffusion.

Answer 35

Movement of solutes down their concentration gradient through transmembrane proteins

Question 36

Channel proteins

Answer 36

provide | corridors in the membrane

Question 37

Carrier proteins

Answer 37

undergo | shape change to pass solutes

Question 38

The nonpolar center of the cell | membrane impedes

Answer 38

passage of | polar molecules and atoms.

Question 39

Active transport

Answer 39

is the use of energy to move solutes against their concentration gradients

Question 40

ATP Powers Cell Activity

Answer 40

``` Energy can be transferred within a cell through formation and breaking of highenergy bonds between phosphate groups. ```

Question 41

An ion

Answer 41

is an atom or group of atoms that has gained or lost | one or more electrons and thereby acquired a charge.

Question 42

A membrane potential

Answer 42

is the unequal distribution of ions | across a membrane that establishes an electrical voltage.

Question 43

electrochemical gradient

Answer 43

The combined forces of the concentration gradient and the | membrane potential is the electrochemical gradient.

Question 44

A proton pump

Answer 44

is a transmembrane protein that moves H+ out of the cell by active transport to build up an electrochemical gradient of H+ across the membrane.

Question 45

In cotransport

Answer 45

the movement of ions down their electrochemical gradient can power the movement of another substance up its gradient.

Question 46

Bulk Transport

Answer 46

Very large molecules (e.g. proteins or polysaccharides) cannot cross the membrane via transport proteins but must be transported within vesicles

Question 47

Bulk transport across the plasma

Answer 47

membrane occurs by | exocytosis (out of the cell) and endocytosis (in to the cell).

Question 48

Exocytosis

Answer 48

``` In exocytosis transport vesicles migrate to the plasma membrane, fuse with it, and release their contents ```

Question 49

Endocytosis

Answer 49

In endocytosis the cell takes in macromolecules by | forming new vesicles from the plasma membrane

Question 50

Three types of endocytosis are used

Answer 50

1. phagocytosis 2. pinocytosis 3. receptor-mediated endocytosis

Question 51

In phagocytosis a cell | engulfs a particle by

Answer 51

wrapping pseudopodia around it and pulling it into a space enclosed by phospholipid bilayer.

Question 52

Pinocytosis

Answer 52

Pinocytosis is the transport of extracellular fluid into the cell by formation of vesicles.

Question 53

Receptor-Mediated Endocytosis

Answer 53

Receptors on the extracellular side of the membrane can | bind specific molecules to be transported into vesicles.