c2.1 (chemical signalling)

Question 1

what is a ligand? give 4 examples of signaling ligands in animals

Answer 1

a chemical that binds to another specific molecule

horomones, neurotransmitters, cytokines, calcium ions

Question 2

define specificity (in relation to binding)

Answer 2

the ability of the binding site of a receptor to bind specific ligands

Question 3

define quorum sensing

Answer 3

is a mechanism which allows bacteria to modulate group behaviour

Question 4

look at c2.1 slides 8 & 9

Answer 4

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Question 5

what are cytokines?

Answer 5

small signaling proteins

Question 6

calcium ions are used for signaling within ___ and ____. how does each process involve calcium ions?

Answer 6

muscle fibres = upon signal for contraction, calcium ions move out of sarcoplasmic reticulum, attach to proteins of the sarcomere, triggering muscle contraction

neurons = calcium ions trigger secretion of a neurotransmitter into the synaptic gap via exocytosis

Question 7

amines are small molecules synthesized by modification of amino acids. give 2 examples of amines & what they were synthesized from

Answer 7

melatonin from tryptophan
epinephrine (adreneline) from tyrosine

Question 8

steroid hormones are ____ derived from _____

Answer 8

lipids, cholesterol

Question 9

1 example of ligand used in local signaling & 1 example of ligand used in distant signaling

Answer 9

local = neurotransmitters across the synaptic gap
distant = hormones travelling in the bloodstream

Question 10

receptor proteins can be classified by their location on or in a cell. what are the 2 main types & where are they found?

what signalling molecules typically bind to each one?

Answer 10

cell surface receptors, also known as transmembrane receptors, are integral membrane proteins (peptide horomones & neurotransmitters bind)

intracellular receptors are those found inside the cell (steroids bind)

Question 11

hydrophilic signaling molecules cannot cross the membrane lipid bilayer. what type of receptors do they bind to?

Answer 11

transmembrane receptors

Question 12

transmembrane receptor structure x3

Answer 12

an extracellular portion that binds the signalling molecule

a region of hydrophobic amino acids that are able to interact with the hydrophobic tails of the phospholipids in the core of the membrane

an intracellular portion composed of hydrophilic amino acids that are in contact with the aqueous solution of the cytoplasm

Question 13

types of transmembrane receptors x3

Answer 13

GPCRs (G protein-coupled receptor)
enzymatic receptors
ion channels

Question 14

why do intracellular receptors have hydrophilic amino acids arranged on their surface?

Answer 14

so they can remain dissolved in the aqueous fluids

Question 15

define signaling pathway & its 3 main steps

Answer 15

the process in which binding of an extracellular chemical to a receptor is translated into changes in the cell

reception: the process by which a cell detects a signal in the environment
transduction: the process of activating a change within the cell
response: the change that occurs in the cell as a result of the signal

Question 16

when a signaling molecule binds to its receptor, what happens?

Answer 16

a change in the shape of the receptor

Question 17

(in relation to transduction) activated receptors act in four general ways: (each with example)

Answer 17

intracellular receptors that directly alter gene transcription (such as the testosterone receptor)

transmembrane receptors that are ligand-gated ion channels and allow specific ions to flow into or out of the cell (such as the nicotinic acetylcholine receptor)

transmembrane receptors that activate GTP binding proteins (G-proteins) inside the cell (such as the epinephrine receptor)

transmembrane receptors with enzymatic activity (such as the insulin receptor)

Question 18

define signaling cascade

Answer 18

a series of metabolic reactions in which one reaction triggers the next, in a linear fashion

Question 19

first messengers = ?
second messengers = ?

Answer 19

1st = signaling molecules
2nd = intracellular signaling molecules released by the cell in response to extracellular signaling molecules

Question 20

what are some common second messengers? x3

Answer 20

cAMP, nitric oxide and Ca2+ ions

Question 21

signaling cascades are only necessary for what (& why)?

Answer 21

hydrophilic ligands that must bind transmembrane receptors because they cannot cross the plasma membrane

Question 22

different types of cellular responses to a chemical signal x3

Answer 22

changes in gene expression
changes in cell metabolism
changes in cell shape or movement

Question 23

two major types of gated channel proteins & how they work

Answer 23

voltage gated: open and close in response to changes in the electrical potential of a cell membrane

ligand gated: open to allow ions to pass through the membrane only when a chemical messenger, or ligand, has also bound to the channel

Question 24

watch a video on Ach & binding

Answer 24

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Question 25

all GPCRs consist of ___ and embedded in a ____ (look at image after)

Answer 25

a single polypeptide that is folded into a globular shape cell's plasma membrane

Question 26

in GPCRs, what is attached/attaches to the extracellular loops?

Answer 26

signalling molecules

Question 27

in GPCRs, what is attached/attaches to the intracellular loops?

Answer 27

a protein complex called a G-protein composed of 3 subunits (alpha 𝞪, beta 𝛃, and gamma 𝞬)

Question 28

watch a video or read something on inactive GPCRs

Answer 28

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Question 29

GPCR activation occurs when: x5 steps

Answer 29

a ligand binds to the GPCR, causing the receptor to change shape the shape changes causes GDP to detach from the alpha subunit of the G-protein. GTP (guanosine triphosphate) binds in its place binding of GTP causes the G protein subunits to dissociate into two parts: the GTP-bound alpha subunit and a beta-gamma dimer both parts remain anchored to the plasma membrane, but they are no longer bound to the GPCR, so they can now diffuse to interact with other membrane proteins

Question 30

humans alone have nearly 1,000 different GPCRs, and each one is highly specific to a particular signaling molecule, including: x4

Answer 30

odor molecules and pheromones taste molecules hormones (such as glucagon, epinephrine, GnRH, and oxytocin ) neurotransmitters (such as acetylcholine)

Question 31

common examples of medicinal drugs which are aimed at GPCRs x3

Answer 31

depression medications, chemotherapy drugs, diabetes medicines

Question 32

effects which adrenaline has x6

Answer 32

increase in ventilation rate hydrolysis of glycogen by the liver, releasing glucose into the bloodstream stimulates skeletal muscle contraction release of sweat increase in heart rate constrict muscles around artery walls to increase blood pressure

Question 33

epinephrine binds to cells with a transmembrane receptor called the ____

Answer 33

adrenergic receptor (a GPCR)

Question 34

epinephrine signal transduction begins when the activated alpha subunit of the G-protein activates an enzyme in the cell membrane called ______

Answer 34

adenylate cyclase

Question 35

The activated adenylate cyclase catalyzes the conversion of ___ in the cytoplasm to ______

Answer 35

ATP, cyclic AMP (cAMP)

Question 36

what does cyclic AMP (cAMP)'s structure look like?

Answer 36

a single phosphate is attached to two carbons of the ribose sugar linked to adenine

Question 37

insulin is used to integrate the response of multiple organs in an effort to do what? how is this done?

Answer 37

maintain blood glucose homeostasis insulin causes cells to uptake glucose from the blood to be used in cellular respiration or converted to glycogen

Question 38

insulin binds to cells with a type of transmembrane receptor called what? the intracellular tail of the receptor is a what? what process can it perform?

Answer 38

receptor tyrosine kinase (RTK) tyrosine kinase enzyme that can transfer a phosphate group from ATP to another molecule (phosphorylation)

Question 39

insulin receptor activation occurs when: x3 steps

Answer 39

insulin binds to the receptor the binding of insulin causes structure of receptor to change, making the two tails connect tyrosine kinase in the tail of the receptor phosphorylates multiple tyrosines on the other tail

Question 40

one of the results of the insulin signaling cascade is the movement of ____ embedded with _____ proteins to the plasma membrane when the ____ fuse with the plasma membrane, the protein becomes part of the plasma membrane

Answer 40

vesicles, glucose-transport (GLUT) vesicles

Question 41

binding of a steroid hormone to its receptor leads to changes in gene expression. what are the 6 steps to this?

Answer 41

hormone diffuses through the cell membrane hormone binds to the receptor within the cytoplasm or nucleus, forming a hormone-receptor complex hormone-receptor complex attaches to the DNA at a specific gene hormone-receptor complex acts as a transcription factor, turning “on” the transcription of the DNA into mRNA mRNA is translated into a protein at the ribosome protein has an effect in the cell

Question 42

how does binding of testosterone to its receptor leads to muscle growth? x6 steps

Answer 42

testosterone diffuses through the cell membrane of a muscle cell testosterone binds to its receptor within the cytoplasm, forming a hormone-receptor complex the hormone-receptor complex moves into the nucleus through a nuclear pore, where it acts as a transcription factor. the hormone-receptor complex attaches to the DNA at the gene that codes for a protein called the serum response factor binding of the hormone-receptor complex to the DNA activates the transcription of the serum response factor gene into mRNA mRNA is translated into a serum response factor protein serum response factor protein causes growth of the muscle cell

Question 43

binding of oestradiol to its receptors in the hypothalamus can either inhibit or promote release of gonadotropin-releasing hormone (GnRH). what are the steps for the positive feedback of oestradiol on the hypothalamus that leads to ovulation? x6

Answer 43

oestradiol diffuses through the cell membrane of a hypothalamus cell oestradiol binds to its receptor within the cytoplasm, forming a hormone-receptor complex hormone-receptor complex moves into the nucleus through a nuclear pore, where it acts as a transcription factor and attaches to the DNA at the gene that codes for the gonadotropin-releasing hormone (GnRH) activates the transcription of the GnRH gene into mRNA the mRNA is translated into a GnRH protein the GnRH protein causes the pituitary to release a surge of luteinizing hormone (LH), in turn triggering ovulation

Question 44

binding of progesterone to its receptor in cells of the uterus leads to proliferation of the endometrium during the uterine cycle. what are the steps for progesterone's growth of the endometrium during the menstrual cycle and pregnancy? x6 steps

Answer 44

progesterone diffuses through the cell membrane of endometrial cell progesterone binds to its receptor within the cytoplasm, forming a hormone-receptor complex hormone-receptor complex moves into the nucleus through a nuclear pore, where it acts as a transcription factor, where the hormone-receptor complex attaches to the DNA at the gene that codes for a protein called the insulin-like growth factor binding of the hormone-receptor complex to the DNA activates the transcription of the insulin-like growth factor gene into mRNA mRNA is translated into a insulin-like growth factor protein insulin-like growth factor protein causes cellular proliferation, which leads to the growth of the endometrium during the menstrual cycle and pregnancy.

Question 45

in negative feedback, a product of the signal transduction pathway does what?

Answer 45

INHIBITS another component at the start of the pathway, reducing the signal cascade (the end-products inhibits its own production)

Question 46

testosterone production is regulated by negative feedback. what are the steps to this? x4

Answer 46

testosterone produced in the testes enters the bloodstream and travels to the hypothalamus and pituitary gland hypothalamus detects the level of testosterone in the blood if testosterone levels are too high, the hypothalamus sends a signal to the pituitary gland to stop sending signals to the testes pituitary gland stops sending signals to the testes, which results in a decrease in testosterone production

Question 47

in positive feedback, a product of the signal transduction pathway does what?

Answer 47

further ACTIVATES another component of the pathway, enhancing the signal cascade