Chapter 3 Cells: The Living Units

Question 1

Describe the Fluid Mosaic Model?

Answer 1

The cell membrane is dynamic. The membrane is made of a phospholipid bilayer with proteins randomly embeded in it. The membrane is more fluid than solid.

Question 2

What components is the cell membrane made up of and what is their purpose?

Answer 2

• Phospholipid Bilayer: Form basic structure of the cell and hydrophobic (non-polar) tails prevent water soluble substances from crossing.
• cholesterol: Stiffens the membrane and further decreases water solubility.
• proteins: Determine functions of membrane, transport, communication,.
• carbohydrates: Idenity molecules that form a coating called the* glycocalyx*

Question 2

What substances move easily across the cell membrane?

Answer 2

Lipid soluble molecues.

Question 3

What is the glycocalyx?

Answer 3

Carbohydrates attached to the protein (glycoproteins) or lipids (glycolipids) ouside of the cell membrane. The primary function is to act as an identifer in cell to cell communication. Especially important when interacting with immune cells.

Question 4

Role of Mitochondria?

Answer 4

ATP Synthesis

Question 5

Role of Ribosomes?

Answer 5

Protein synthesis. Ribosomes can be free floating in the cytoplasm or bound.

Question 6

Role of the Rough Endoplasmic Reticulum?

Answer 6

Takes proteins made from bound ribosomes and processes them to secondary, tertiary stages. Proteins are then transported to thje golgi apparatus via vesicles.

Question 7

What is the role of the smooth endoplasmic reticulum?

Answer 7

Site of lipid and carbohydrate systhesis and stores calcium.

Question 8

What is the role of the golgi apparatus?

Answer 8

Further processes, packages, and stores proteins before secretion to the cell membrane via vesicles.

Question 9

Role of the cell nucleus?

Answer 9

Control center of the cell, responsible for transmitting genetic information and providing instructions for protein synthesis.

Question 10

What are the three membrane junctions and their roles?

Answer 10

• Tight Juctions: Impermeable junctions that form continous seals preventing molecules from passing between cells.
• Desmosomes: Anchoring juctions that bind adjacent cells together similar to velcro.
• Gap Junctions: Channels between cells that allow ions and small molecules through. Important for communication between cells.

Question 11

What are passive transport processes across the plasma membrane?

Answer 11

• Simple Diffusion: Something is moving from an area of high concentration to low concentration down a concentration gradient.
• Facilitated Diffusion: Something is helped across the plasma membrane. Examples are carrier-mediated diffusion and channel-mediated diffusion.
• Osmosis: Diffusion of water accross a semi-permeable membrane.

Question 12

What does it mean when it is stated that the plasma membrane is selectively permerable.?

Answer 12

This means that the membrane selects what comes into or leaves the cell.

Question 13

What is carrier-mediated facilitated diffusion?

Answer 13

A carrier helps something move accross the bilayer from an area of high concentraion to an area of low concentration. These arte usaually polar, water soluble, and hydrophilic.

Question 14

What is channel-mediated facilited diffusion?

Answer 14

Usually used for ions, a channel will only let specific ions through the bilayer.

Question 15

What are active transport processes accross the cell membrane?

Answer 15

• Primary: A process that moves molecules aganist their concentraion gradient at the cost of ATP.
• Seconday: A process that moves molecules against their concentration gradent as a result of primary active transport.
• Example: Na+/K+ pump (primary), where 3 Na+ are moved out of the cell, two K+ are moved into the cell at the cost of 1 ATP. Once Na+ is outside the cell it diffuses back accross the membrane through a cotransporter protein. Duing this process it drives glucose aganist its gradient into the cell (secondary).

Question 16

What are the two types of vesicular transport and their function?

Answer 16

• Exocylosis: The secretion of a substance out of a cell by way of a vesicle.
• Endocytosis: Something is entering the cell by way of of a vesicle.

Question 16

What is the difference between passive and active transport processes?

Answer 16

Passive processes move molecules down their concentration gradient without using ATP, while passive moves molecules against their concentration gradient at the cost of ATP.

Question 17

What are the three types of endocytosis and their function?

Answer 17

• Phagocytosis: The bilayer engulfs a large particle.
• Bulk-Phase Endocytosis/Pinocytosis: Non-specific, internalizes anything.
• Receptor-Mediated Endocytosis: Something must bind with a specific receptor to be let into the cell.

Question 18

What is resting membrane potential?

Answer 18

The electrical difference in potential across a cell’s membrane when the cell in not actively sending signals. Inside the cell in generally negative compare to outside the cell which is positive.

Question 19

What is the cytoplasm?

Answer 19

The area between the cell membrane and necular membrane.

Question 20

What is the role of peroxisomes?

Answer 20

These are membranous sacks containing emzymes that detoxify a number of different substances.

Question 21

What is the role of lysosomes?

Answer 21

These are membranous sacks containing acid and are the sites of intracellular digestion.

Question 22

What is the role of microtubules?

Answer 22

Support the cell and give it shape. Involved in intracellular and cellular movement.

Question 23

What is the role of intermediate filaments?

Answer 23

Stable cytoskeleton elements that resist mechanical forces acting on the cell.

Question 24

What is the role of microfilaments?

Answer 24

Involved in muscle contraction and other types of intracellular movement. Also help form the cells cytoskeleton.

Question 25

What is the role of centrioles?

Answer 25

Organize the microtubule network. Involved in mitosis and form the bases of cilla and flagella.

Question 26

What is the role of the nuclear envelope?

Answer 26

Seperates the nucleoplasm from the cytoplasm and regulates the movement of substances into and out of the nucleus.

Question 27

What is the role of the Nucleolus?

Answer 27

The site of ribosome subunit manufacture.

Question 28

What is osmolarity?

Answer 28

The concentration of a solute expressed as the total number of solute particles per liter.

Question 29

What is an isotonic solution and what happens when a cell is placed in it?

Answer 29

An isotonic solution is when the solute concentration is the same inside and outside the cell. The cell will retain its orginal shape as then is no net flow of water into or out of the cell.

Question 30

What is a hypotonic solution and what happens to a cell placed in it?

Answer 30

The concentration of solute is greater inside the cell than outide, resulting in the osmosis of water into the cell. The cell will swell and possibly burst.

Question 31

What is a hypertonic solution and what happens to a cell placed in it?

Answer 31

The concentration of solute is greater outside the cell than inside. This will result in a net loss of water out of the cell. The cell will shrink and lose function.