04 Chemistry and Biochemistry 2

Question 1

What are the largest molecules in the body, what are the most common and what do they store?

Answer 1

Nucleic acids.
Common are DNA & RNA.
Store our genetic information.

Question 2

What are the building blocks of nucleic acids?
What 3 sub-units do they consist of?
What are the two types of bases that form nucleotides?

Answer 2

Nucleotides.
A 5-carbon sugar ring, a base, one or more phosphate groups.
Purines - double ringed structures and, pyrimidines - single ringed structures.

Question 3

What 5 carbon sugar does DNA contain?

What 4 bases do DNA nucleotides contain and state is purine or pyrimidine?

Answer 3

Deoxyribose.

1) Adenine (A) - Purine
2) Cytosine (C) - Pyrimidine
3) Guanine (G) - Purine
4) Thymine (T) - Pyrimidine

Question 4

What are the two strands that twist together within DNA?

What are the sides of the DNA formed from and what bond is used.

Answer 4

The double helix.

Formed by the phosphate of one nucleotide and the sugar of the next by a covalent bond.

Question 5

Where are the bases situated and how arranged in a DNA strand?
Which bases pair with which?

Answer 5

Point inward and join with a base on the other strand forming pairs.
Each pair is one purine and one pyrimidine which form a hydrogen bond.
A with T and, C with G.

Question 6

How many strands of nucleotides in RNA and what type of sugar does it contain?
What prevent RNA stands being able to pair properly?

Answer 6

Single strand.
Uses ribose sugar instead of deoxyribose.
An extra OH group on the ribose sugar prevents pairing of the bases.

Question 7

What bases is replaced by what in RNA?

Answer 7

Thymine is replaced by Uracil.

Question 8

What does DNA act as a template for?
What does each strand of the DNA do and what are their names?
What is the RNA used for?

Answer 8

Template for protein synthesis.
One strand codes the sequence of amino acids in a protein and is called the sense strand.
The other strand carries a sequence of complementary bases an called the anti-sense strand.
Used to copy DNA code and translate it into proteins.

Question 9

What actually IS the genetic code and what is it used for?

What is a triplet code and what is each triplet code called?

Answer 9

The sequence of bases.
Used for making all proteins in the body for muscle tissue to enzymes.
Bases are read in sets of 3 where each triplet corresponds to an amino acid, or a start/stop at the end of a protein chain.
Triplet Codon.

Question 10

Explain transcription.

Answer 10

Section of code for the necessary protein is unzipped in the DNA strand.
Free bases in the nucleus join together according to the code section sequence and becomes mRNA (Messenger RNA).
mRNA then moves out of the nucleus into the cytoplasm.

Question 11

Explain translation and protein synthesis.

Answer 11

Ribosomes in the cytoplasm, bind to the mRNA.
The ribosome reads the code in the mRNA and produces chains made up of amino acids (20 different types)
tRNA molecules (Transfer RNA) carry the amino acid to the ribosome and the mRNA is read 3 bases at a time.
As each triplet code is read, the tRNA delivers the corresponding amino acid, which makes a growing chain of amino acids.
Once the last amino acid has been added, the chain folds to make the protein/polypeptide.

Question 12

What is an enzyme, what do they do and can they be used more than once.
In an enzymatic reaction what do we call the starting molecule and after enzymatic conversion, what are they called?

Answer 12

Biological catalysts made from proteins.
Speed up reactions without being changed themselves, so used over and over.
Pre-molecule is called the substrate and after called the product.

Question 13

What suffix do most enzymes have in their name and how are they grouped together?

Answer 13

-ase.

Grouped together by their function.

Question 14

What is the function of the following enzyme groups:
Oxidases,
Dehydrogenases,
Kinases (Phosphotransferases),
ATPases,
Anhydrases,
Proteases,
Lipases,
Isomerases,
Mutases,
Lysases,
Ligases (Synthanases).

Answer 14

Oxidases - add oxygen
Dehydrogenases - remove hydrogen
Kinases (Phosphotransferases) - add phosphate from ATP to another compound
ATPases - split ATP
Anhydrases - remove water
Proteases - split proteins
Lipases - split triglycerides
Isomerases - isomerisation processes
Mutases - change position of the phosphate group within the molecule
Lysases - breaks various chemical bonds
Ligases (Synthanases) - condenses chemical bonds.

Question 15

What is the part of the enzyme that the substrate binds to?
Explain it’s shape.
What is this model usually called?

Answer 15

Substrate binds to the active site of an enzyme.
The active site has a unique shape that compliments the shape of the substrate molecule.
Lock and key.

Question 16

What do some enzymes require in order to work, and what is the enzyme without it’s co-factor called?

Answer 16

Some require co-factors like metal ions or vitamin derivatives.
Without them, they are called an apoenzyme.

Question 17

What is the advantage of a higher temperature and enzymes?
What is it’s disadvantage?
What is usually the optimum temperature to help enzymes work?

Answer 17

Heat makes molecules move and vibrate faster, leading to more collisions and therefore faster reaction rate.
Heat can make atoms in an enzyme vibrate too much and break weak bonds, denaturing the enzyme and stops it working.
Optimum around 40ºc

Question 18

How can changes in the pH of the body affect enzymes?

Answer 18

In overly acidic environment, amino acid side chains can bind to H+, whereas in a base environment, they can lose H+.

Question 19

What is an inhibitor?

What two types of inhibitors are there?

Answer 19

Slows down the speed at which the enzyme works.
Reversible inhibitor - binds to an enzyme by covalent bonds, but can also disengage. If inhibitor detaches, enzymes continues to work as normal.
Irreversible - cannot detach from the enzyme.

Question 20

What is a competitive inhibitor? How can they be overcome?

What are non-competitive inhibitors and are they reversible? Reversible?

Answer 20

Compete with the binding site of the enzyme, with the substrate. Reversible. Overcome with supply of more substrate.
Non-comp bind to a different site on the enzyme which causes a change in the shape of the active site, which means the substrates can not longer be converted.
Can be reversible or irreversible.

Question 21

Why are enzyme inhibitors used as drugs?

How does penicillin work?

Answer 21

To decrease the rate of natural biological reactions.
Works by inactivating and enzyme necessary for the cross-linking of bacteria cells walls - cell wall construction stops and bacteria soon die.

Question 22

What is ATP, what is it used for and made out of?

Answer 22

Adenosine triphosphate - energy currency of the body.
Used to capture the energy released by reactions in the body.
Contains the sugar ribose, the base adenine and 3 phosphate groups.

Question 23

What are 5 functions of ATP?

Answer 23

Capture energy from oxidation process.
Drive synthetic reactions.
Fuel movement.
Transport substances across membranes.
Cell division.

Question 24

What is another energy carrying molecule?
What does it carry instead of phosphate groups?
How does NAD+ oxidize substrates, what does it become?

Answer 24

NAD+
High energy electrons in the form of hydride ion H-.
Oxidises substrates by stealing H-, becomes NADH and is reduced.

Question 25

Hows FAD similar to NAD+, and what does it become after oxidising other molecules?
What 2 things is FAD used in?
What is it derived from?

Answer 25

Also an energy carrying molecule.
Becomes FADH2.
Used in aerobic energy production and fat metabolism..
Derived from riboflavin (vit B2).

Question 26

What is cellular respiration and and what is it’s 4 steps?

Answer 26

Energy from carbohydrates, where carbs are broken down into glucose in the digestive process.
Glucose is then oxidised to form ATP.
1. Glycolysis or anaerobic respiration.
2. Formation of Acetyl  CoA
3. Kreb cycle
4. Electron transport chain.

Question 27

How many enzymatic reactions does it take for glycolysis?
How many ATP’s does it use and how many are produced?
What are the other molecules created?

Answer 27

Approx 10 reactions.
Takes 2 ATP, yields 4.
Also produces, 2 NADH and 2 Pyruvate molecules.

Question 28

In anaerobic conditions when there is no oxygen present, where does the pyruvate remain and what is it converted into in yeast and muscle cells?

Answer 28

It remains in the cytosol.

In yeast cells, it’s converted to ethanol, and muscle cells it’s converted to lactic acid.

Question 29

Once the glucose enters the cell, depending on whether the environment is aerobic or anaerobic, what happens to the pyruvate?

Answer 29

Anaerobic - turned into ethanol or lactic acid.

Aerobic - enters the mitochondria and converted into Co-Enzyme A (CoA) ready for the Krebs cycle.

Question 30

What is Co-Enzyme A?

What does it carry and what is it called when bonded with an acetyl group?

Answer 30

A carrier molecule which is a form of pantothenic acid (vit B5).
Carries energy and call Acetyl CoA when bonded with Acetyl.

Question 31

What is the Krebs Cycle also known as and where does it occur?

Answer 31

Citric Acid Cycle.

Occurs in the mitochondria.

Question 32

What is the final step of the Krebs Cycle? Explain.

Answer 32

Degradation process - oxidative phosphorylation.
Electrons are passed from the electron carriers NADH and FADH2 to the electron-transport chain embedded in the folds of the mitochondria which eventulaly gives up it’s energy.

Question 33

What is the net result of ATP made from 1 molecule of glucose during aerobic respiration, and how many from anaerobic respiration?

Answer 33

36 from aerobic
2 from anaerobic
38 in total

Question 34

What hormone is fat metabolism stimulated by?
What splits the fatty acids from the triglycerides?
The fatty acids are then carried where and by what, what then occurs?
What is the process called that converts fatty acids into Acetyl CoA, and then what part of the ATP creation cycle can the Acetyl CoA enter?

Answer 34

Epinephrine (Adrenaline).
Lipase’s split the fatty acids.
Carried to the liver by blood albumin. Oxidation occurs.
Beta Oxidation Process. Acetyl CoA then enters the Krebs cycle as normal.

Question 35

Can the glycerol from the Triglyceride also be used for energy?
What must it be converted to first and by what?
What helps transport the fatty acids into the mitochondria?

Answer 35

Yes.
Must be converted to glyceraldehyde 3-phosphate by the liver.
L-Carnitine.

Question 36

What are the 4 repetitive steps of beta oxidation?

Answer 36

Oxidation by FAD
Hydration
Oxidation by NAD+
Thiolysis

Question 37

After each cycle of the beta oxidation process cycle, how many carbons are cleaved off each time and creating what?
How much energy is produced from a fatty acid chain?

Answer 37

Cleaved off 2 carbons at a time into Acetyl CoA molecules, until entire fatty acid is used up.
Depends on how long the fatty acid chain is.

Question 38

Can body tissues and the brain use fatty acids for energy when carbohydrate is in short supply?
If not, what can be used and how are these made?
What happens to them once in the brain?

Answer 38

Body tissues can, brain can’t.
Brain can use Ketones.
Liver can convert Acetyl CoA into ketones for the brain.
They are then converted back to Acetyl CoA in the brain for use for energy.

Question 39

What is the production of ketones called, what is the state where a person is making ketones and what is called when a person is at a dangerous level and what causes it?
What type of person is ketoacidosis commonly found?

Answer 39

Ketogenesis.
Ketosis.
Ketoacidosis - caused when too many acidic ketones in the blood, causing the pH of the blood to drop and become acidic.
Commonly found in alcoholics and diabetics.

Question 40

Once an amino acids has been broken down and catabolised, can it then enter the Krebs Cycle?
How much of the body’s energy production comes from catabolised proteins/amino acids?

Answer 40

Yes it can enter the Krebs Cycle.

10-15% of body energy comes from proteins.

Question 41

What is lost in the degradation of amino acids in order to enter the Krebs Cycle, what group is this and what does this create?
Where is this waste excreted, but what is most converted to?

Answer 41

They lose nitrogen – their amine group (NH2).
Results in the creation of ammonia (NH3).
Some excreted in the urine, but most is converted to urea in the urea cycle.

Question 42

What is the term for the synthesis of carbohydrate from non-carbohydrate sources?
Name some source.
Where does this take place, when does it occur and what does it require?

Answer 42

Gluconeogenesis.
Pyruvate, lactate, glycerol, some amino acids.
Mostly takes place in the liver and to a lesser extent, in the kidneys.
Occurs during fasting, starvation or intense exercise.
Requires ATP.

Question 43

What is glyconeogenesis similar to in reverse, but how many key differences?

Answer 43

Like glycolysis in reverse, but 3 key differences.

Question 44

What percentages of adult energy are obtained from carbs, fat and protein?
In fasting states, what order does the body obtain it’s energy?

Answer 44

Carbs 47%, Fat 38%, Protein 15%.

While fasting, the body will use glycogen stores, then fat stores, the protein/muscle.

Question 45

What 4 parts of the body can use glucose for energy?
What 4 parts of the body can use fatty acids for energy?
What 4 parts of the body can use ketones for energy?

Answer 45

Red blood cells, Lymphocytes, Brain, Skeletal Muscle.
Liver, Kidney Cortex, Cardiac and Skeletal Muscle.
Cardiac Muscle, Kidney Cortex, Brain, Skeletal Muscle.