Biology 225 Midterm 1

Front 1

Define Endocrine Signalling

Back 1

Signal travels to distant cells via the bloodstream.

Front 2

Define Paracrine Signalling

Back 2

Signal travels to nearby target cells.

Front 3

Define Neuronal Signalling

Back 3

Signal travels between neurons (neurotransmitters released in synapse).

Front 4

Define Contact-Dependent Signalling

Back 4

Signalling cell and target cell are in contact; the signal molecule is bound to the membrane.

Front 5

Effects of Adrenaline?

Back 5

Increases blood pressure, heart rate, metabolism.
Origin: Adrenal gland.
Type: Hormone.
Nature: Tyrosine derivative.

Front 6

Effects of Cortisol?

Back 6

Affects metabolism of carbohydrates, proteins, and lipids in most tissues.
Origin: Adrenal gland.
Type: Hormone.
Nature: Steroid.

Front 7

Effects of Estradiol?

Back 7

Induces & maintains female secondary sexual characteristics.
Origin: Ovaries.
Type: Hormone.
Nature: Steroid.

Front 8

Effects of Testosterone?

Back 8

Induces & maintains male secondary sexual characteristics.
Origin: Testes.
Type: Hormone.
Nature: Steroid.

Front 9

Effects of Glucagon?

Back 9

Stimulates glycogen (& lipid) breakdown & glc synthesis (e.g. fat and liver cells).
Origin: cells of pancreas.
Type<: Hormone.
Nature: Polypeptide.

Front 10

Effects of Insulin?

Back 10

Stimulates glc uptake, protein & lipid synthesis (e.g. liver cells).
Origin: cells of pancreas.
Type: Hormone.
Nature: Polypeptide.

Front 11

Effects of EGF?

Back 11

Stimulates many cell types to proliferate.
Origin: various cells
Type: Local Mediator
Nature: polypeptide

Front 12

Effects of PDGF?

Back 12

Stimulates many cell types to proliferate
Origin: various cells, including platelets.
Type: Local Mediator
Nature: Polypeptide

Front 13

Effects of NGF?

Back 13

Promotes growth & survival of neurons
Origin: Various innervated tissues
Type: Local Mediator
Nature: Polypeptide

Front 14

Effects of histamine?

Back 14

Aids inflammator response by causing blood vessels to dilate and become leaky.
Origin: Mast cells
Type: Local mediator
Nature: Histidine derivative

Front 15

Effects of NO?

Back 15

Smooth muscle relaxation; regulates nerve cell activity.
Origin: Nerve cells; endothelia of blood vessels
Type: Local mediator
Nature: dissolved gas

Front 16

Effects of Acetylcholine?

Back 16

Excitatory neurotransmitter at many nerve-muscle synapses & in the CNS
Origin: Nerve terminals
Type: Neurotransmitter
Nature: Choline derivative

Front 17

Effects of GABA?

Back 17

Inhibitory neurotransmitter in CNS
Origin: Nerve Terminals
Type: Neurotransmitter
Nature: Glutamate derivative

Front 18

Difference between hydrophillic and hydrophobic signals?

Back 18

Hydrophillic signals bind to receptors at the cell's surface. Hydrophobic signals pass through the cell membrane and bind intracellular receptors.

Front 19

Two major types of molecular switches?

Back 19

1. Phosphorylation/dephosphorylation by kinases and phosphotases (some are on when phosphorylated, and some are off when phosphorylated)

2. GTP-binding proteins

Front 20

GTP-binding proteins - when are then "On", and when are they "Off"?

Back 20

They are "On" when GTP is bound, and "Off" when GDP is bound.

Front 21

Give an example of how a signal molecule can induce different responses in different target cells

Back 21

Acetylcholine decreases frequency of contraction in heart muscle cells; it causes contraction in skeletal muscle cells; and it causes secretion in salivary gland cells.

Front 22

Explain the difference between cell-surface receptors and intracellular receptors

Back 22

Cell-surface receptors are for hydrophilic signal molecules to bind to - they are on the surface of the cell, embedded in the membrade. Intracellular receptors reside inside the cell, and hydrophobic signal molecules travel right into the cell, and bind to them.

Front 23

How does nitroglycerine work to relieve angina?

Back 23

NO dilates the small muscles of blood vessels serving the heart, improving blood flow.

Front 24

How does viagra work to relieve erectile dysfunction?

Back 24

It inhibits the breakdown of cGMP by cGMP phosphodiesterase

Front 25

What are GAPS and how do they work?

Back 25

GTPase activating proteins. They accelerate G protein's intrinsic GTPase activity (they are an accessory protein, which aid cycling between active and inactive states of a G-protein switch by binding to the G-protein)

Front 26

What are GEFs and how do they work?

Back 26

Guanine nucleotide-exchange factors. They bind inactive G proteins and stimulate exchange reaction.
(they are an accessory protein, which aid cycling between active and inactive states of a G-protein switch by binding to the G-protein)

Front 27

What are GDIs and how do they work?

Back 27

Guanine nucleotide-dissociation inhibitors. They inhibit release of bound GDP thus maintaining the protein in its inactive state.
(again, part of the g-protein switch)

Front 28

Three ways that a signal can affect a cell?

Back 28

1. Altered protein function
2. Altered gene expression
3. Altered cytoplasmic machinery

Front 29

Name three types of cell surface receptors for hydrophilic signalling molecules.

Back 29

G-protein-coupled receptors (GPCRs); Enzyme-linked receptors; Ion-channel-linked receptors.

Front 30

How do GPCRs work?

Back 30

Cytosolic domain binds heterotrimeric G-proteins.

Front 31

How do enzyme-linked receptors work?

Back 31

Cytosolic domain either acts as an enzyme (eg RTKs), or complexes with an enzyme. Most dimerize upon binding ligand. Primarily, they regulate growth, survival, and differentiation.

Front 32

How do ion-channel-linked receptors work?

Back 32

e.g. the nicotinic Ach receptor

Front 33

What is the most frequent effector targeted by heterotrimeric G-proteins?

Back 33

adenylate cyclase; phospholipase c (PLC) is also a major target

Front 34

What does cAMP usually do?

Back 34

activates PKA (protein kinase A)

Front 35

Give some examples of induced calcium release

Back 35

cardiac muscle, skeletal muscle

Front 36

What is CREB?

Back 36

(Cyclic-AMP Response Element Binding) proteins are transcription factors which bind to certain sequences called CRE elements in DNA and thereby increase or decrease the transcription of certain genes.

Front 37

What is calmodulin?

Back 37

Calmodulin (CaM) is a Ca2+-binding protein that is a key component of the Ca2+ second-messenger system and is involved in the modulation of protein kinases and other enzymes.

Front 38

What is the role of calcium in cell signalling?

Back 38

A second messenger.

Front 39

How many calcium binding sites does calmodulin have?

Back 39

4 Ca2+ binding sites.

Front 40

What is Troponin C?

Back 40

A protein - modulator of muscle contraction.

Front 41

What is Calretinin, retinin?

Back 41

A protein - activator of guanylyl cyclase.

Front 42

What is PI-specific PLC?

Back 42

A protein - generates IP3 and diacylglycerol.

Front 43

What is PKC?

Back 43

A protein kinase.

Front 44

What is an IP3 receptor?

Back 44

Effector of intracellular Ca2+ release.

Front 45

What is arrestin?

Back 45

Terminator of photoreceptor response.

Front 46

How does cholera toxin (cholera) modify G-proteins?

Back 46

It catalyzes ADP ribosylation of Gs... can no longer hydrolyze bound GTP, so permanently on.

Front 47

How does pertussis toxin (whooping cough) modify G-proteins.

Back 47

It catalyzes ADP ribosylation of Gi... cannot interact with receptors. Retains GDP, so permanently off. Also interferes with signally pathway that the host cells require to defend themselves against the pathogen.

Front 48

What are phorbol esters?

Back 48

Tumour promotes that imidiate DAG - activate PKC

Front 49

What are oncogenes?

Back 49

Mutated receptor genes or mutated genes, encoding components of Ip3/DAG pathway.

Front 50

What is DAG?

Back 50

Diacylglycerol (DAG) is a second messenger molecule made by phospholipase C (a membrane-bound enzyme), together with inositol triphosphate. Although inositol triphosphate diffuses into the cytosol, diacylglycerol stays close to the plasma membrane, due to its hydrophobic properties.

Front 51

Difference between PKA & PKC, and RTKs

Back 51

PKA & PKC are serine & threonin kinases that primarily regulate intermediate metabolism. RTKs are tyrosine kinases that primarily regulate cell growth, survival, and differentiation.

Front 52

What are RTKs?

Back 52

Receptor tyrosine kinases. Most are monomeric, bitopic transmembrane proteins. Most dimerize after binding ligands.

Front 53

Examples of RTKs

Back 53

EGF, PDGF, NGF, insulin

Front 54

What is Ras?

Back 54

A small monomeric g-protein. Hydrolyzes GTP. Inactive form has GDP-bound; active form has GTP-bound. Has very weak intrinsic GTPase activity. Member of several signalling pathways. Important in cancer! (ras oncogenes are known to occur in ~30% of all human tumours).

Front 55

What makes cAMP?

Back 55

Adenylyl cyclase

Front 56

What does cAMP usually bind to?

Back 56

PKA (Protein kinase A) - it binds to inhibitory subunits, allowing the catalytic subunits to be active.

Front 57

What does phosphorylation of glycogen synthase do?

Back 57

Inhibits conversion of glucose to glycogen.

Front 58

What does PKA do?

Back 58

Mobilizes glucose.

Front 59

How does PKA mobilize glucose?

Back 59

Phosphorylation of glycogen synthase, and phosphorylation of phosphorylase kinase.

Front 60

What does phosphorylase kinase do?

Back 60

Activates the enzyme to catalyze the transfer of phosphate groups to glycogen phosphorylase molecules (speeding up glycogen phosphorylase).

Front 61

Eicosanoids?

Back 61

Nonpolar molecules - regulate a variety of processes including pain, inflammation, blood pressure, and blood clotting. Several over-the-counter drugs that are used to treat headaches and inflammation inhibit eicosanoids.

Front 62

How many transmembrane alpha helices do GPCRs contain?

Back 62

Seven.

Front 63

What do RTKs usually do?

Back 63

Receptors - typically involved in the regulation of cell division and differentiation.

Front 64

What do ligand-gated channels usually function as?

Back 64

Receptors for neurotransmitters.

Front 65

Troponin C?

Back 65

Modulator of muscle contraction (activated by Ca2+)

Front 66

IP3 receptor?

Back 66

Effector of intracellular Ca2+ release.

Front 67

Ryanodine receptor?

Back 67

Effector of intracellular Ca2+ release.