Biochemistry Exam 3 (Chapters 11-17)

What are the five classes of lipids

1. Free fatty acids: A common fuel.

2. Triacylglycerols: Storage form of fatty acids.

3. Phospholipids: Membrane lipids.

4. Glycolipids: Membrane lipids composed in part of carbohydrates.

5. Steroids: Polycyclic hydrocarbons with a variety of functions.

How many carbons do typical biological lipids contain (give a range)

14-24 (Most common be 16C and 18C)

Which of the two fatty acids has a higher melting point and why

Stearate because the tight packing allows for van der waals interactions which raises the MP; whereas in trans-please the lack of tight packing from the double bond (unsaturation) does not and lowers the MP

What is the relationship between MP and fatty acid saturation

The more saturated a fatty acid is the higher the Mp

What is the relationship between MP and unsaturation

The more unsaturated the lower the MP

What properties determine MP for fatty acids

Chain length and saturation

# of cis-double bonds (decreases MP)

Longer chains mean more VDW forces; longer chains mean higher MP

Lipids that contain fatty acids (complex lipids) are found to be/function as

Storage and membrane

Lipids WITHOUT fatty acids

Cholesterol, vitamins, pigments, etc.

Is glycogen better at energy storage or is triglycerol? Why?

Triglycerol is better at energy storage because one triglycerol contains 3 fatty acids which means they can store more energy. Fatty acids are also more reduced and carry less water per gram due to fats being nonpolar

What are the 3 types of membrane lipids

1. phospholipids

2. Glycolipids

3. Cholesterol

What is this

Phospholipid/ phosphoglyceride

What is this

Glycolipid

Some lipid molecules are said to be amphipathic, meaning that they have:

A. asymmetric carbons and can exist in left- and right-handed forms.

B. have a dual nature with part of the molecule being hydrophobic and the other

part being hydrophilic.

C. are capable of moving rapidly from one side of a lipid bilayer to the other.

D. carry a positive charge on one end and a negative charge on the other end.

have a dual nature with part of the molecule being hydrophobic and the other part being hydrophilic

Unsaturated fatty acids have double bonds that are in the cis configuration. One of the consequences of this configuration is:

A. an alteration in the charge of the molecule.

B. an alteration in the number of carbons in the molecule.

C. a bend in the molecule.

D. enhanced flexibility of the molecule.

a bend in the molecule.

In phosphoglycerides, fatty acids are esterified at

A. C-1 and C-2 of glycerol.

B. C-1 and C-3 of glycerol.

C. any two of the three glycerol carbons.

D. a glycerol carbon and the phosphate group

C-1 and C-2 of glycerol.

The fatty acid oleate contains 18 carbons and a cis double bond after C-9. Which designation describes the composition and structure of oleate?

18:1

In biological systems, fatty acids usually contain an even number of carbon atoms.

Which fatty acids are MOST common in biological systems?

Fatty acids with 16 and 18 carbons

A triacylglycerol consists of fatty acids attached to:

A. three cholesterols.

B. one glycerol phosphate.

C. two glycerol phosphates.

D. one glycerol.

One Glycerol

What is the make up of a triacylglycerols ( compounds and bonds)

3 fatty acids + Glycerol; linked by ester linkages

If a lipid has a sphingosine backbone it is referred to as

Sphingolipid

What type of backbone do glycolipids use

Sphingosine

Why is it necessary to break down food in smaller pieces?

The body cannot directly absorb and utilize the large, complex molecules found in food

Why are enzymes packaged as zymogens?

To prevent premature/uncontrolled enzymatic activity that could damage cells (regulation)

Proteins are digested into small fragments. What are these fragments called?

Oligopeptides

Oligopeptides are broken down by peptidases into…

Amino acids, dipeptides, and tripeptides

alpha-amylase cleaves what type of bonds

1,4 glycosidic bonds

What other enzymes can digest carbs

Alpha- dextrinase, alpha-glucosidase, lactase (lactose), sucrase (sucrose)

Lipases hydrolyze lipids. What are the products of a broken triacylglycerol

Two fatty acids and a monocylglycerol

Enzymes that are activated by specific proteolytic cleavage are called

Zymogens

The process of digestion in the stomach is carried out in two main ways. One way involves the environment that exists in the stomach. What environmental condition within the stomach promotes digestion?

Low pH (acidity)

Increased levels of cholecystokinin (CCK) lead to a feeling of satiety. CCK is a family of peptide hormones released from the

Small intestine

Saliva is an aqueous solution of which ion?

HCO3− (Bicarbonate ion)

Chylomicrons are

A. micelles.

B. lipoprotein transport particles.

C. comprised of disaccharides and protein.

D. transported from the intestinal lumen to mucosal cells.

lipoprotein transport particles.

Bile salts, which aid in lipid adsorption, are synthesized from cholesterol in the liver and released into the small intestine from the

Gallbladder

What do micelles and chylomicrons have in common?

They both contain fatty acids

What are Cholymicrons composed of

Triacylglycerol and lipoprotein

All digestive molecules (proteases, amylases, and lipases) are hydrolases. This means that they break down substrate using

Water

What transporter does fructose use

GLUT 5

What cotransporter does glucose and galactose use. (Bonus if you name the ion they cotransport with)

SGLT (sodium)

Catabolism/ Catabolic Rxns

Degrade molecules to produce energy

Anabolism/ Anabolic Rxns

Synthesize molecules and requires energy

Amphibolic

Pathways that can function anabolically or catabolically

How many phosphoanhdride bonds in ATP, ADP and AMP?

ATP: 2

ADP: 1

AMP: 0

Why does ATP have a high phosphoryl-transfer potential

1. Charge Repulsion/ Charges

2. Resonance Stabilization

3. Entropy (Increase)

4. Stabilization by hydration

How many negative charges on ATP?

4 negative charges

Why are Phosphate and its esters are especially prominent in biology

Phosphate esters are thermodynamically unstable, yet they are kinetically stable. ( Dumb terms: stable bc the negative charge prevent them from getting broken down by hydrolysis, can be regulated by enzymes)

Metabolic Processes Are Regulated in Three Principal Ways

1. The amount of enzymes present

2. The catalytic activity of enzymes

3. The accessibility of substrates

Which statement correctly describes metabolic reactions?

A. Anabolic processes break down material and transform fuels into cellular energy, whereas catabolic processes require energy for biosynthesis.

B. Catabolic processes break down material and transforms fuels into cellular energy, whereas anabolic processes require energy for biosynthesis.

C. Intermediary metabolism breaks down material and transforms fuels into cellular energy, whereas metabolism requires energy for biosynthesis.

D. Metabolism breaks down material and transform fuels into cellular energy, whereas intermediary metabolism requires energy for biosynthesis.

Catabolic processes break down material and transforms fuels into cellular energy, whereas anabolic processes require energy for biosynthesis.

In a metabolic pathway,

A. a reaction with a positive Δ𝐺 can occur if it is coupled to a reaction with a more negative Δ𝐺.

B. a reaction with a positive Δ𝐺 cannot occur.

C. it is Δ𝐺°, not Δ𝐺, that determines whether a reaction can occur.

D. a reaction with a positive Δ𝐺 can occur if there is an increase in the concentration of the reaction's products.

A. a reaction with a positive Δ𝐺 can occur if it is coupled to a reaction with a more negative Δ𝐺.

Which factor does NOT contribute to the high phosphoryl-transfer potential of ATP?

A. resonance stabilization

B. the adenine ring structure

C. charge repulsion

D. the ability of water to interact more favorably with the products of ATP hydrolysis than with ATP itself

the adenine ring structure

The hydrolysis of ATP drives metabolism by

A. shifting the equilibrium of coupled reactions.

B. providing part of the activation energy for a key reaction.

C. providing energy in the form of heat.

D. altering the conformation of metabolic reactants.

shifting the equilibrium of coupled reactions.

What material in vertebrate muscle serves as a reservoir for high-energy

phosphate groups?

A. glycogen

B. phosphoenolpyruvate

C. creatine phosphate

D. glucose 6-phosphate

creatine phosphate

During catabolic processes, the oxidation of energy-rich molecules often results in

the reduction of NAD+ to NADH.

What comparable molecule is the most commonly used reductant for reductive steps in anabolic processes?

A. FAD

B. NADPH

C. coenzyme A

D. FMNH2

E. ATP

B. NADPH

Acyl groups generated during metabolic processes involving carbohydrates and fatty acids are activated by attachment to

A. glyceraldehyde 3-phosphate.

B. pyruvate.

C. coenzyme A.

D. biotin

C. coenzyme A.

NADPH is commonly found in

Reductive bioSYNTHESIS