Plasma Membrane & Organelles

Question 1

What is the primary function of the plasma membrane?

Answer 1

Controls movement of substances in and out of the cell

The plasma membrane is a semi-permeable barrier that allows passage of oxygen, nutrients, and waste.

Question 2

What limits the maximum size of a cell?

Answer 2

Interaction with the environment

A small cell has a greater surface to volume ratio than a larger cell.

Question 3

What is the structure of the plasma membrane?

Answer 3

Double layer of phospholipids with various embedded or attached proteins

Question 4

What characterizes saturated fats in the plasma membrane?

Answer 4

Packed tightly together, less fluidity

Question 5

What is the effect of high temperatures on membrane fluidity?

Answer 5

Increases fluidity

Question 6

What role does cholesterol play in the plasma membrane?

Answer 6

Stabilizes membrane fluidity

Question 7

What is the function of membrane proteins?

Answer 7

Determine function of the membrane

Thousands of membrane proteins have been identified and classified, often specific to a cell type.

Question 8

What are glycoproteins involved in?

Answer 8

Cell recognition

Question 9

What is the role of proteins in intercellular joining?

Answer 9

Form long-lasting connections between cells

Question 10

What allows a cell to connect with the extracellular matrix?

Answer 10

Linking Cytoskeleton & Extracellular Matrix

Question 11

What types of transport are involved in membrane transport?

Answer 11

Passive and active transport

Question 12

What factors influence how substances move across membranes?

Answer 12

What the molecules are, how big the substances are, how much is moving at once

Question 13

What is bulk transport?

Answer 13

Transport of large substances/large volumes

Question 14

What is diffusion?

Answer 14

Movement of molecules down their concentration gradient without energy

Question 15

What is facilitated diffusion?

Answer 15

Movement of hydrophilic molecules via membrane proteins called channels and carriers

Question 16

What is osmosis?

Answer 16

Movement of water from high water (low solute) concentration to low water (high solute) concentration

Question 17

What is required for active transport?

Answer 17

Transport proteins that use energy (ATP)

Question 18

What does active transport allow a cell to do?

Answer 18

Have an internal concentration of a substance that is different from its surroundings

Question 19

What is an example of active transport?

Answer 19

Sodium-potassium pump

Question 21

What is co-transport?

Answer 21

Co-transport is a form of indirect active transport where one substance is pumped across the membrane, and its concentration gradient is used to power the movement of a second substance against its concentration gradient.

Question 22

What are organelles?

Answer 22

Organelles are specialized compartments within a cell that provide special conditions for specific processes, keep incompatible processes apart, allow specific substances to be concentrated, form concentration gradients, and package substances for transport or export.

Question 23

What is the structure of cellular organelles?

Answer 23

Cellular organelles are bounded by membranes, each providing its own special conditions. Examples include the endoplasmic reticulum, lysosomes, mitochondria (two membranes), and the nucleus (nuclear envelope - two membranes).

Question 24

What is the composition of cellular membranes?

Answer 24

All cellular membranes are composed of a phospholipid bilayer.

Question 25

What is the nature of the plasma membrane?

Answer 25

Cells are bounded by a semi-permeable membrane that is dynamic and contains many proteins with key functions.

Question 26

What is necessary for membrane transport?

Answer 26

Membrane transport is necessary to move substances across the plasma membrane, and different molecules require different mechanisms.

Question 27

What are the key functions of membrane proteins?

Answer 27

Membrane proteins have key functions in facilitating transport and communication across the plasma membrane.

Question 28

What is the difference between passive and active transport?

Answer 28

Passive transport does not require energy and moves substances along their concentration gradient, while active transport requires energy to move substances against their concentration gradient.

Question 29

What sort of molecules can passively diffuse across the plasma membrane?

Answer 29

Small, nonpolar molecules can passively diffuse across the plasma membrane.

Question 30

What happens during co-transport of molecules?

Answer 30

During co-transport, the movement of one substance down its concentration gradient powers the movement of another substance against its concentration gradient.

Question 31

What should you be able to describe after revising this lecture?

Answer 31

You should be able to describe the structure of the plasma membrane and outline its importance to cell function.

Question 32

What should you outline regarding membrane proteins?

Answer 32

You should outline the role of membrane proteins.

Question 33

What mechanisms should you outline for substances crossing the plasma membrane?

Answer 33

You should outline mechanisms such as passive transport, active transport, and co-transport.

Question 34

What is the importance of organelles and sub-cellular compartments?

Answer 34

You should outline the importance of organelles and sub-cellular compartments.

Question 35

What should you identify in eukaryotic cells?

Answer 35

You should identify some of the key organelles in eukaryotic cells.