Summary of hard questions

Question 1

Name intermediates of the citric acid cycle

Answer 1

Citrate-Isocitrate-a-ketoglutarate-succinyl-CoA-succinate-fumarate-malate-oxalacetate

Question 2

Name enzymes of the citric acid cycle

Answer 2

citrate synthase-aconitase-isocitrate dehydrogenase-a-ketoglutarate dehydrogenase-succinyl-CoA synthase-succinate dehydrogenase-fumarase-malate dehydrogenase

Question 3

Name key intermediates of glycolysis

Answer 3

Glucose-Fructose-1,6-biphostphate-2 molecules of glyceralaldehyd-3-phostphate-2 molecules of pyruvate

Question 4

What’s the energy yield of glycolysis and citric acid cycle?

Answer 4

Glycolysis: 2ATP and 2 NADH

Citric acid cycle: 4 ATP, 10 NADH + H+, and 2 FADH2

Question 5

Draw a picture of the electorn transport chain

Answer 5

Draw picture

Question 6

What’s the energy exchange for NADH and FADH2

Answer 6

Each NADH+H+ yield approximatly 2.5ATP

Each FADH2 yield approximatly 1.5ATP

Question 7

Describe the purpose of gluconeogenesis, and from which molecule it starts

Answer 7

The purpose of gluconeogenesis is to convert molecules such as lactate, pyruvate, glycerol, amino acids and intermediates of the TKA cycle into glucose. Gluconeogenesis is important since the brain requires 20g of glucose every day and it’s important this energy need can be met.

Question 8

Name some allosteric regulators of gluconeogenesis and glycogenolysis

Answer 8

F-2,6-BP and AMP with inhibit gluconeogenesis and accelerate glycolysis. Citrate amplifies gluconeogenesis and inhibits glycogenolysis.

Question 9

Name key enzymes for glycogenolysis and describe what they do

Answer 9

Phosphorylase kinase stimulate glycogen degredation and glycogen phosphorylase catalyze the reaction that turns glycogen into Glucose-1-phostphate

Question 10

Name key enzymes for glucogenesis and what they do

Answer 10

pyruvate carboxylase makes pyruvate into oxaloacetate, PEP carboxykinase catalyzes an irreversible step of gluconeogenesis, the process whereby glucose is synthesized, fructose 1,6-bisphosphatase catalyzes the hydrolysis of fructose-1,6-bisphosphate to fructose-6-phosphate, and glucose 6-phosphatase catalyses the terminal step of gluconeogenesis.

Question 11

Describe the key steps in fatty acid oxidation, and where they occur

Answer 11

Fatty acid oxidation occurs in the mitochondria and it breaks down one CH2 at a time with thiolysis (HS-CoA). Four repeatable reactions generate FADH2, NADH and acetylCoA. B-oxidation occurs at the B carbon of the fatty acid. There are four steps in fatty acid oxidation, oxidation, hydration, oxidation, thiolysis.

Question 12

Name the key enzymes in fatty acid synthesis, and where they can be found

Answer 12

Acetyl-CoA carboxylase catalyzes the commitment step in fatty acid synthesis. Fatty acid synthase catalyzes a series of reactions by adding two carbons to a growing fatty acid chain. Fatty acid synthesis occurs in the cytoplasma and ER in the liver and adipose tissue

Question 13

Describe the basic structure and function of the proteasome

Answer 13

The proteosome has 2 alpha rings and one B ring, 2 S cap and one S core. The proteosome control cell cycle progression, apoptosis and protein degredation.

Question 14

Name the end products of amino acid breakdown

Answer 14

The nitroge group is used for amino acids, nucleotides, biological amines or turns into carbomylphostphate to enter the urea cycle. The carbon skeleton can either enter the citric acid cycle to get ATP, become pyruvate or excalacetrate to becom glucose, or acetylCoA to become ketone bodies and fatty acids.

Question 15

Name the different mechanisms for amino group removal

Answer 15

Any amino acid can be converted into an intermediate of the citric acid cycle. Once the amino group is removed, usually by transamination, the α-keto acid that remains is catabolized by a pathway unique to that acid and consisting of one or more reactions.

Question 16

Name the five key steps of the urea cycle, and where they occur

Answer 16

1)Formation of carbamoyl phosphate in the mitochondrial matrix 2)Formation of citrulline3)Formation of arginosuccinate4)Arginosuccinate is cleaved into fumarate and arginine.5)Arginine is converted into urea and ornithine. Step 1 and 2 occur in the mitochondria matrix, step 3,4, and 5 occur in the cytosol.

Question 17

Describe how glycolysis and the citrate cycle are connected to protein biosynthesis

Answer 17

Amino acids are derived from seven metabolic intermediates in three metabolic processes: Glycolysis, Pentose phosphate pathway, Citrate cycle

Question 18

Name key components required for cell signaling (receptor, signal, transducers, effectors) and where they are usually located

Answer 18

Most signals bind to receptors that are located on the outside of the cell membrane and does not enter the cell. The cell receptors act as signal transducer by converting the extracellular ligand binding to an intracellular signal that is amplified and carried on by second maéssanger that will bind to effectors that alters the cell’s behavior for example by affection protein synthesis.

Question 19

Name the four receptor families with examples, and their respective subtypes

Answer 19

G-protein coupled receptors: A,B,V and Fizzled/TAS2.
Nuclear receptors: I,II,III and IV
Ligand gated ion channels: cys loop receptors, ionotropic glutamate receptors and ATP gated channels
Enzyme linked receptors: Tyrosine kinases, Tyrosine-kinase associated, Receptor like tyrosine phosphatases, Serine/threonine kinases, Receptor guanylyl cyclases, Histidine-kinase associated receptors.

Question 20

Describe the basic structure of the four receptor families and, in general terms, their mode of action

Answer 20

Ion channel-coupled receptors also known as channel linked receptors are ionotropic receptors are fast acting and can be found in nerve and muscle cells for example. They act through a small humber of neurotransmitter that open or close ion channels by binding to them, temporarily changing the ion permeability of the cell membrane causing hyperpolarization and depolarization.

G protein coupled receptors are found in the cell membrane and can be activated with a signal molecule. As it is activated it changes shape and moves down the cell membrane to bind to the inactivated G protein and as a result activates it. GTP will then take the place of the GDP. The activated protein will then detach from the receptor and bind to the enzyme. The enzymes will then catalyze the intracellular response and the receptor and protein goes back to it’s previous form.

Enzyme linked receptors act slowly over hours and often catalyze reactions such as growth hormone for example and act over long periods of time. The receptors either function as enzymes or dissociate from enzymes. They often have their ligand binding site outside the cell membrane and their catalytic or enzyme binding site on the inside of the membrane.

Nucleus receptors act over hours and affect transcription thus affecting the cell very long term. The receptor is inside the nucleus so the signaling molecule enters the cell membrane and the nucleus to activate the receptor.

Question 21

Name and describe the function of second messengers

Answer 21

Calcium ions, AMP and GMP. They amplify and carry on the signal within the cytosol.

Question 22

Identify the major tissues that make up the endocrine system, and the main hormones derived from them

Answer 22

Pineal makes melatonin, Pitutary makes growth hormones and cortisol, Thyroid makes thyroid hormones, Testis and Ovaroes make sex hormones, Pancreas makes insulin and glucagon, Adrenal gland makes cortisol, adrealine, nordadrealine.

Question 23

Name the three major hormone classes and their respective subclasses

Answer 23

Steroid: progestogens, (corticoids), androgens, and estrogens.
Amino acid: epinephrine and norepinephrine

Question 24

Describe, in basic terms, the mode of signaling for all hormone classes

Answer 24

Steroid hormones which are lipid derived and can pass through the cell membrane. Steroid hormones are made from cholesterol, all cells produce cholesterol but few can turn the cholesterol into steroid hormones. Amino acid hormones are mostly derived from tyrosine and act on membrane receptors. Peptide hormones are complex molecules, encoded in the DNA and also act on transmembrane receptors. Eicosanoid (non cholesterol lipid) hormones are mostly derived from poly unsaturated fatty acids and act mainly short range.