Quiz 4 - Biosignaling, Carbohydrates

Question 1

6 Requirements for effective signal transduction

Answer 1

1. Specificity
2. Amplification
3. Modularity - discrete components that interact
4. Integration - Different signals combine to create response
5. Feedback
6. Fidelity - doesn’t decay over time and space

Question 2

Autocrine

Answer 2

Signals bind to same cell

Question 3

Paracrine

Answer 3

Signals bind to nearby cell

Question 4

Synaptic

Answer 4

Involve signals crossing narrow synapse

Question 5

Endocrine

Answer 5

Signals travel in bloodstream to distant targets

Question 6

4 Components of Signal Transduction

Answer 6

1. Signal
2. Receptor
3. Transduction Pathway
4. Target

Question 7

3 Types of signals

Answer 7

1. Soluble - Proteins, amino acids, lipids, fatty acids, carbohydrates
2. Linked - Integrins
3. Physical - mechanical, light, temperature

Question 8

G Protein-Coupled Receptors

Answer 8

External ligand binds to receptor, activates GTP binding protein that regulates another enzyme that creates intracellular second messengers

Question 9

Receptor Tyrosine Kinase

Answer 9

Ligand binding activates TYR Kinase activity and autophosphorylation

Question 10

Receptor Guanylyl Cyclase

Answer 10

Convert GTP to cGMP second messenger

Question 11

Gated Ion Channel

Answer 11

Open or close in response to concentration of signal ligand or membrane potential

Question 12

Adhesion receptor (integrin)

Answer 12

Interact with things out in the ECM and affect the cytoskeleton

Question 13

Nuclear receptor

Answer 13

Hormones enter the nucleus through the membranes and bind to DNA

Question 14

Dissociation Constant (Kd)

Answer 14

Measure of amount of bound ligand compared to free.
High affinity receptor requires little ligand to reach dissociation (low Kd)
Low affinity receptor requires more ligand to reach dissociation

Question 15

4 roles of plasma membrane in signaling

Answer 15

1. Receptor Localization
2. Ligand Exposure
3. Signaling Complex Formation
4. Endocytosis

Question 16

Protein Scaffold

Answer 16

Protein binds a series of signaling proteins together at the membrane to speed up signaling. Ex.) AKAP5 scaffold protein

Question 17

Signaling Endosome

Answer 17

Small membrane bound endosomes that group signaling proteins

Question 18

Lipid raft types and functions

Answer 18

1. Calveolar - Calveolin creates a dip in the membrane
2. Planar - level with rest of membrane
   A. Signal promotion - groups signaling proteins together
   B. Signal inhibition - separates proteins to prevent signaling

Question 19

Endocytic Pathway

Answer 19

Sort internalized vesicles
Vesicular Fusion and Excision
Transport can occur between every compartment
Rab GTPase proteins critical
pH decreases along pathway

Question 20

Endocytic pathway spatially and temporally regulates signaling

Answer 20

1. Signal downregulation - endocytose and degrade or re-exocytose a receptor
2. Signal maintenance - Increases concentration of receptor and ligand by reducing volume
3. Signal generation - When downstream components of pathway are not membrane bound, endocytosis can bring signal to the enzymes

Question 21

Signal transduction process

Answer 21

First messenger -> Receptor -> Signal Transducer -> Primary Effector -> Second Messenger -> Secondary Effector

Question 22

How do chemical reactions transfer information?

Answer 22

1. Complex formation or dissociation
2. Structural change
3. Post-translational modification

Question 23

Post-Translational Modifications

Answer 23

Phosphorylation - kinase
Ubiquitination - ubiquitin ligase
Glycosylation
Oxidation
Methylation - methyl-transferase
Acetylation - acetyltransferase
SUMOylation

Question 24

Mitogen-Activated Protein Kinase (MAPK) Signaling

Answer 24

Monomeric GTP-ase activates MAP Kinase kinase kinase > MAP kinase kinase > MAP kinase > downstream chain
Ex.) Insulin activating transcription

Question 25

Janus Kinase (JAK-STAT) Signaling

Answer 25

Janus kinase dimer binds to a cytokine > STAT is phosphorylated > STAT enters nucleus and affects transcription

Question 26

Phosphatidylinositol 3-Kinase (PI3K) Signaling

Answer 26

Growth factor binds to an RTK > PIP2 is phosphorylated to PIP3 > chain of proteins activated Ex.) Insulin activating glycogen synthesis

Question 27

Phospholipase C Signaling

Answer 27

Ligand binds to GPCR > alpha subunit of G-protein binds to Phospholipase C > PLC cleaves PIP 2 to create IP3 > IP3 binds to Ca2+ channels to affect other signal pathways Ex.) Norepinephrine causing vasoconstriction

Question 28

Targets are effected to change cell function

Answer 28

Nucleus - transcription, cell division Actin/tubulin/filaments - cell structure and motility Enzymes - initiate metabolic pathways Receptors - alter signal transduction Transporters - change intracellular environment Ion channels - change membrane potential

Question 29

Epinephrine pathway

Answer 29

Epinephrine binds to Beta-adrenergic receptor > G protein phosphorylated > alpha subunit activates Adenylyl cyclase > AC converts ATP to cAMP > Causes smooth muscle relaxation and vasodilation

Question 30

Norepinephrine Pathway

Answer 30

Norepinephrine binds to alpha adrenergic receptor > G protein phosphorylated > alpha subunit activates Phospholipase C > PLC cleaves IP3 from PIP2 > IP3 opens Ca2+ channels > Ca2+ activates Calmodulin > Causes smooth muscle contraction and vasoconstriction

Question 31

Insulin division pathway

Answer 31

Insulin binds to TYRK > TYRK phosphorylates IRS1 > IRS1 uses a chain of proteins to activate RAS (G protein) > RAS activates Raf-1 (MAP Kinase kinase kinase) > Raf activates MEK (MAP Kinase kinase) > MEK activates ERK (MAP Kinase) > ERK affects transcription factors

Question 32

Insulin Glycogenesis pathway

Answer 32

Starts same as Insulin division > IRS activates PI3K > PI3K converts PIP2 to PIP3 > Factors activated to convert Glucose to glycogen

Question 33

Toll-Like Receptors

Answer 33

Specific receptors recognize bacterial cell walls (Gram - or Gram +)

Question 34

Monosaccharides

Answer 34

Single units of sugars. Can have 3-8 carbons

Question 35

Glyceraldehyde

Answer 35

Monosaccharide. An aldotriose (3 carbons, =O on terminal carbon)

Question 36

D-Glucose

Answer 36

Monosaccharide. An aldohexose (6 carbons, =O on terminal carbon)

Question 37

D-fructose

Answer 37

Monosaccharide. A ketohexose (6 carbons, =O on 2nd carbon)

Question 38

Constitutional isomers

Answer 38

Same atoms, but differ in attachment of atoms

Question 39

Stereoisomers

Answer 39

Atoms are connected in the same order but differ in spatial arrangement

Question 40

Enantiomers

Answer 40

Mirror image of a molecule

Question 41

Diastereomers

Answer 41

Isomers that are not mirror images

Question 42

Formation of cyclic sugars

Answer 42

Aldehyde sugars are highly reactive in linear form, form cyclic, form 6 carbon ring Ketone sugars are less reactive, form 5 carbon ring

Question 43

Pyranose

Answer 43

6 Carbon ring. Glucose forms 2 different conformations in solution. Form Chair and Boat conformations

Question 44

Furanose

Answer 44

5 carbon ring. Fructose forms 2 different conformations in solution

Question 45

Reducing Sugar

Answer 45

Able to reduce another molecule or element Ex.) Cu2+ --> Cu+ Sugar is oxidized Important indicator of blood glucose testing. Reducing sugar has free aldehyde or ketone group. All monosaccharides are reducing sugars, glucose is more effective than fructose

Question 46

Complex sugars

Answer 46

Glucose can be modified by acetylation, phosphorylation, etc.

Question 47

Disaccharides

Answer 47

2 sugars joined together Lactose = Galactose + Glucose 1-4 linkage Sucrose = Glucose + Fructose 1-2 linkage

Question 48

Polysaccharides

Answer 48

Chains of sugar monomers

Question 49

Amylose

Answer 49

Chain of alpha 1-4 glucose links

Question 50

Amylopectin

Answer 50

Branched chain of glucose attached to main branch by 1-6 link

Question 51

Glycogen

Answer 51

Chain of amylose and amylopectin Amylopectin branch chains maximum of 10 glucoses Storage carbohydrate

Question 52

Starch

Answer 52

Chain of amylose and amylopectin | Amylopectin branch chains maximum of 30 glucoses

Question 53

Chitin

Answer 53

Monomer is N-acetyl glucosamine Alpha 1-4 linkage Structural carbohydrate (insect exoskeleton)

Question 54

Cellulose

Answer 54

Beta 1-4 and 1-6 linkages | Requires cellulase enzyme to digest

Question 55

N- and O- glycosylation

Answer 55

Carbohydrates bind to amino acids. Bound to serine = O link Bound to Asparagine = N link Forms specific pattern of cell surface proteins on cell membranes involved in organ transplant rejection, immune response, etc.

Question 56

Glycoconjugate purposes

Answer 56

``` Major component of ECM Filter substances in ECM Serves as lubricants between cells Bind to cations Regulate movement of molecules ```

Question 57

Glycosidic bond

Answer 57

Aldehydes and Ketones react in alcohol to become hemiacetals or hemiketals, changing the chiral center. Substitution of a second alcohol produces an acetal or ketal via a glycosidic bond.

Question 58

Glycosaminoglycans

Answer 58

``` Large polysaccharides with amines. Have negative charges (polyanionic) Hyaluronate Chondroitin Keraten sulfate Heparin ```

Question 59

Hyaluronate

Answer 59

Found in connective, epithelial and neural tissues. Found in aqueous and vitreous humour.

Question 60

Chondroitin

Answer 60

Major constituent of connective tissues. Lubricant of joints

Question 61

Heparin

Answer 61

Made in liver, anticoagulant

Question 62

Keratin Sulfate

Answer 62

Large, highly hydrated molecules in joints that absorb mechanical shock, contributes to glial scar formation

Question 63

Mucins

Answer 63

Principle organic constituent of saliva, protects, lubricates, has antimicrobial effects