Levels of Organization & the Plasma Membrane Pt. 2

Question 1

Cell

Answer 1

A single basic living, structural, and functional unit enclosed by a membrane (3 main parts)
- Various shapes = diverse physiological capacities (aka function)

Question 2

3 main parts of a cell:

Answer 2

1. Plasma Membrane
2. Cytoplasm
3. Nucleus

Question 3

Plasma Membrane

Answer 3

A highly selective permeable membrane enclosing all the internal contents of a living cell.
- Forms the cell’s flexible outer surface
- Holds the interior structure in place (cytoskeleton) in place to maintain shape.

Question 4

Cytoplasm

Answer 4

Consists of all the cellular contents inside the cell between the plasma membrane and the nucleus. this EXCLUDES the nucleus (has 2 main components: Cytosol + Organelles)

Question 4

Selective Permeability

Answer 4

Is 1 of the important properties of a membrane… meaning each individual substance has its own unique permeability through a specific type of membrane. a.k.a. it lets some things through but not others
-Allows the intracellular conditions/environment to be very different from the extracellular environment.

Question 5

2 Main Components of Cytoplasm:

Answer 5

1. Cytosol (aka intracellular fluid): the fluid portion of the cytoplasm + includes water, dissolved solute, + suspended particles (ex. proteins & nucleic acids)
2. Organelles: Structures enclosed with discrete intracellular membrane in various shapes, sizes, & functions.
   
   • Mitochondria
   • Endoplasmic Reticulum [ER]
   • Golgi complex
   • Lysosome

Question 6

Endoplasmic reticulum (ER)

Answer 6

• 2 Forms (smooth & rough)
  Smooth ER-> sites for lipids, phospholipids, and steroids synthesis
  Rough ER-> with ribosomes as the sites for protein synthesis.

Question 7

Mitochondria

Answer 7

For energy production in the form of ATP

Question 8

Golgi complex/body

Answer 8

A processing station that participates in protein maturation and targets newly synthesized proteins to their appropriate subcellular destinations.

Question 9

Nucleus:

Answer 9

A structure associated with gene expression + cell division. it serves as a cell’s depot for chromosomal DNA.

Question 9

Phospholipids

Answer 9

Are amphipathic molecules that have both polar and nonpolar parts
Polar region–> the “head” region containing phosphate (hydrophilic-water loving)
Nonpolar region–> the “tails” region containing 2 long chains of fatty acid (hydrophobic-water fearing)
- Phospho=phosphate->Head
- Lipids= fatty acid-> Tails

Question 10

Lysosome

Answer 10

cell’s digestive organelle

Question 11

4 General Functions of the Plasma Membrane:

Answer 11

1) Structural support (cytoskeleton)
2) Physical isolation (separates intracellular & extracellular environment)
3) Regulation of exchange (barrier to regulate the flow of materials into/out of the cell)
4) Communication (establishes communication b/w cells and the external environment)

Question 12

Fluid Mosaic Model

Answer 12

used to describe the structural model of the plasma membrane (ex. the plasma membrane is a mosaic of lipids with various proteins as part of the products)

Question 13

What is the basic structural framework of the plasma membrane?

Answer 13

The lipid bilayer

Question 14

Membrane Proteins (2 main categories):

Answer 14

1) Integral membrane proteins (tightly attached to the membrane)
2) Peripheral membrane proteins (loosely attached to the membrane)

Question 15

Integral Membrane Proteins

Answer 15

a) Lipid-anchored proteins - membrane proteins that insert themselves into either side of the cell membrane (covalently bounded to lipid tail-squeezes head off tail)
b) Transmembrane Proteins - span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid (membrane-spanning proteins)
- functions as a channel for the transport of specific substances

Question 16

General functions of membrane proteins:

Answer 16

1) Ion Channels-> form pores that allow a specific ion to pass through
2) Receptors-> serve as cellular recognition sites with each type of receptor recognizes and binds a specific type of molecule (attaches to channel + acts as security)
3) Carriers/Transporters-> selectively moving a molecule or ion across the membrane
4) Enzymes (proteins)-> catalyze specific biological reactions inside/outside the cell
5) Linkers-> anchor plasma membrane of neighboring cells to one another.
Cell-Identity Markers-> identifies a cell as its own or if its foreign

Question 16

Peripheral Membrane Proteins.

Answer 16

Peripheral membrane proteins are those membrane protein that are loosely attached to either the polar head or other membrane proteins.

Question 17

6 Basic Transport Mechanisms:

Answer 17

i) Diffusion
ii) Osmosis
iii) Facilitated Diffusion
iv) Active Transport
v) Cotransport (symport)
vi) Counter transport (antiport)

Question 18

6 Basic Transport Mechanisms - Diffusion:

Answer 18

Movement of a solute within a medium and a membrane in a biological system Via a concentration gradient.
- moves from concentrated to diluted OR from High to low

Question 19

Aquaporins

Answer 19

Water channels

Question 19

6 Basic Transport Mechanisms - Osmosis

Answer 19

The movement of a solvent through a membrane by the means of a concentration gradient.
- moves from diluted (low osmolality) to concentrated (high osmolality) OR from Low to high
- requires aquaporins (water channels)

Question 20

6 Basic Transport Mechanisms - Facilitated Diffusion:

Answer 20

A type of Carrier-mediated transport (uses carrier proteins).
- moves from higher to lower concentration
- used for transport of large or electrically charged molecules (ex. glucose, amino acids, etc)

Question 21

6 Basic Transport Mechanisms - Active Transport

Answer 21

An energy dependent carrier mediated transport. it requires adenosine triphosphate (ATP)

Question 22

6 Basic Transport Mechanisms - Cotransport (Symport):

Answer 22

A carrier mediated simultaneous movement of 2 or more solutes in the SAME direction
- a type of secondary active transport
- e.g. moving K+ from extracellular to intracellular space by NKCC channels-> against conc. gradient

Question 23

6 Basic Transport Mechanisms - Counter-transport (Antiport)

Answer 23

Very similar to cotransport but the transported molecules are moving in the OPPOSITE direction

Question 24

4 Main Categories of Transport processes.

Answer 24

1) Bulk flow
2) Diffusion
3) Protein-mediated transport
4) Vesicular transport

Question 25

1st Category of Transport Processes - Bulk Flow

Answer 25

Requires pressure gradient and flows from high to low pressure
- e.g. Blood flow within a blood vessel (or) air moving in and out of lungs

Question 26

2nd Category of Transport Processes - Diffusion

Answer 26

Requires concentration gradient such as chemical, electrical, both (electrochemical gradient)
- Flow from high concentration to low-could take place in a open system or through a plasma membrane
- Is a passive process (no energy) + will finish when dynamic equilibrium is established

Question 27

Gradient

Answer 27

gradient is the difference in the driving force required for the movement of a substance between 2 regions.

Question 28

The rate of diffusion through membrane is a function of:

Answer 28

• Membrane surface area
• Molecular size
• Concentration gradient
• Membrane composition
• Lipid solubility

Question 29

What does each element of Fick’s law of the Rate of Diffusion through Membrane mean:
V = D (A/T)(P1 - P2)

Answer 29

V = Rate of diffusion
D = Diffusion constant (related to membrane permeability)
A = Area of the membrane
T = Thickness of the membrane
(P1 - P2) = Difference in concentration

Question 30

Ability of a molecule to dissolve into the lipid bi-layer plasma membrane depends on:

Answer 30

a) Chemical nature of the molecule: only non-polar lipophilic (lipid soluble) molecule can dissolve in the central lipid region of the membrane.
b) Cholesterol content within the membrane: high cholesterol decrease membrane permeability.

Question 31

The main structural component of the plasma membrane is:

Answer 31

Phospholipid bilayers

Question 32

What are the nonpolar parts of phospholipids?

Answer 32

Fatty acid tail groups

Question 33

The more metabolically active a membrane is, the more ______ it contains?

Answer 33

Proteins

Question 34

Plasma membranes are _____, which means that some chemicals move easily through plasma membrane while other chemicals do not.

Answer 34

Highly selective permeable membranes.

Question 35

Which of the following(s) can influence the rate of diffusion of a chemical across a plasma membrane?
a) concentration gradient of the chemical across the membrane
b) mass of the diffusing chemical
c) distance that the chemical has to diffuse
d) all of the above

Answer 35

d) all the above

Question 36

What type of membrane protein extends across the entire lipid bilayer of the plasma membrane touching both intracellular fluid and the extracellular fluid?

Answer 36

Transmembrane protein

Question 37

In this type of transport process, a solute binds to a specific carrier protein on one side of the membrane. This binding induces a conformational change in the carrier protein that results in the other type of solute moving down its concentration gradient to the other side of the membrane.

Answer 37

Facilitated diffusion

Question 38

In what transport process, is the energy from hydrolysis of ATP is used to drive substances across the membrane against their own concentration gradients.

Answer 38

Primary active transport