Chapter 3: The Cellular level - PART 1

Question 1

define cells

Answer 1

—living structural and functional units enclosed by a membrane

Question 2

define cell biology

Answer 2

the study of cellular structure and function.

Question 3

What are the 3 main components of a cell

Answer 3

1) plasma membrane: cell’s outer surface, separating the cell’s internal from the external environment. It is a selective barrier that regulates the flow of materials into and out of a cell
2) cytoplasm: all the cellular contents between the plasma membrane and the nucleus
3) nucleus: large organelle that houses most of a cell’s DNA

Question 4

What are the two components of the cytoplasm

Answer 4

1) cytosol

2) organelles

Question 5

what is a chromosome

Answer 5

inside the nucleus a single molecule of DNA associated with several proteins, contains thousands of hereditary units called genes that control most aspects of cellular structure and function.

Question 6

What is the plasma membrane?

Answer 6

a flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell, is best described by using a structural model called the fluid mosaic model

Question 7

What is the lipid bilayer

It is made of what 3 lipid molecules?

Answer 7

two back-to-back layers made up of three types of lipid molecules—1) phospholipids: contain phosphoru

2) cholesterol: a steroid with an attached -OH (hydroxyl) group
3) glycolipids: lipids with attached carbohydrate groups.

Question 8

how does the bilayer arrangement occur?

Answer 8

b/c lipids are amphipathic (have polar and non polar parts)

*** phosphate-containing “head,” hydrophilic, nonpolartwo long fatty acid “tails,” which are hydrophobic

Question 9

define integral protein, and transmembrane protein

Answer 9

integral: extend into or through the lipid bilayer among the fatty acid tails and are firmly embedded in it (they are also amphipathic)
* * most integral proteins are transmembrane proteins ( span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid.)

Question 10

Define peripheral protein and glycoprotein

Answer 10

peripheral: not as firmly embedded in the membrane. They are attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane
most peripheral proteins are glycoproteins (with carbo- hydrate groups attached to the ends that protrude into the extra- cellular fluid)

Question 11

what are the 5 functions of integral membrane proteins?

Answer 11

1) form (selective) ion channels that specific ions, such as potassium ions (K+), can flow through to get into or out of the cell
2) act as carriers, selectively moving a polar substance or ion from one side of the membrane to the other
3) receptors (cellular recognition sites) which binds a specific type of molecule (called a ligand)
4) enzymes that catalyze specific chemical reactions at the inside or outside surface of the cell
5) s linkers that anchor proteins in the plasma membranes of neighbouring cells to one another or to protein filaments inside and outside the cell.

Question 12

What do peripheral proteins serve as

Answer 12

enzymes and linkers

Question 13

Membrane glycoproteins and glycolipids often serve as _______. which enable a cell to… (2 things)

Answer 13

cell- identity markers.
They may enable a cell to (1) recognize other cells of the same kind during tissue formation or (2) recognize and respond to potentially dangerous foreign cells.

Question 14

what determines membrane fluidity?

Answer 14

1) the number of double bonds in the fatty acid tails of the lipids b/c each puts a “kink” in the fatty acid tail which prevents lipid molecules from packing tightly in the membrane.
2) the amount of cholesterol present.

Question 15

What effect does cholesterol have on membrane fluidity?

Answer 15

cholesterol makes the lipid bilayer stronger but less fluid at normal body temperature. At low temperatures, cholesterol has the opposite effect—it increases membrane fluidity.

Question 16

what is selective permeability?

Answer 16

Plasma membranes permit some substances to pass more readily than others

Question 17

what is a concentration gradient?

Answer 17

a difference in the concentration of a chemical from one place to another, such as from the inside to the outside of the plasma membran

Question 18

what is an electrical gradient?

Answer 18

. A difference in electrical charges between two regions

Question 19

What is membrane potential?

Answer 19

difference in the distribution of positively and negatively charged ions between the two sides of the plasma membrane. Typically, the inner surface of the plasma membrane is more negatively charged and the outer sur- face is more positively charged.

Question 20

what is an electrochemical gradient

Answer 20

. The combined influence of the concentration gradient and the electri- cal gradient on movement of a particular ion

Question 21

What are the passive and active processes that move substances across cellular membranes? plus examples.

Answer 21

1) passive processes, a substance moves down its concentration or electrical gradient to cross the membrane using only its own kinetic energy (energy of motion) - ex. diffusion
2) active processes cellular energy (adenosine triphosphate (ATP)) is used to drive the substance “uphill” against its concentration or electrical gradient. ex. active transport and vesicles in endocytosis

Question 22

what is diffusion?

Answer 22

a passive process in which the random mixing of particles in a solution occurs be- cause of the particles’ kinetic energy.
> the solute and solvent diffuse down their concentration gradients until they are evenly mixed in solution— at equilibrium

Question 23

What 5 things effect the rate of diffusion?

Answer 23

1) Steepness of the concentration gradient. The greater the difference, the higher is the rate of diffusion
2) temperature. The higher the temperature, the faster the rate of diffusion.
3) Mass of the diffusing substance. The larger the mass of the diffusing particle, the slower its diffusion rate
4) Surface area. The larger the membrane surface area available for diffusion, the faster is the diffusion rate
5) Diffusion distance. The greater the distance over which diffu- sion must occur, the longer it takes

Question 24

what is simple diffusion?

Answer 24

passive process in which substances move freely through the lipid bilayer of the plasma membranes of cells without the help of membrane transport proteins
ex. nonpolar hydrophobic molecules, and uncharged polar molecules (water)

Question 25

What is facilitated diffusion?

Answer 25

an integral membrane protein assists a specific substance across the membrane. The integral membrane protein can be either a membrane channel or a carrier (for Solutes that are too polar or highly charged)

Question 26

what is channel- mediated facilitated diffusion,

Answer 26

solute moves down its con- centration gradient across the lipid bilayer through a membrane channel
-mostly ion channels (integral transmembrane proteins that allow passage of small, inorganic ions)

Question 27

what is a gated channel?

Answer 27

when part of the channel protein acts as a “plug” or “gate,” changing shape in one way to open the pore and in another way to close it

Question 28

what is carrier- mediated facilitated diffusion

Answer 28

a carrier (also called a transporter) moves a solute down its concentration gradient across the plasma membrane
>solute binds to a specific carrier on one side of the membrane and is released on the other side after the carrier undergoes a change in shape.

Question 29

what is osmosis

Answer 29

a type of diffusion in which there is net movement of a solvent (water) through a selectively permeable membrane.

Question 30

During osmosis, water molecules pass through a plasma membrane in what two ways:

Answer 30

(1) by moving through spaces b/w neighbouring phospholipid molecules in the lipid bilayer via simple diffusion
(2) by moving through aquaporins - integral membrane proteins that function as water channels.

Question 31

what is osmotic pressure?

Answer 31

The force exerted by the solution with an impermeable solute
> The osmotic pressure of a solution is proportional to the concentration of the solute particles that cannot cross the membrane—the higher the solute concentration, the higher the solution’s osmotic pressure

Question 32

what is a solution’s tonicity?

Answer 32

a measure of the solution’s ability to change the volume of cells by altering their water content

Question 33

What is an isotonic solution?

Answer 33

any solution in which a cell—for example, a red blood cell (RBC)—maintains its normal shape and volume
** The concentrations of solutes that cannot cross the plasma membrane are the same on both sides of the membrane in this solution

Question 34

What is a hypotonic solution?

Answer 34

a solution that has a lower concentration of solutes than the cytosol inside the RBCs
- water molecules enter the cells faster than they leave, causing the RBCs to swell and eventually to burst

Question 35

The rupture of RBCs in a hypotonic solution is called ______

Answer 35

hemolysis

Question 36

The rupture of cells other than RBCs in a hypotonic solution is called ______

Answer 36

lysis

Question 37

What’s an example of a very hypotonic solution?

Answer 37

pure water

Question 38

What is a hypertonic solution

Answer 38

a higher concentration of solutes outside than does the cytosol inside RBCs
- water molecules move out of the cells faster than they enter, causing the cells to shrink

Question 39

What is shrinkage of cells in hypertonic solutions called?

Answer 39

crenation

Question 40

what is active transport? when is it required?

Answer 40

when polar or charged solutes need to move “uphill,” against their concentration gradients
active transport: energy is required for car- rier proteins to move solutes across the membrane against a con- centration gradient.

Question 41

What are the two sources of cellular energy used in active transport? when is each type used?

Answer 41

(1) Energy obtained from hydrolysis of adenosine triphosphate (ATP) is the source in primary active transport;
(2) energy stored in an ionic concentration gradient is the source in secondary active transport.

Question 42

What happens in primary active transport?

Answer 42

energy derived from hydrolysis of ATP changes the shape of a carrier protein, which “pumps” a substance across a plasma membrane against its concentration gradient.

Question 43

What is the sodium potassium pump? (Na+/K+ ATPase)

Answer 43

most prevalent primary active transport mechanism ex- pels sodium ions (Na􏰈) from cells and brings potassium ions (K􏰈) in.
- works nonstop to main- tain a low concentration of Na􏰈 and a high concentration of K􏰈 in the cytosol.

Question 44

what are the 4 steps of the sodium potassium pump?

Answer 44

1) 3 Na+ in the cytosol bind to the pump protein.
2) Binding of Na+ triggers the hydrolysis of ATP into ADP, this rxn also attaches a phosphate group to the pump protein. which changes shape of the protein, expelling the 3 Na+ into ECF. Now the shape of the] protein favors two K+ in the EFC to the pump protein.
3) binding of K+ triggers release of the P group from the pump . This rxn causes the shape to change.
4) As the pump protein reverts to its original shape, it releases K+ into the cytosol
the cycle repeats.

Question 45

What occurs in secondary active transport? Where does it get it’s energy?

Answer 45

the energy stored in a Na􏰈 or H􏰈 concentration gradient is used to drive other substances across the membrane against their own concentration gradients
*** secondary active transport indirectly uses energy obtained from the hydrolysis of ATP.
> secondary active trans- port proteins harness the energy in the Na􏰈 concentration gradi- ent by providing routes for Na􏰈 to leak into cells

Question 46

what is endocytosis? exocytosis?

Answer 46

1) materials move into a cell in a vesicle formed from the plasma mem- brane
2) materials move out of a cell by the fusion with the plasma membrane of vesicles formed inside the cell

Question 47

what is receptor mediated endocytosis?

Answer 47

a highly selective type of endocytosis by which cells take up specific ligands
>A vesicle forms after a receptor protein in the plasma membrane recognizes and binds to a particular particle in the extracellular fluid

Question 48

What is phagocytosis?

Answer 48

a form of endocytosis in which the cell engulfs large solid particles, such as worn-out cells, whole bacteria, or viruse

Question 49

Only a few body cells, termed ______ are able to carry out phagocytosis
what are the two types?

Answer 49

Phagocytes

1) macrophages
2) neutrofils

Question 50

Phagocytosis begins when the particle binds to a plasma membrane receptor on the phagocyte, causing it to extend ________ projections of its plasma membrane and cytoplasm.

Answer 50

pseudopods

- which form a vesicle around the particle

Question 51

Most body cells cary out bulk phase endocytosis (or pinocytosis) what is this?

Answer 51

a form of endo- cytosis in which
the plasma membrane folds inward and forms a vesicle containing a droplet of extracellular fluid.
the droplet then fuses with a lysosome

Question 52

What two types of cells is exocytosis especially important in?

Answer 52

(1) secretory cells that liberate digestive enzymes, hormones, mucus, or other secretions and
(2) nerve cells that release substances called neurotransmitters

Question 53

What is transcytosis?

Answer 53

vesicles undergo endocytosis on one side of a cell, move across the cell, and then undergo exocytosis on the opposite side.