IB Bio HL C2 Quiz Review: Signalling and Muscles

need to add c2.1.12, c2.1.13, c2.1.14 and 3.3.1-.9

What are two examples of chemical signaling?

Neurotransmitters and hormones

What are the 3 types of hormones?

amines, peptides/proteins, steroids

What are hormones?

Chemical signals secreted from endocrine glands that travel through the blood stream to receptors in cells

What are amine hormones?

Small molecules synthesized by modification of amino acids

What are 2 examples of amine hormones?

Melatonin and epinephrine

What is melatonin derived from?

Tryptophan

What is epinephrine derived from?

Tyrosine

What is the purpose of melatonin?

Secreted by the pineal gland to regulate the circadian rhythm

What is the purpose of epinephrine?

Secreted by the adrenal glands to activate flight vs fight response

Peptides and proteins are ________ and therefore can’t pass through hydrophobic center of plasma membranes of cells, so their receptors are found on the surface of target cells

water soluble

A ________ forms a peptide bond between amino acids

condensation reaction

Examples of peptides (short polypeptide chains)

antidiuretic hormone (water retention in kidneys), oxytocin (contractions), and gonadotropin-releasing hormone (puberty)

Examples of protein (larger polypeptide chains)

insulin (lowers blood glucose levels), glucagon (raises blood glucose levels)

Examples of glycoprotein (larger polypeptide chains)

FSH and LH (menstrual cycle and production of eggs and sperm)

What are steroid hormones?

Lipids derived from cholesterol

steroid hormones are ____ in water

insoluble

Examples of steroid hormones:

1. estrogen (ovaries- female sex characteristics/mesntrual cycle)

2. progesterone (ovaries/placenta- prepares for fertilized egg/pregnancy/milk secretion)

3. testosterone (testes- male sex characteristics)

What are neurotransmitters?

Chemicals that transmit signals across a synpase, ONLY HAVE LOCAL EFFECT

What are the types of neurotransmitters based on chemical structure?

• amines

• amino acids

• peptides

• esters

• gasses

What are examples of neurotransmitters?

amino acids: glutamic acid, GABA

amines: dopamine, serotonin

peptides: endorphines

esters: acetylcholine

gases: nitric oxide, carbon monoxide, hydrogen sulfide

________ signaling involves the use of a chemical signal from a sending cell to a receiving cell that had the complementary receptor

Cell-to-cell

____ signaling involves diffusion between adjacent cells while _____ signaling involves molecules being transported all throughout the body

Local, distant

Ligand

chemical that binds to another specific molecule

Examples of signaling ligands:

Hormones, neurotransmitters, cytokines, calcium ions

Receptor

Protein in or on the target cell that sets off a response when the ligand binds to it

Transmembrane receptors (cell surface receptors) are

integral membrane proteins

Ex of transmembrane receptors (cell surface receptors):

• ligand gated ion channels

• g-protein coupled receptors

• enzyme-linked hormone receptors

intracellular receptors are

found inside the cell

Ex of intracellular receptors

• cytoplasmic and nuclear receptors for steroid hormones

Transmembrane receptors contain 3 parts:

1. Extracellular part that binds to signalling molecule

2. Hydrophobic amino acid part that interacts with the hydrophobic tails inside the membrane

3. Intracellular portion that’s composed of hydrophilic amino acids that interacts with the cytoplasm

Ion channel linked receptors (transmembrane), like the nicotinic acetylcholine receptor work by

Opening when the ligand binds, allowing ions to diffuse into the cell, changing the voltage across the plasma membrane

Epinephrine receptors are _____

G-protein linked receptors

G-protein linked receptors work by:

Using 7 membrane spanning regions to activate G-proteins in a cell

Enzyme linked receptors work by:

Activating a sequence of reactions in a cell when a ligand binds to it’s receptor site

Insulin receptors are an example of _________

Enzyme linked receptors

Intracellular receptors are

small signaling molecules that can cross the lipid bilayer

Intracellular receptors have _______ ______ _____ on their surface so they can remain dissolved in aqueous solutions

hydrophilic amino acids

The three steps of the chemical sign

1. Reception: cell detects a signal in environment

2. Transduction: change is activated

3. Response

Signalling molecules are called _____ __________

first messengers

first messengers are often

hormones or neurotransmitters that bind to specific receptors

Peptide hormones and neurotransmitters typically ______ molecules that must bind to transmembrane receptors

hydrophilic

Can steroid hormones pass through the phospholipid bilayer?

Yes

Steroid hormones are hydrophobic/hydrophilic?

hydrophobic

Transduction happens when the binding of the signaling molecule to the receptor induces:

a change in the shape of the receptor

Signalling cascade

series of metabolic reactions in which one reaction triggers the next

Second messengers

Small molecules in the cell that act as intracellular messengers in response to extracellular molecules

Examples of secondary messengers

cAMP, nitric oxide and Ca2+ ions

Signalling cascades are only necessary for _____ hydrophilic ligands

hydrophilic

2 types of channel gated proteins:

1. voltage gated channel

2. ligand gated channel

Gated channel proteins are selectively permeable meaning:

they can open or close in response to a signal

Voltage gated channels’ purposes:

muscle cell contraction and neuronal signaling

Ligand gated channels work by

Opening to allow positively charged ions to pass through ion channel when ligand has bound to the channel

Acetylcholine receptors work by:

accepting Ach that’s diffused across membrane from presynaptic neuron to bind to transmembrane acetylcholine receptor on the posynaptic cell

When Ach binds, the acetylcholine receptor (AchR) undergoes conformational change which:

open pore in protein allowing sodium ions to move through facilitated diffusion

The Na+ ions that move in after the AchR changes shape causes the postsynaptic cell to

depolarize, triggering action potential

All G-protein coupled receptors (GPCRs) consist of

single polypeptide folded in a globular shape embedded in plasma membrane

What does the extracellular loop of the GPCR do?

Forms binding site that signaling molecules attach to

What does the intracellular loop of the GPCR do?

Attach to G-protein complex which contains alpha, beta and gamma protein subunits

______ is bound to alpha subunit of the G-protein complex and the entire GPC is attached to a nearby GPCR

GDP (guanosine diphosphate)

GPCR activation occurs when

1. Ligand binds to GPCR, changing shape

2. Shape change causes GDP to detach from alpha subunit

3. GTP binds in its place

4. GTP binding causes GP subunits to separate

   1. GTP-bound alpha subunit

   2. GTP-bound beta-gamma subunit

5. Both remain anchored to plasma membrane but can diffuse to interact with other membrane proteins

Odor/taste molecules, pheromones, hormones (glucagon, epinephrine, gonadotropin-releasing hormone, oxytocin) and neurotransmitters (acetylcholine) are examples of _________

GPCRs

Epinephrine is an _____ hormone

amine

Adrenaline means

ad (at) + renal (kidney)

Epinephrine means

epi (above) + nephron (kidney)

Effects of epinephrine reaction:

• Hydrolysis of glycogen by liver releasing glucose into bloodstream

• Increase of ventilation rate

• Dilation of bronchioles

• Stimulation of skeletal muscle contraction

• Triggers sweat

• Increase of heart rate by firing of SA node of heart

Epinephrine is _____ and cannot pass through hydrophobic center of the membrane

hydrophilic

Epinephrine receptors are found on ______ of target cells

surface

Epinephrine binds to transmembrane receptors known as

adrenergic receptors

Epinephrine receptor activation occurs when:

1. Epinephrine binds to GPCR causing conformational change

2. Change causes GDP to detach from alpha subunit

3. GTP binds in its place

4. GTP binding causes GP subunits to separate into alpha and beta-gamma

5. Subunits diffuse laterally to interact w other membrane proteins

Epinephrine signal transduction occurs when activated alpha subunit of GP activates enzyme known as

adenylate cyclase

Epinephrine _____ adenylyl cyclase while melatonin ______ it.

activates, inhibits

Epinephrine signal transduction

1. Adenylyl cyclase is activated by alpha subunit

2. Activated adenylyl cyclase catalyzes the conversion of ATP to cyclic AMP

cAMP (modified adenine nucleotide) is composed of

single phosphate attached to two carbons of ribose sugar that’s linked to adenine

epinephrine response occurs when

1. cAMP (2ndary messenger) rapidly diffuses through cytoplasm

2. cAMP activates other molecules that propagates signal into physiological change

Insulin is a _____ hormone

protein

Insulin is made up of

non-conjugated protein (made of folded amino acid chains)

Insulin’s function:

causes cells to uptake glucose from the blood to be:

1. used in cellular respiration

2. converted to glycogen

Insulin stimulates

• skeletal muscles

• liver

• adipose tissue

Is insulin hydrophilic or hydrophobic?

hydrophilic

What hormone binds to a Receptor Tyrosine Kinase?

Insulin

What is a kinase?

Enzyme that can transfer a phosphate group from ATP to another molecule (phosphorylation)

Insulin receptor activation occurs when

1. Insulin binds to the receptor

2. Binding causes receptors tails to connect

3. Tyrosine kinase in receptor tail phosphorylates tyrosines in the other tail

Insulin signal transduction occurs when

phosphorylated tyrosine kinase launches metabolic reactions within cell

Insulin response occurs when:

1. vesicles embedded with glucose-transport proteins move to plasma membrane

2. vesicles fuse w/ membrane and transport protein becomes part of plasma membrane

3. glucose transport then allows glucose into the cell through facilitated diffusion

Process of steroid hormone

1. Hormone diffuses through the cell membrane

2. Binds to the receptor in cytoplasm/nucleus, forming hormone-receptor complex

3. Hormone-receptor complex attaches to the DNA at a specific gene.

4. Hormone-receptor complex acts as a transcription factor, turning “on” the transcription of the DNA into mRNA

5. The mRNA is translated into a protein at the ribosome

6. The protein has an effect in the cell   

How does testosterone cause a response in the cell?

1. Testosterone diffuses thru the cell membrane of a muscle cell

2. Testosterone binds to its receptor within the cytoplasm, forming a hormone-receptor complex

3. The hormone-receptor complex moves into the nucleus through a nuclear pore, where it acts as a transcription factor, attaches to the DNA at the gene that codes for a protein called the Serum Response Factor

4. Binding of the hormone-receptor complex to the DNA activates the transcription of the Serum Response Factor gene into mRNA

5. The mRNA is translated into a Serum Response Factor protein

6. The Serum Response Factor protein causes growth of the muscle cell

What are 3 examples of steroid hormones in humans?

Estrogen, progesterone, and testosterone

Where is estrogen secreted from?

ovaries