BioE Sig: Membranes & Exocytosis

Question 1

What is the Epineurium?

Answer 1

The connective tissue-type covering, surrounding the entire outer part of the nerve; binds fascicles together

Question 2

What is the Perineurium?

Answer 2

The connective tissue-type covering, surrounding a group of neurons

Question 3

What is the Endoneurium?

Answer 3

The connective tissue-type covering; surrounding each individual neuron

Question 4

What is a Fascicle?

Answer 4

a group of neurons

Question 5

What are the 6 characteristics of the Plasma Membrane?

Answer 5

1. sheet-like structure
2. comp of lipids and proteins
3. hydrophilic &phobic (bilayer)
4. Protein;Function specificity
5. Polarized Structures
6. Fluid Structures

Question 6

What is meant by “Polarized Structures” of Plasma Membranes?

Answer 6

The separation of charges inside and outside of the cell; usually, the inside of the cell is more electronegative

Question 7

What is meant by the “protein-function specificity” of Plasma Membranes? -list the poss. functions.

Answer 7

Function of membranes vary depending on the proteins;

4 poss. functions include:
- channels
- pumps
- energy transducers
- receptors

Question 8

What does the Fluid Mosaic Model describe?

Answer 8

It describes the membrane as being dynamic and not rigid

Question 9

What are the 4 characteristics of Membrane Proteins?

Answer 9

1. Transport & Attachment
   (of other mols into and out of cell)
2. Signal transduction
   exterior signals/mols to interior
3. Larger than lipids making them move slower through membranes
4. Immobile; are anchored to cytoskeleton

Question 10

What are Cytoskeletal Proteins?

Answer 10

They are immobile proteins of membranes, anchored to the cytoskeleton.

They provide structure and support to the interior and exterior of the cell.

Question 11

Describe the process of membrane proteins being involved in exterior signal transduction

Answer 11

a protein will bind an exterior signal or molecule;
binding initiates a series of intracellular changes

Question 12

What is the thickness of a plasma membrane?

Answer 12

60–100 Å

Question 13

What is the usual resting membrane potential (RMP) of a cell?

Answer 13

Approximately -60 mV

Question 14

Why are plasma membranes described as “fluid structures”?

Answer 14

Lipids diffuse rapidly within the plane of the membrane, but lipids and proteins do not rotate out of the membrane

Question 15

What connective tissue surrounds a group of neurons?

Answer 15

Perineurium

Question 16

What is the purpose of the endoneurium?

Answer 16

It isolates individual neurons in an organized manner

Question 17

What are the four basic functions of membrane proteins?

Answer 17

Transport, enzyme activity, signal transduction, and attachment/recognition

Question 18

What is an example of a receptor protein and its function?

Answer 18

Insulin, which binds to the surface of a cell to initiate signal transduction.

Question 19

What do cell adhesion molecules (CAMs) do?

Answer 19

They adhere cells together

Question 20

What are examples of channel proteins?

Answer 20

Aquaporins (water channels) and gated ion channels like Na⁺ or K⁺ channels

Question 21

What is the structure of an integral membrane protein?

Answer 21

It spans the entire membrane, with hydrophilic and hydrophobic regions

Question 22

Where are peripheral membrane proteins located?

Answer 22

On one side of the membrane, attached via hydrogen or ionic bonds

Question 23

What is an example of a peripheral protein?

Answer 23

Cytoskeletal proteins

Question 24

What is the concentration of sodium ions (Na⁺) in the extracellular fluid (ECF) vs. intracellular fluid (ICF)?

Answer 24

Higher in ECF (142 mEq/L) than ICF (10 mEq/L)

Question 25

What is the primary role of potassium ions (K⁺)?

Answer 25

To maintain intracellular electrical charge

Question 26

What is the difference in calcium (Ca²⁺) concentration between ECF and ICF?

Answer 26

Extremely high in ECF (2.4 mEq/L) and very low in ICF (0.0001 mEq/L)

Question 27

What establishes the resting membrane potential (RMP)?

Answer 27

The unequal distribution of ions (e.g., K⁺ efflux and Na⁺ influx).

Question 28

How do oxygen and carbon dioxide gradients drive their movement across the membrane?

Answer 28

O₂ flows into the cell due to higher pressure in ECF, while CO₂ flows out due to higher pressure in ICF

Question 29

Why is the intracellular pH slightly acidic?

Answer 29

Acid production occurs due to metabolic processes (e.g., CO₂ → carbonic acid formation).

Question 30

What is the primary function of the plasma membrane?

Answer 30

To act as a selective barrier, regulating the entry and exit of ions and molecules

Question 31

What ratio of lipids to proteins is seen in plasma membranes?

Answer 31

Varies between 1:4 to 4:1 depending on the cell type

Question 32

How does the plasma membrane achieve selective permeability?

Answer 32

Through embedded proteins like channels, pumps, and receptors

Question 33

What is the role of cholesterol in the plasma membrane?

Answer 33

It maintains fluidity and stability

Question 34

What is membrane permeability?

Answer 34

Net rate of diffusion of a substance through each unit area of the membrane

Question 35

What determines the movement of substances across the membrane?

Answer 35

The concentration difference on either side of the membrane

Question 36

Why is membrane permeability important for bioelectrical energy generation?

Answer 36

It explains how the selective movement of molecules across the membrane supports processes like neuronal signaling

Question 37

How does membrane thickness affect diffusion rate?

Answer 37

Thicker membranes decrease diffusion rate

Question 38

Why does increased membrane thickness slow down diffusion?

Answer 38

Molecules or ions must travel a longer distance through the membrane

Question 39

How does lipid solubility affect membrane permeability?

Answer 39

Molecules with higher lipid solubility diffuse faster

Question 40

Why do lipid-soluble molecules diffuse faster?

Answer 40

They form favorable and reversible bonds with the fatty acid tails of the phospholipid bilayer

Question 41

How does the number of protein channels impact diffusion?

Answer 41

A greater number of protein channels increases the rate of transport

Question 42

What role do protein channels play in membrane permeability?

Answer 42

They allow specific ions or molecules to move into or out of the cell

Question 43

How does temperature affect diffusion through the membrane?

Answer 43

Diffusion increases directly with temperature.

Question 44

Why does higher temperature increase diffusion rates?

Answer 44

Higher temperature enhances the movement of molecules through the phospholipid bilayer

Question 45

How does molecular weight affect diffusion?

Answer 45

Diffusion rate is inversely proportional to the molecular weight

Question 46

Why do larger molecules move slower through the membrane?

Answer 46

Heavier molecules have lower thermal motion velocity, reducing their diffusion rate

Question 47

What does it mean for a membrane to be selectively permeable?

Answer 47

It allows specific molecules to enter or exit the cell based on factors like lipid solubility, protein channels, and molecular weight.

Question 48

What factors critically affect bioelectrical signaling in neurons?

Answer 48

Membrane composition, protein channels, and environmental temperature

Question 49

What is exocytosis?

Answer 49

The movement of molecules or ions from the interior of the cell to the exterior via specialized mechanisms

Question 50

What are the main roles of exocytosis?

Answer 50

Adding membrane components, recycling endocytosed products, and secretion of substances

Question 51

What role does exocytosis play in adding membrane components?

Answer 51

Molecules from the vesicle interior are incorporated into the cell membrane

Question 52

What is an example of a molecule added to the cell membrane via exocytosis?

Answer 52

GLUT4 (Glucose Transporter Type 4)

Question 53

What triggers GLUT4 vesicles to move toward the membrane?

Answer 53

Insulin

Question 54

What happens to GLUT4 after exocytosis?

Answer 54

GLUT4 becomes embedded in the membrane to facilitate glucose transport without fully exiting the cell

Question 55

What is the function of exocytosis in recycling endocytosis products?

Answer 55

Repackaging and adding products back to the membrane or releasing them to the cell exterior

Question 56

What are the two outcomes for recycled endocytosed products in exocytosis?

Answer 56

They can be added to the cell membrane or completely released to the exterior

Question 57

What is the function of exocytosis in secretion?

Answer 57

Releasing substances from the cell interior to the exterior

Question 58

What are examples of substances secreted via exocytosis?

Answer 58

Antibodies (by white blood cells), neurotransmitters (e.g., acetylcholine), and mucus (in respiratory and digestive systems)

Question 59

What are secretory vesicles, and what do they contain?

Answer 59

Vesicles that contain molecules to be released or incorporated into the membrane

Question 60

What happens to secretory vesicles when a signal is received?

Answer 60

They move toward the plasma membrane

Question 61

What is the process by which vesicles release their contents in exocytosis?

Answer 61

Vesicles fuse with the plasma membrane, and their contents are either added to the membrane or released into the extracellular space

Question 62

What are examples of contents released during exocytosis?

Answer 62

Neurotransmitters (e.g., acetylcholine), antibodies, and mucus

Question 63

What role does the endoplasmic reticulum (ER) play in exocytosis?

Answer 63

Granular ER: Modifies proteins via glycosylation Smooth ER: Synthesizes lipids and assembles transport vesicles

Question 64

What is the role of the Golgi apparatus in exocytosis?

Answer 64

Processes, packages, and ships molecules to secretory vesicles

Question 65

What do secretory vesicles do during exocytosis?

Answer 65

Deliver molecules to the membrane or release them to the exterior

Question 66

Terminal Axon

Answer 66

The portion of a motor neuron that connects with a muscle fiber.

Question 67

Muscle Fibers are identified by the presence of what?

Answer 67

Striations

Question 68

What are Striations ?

Answer 68

Contractile proteins responsible for force production

Question 69

What is the Primary Synaptic Cleft?

Answer 69

The small gap between the terminal axon and the muscle cell membrane

Question 70

What is the Secondary Synaptic Cleft?

Answer 70

The distance between the terminal axon and the inner portion of the membrane folds.

Question 71

What are NT Vesicles?

Answer 71

Small components within the terminal axon that contain neurotransmitters.

Question 72

Describe Vesicle Fusion.

Answer 72

Vesicles fuse with the terminal axon membrane at specific locations

Question 73

Neurotransmitters are released from the _______ into the _________

Answer 73

vesicles ; synaptic cleft

Question 74

Neurotransmitter release causes _____________, initiating __________

Answer 74

muscle cell excitation ; contraction