CH 4, Part 2; CH 5, Part 1-2

Question 1

Active Transport

Answer 1

Requirements:
1) molecules move from low –> high (against gradient)
2) always need energy to move molecules
Two types:
1) Primary
2) Secondary

Question 2

Primary Active Transport

Answer 2

• ATP is energy source
• pumps act as carrier and enzyme
• Na+/K+ pumps

Question 3

Secondary Active Transport

Answer 3

• energy source is diffusion of sodium ion into a cell( an electrochemical gradient previously created by primary active transport)

Question 4

Endocytosis

Answer 4

bringing in of molecules through vesicles

Question 5

Exocytosis

Answer 5

release of molecules through vesicles

Question 6

Apical membrane

Answer 6

portion of the membrane of an epithelial cell that faces the lumen

Question 7

Basolateral membrane

Answer 7

portion of the membrane of an epithelial cell that faces the interstitial fluid

Question 8

Movement of ions and molecules from the lumen of the intestines past epithelial cells and into the blood

Answer 8

SODIUM
Lumen –> Epithelial Cell:
diffusion through channels (passive)
- pores throughout apical membrane to move from high to low
Epithelial Cell –> Blood:
primary active transport
- integral protein uses ATP to move Na+ pas basolateral membrane to ISF from low to high

GLUCOSE
Lumen –> Epithelial Cell:
secondary active transport
- lower in lumen than epithelial cells
- Na+ ions will passively diffuse past integral protein and provide energy to get past apical membrane
Epithelial Cell –> Blood:
facilitated diffusion
- concentration stays low in ISF, so can pass through basolateral membrane from high to low

WATER
Lumen –> Blood:
osmosis
- aquaporins embedded throughout apical and basolateral membranes
- sodium and glucose (solute) when from lumen to ISF to blood, so water follows the higher osmolarity

Question 9

communication through gap junction vs. communication via chemical messengers

Answer 9

• Gap Junctions allow direct communication between adjacent cells
  
  • allows passage of small molecules and ions
• Chemical Messengers are signaling molecules that carry information between cells

Question 10

Ligand

Answer 10

chemical messenger molecule which binds proteins reversibly

Question 11

functional classes of chemical messengers

Answer 11

PARACRINE
cell releases chemical messenger, it travels very short distance and binds to another cell
- reach target cells via simple diffusion

AUTOCRINE
cell will release chemical messenger and travels short distance, binds to itself, and tells itself what to do
- type of paracrine
- act on cell that secreted them

NEUROTRANSMITTER
released by a cell, travels a very short distance, and binds to another cell
- similar to a paracrine, but if a neuron releases the chemical messenger it is considered a neurotransmitter

HORMONE
released by a cell, travels through the bloodstream, and finds another cell in body to bind to
- can travel incredibly long distances
- most often released from glands

Question 12

chemical properties of chemical messengers

Answer 12

can either be hydrophilic or hydrophobic
- some chemical messengers are charged and some are not charged
(1) Hydrophilic: polar/ionic, charged, loves water
(2) Hydrophobic: nonpolar, hates water

Question 13

How are chemical messengers carried in blood?

Answer 13

blood is made of red blood cells and plasma (water)
- hormones travel through blood and exist in blood plasma; not bound to RBCs

(1) hydrophilic hormones
- polar hormone travels through the polar blood plasma
- very easy to transport hydrophilic hormones

(2) hydrophobic hormones
- nonpolar hormone travels through the polar plasma
- nonpolar hormones do not transport in the blood very well
- require transport proteins
- common ex: albumin
- latches onto nonpolar hormones through the blood

Question 14

Receptor location due to chemical properties

Answer 14

• if chemical messenger is HYDROPHILIC (charged), receptor will be on PLASMA MEMBRANE of cells
• if chemical messenger is HYDROPHOBIC (nonpolar), receptor will be in INTRACELLULAR FLUID of cell
  
  • uses simple diffusion

Question 15

Classes of chemical messengers

Answer 15

AMINO ACIDS
- hydroPHILIC
- receptors on plasma membrane
- neurotransmitters

AMINES
- hydroPHILIC
- receptors on plasma membrane
- paracrines, neurotrasnmitters, hormones

PEPTIDES/PROTEINS
- hydroPHILIC
- receptors on plasma membrane
- paracrines, neurotransmitters, hormones

STERIODS
- hydroPHOBIC
- receptors in cytosol
- hormones

EICOSANOIDS
- hydroPHOBIC
- cytosol
- paracrines

Question 16

Role of Aspirin with regard to eicosanoid messengers

Answer 16

• aspirin is an NSAID, which is a COX inhibiter
  
  • COX is the enzyme used to make prostaglandins (eicosanoids)
• by binding to and inhibiting COX, aspirin causes vasoCONSTRICTION to prevent headaches
• headaches are due to vasoDILATION (relaxation of blood vessels

Question 17

Magnitude of effect of chemical messengers

Answer 17

• increased concentration of chemical messengers have a more significant effect
• cells with a greater affinity for one messenger will bind with that messenger more often and it will have an increases affect

Question 18

up-regulation

Answer 18

increased number of receptors due to chronically low messenger concentrations

Question 19

down-regulation

Answer 19

decreased number of receptors due to chronically high messenger concentrations

Question 20

Agonist vs Antagonist (with examples)

Answer 20

AGONIST
ligand that mimics chemical messenger, has ability to bind and activate same receptor
- ex: abuterol
- mimics epinepherine and has same effect
- able to bind and activate epinepherine receptors

ANTAGONIST
ligand that mimics chemical messenger, binds to same receptor, however prevents receptor from working
- ex: beta-blockers
- mimics epinepherine (same structure)
- can bind to epinepherine receptors, but inhibits them (does NOT activate)
- causes a decrease in heart rate
- compete with agonist molecules for receptor binding sites