Week 1 - Chapter 3

Question 1

What unit is used to measure cells?

Answer 1

Micrometers

Question 2

What is a differentiated cell?

Answer 2

A cell that has developed specialized characteristics (e.g. muscle cells, nerve cells, epithelial cells, etc…)

Question 3

What cell shows the components found in most cells?

Answer 3

A Composite Cell

Question 4

What are the 3 Major Parts of a Cell?

Answer 4

Nucleus (genetic material/directs cell activities), Cytoplasm (Organelles with specific functions, suspended in a liquid called Cytosol), and Cell Membrane

Question 5

What is a Cell Membrane and what does it do?

Answer 5

It is the outer boundary of the cell.
It maintains the integrity of the cell.
It separates intracellular fluid (cytosol) from extracellular fluid.

Question 6

What does it mean to be Selectively Permeable?

Answer 6

There is a regulation of entry and exit of substances for the cell.

Question 7

What is Signal Transduction?

Answer 7

Permits the cell to receive and respond to messages.

Question 8

What is the cell membrane comprised of?

Answer 8

Mainly of lipids and proteins, with some carbohydrates.

Question 9

What is a Phospholipid Bilayer?

Answer 9

Cell membrane framework comprised of…

Water-Soluble (Hydrophillic) heads forming the surface,
Water-Insoluble (Hydrophobic) heads forming the interior,
Bilayer which is permeable to lipid-soluble substances BUT not water-soluble substances.

Question 10

What is Cholesterol used for in cells?

Answer 10

It stabilizes the membrane which helps keep it impermeable to water-soluble substances.

Question 11

Some lipids and proteins that can move have what properties?

Answer 11

Fluid Mosaic

Question 12

Membrane proteins have what functions?

Answer 12

Pores, Channels, Receptors, Enzymes, Cell Contact/Identification, CAMS (Cell Adhesion Molecules)

Question 13

What are Carbohydrates used for in the cell?

Answer 13

Cell recognition and interaction, self markers.

Question 14

What are Receptors used for?

Answer 14

Responding to extracellular signals.

Question 15

What are Pores, Channels, and Carriers used for?

Answer 15

Transporting small molecules and ions; transduce signals.

Question 16

What are Enzymes used for?

Answer 16

Catalyzing (speeding up) chemical reactions.

Question 17

What are Cell Surface Proteins used for?

Answer 17

To establish “self” or help in identifying itself to other cells.

Question 18

What are *CAMs (Cell Adhesion Molecules)** used for?

Answer 18

Enabling cells to stick to one another.

Question 19

CLINICAL APPLICATION EXAMPLE

Mutations in Na+ Channels can cause an inability to feel what?

Answer 19

Pain or extreme pain conditions.

Question 20

CLINICAL APPLICATION EXAMPLE

Mutations in K+ Channels can disrupt what?

Answer 20

Electrical activity of the heart which can disturb the heart rhythm, and/or impair hearing.

Question 21

CLINICAL APPLICATION EXAMPLE

Abnormal Cl- Channels are the cause of what?

Answer 21

Cystic Fibrosis which causes the production of thick mucus, causing difficulty breathing, clogged pancreas, or salty sweat.

Question 22

What is Cytoplasm?

Answer 22

A network of membranes and organelles that are suspended in Cytosol.

Cytosol - Fluid portion of the cytoplasm
Organelles - Tiny solid structures with specific functions in the cell

Question 23

The Cytoskeleton can be found in the Cytoplasm and is…

Answer 23

A supporting framework of protein rods and tubules.

Question 24

What are some Physical (Passive) Mechanisms and what does this mean?

Answer 24

Diffusion, Osmosis, Facilitated Diffusion, and Filtration.

This means that they do not require any cellular energy (ATP).

Question 25

What is **Diffusion**?

Answer 25

*The movement of atoms, molecules, or ions from a region of higher concentration to a region of lower concentration until equilibrium is achieved.* Occurs due to constant motion of atoms, molecules, and ions. Only involves substances that the cell membrane is permeable to: oxygen, carbon dioxide, and other lipid-soluble substances. Example: Sugar cube dissolving in water.

Question 26

What is **Facilitated Diffusion**?

Answer 26

Diffusion specifically across the cell membrane *through ion channels or transporters*. Used for substances (not-lipid soluble) that cannot diffuse across the permeable membrane but are still required for function. Water-soluble substances include Na+, K+, Cl-, glucose, or amino acids). No ATP required.

Question 27

What is **Osmosis** or “diffusion of water”?

Answer 27

Movement of water across a selectively permeable membrane from a region of higher water concentration to lower. Typical if one region has higher solute concentration than another (high levels of sodium in solution will draw water towards it). Water moves through **Aquaporins** (water channels). No ATP required.

Question 28

What is **Osmotic Pressure**?

Answer 28

The ability of osmosis to generate pressure to lift a volume of water. This pressure increases as the concentration of impermeant solutes increases in solution. Water moves towards higher osmotic pressure.

Question 29

What is **Tonicity**?

Answer 29

Ability of a solution outside the cell to alter water volume inside the cell.

Question 30

What are the 3 types of **Tonicity** related solutions?

Answer 30

1. **Isotonic Solution** - Same osmotic pressure, cells have *no net gain or loss* of water. 2. **Hypertonic Solution** - Higher osmotic pressure, cells in this solution will *lose* water. 3. **Hypotonic Solution** - Lower osmotic pressure, cells in this solution will *gain* water.

Question 31

What is **Filtration**?

Answer 31

Process that forces molecules through membranes by exerting pressure. Used to separate solids from water, or small particles from large particles. No ATP required.

Question 32

What are the 4 **Active Mechanisms** and what does it mean in relation to energy requirements?

Answer 32

**Active Transport** **Endocytosis** **Exocytosis** **Transcytosis** Required ATP to move substances across cell membranes.

Question 33

What is **Active Transport**?

Answer 33

Movement of substances across a membrane from lower concentration to higher concentration (against the gradient). Uses carrier molecules known as *pumps*. Examples: Sugars, Amino Acids, Ca+2, H+, Na+/K+ Pump. Requires ATP.

Question 34

What is **Secondary Active Transport**?

Answer 34

A carrier protein that uses a Na+ gradient to transport another substance across a cell membrane. No ATP required.

Question 35

What is **Endocytosis** and what are the 3 types?

Answer 35

Movement of a substance into the cell inside a vesicle. Used for substances that are too large to enter through other methods. 1. **Pinocytosis** - Membrane engulfing droplets of liquid. 2. **Phagocytosis** - Membrane engulfing solid particles. 3. **Receptor-Mediated Endocytosis** - Membrane engulfing specific substances, which have bound to receptor proteins onto the membrane.

Question 36

What is **Exocytosis**?

Answer 36

Release of substances/particles from the cell. The vesicle containing the particles re-fuses back into the membrane which releases the contents.

Question 37

What is **Transcytosis**

Answer 37

Involves receptor-mediated endocytosis followed exocytosis. Quickly transports substances from one end of the cell to the other. Moves substances across barriers formed by tightly concentrated cells. Example: Transport of HIV across lining of anus or vagina.