Biochemistry Exam 3: Catabolism

Lectures 15.1-17

Plants give us ____ for cellular respiration, and we produce ______, _________, ________

O2, CO2, Chemical Energy (work), Heat

What are the five energy requirements

Energy must be released from food gradually

Energy stored in readily accessible forms

Release of energy controlled so its released at the right time

Just enough energy must be released to maintain body temp.

Non-heat energy available for non-favorable body temp. reactions

Catabolism

Breakdown of large molecules to smaller ones - produces energy

Digestion of macromolecules into subunits

Stage 1 of catabolism

Breakdown of subunits into an oxidized form (acetyal-SCoA)

Stage II of catabolism

Acetyl-SCoA oxidized to produce CO2 and reduced coenzymes

Stage III of catabolism

Oxidative phosphorylation to produce ATP & H2O

Stage IV of catabolism

Four principles of metabolic pathways

Metabolic pathways are highly exergonic and irreversible needing different pathways (-686kcal one way, +686 kcal other way)

Committed steps

Regulated

Specific locations - Due to tight regulation

Spiral sequence

One enzyme or group of enzymes breakdown a polymer one monomer at a time.

Name the 4 high energy molecules (3 coenzymes)

Acety-SCoA (B5)

NADH (B3)

FADH2 (B2)

ATP

FAD is the ______ form of FADH2. This means it has _____ energy

Oxidized - less bonds to H, low

Monosaccharide with the -OH group on the chiral carbon farthest from the carbonyl group (closest to the alcohol) pointed to the RIGHT

D isomer

Monosaccharide with the -OH group on the chiral carbon farthest from the carbonyl group (closest to the alcohol) pointed to the LEFT

L isomer

Carbon atom bonded to both an -OH and an -OR group

Hemiacetal

The carbon that was originally the carbon on the carbonyl group in its ring shape. Positioned as part of a hemiacetal

Anomeric carbon

If the OH group is above the anomeric carbon, the ring is…

Beta

If the OH group is below the anomeric carbon, the ring is…

Alpha

A carbohydrate with an anomeric carbon as part of a hemiacetal group. In a disaccharide, one of these anomeric carbons is free.

Reducing sugar (fully reduced)

You have a cyclic reducing sugar. You oxidize it. You’re adding _____ to the anomeric carbon

Oxygen

______ an aldehyde group gives you a carboxylic acid group

Oxidizing

A bond between the anomeric carbon atom of a monosaccharide and -OR group.

Glycosidic bond

A glycosidic bond between the anomeric C in the C1 position of one monosaccharide, whose hydroxyl group is in the alpha position (below the anomeric carbon), and the hydroxyl group on C4 of another monosaccharide.

Alpha - 1,4 linkage

Maltose has a _____________ linkage

Alpha - 1,4

Lactose has a _________ linkage

B -1,4

Sucrose is not a reducing sugar because…

The anomeric carbons of both structures make up the glycosidic bond.

Reducing sugars have a free anomeric carbon that can open to form an aldehyde in aldoses or a ketone in ketoses. This lets them donate electrons.

Tooth bacteria is able to decay teeth by dissolving minerals in teeth via ________________

H+ increasing, lowering pH/acidity

Five roles of carbohydrates in the body

Source of energy

Phosphorylated to create forms of high energy

Lubricants

Cell receptors

Determines blood type

Two roles of carbohydrates in environment

Cell walls/exoskeletons of invertebrates

Structural stability in plants

Carbohydrates that determine blood type are covalently bonded to membrane proteins and lipids that are…

On the surface of the cell

Conversion of glucose to pyruvate while producing energy

Glycolysis

Synthesis of glucose from amino acids, pyruvate and non-carbohydrates

Gluconeogenesis (new glucose created)

Synthesis of glycogen from glucose

Glycogenesis (glycogen created)

Breakdown of glycogen to glucose

Glycogenolysis

Conversion of glucose to five-carbon sugar phosphates

Pentose phosphate pathway

ATP and citrate or ______ allosteric regulators; ADP and AMP are ______ allosteric regulators

Negative, positive

Cellulose

Most abundant polysaccharide

b-D-glucose units linked by b1,4 glycosidic bonds

Fibrous substance that provides structure in plants

Humans do not produce the enzymes necessary to digest

What two polysaccharides make up plant starch?

Amylose (20%), amylopectin (80%)

Human long term energy

Lipids/fats

Human medium-term energy found in liver and muscles

Glycogen

Glycogen is made up of repeating units of

_______ that are linked by _______

glycosidic bonds and humans _______

digest.

Beta d-glucose, alpha 1-4, can

6-10 (energy phase)

What steps of glycolysis use G3P

What kind of enzyme is G3P

Oxidoreductase

What steps of glycolysis use transferases

1, 3, 7, 10

What steps of glycolysis use isomerases

2, 5, 8

What steps of glycolysis use lyases

4, 9

Purpose of glycolysis

Convert glucose to two molecules of pyruvate while producing energy

A transferase/kinase, hexokinase, adds a phosphate to make glucose-6-phosphate, using 1 ATP in the process. Irreversible step.

Step 1

Isomerase changes glucose-6-phosphate to fructose-6-phosphate by covalent modification

Step 2

Kinase uses 1 ATP to phosphorylate fructose-6-phosphate to make fructose 1, 6 - bis phosphate. The irreversible, committed step of glycolysis.

Step 3

Lyase splits fructose 1, 6 - bis phosphate into two 3-carbon sugars

Step 4

Isomerase takes one of the 3-carbon sugars and rearranges it to make G3P

Step 5

Oxidoreductase/dehydrogenase oxidizes bothG3Ps to produce 2 NADHs

Step 6

Transferase/kinase takes oxidized G3Ps and donates phosphate to ADP to make ATP and 3-phosphoglycerate

Step 7

Mutase/isomerase moves phosphate in 3-phosphoglycerate to make 2-phosphoglycerate

Step 8

Lyase removes water from 2-phosphoglycerate to make phosphoenolpyruvate

Step 9

Transferase/kinase removes the phosphate group from phosphoenolpyruvate to make ATP and pyruvate. Irreversible step

Step 10

1 glucose molecule net yields…

2 NADH, 2 ATP, 2 Pyruvate

NADH and pyruvate are used as…

Energy carriers

What step uses an oxidoreductase/dehydrogenase?

6

When blood glucose levels are high, what is released to create more long-term energy sources (proteins/lipids). Glycolysis speeds up.

Insulin

When blood glucose levels are low, what is released to increase gluconeogenesis

Glucagon

A hormone similar in function to glucagon, but in muscle cells. Creates immediate, instant energy, although it isn’t related to blood glucose levels.

Epinephrine

Insulin is mostly ______ whereas glucagon is mostly _______

Anabolic, cataboli

Insulin binds in the _____ to store glucose as _______

Liver, glycogen

Glucagon binds in the ________ to breakdown _______ to release ______ into the blood

Liver, glycogen, glucose

Glucagon and epinephrine phosphorylate ________ _______ to deactivate the enzyme, inhibiting the ___________

Glycogen synthase, storage of glucose as glycogen

Glucagon and epinephrine phosphorylate _______ _______ to activate the enzyme, inhibiting the _____________________

Glycogen phosphorylase, storage of glucose as glycogen

Insulin dephosphorylates ________ ______ to activate the enzyme, inhibiting the ________________

Glycogen synthase, release of glucose into the bloodstream

Insulin dephosphorylates ________ ______ to deactivate the enzyme, inhibiting the ________________

Glycogen phosphorylase release of glucose into the bloodstream

Epinephrine and glucagon want ______ - the release of glucose into the bloodstream

Glycogenolysis

Insulin wants _______ - the creation of glycogen from glucose

Glycogenesis

Van Gierke’s Disease

Cannot release enough glucose to maintain a high enough blood sugar level