Chapter 5: Membranes: The Interface Between Cells and Their Environment

Question 1

What are the 2 primary components that make up membranes?

Answer 1

phospholipids and proteins

Question 2

What is the key feature of the phospholipid bilayer ?

Answer 2

It’s amphipathic; hydrophilic heads face outward and hydrophobic tails face inward

Question 3

TRUE OR FALSE: Lipids and proteins work against each other

Answer 3

FALSE, lipid and proteins work together to carry out various functions in a cell.

Question 4

What is the main characteristic of a TRANSMEMBRANE PROTEIN?

Answer 4

A transmembrane protein spans to both layers (leaflets) of the phospholipid bilayer

Question 5

Where is a lipid-anchored protein located ?

Answer 5

They are located in HYDROPHOBIC areas of the membrane; the amino acid of the protein is covalently attached to a lipid

Question 6

Where are peripheral membrane proteins located ?

Answer 6

They are either non-covalently bonded to parts of other proteins or located in the hydrophilic(polar) regions of the phospholipid bilayer.

Question 7

What are the two integral proteins ?

Answer 7

Transmembrane proteins and lipid-anchored proteins; they are integrated into a hydrophobic region of the phospholipid bilayer.

Question 8

Is the structure of a membrane fluid?

Answer 8

It’s semifluid; lipids and proteins can move in 2 dimensions within the plane of the membrane

Question 9

How does the length of non polar tails affect the fluidity of a membrane?

Answer 9

The shorter the tail, the less likely they are to interact thus creating a more fluid membrane

Question 10

How does the presence of double bonds effect fluidity ?

Answer 10

Double bonds prevent phospholipids from packing tightly, making it more fluid.

Question 11

Define SELECTIVE PERMEABILITY

Answer 11

Membranes allow some molecules and ions to pass but not all; allows cells to maintain a favorable internal environment.

Question 12

How does simple diffusion move ?

Answer 12

down the gradient WITHOUT the use of a transport protein

Question 13

How does facilitated diffusion move?

Answer 13

Down the gradient WITH the use of a transport protein

Question 14

What makes active transport different from simple and facilitated diffusion ?

Answer 14

Substances move AGAINST the gradient, WITH aid of a transport protein AND requires energy

Question 15

When is a gradient present?

Answer 15

When concentration solute is uneven from one side to the other.

Question 16

Why do cells have gradients ?

Answer 16

to maintain internal and external environment

Question 17

What is a solution called when it has the SAME concentration on both sides of the membrane ?

Answer 17

ISOTONIC

Question 18

What is a solution called when it has HIGHER concentration on the outside than the inside of the membrane ?

Answer 18

HYPERTONIC

Question 19

What kind of solution has LOWER concentration on the outside of the membrane ?

Answer 19

HYPOTONIC

Question 20

What is the term for water diffusion across a membrane from high to low?

Answer 20

Osmosis

Question 21

What are the two types of passageways for cells to interact ?

Answer 21

Channels and Transporters

Question 22

What is the difference between channels and transporters ?

Answer 22

Transporters have specific binding sites for ions, and they go through structural changes.

Question 23

What is the difference between PRIMARY active transport and SECONDARY active transport?

Answer 23

Primary active transport directly uses ATP while secondary uses stored ATP

Question 24

What is the function of a gap junction? What about plasmodesmata?

Answer 24

Gap junctions (in animal cells) provide passageways for intercellular transport; plasmodesmata (in place cells) are channels that connect the cytoplasm of adjacent cells

Question 25

An animal cell is placed in pure water (which contains no solutes). In what direction will water move?

Answer 25

Water will move into the cell from the outside because water moves from areas of high free water concentration to areas of lower water concentration.

Question 26

What is this an image of? Label 1-9.

Answer 26

This is a close up of a phospholipid bilayer. 1) integral membrane protein, 2) glycoprotein, 3) glycolipid, 4) carbohydrate, 5) phospholipid bilayer, 6) extracellular leaflet, 7) cytosolic leaflet, 8) cholesterol, 9) peripheral membrane proteins

Question 27

T or F: The two leaflets of a lipid bilayer are formed because the non polar phospholipid tails can interact with the polar interior and the exterior of the cell.

Answer 27

FALSE; the POLAR head groups of the phospholipids can interact with the polar interior and exterior of the cell

Question 28

What is this an image of? Label 1-4.

Answer 28

This is a close up of the phospholipid bilayer. 1) transmembrane protein, 2) lipid, 3) lipid-anchored protein, 4) peripheral membrane protein

Question 29

Cellular membranes play a role in which cell functions?

Answer 29

1) cell and nuclear division 2) cell signaling 3) anchoring the cytoskeleton 4) protein sorting

Question 30

What are the three molecular components of cellular membranes?

Answer 30

carbohydrates, phospholipids, and proteins

Question 31

The cell membrane is referred to as a mosaic because it is a mixture of what types of molecules?

Answer 31

carbohydrates, lipids, and proteins

Question 32

Define exocytosis.

Answer 32

The process by which cells move materials from within the cell into the extracellular fluid, via vesicles

Question 33

What are the three biochemical properties of phospholipids that affect fluidity?

Answer 33

1) length of non-polar tails 2) presence of double bonds 3) presence of cholesterol (in animal cells)

Question 34

What is one way that solutes that cannot diffused across the membrane can still gain access to the interior of the cell?

Answer 34

transport proteins

Question 35

This is a close up of the phospholipid bilayer in the cell membrane. Label 1-5.

Answer 35

1) fiber in the ECM, 2) plasma membrane, 3) cytoskeletal filament, 4) linker protein, 5) transmembrane protein

Question 36

This is an image of three different types of diffusion. Label them, left to right.

Answer 36

Left: simple diffusion Middle: facilitated diffusion Right: active transport

Question 37

The ability of solutes to cross the bilayer by simple diffusion depends on what?

Answer 37

size (small diffuse faster than large), polarity (non polar diffuses faster than polar), and charge (non-charged diffuse faster than charged)

Question 38

Passive transport is energetically ______ and tends to _______ the magnitude of a pre-existing gradient.

Answer 38

favorable; decrease

Question 39

The primary difference between endocytosis and exocytosis is?

Answer 39

the direction of transport

Question 40

Label a-c.

Answer 40

a) isotonic b) hypertonic c) hypotonic

Question 41

This is an image of different types of transporters. Label a-c.

Answer 41

a) uniporter b) symporter c) antiporter

Question 42

This is an image of two types of active transport. Label them.

Answer 42

a) primary active transport b) secondary active transport

Question 43

There are four different types of anchoring junctions. This is an image of all four. Label a-d. Label 1-4.

Answer 43

a) adherens junctions b) desmosomes c) hemidesmosomes d) focal adhesions 1) cadherins 2) intermediate filaments 3) linker proteins 4) actin filament

Question 44

What is the function of an anchoring junction? What about a tight junction?

Answer 44

anchoring junctions link cells to each other and to the ECM; tight junctions form a tight seal between cells and prevent material from leaking between adjacent cells

Question 45

1) Materials inside the cell are packaged into vesicles and excreted to the extracellular environment. 2)The plasma membrane invaginates to form a vesicle that brings substances into the cell. Name these two processes.

Answer 45

1) exocytosis 2) endocytosis

Question 46

During osmosis, what direction does water move across a plasma membrane?

Answer 46

Toward the side with a hypertonic concentration of solutes.

Question 47

The sodium-potassium pump functions to pump?

Answer 47

sodium ions out of the cell and potassium ions into the cell