Test 2 - hw content

Question 1

What do Reductase enzymes do?

Answer 1

Reductase enzymes belong to the E.C. 1 class of oxidoreductases and catalyze reduction reactions. A reduction reaction involves the gain of electrons; it is usually coupled to oxidation and termed a redox reaction. Reductases lower the activation energy needed for redox reactions to occur.

Question 2

what do ligase enzymes do

Answer 2

Question 3

what do polymerase enzymes do

Answer 3

Function: Catalyze the polymerization (synthesis) of macromolecules.

Example: DNA polymerase in DNA replication, RNA polymerase in transcription.

Question 4

what do carboxylase enzymes do

Answer 4

Function: Catalyze the addition of carboxyl groups ( − 𝐶 𝑂 𝑂 − −COO − ) to substrates. Example: Acetyl-CoA carboxylase is key for fatty acid synthesis by converting acetyl-CoA to malonyl-CoA.

Question 5

what do kinase enzymes do

Answer 5

Function: Transfer phosphate groups from ATP to other molecules (phosphorylation), regulating activity.

Example: Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) in photosynthesis.

Question 6

what do isomerase enzymes do

Answer 6

Function: Convert molecules into their isomeric forms.

Example: Phosphoglucoisomerase in glycolysis and gluconeogenesis.

Question 7

Answer 7

different for different cell types with identical receptors

Question 8

What effect will a signaling molecule have on a target cell if its receptor is present in different amounts or if the molecule is present at varying concentrations

Answer 8

The response depends on the concentration of the signaling molecule

Question 9

In a chemical pathway, what’s the signal?

Answer 9

The signal refers to the primary ligand or molecule that initiates the response.

Question 10

In a chemical pathway, what’s the transducer?

Answer 10

A transducer converts one type of signal into another.

Question 11

In a chemical pathway, what’s the effector

Answer 11

An effector is the molecule that directly brings about a physiological change.

Question 12

In a chemical pathway, what’s the second messenger

Answer 12

Second messengers are small molecules that propagate and amplify the signal within the cell.

Question 13

List the steps/mechanisms of a chemical pathway

Answer 13

the signal, the transducer, the effector, the second messenger.

Question 14

SKIP For each step of the pathway, indicate what happens when epinephrine binds to the beta-adrenergic receptor.

Answer 14

signal: Epinephrine (adrenaline) binds to the beta-adrenergic receptor (GPCR) on the target cell membrane.
transducer: The G protein (Gs) is activated when the receptor undergoes a conformational change.

The alpha subunit of the G protein exchanges GDP for GTP, activating the protein.

The G protein dissociates and interacts with the next step (effector).
effector: The effector is adenylyl cyclase, an enzyme that catalyzes the conversion of ATP into cyclic AMP (cAMP).
the second messenger: cAMP acts as the second messenger by activating protein kinase A (PKA).

PKA then phosphorylates other proteins, leading to physiological responses such as:

Increased heart rate (in cardiac cells)

Glycogen breakdown (in liver cells)

Question 15

what type of compound is
thyroxine
epinephrine
testosterone
estrogen
norepinephrine
melatonin
ADH (antidiuretic hormone)
oxytocin

Answer 15

thyroxine: thyroid hormone
epinephrine: catecholamine - neurotransmitter/hormone
testosterone: steroid hormone
estrogen: steroid hormone
norepinephrine: catecholamine neurotransmitter
melatonin: hormone
ADH (antidiuretic hormone): peptide hormone
oxytocin: peptide hormone

Question 16

whats a peptide hormone

Answer 16

Peptide hormones are made of amino acids (short chains or full proteins) and are water-soluble.

Question 17

whats a steroid hormone

Answer 17

Steroid hormones are derived from cholesterol, making them lipid-soluble.

Question 18

what’s a catecholamine neurotransmitter

Answer 18

Catecholamines are derived from tyrosine and act as both hormones and neurotransmitters.

Question 19

Does vitamin D bind to a cell on the outside of the cell membrane?

Answer 19

Hydrophilic molecules bind outside of the cell (cant pass through the lipid bilayer) while hydrophobic molecules bind inside of the cell.

Vitamin D is lipid soluble so it binds inside of the cell (acts like a steroid hormone).

Question 20

fill in: G proteins are composed of alpha, beta and _____ subunits

Answer 20

gamma

Question 21

Catabolic or anabolic? FAD, reductase, dehydrogenase, NADPH, NAD+

Answer 21

catabolic: NAD+, FAD, hydrogenase
anabolic: NADPH, reductase

Question 21

True or false: lipid soluble compounds bind to intracellular receptors. give an example.

Answer 21

TRUE, vitamin D

Question 21

What are the three steps of signal transduction

Answer 21

Reception – The target cell detects a signaling molecule (ligand) that binds to a receptor protein.

Transduction – The binding of the signaling molecule changes the receptor protein in some way, initiating a signal transduction pathway.

Response – The transduced signal triggers a specific cellular response (like gene expression, enzyme activation, etc.).

Question 22

True or false: signal transduction cascades directly transmit a single stimulus to a single target cell

Answer 22

Incorrect because cascades amplify and diversify the signal to multiple targets.

Question 23

What happens if the G alpha subunit eliminated its GTPase activity? how does this turn into a mutation?

Answer 23

it would be unable to hydrolyze GTP to GDP. - The signaling pathway could be activated for an extended period, possibly resulting in undesirable cell proliferation. - The concentration of cAMP in the cell would be continuously elevated. - Gα would be activated for an extended period.

Question 24

What event must take place for the termination of a signal generated by the binding of a ligand to a receptor tyrosine kinase

Answer 24

Phosphatases hydrolyze key phosphorylated residues Receptor tyrosine kinases (RTKs) are activated when a ligand binds, causing them to dimerize and autophosphorylate (they add phosphate groups to themselves on tyrosine residues). This phosphorylation triggers downstream signaling. To terminate the signal, phosphatases remove (hydrolyze) these phosphate groups.

Question 25

Does estrogen bind to a cell on the outside of the cell membrane?

Answer 25

no lipid soluble steroid

Question 26

Does glucagon bind to a cell on the outside of the cell membrane?

Answer 26

yes, its water-soluble (peptide hormone)

Question 27

Does testosterone bind to a cell on the outside of the cell membrane?

Answer 27

no, lipid soluble steroid

Question 28

separate into hydrophobic and hydrophilic peptide hormones protein hormones steroid hormones catecholamines thyroid hormones

Answer 28

hydrophobic: steroid, thyroid hormones hydrophilic: peptide, protein hormones and catecholamines

Question 29

fill in the blank: the g protein alpha subunit binds GTP when its ___

Answer 29

active

Question 30

fill in the blank: one common ___ _____ triggered by GPCR signals is ____

Answer 30

second messenger, cAMP

Question 31

fill in the blank: in the absence of a signal GDP attaches to the ____ subunit

Answer 31

alpha

Question 32

true or false and why? "GPCRs possess five membrane spanning segments."

Answer 32

False. GPCRs have seven transmembrane (helical) segments, not five.

Question 33

True or false: steroid hormones bind to receptors outside of the cell. give an example.

Answer 33

false, they bind inside. testosterone estrogen

Question 34

True or false: peptide hormones bind to receptors outside of the cell. give an example.

Answer 34

true, water soluble ex glucagon

Question 35

true or false: A second messenger carries a signal from a tissue or organ to a target cell.

Answer 35

Incorrect because second messengers operate within a cell, not between tissues/organs.

Question 36

true or false: A ligand phosphorylates protein residues, ending the signaling cascade inside the cell.

Answer 36

Ligands don't phosphorylate proteins directly — kinases do. And phosphorylation usually propagates the signal rather than ends it.

Question 37

true or false: A ligand, such as a hormone, binds to a specific cell surface receptor on a target cell.

Answer 37

true

Question 38

true or false: A receptor may pass on a signal by interacting with another protein or by acting as an enzyme.

Answer 38

true

Question 39

true or false: Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly.

Answer 39

true

Question 40

true or false: Phosphatases remove phosphoryl groups from polypeptides, regulating a cell's response.

Answer 40

true

Question 41

true or false: A receptor changes conformation upon binding, transmitting a signal across the cell membrane.

Answer 41

true

Question 42

true or false: A second messenger may carry a signal from the cell membrane to an organelle.

Answer 42

true

Question 43

how do you hydrolyze GTP to GDP?

Answer 43

Signal comes in → Ligand binds to GPCR. GPCR activates Gα, which swaps GDP for GTP → Gα is now active. Active Gα goes off and activates effectors (like adenylyl cyclase → cAMP). Eventually, Gα hydrolyzes GTP to GDP using its GTPase activity. This hydrolysis switches Gα off, and it reunites with the βγ subunit = back to resting state.

Question 44

true or false: phosphates phosphorylate

Answer 44

wrong, phosphatases remove phosphate groups.

Question 45

true or false: kinases phosphorylate causes the activation of a signal

Answer 45

true

Question 46

true or false: kinases hydrolyze

Answer 46

kinases don’t hydrolyze phosphate groups; that’s what phosphatases do.

Question 47

explain the pentose phosphate pathway

Answer 47

The Pentose Phosphate Pathway (PPP) is an alternative route for glucose-6-phosphate (instead of glycolysis) that helps the cell: - Make NADPH (Making fatty acids and cholesterol, Neutralizing reactive oxygen species (with glutathione)) - Make ribose-5-phosphate (for building nucleotides/DNA/RNA) 1. Oxidative Phase (Irreversible) Goal: Make NADPH and ribulose-5-phosphate Steps: Glucose-6-phosphate → oxidized by G6PD (glucose-6-phosphate dehydrogenase) Generates NADPH Releases CO₂ Produces ribulose-5-phosphate ✅ Key products here: 2 NADPH and 1 CO₂ per glucose-6-phosphate 2. Non-Oxidative Phase (Reversible) Goal: Make ribose-5-phosphate or convert sugars back into glycolysis intermediates Depending on what the cell needs: If the cell wants nucleotides, it keeps ribose-5-phosphate If the cell doesn't need nucleotides, it recycles the carbon into fructose-6-phosphate and glyceraldehyde-3-phosphate (glycolysis intermediates)

Question 48

give the steps of glycolysis

Answer 48

Question 49

what happens if lactate dehydrogenase is absent during glycolysis

Answer 49

NADH builds up NAD⁺ runs out

Question 50

whats the difference between glycolysis and glucogenesis

Answer 50

Question 51

true or false: Hexokinase is a type of transferase that catalyzes the transfer of a phosphoryl group from ATP to a hexose.

Answer 51

true

Question 52

true or false: Hexokinase is found in the cytosol.

Answer 52

true

Question 53

true or false: Because hexokinase brings the OH of glucose close to ATP, the hydroxyl group of water can enter the active site and hydrolyze ATP to ADP and Pi

Answer 53

False — hexokinase prevents water from accessing the active site to avoid unwanted ATP hydrolysis. It ensures ATP is used productively to phosphorylate glucose.

Question 54

true or false: Hexokinase transfers the terminal phosphate of ATP to carbon 3 of glucose.

Answer 54

False — the phosphate is transferred to carbon 6, not carbon 3. → The product is glucose-6-phosphate, not glucose-3-phosphate.

Question 55

in anaerobic conditions, how many atp gets produced by glycolysis

Answer 55

2 atp per glucose

Question 56

why is insulin released

Answer 56

Insulin is released due to high glucose levels and results in the inactivation of glycogen phosphorylase.