Chapter 7

Question 1

Why do cells need to move substances through their membrane?

Answer 1

To bring in nutrients, oxygen, and water and to release wastes, carbon dioxide, and excess water

Question 2

What is a phospholipid?

Answer 2

A lipid made up of glycerol joined to two fatty acids and a phosphate group.

Question 3

What chemical properties of the phospholipid are important to a plasma membrane?

Answer 3

The hydrocarbon chains of the fatty acids act as non-polar, hydrophobic tails while the rest of the molecule acts as a polar, hydrophilic head.

Question 4

Why are phospholipids called amphipathic

Answer 4

They have both hydrophilic and hydrophobic parts.

Question 5

What is a plasma membrane?

Answer 5

The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition.

Question 6

Name and describe the components of a phospholipid bilayer.

Answer 6

• Contains a phosphate group and two fatty acid chains.

- The phosphate heads are polar + hydrophilic and the tails are nonpolar + hydrophobic

Question 7

How do phospholipids form the bilayer?

Answer 7

The heads face the water while the tails face each other, creating a bilayer.

Question 8

In what kind of solvent does the process of phospholipids forming a bilayer occur?

Answer 8

Occurs in water

Question 9

What’s the difference between a saturated and an unsaturated lipid?

Answer 9

Saturated lipids are solid at room temperature, while unsaturated lipids are not.

Question 10

In what way is the phospholipid bilayer “fluid”?

Answer 10

unsaturated hydrocarbon tails cannot pack closely making the membrane more fluid.

Question 11

What effect does cholesterol have on a membrane?

Answer 11

Cholesterol affects it by not allowing the phospholipids to rotate, flex or move around as efficiently.

Question 12

What is meant by selective permeability?

Answer 12

a substance which allows only certain materials to pass through it.

Question 13

What types of solutes pass easily across the lipid bilayer?

Answer 13

Small nonpolar molecules

Question 14

Which cross the lipid bilayer only to a limited extent?

Answer 14

Small uncharged polar molecules

Question 15

Which cannot cross the lipid bilayer at all?

Answer 15

Charged molecules

Question 16

Can solutes enter a cell? If so, how?

Answer 16

Yes, through transport proteins

Question 17

Osmosis

Answer 17

the diffusion (high to low concentration) of water across a selectively permeable membrane

Question 18

Diffusion

Answer 18

Movement of molecules from an area of higher concentration to an area of lower concentration.

Question 19

Concentration gradient

Answer 19

the process of particles moving through a solution from an area of higher number of particles to an area of lower number of particles.

Question 20

Equilibrium

Answer 20

A system in a steady state since forward reaction and backward reaction occur at the same rate.

Question 21

In what direction does the net movement of water occur when a cell is placed in a hypertonic solution?

Answer 21

water moves out of the cell

Question 22

In what direction does the net movement of water occur when a cell is placed in an isotonic solution?

Answer 22

no movement

Question 23

In what direction does the net movement of water occur when a cell is placed in a hypotonic solution?

Answer 23

water moves into the cell (cell could burst)

Question 24

How a hypertonic solution affects animal cells

Answer 24

it results in crenation where the shape of the cell becomes distorted and wrinkled and water leaves the cell.

Question 25

How a hypertonic solution affects plant cells

Answer 25

the water inside the cells is drawn out with osmosis causing plants to wilt.

Question 26

How a hypotonic solution affects animal cells

Answer 26

causes animal cells to swell and become bloated and they then can burst.

Question 27

How a hypotonic solution affects plant cells

Answer 27

affects plant cells by filling their cells up to full capacity.

Question 28

How an isotonic solution affects animal and plant cells

Answer 28

causes no change and cells are at equilibrium.

Question 29

Tonicity

Answer 29

The ability of a surrounding solution to cause a cell to gain or lose water.

Question 30

What role does tonicity play in osmoregulation?

Answer 30

This plays a role in osmoregulation because it has to do with whether a cell can maintain water balance.

Question 31

How is an integral protein different from a peripheral protein?

Answer 31

Integral protein

• inscribed in the bilayer
• pass through the bilayer and have domains that go from the outside to the inside of the cell

Peripheral protein

• under the phospholipid bilayer
• are only on one side of the lipid bilayer (outside or inside of cell)

Question 32

How are proteins arranged in the cell membrane?

Answer 32

Proteins are embedded inside the bilayer and loosely connected to the surface.

Question 33

Functions of membrane proteins

Answer 33

• transport
• enzymatic activity
• signal transduction
• cell-cell recognition
• intercellular joining
• attachment to the cytoskeleton and ECM

Question 34

Transport

Answer 34

Movement of chemicals into or around cell

Question 35

enzymatic activity

Answer 35

A protein built into the membrane with active site exposed

Question 36

Signal transduction

Answer 36

A mechanism linking a mechanical or chemical stimulus to a cellular response

Question 37

Cell-cell recognition

Answer 37

Some glycoproteins serve as identification tags that are specifically recognized by other cells.

Question 38

intercellular joining

Answer 38

membrane proteins of adjacent cells hook together to form various junctions

Question 39

Attachment to the cytoskeleton and the extracellular matrix (ECM)

Answer 39

helps maintain cell shape and stabilizes the location of certain proteins

Question 40

Facilitated diffusion

Answer 40

Certain proteins in the membrane asset this permitting only certain molecules to pass across the membrane. From a region with a higher concentration to a region of lower.

Question 41

How do channel proteins aid in facilitated diffusion?

Answer 41

Channel proteins have a hydrophobic channel that certain molecules that ions can use as a tunnel.

Question 42

How do carrier proteins aid in facilitated diffusion?

Answer 42

Carrier proteins bind to molecules and change shape to shuttle them across the membrane.

Question 43

What is an electrochemical gradient and why does a cell maintain it?

Answer 43

It is a combination of chemical force and strict force. The electrochemical gradient moves sodium into cell and potassium out.

Question 44

Why is maintaining an electrochemical gradient useful or important to a cell?

Answer 44

Cells use ATP to move a substance against concentration.

Question 45

Describe the process the sodium-potassium pump used to actively transport these ions across the cell membrane.

Answer 45

It is a type of active transport and generates voltage difference across a membrane. This is created by differences in the distribution of positive and negative ions across a membrane.

Question 46

Mechanisms that permit bulk transport across the cell membrane.

Answer 46

Exocytosis and endocytosis

Question 47

Exocytosis transport

Answer 47

vesicles migrate to the membrane, fuse with it, and release their contents.

Question 48

endocytosis transport

Answer 48

the cell takes in macromolecules by forming vesicles from the plasma membrane.

Question 49

three types of endocytosis

Answer 49

• Phagocytosis
• pinocytosis
• receptor-mediated endocytosis

Question 50

Phagocytosis

Answer 50

cell engulfs a particle in a vacuole

Question 51

pinocytosis

Answer 51

cell takes in extracellular fluid

Question 52

receptor-mediated endocytosis

Answer 52

ligands bond to receptor proteins and cause vesicle formation