Chapter 1: Cell Membrane

Question 1

What does a cell membrane do?

Answer 1

Maintains the contents of the cell and regulates movement of substances into and out of the cell

Question 2

What does the fluid mosaic phospholipid bilayer model suggest about cell membranes?

Answer 2

It describes them as having a double layer of lipids, a lipid bilayer, that has the ability to change shape

Question 3

What are phospholipids?

Answer 3

Is a type of lipid where the head is hydrophobic and the tail is hydrophobic; a major component of cell membranes

Question 4

What is the role of cholesterol in the cell membrane?

Answer 4

It is an essential structural component that stabilises and strengthens the membrane and maintains it at a suitable fluidity

Question 5

What is the plant version of cholesterol?

Answer 5

Phytosterol

Question 6

How are cell membranes fluid?

Answer 6

During cell division and vesicle formation, membranes can break apart and reassemble themselves

Question 7

What are the advantages of having a fluid membrane?

Answer 7

It enables cells to repair themselves before some of the cytoplasm can leak out

Question 8

What is the function of protein channels?

Answer 8

Protein channels act as a passageway that allows specific substances to move across the membrane

Question 9

What is passive movement?

Answer 9

Movement that does not require energy

Question 10

What is diffusion?

Answer 10

The passive movement of molecules from a region of high concentration to region of low concentration

Question 11

What is the concentration gradient?

Answer 11

The difference in concentration of a substance between two different regions

Question 12

What happens when an equilibrium is reached?

Answer 12

Particles will move at equal rates in all directions

Question 13

What can increase the rate of diffusion?

Answer 13

Temperature, due to the particles moving faster with higher temperatures, and increasing the concentration gradient

Question 14

What substances can easily move through a cell membrane by diffusion?

Answer 14

O2, H2O, CO2, and other small, uncharged particles

Question 15

What is facilitated diffusion?

Answer 15

A form of diffusion that requires a substance to be attached to a specific carrier molecule to move across a membrane

Question 16

What particles require facilitated diffusion?

Answer 16

Charged particles, such as sodium and potassium ions, and relatively large molecules, such as glucose and amino acids

Question 17

What two types of transport proteins are involved in facilitated diffusion?

Answer 17

Carrier proteins and channel proteins

Question 18

How to carrier proteins assist with facilitated diffusion?

Answer 18

They bind to specific molecules on one side of the membrane, change shape, and release on the other side

Question 19

How is glucose diffused into the cell?

Answer 19

Through the glucose transport protein, located in the plasma of all mammalian cell types

Question 20

What is osmosis?

Answer 20

The movement of water across a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration

Question 21

What is isotonic?

Answer 21

Fluid with an equal solute concentration to another fluid

Question 22

What is hypotonic?

Answer 22

Solution with a lower solute concentration than another solution

Question 23

What is hypertonic?

Answer 23

Solution with a higher solute concentration than another solution

Question 24

What does permeable mean?

Answer 24

Able to be passed through

Question 25

What does turgid mean?

Answer 25

Describes a cell that is tight and rigid from absorbing water

Question 26

How does a plant cell become turgid?

Answer 26

Water enters the cell through osmosis, where the water first goes to the cytoplasm and then into the vacuole, this causes the vacuole to swell and to much against the cell wall and membrane

Question 27

What is the purpose of turgor?

Answer 27

It maintains their shape and form and helps to keep them rigid, and keeps non-woody stems erect as well as keeping leaves open

Question 28

What is plasmolysis?

Answer 28

The point at which the cell membrane pulls away from the cell wall because of water loss

Question 29

What are contractile vacuoles?

Answer 29

A vacuole found in some freshwater unicellular organisms that maintains osmotic balance by collecting water and emptying it from the cell

Question 30

What is active transport?

Answer 30

The process of using energy to move a substance across a membrane from a region of low concentration to a region of higher concentration

Question 31

What is the function of the mitochondria?

Answer 31

To make energy available to the cell

Question 32

What is the energy source for active transport of most substances?

Answer 32

Adenosine Triphosphate (ATP)

Question 33

What is the sodium-potassium pump used for?

Answer 33

To create high concentrations of potassium ions but low concentrations of sodium ions in animal cells

Question 34

What is the sodium-potassium pump?

Answer 34

A membrane protein that's uses energy to transport sodium ions into cells against their concentration gradient

Question 35

What is endocytosis?

Answer 35

The movement of solids or liquids from the environment into a cell via vesicle formation

Question 36

What is the process of endocytosis?

Answer 36

The cell changes shape by sending out projections that surround the material, when the projections meet, the membrane fuses and forms a vesicle, which then stores or transports the substance within the cytoplasm

Question 37

What is phagocytosis?

Answer 37

The bulk transport of solids into a cell inside a vesicle. It is a form of endocytosis in which large particles, such as cells or cellular debris, are transported into the cell

Question 38

What is exocytosis?

Answer 38

The movement of solids or liquids from a cell to the environment via vesicle formation

Question 39

What is the process of exocytosis?

Answer 39

A membrane-bound vesicle moves to the plasma membrane, fuses with it and then releases its contents to the exterior of the cell

Question 40

What particles are able to easily pass through membranes?

Answer 40

Uncharged molecules

Question 41

What particles cannot pass the hydrophobic interior of the membrane?

Answer 41

Charged particles

Question 42

What does polar mean?

Answer 42

A molecule with an uneven distribution of charge, giving it distinct charged ends

Question 43

What is the surface-area-to-volume ration?

Answer 43

The mathematical ratio of the size of the surface area (in two dimensions) to the volume of an object (in three dimensions)

Question 44

What would be better, a big SA:V ratio or a smaller one?Why?

Answer 44

A smaller one, due to cells obtaining its nutrients and removing waste through the cell membrane, if the volume of the cell is too big compared to the SA, then the cell will not get enough nutrients