Carbohydrates and Lipids

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Questions and Answers

Why does the ketose family have half the number of stereoisomers compared to the aldose family for a given number of carbon atoms?

The ketone functional group in ketoses eliminates a chiral center present in aldoses. (correct)
Ketoses are only found in L-isomeric forms, reducing the variety.
Cyclization of ketoses is less favorable, limiting the diversity of cyclic forms.
Ketoses are less stable than aldoses, leading to fewer possible structures.

In a Fischer projection, horizontal lines represent bonds angled away from the viewer, while vertical lines represent bonds angled towards the viewer.

False (B)

During the cyclization of an aldose sugar like D-glucose, which carbon atom typically attacks the carbonyl carbon, and what new functional group is formed as a result?

The 5th carbon atom attacks the carbonyl carbon, forming a hydroxyl group.

The only triose sugar in the ketose family is ______.

dihydroxyacetone Signup and view all the answers

Match the following monosaccharides with their classification:

D-Glucose = Aldohexose D-Fructose = Ketohexose Dihydroxyacetone = Ketotriose D-Ribose = Aldopentose Signup and view all the answers

How does the length of a saturated fatty acid affect its melting point?

Longer saturated fatty acids have higher melting points. (C) Signup and view all the answers

Unsaturated fatty acids have a positive correlation between their length and melting point.

False (B) Signup and view all the answers

What is the primary function of triacylglycerols (TAGs) in the body?

long-term energy storage Signup and view all the answers

The process of splitting a triacylglycerol into three fatty acids and glycerol is called ______.

lipolysis Signup and view all the answers

During beta oxidation, what molecule is generated every two carbons that are cleaved from a fatty acid?

Acetyl-CoA (D) Signup and view all the answers

If an 18-carbon fatty acid undergoes beta oxidation, how many molecules of acetyl-CoA will be produced?

9 (C) Signup and view all the answers

Carbohydrates are better suited for long-term energy storage compared to triacylglycerols due to their higher energy density.

False (B) Signup and view all the answers

Match the energy storage molecule with its characteristic.

Carbohydrates such as Glycogen = Short-term energy storage Triacylglycerols = High energy density Carbohydrates = Hydrophilic Signup and view all the answers

Why do multiple branches in glycogen provide an advantage for animals?

Branches create more non-reducing ends, enabling more enzymes to bind and break down glucose simultaneously. (C) Signup and view all the answers

What role do the surrounding amino acids in the enzyme pocket play in an enzymatic reaction?

They create the optimal environment for both the substrate and the transition state. (D) Signup and view all the answers

Lipids are defined primarily by their chemical structure, particularly the presence of a glycerol backbone.

False (B) Signup and view all the answers

What is the primary difference between amylose and glycogen in terms of structure?

Amylose has only 1,4-glycosidic linkages, creating a linear structure, while glycogen has both 1,4- and 1,6-glycosidic linkages, resulting in a branched structure. Signup and view all the answers

In the enzymatic process represented as E + S ↔ ES → EP ↔ E + P, the conversion of ES to EP is always an irreversible reaction.

False (B) Signup and view all the answers

In the omega naming system for fatty acids, the position of the last double bond is determined by counting backwards from the ______ carbon.

omega Signup and view all the answers

In an enzymatic reaction, what is the significance of ensuring that the enzyme is regenerated at the end of the process?

To be reused for further catalysis Signup and view all the answers

Match the following characteristics with the appropriate polysaccharide:

Amylose = Helical structure with 1,4-linkages, used for energy storage in plants. Glycogen = Branched structure with 1,4- and 1,6-linkages, used for energy storage in animals. Signup and view all the answers

In the enzymatic reaction E + S ↔ ES → EP ↔ E + P, ES and EP represent reaction ________.

intermediates Signup and view all the answers

Which of the following is a key distinction between ether and ester linkages in lipids?

Ether linkages are more resistant to breakdown compared to ester linkages. (B) Signup and view all the answers

Match the energy states with their relative stability and impact on the enzymatic reaction:

E + S = Less stable than ES; initial state of the reaction. ES = More stable than E + S; intermediate complex formation. E + P = Lowest energy state; drives the reaction forward. Signup and view all the answers

Cis-bonded fatty acids are less common in biological systems than trans-bonded fatty acids.

False (B) Signup and view all the answers

A fatty acid is designated as 20:2n-6. What does this naming convention indicate about the fatty acid's structure?

The fatty acid has 2 double bonds, 20 carbons and the last double bond is located 6 carbons from the methyl end. (A) Signup and view all the answers

How do enzymes increase the rate of a reaction?

By lowering the activation energy (A) Signup and view all the answers

The ΔG of a reaction provides information about the kinetics of the reaction.

False (B) Signup and view all the answers

What is the significance of geometric and electronic complementarity in enzyme-substrate interactions?

specificity Signup and view all the answers

Enzymes use ________ to separate and concentrate bio-components in specific subcellular sections.

compartmentalization Signup and view all the answers

Match the following terms related to enzyme function with their correct description:

Active Site = The region of an enzyme where the substrate binds and catalysis occurs. Regulatory Site = A secondary binding site on an enzyme that modulates activity. Allostery = The modulation of enzyme activity through binding at a site other than the active site. Transition State = A high-energy intermediate state during a chemical reaction that an enzyme stabilizes. Signup and view all the answers

What is the primary function of the active site in an enzyme?

To bind the substrate and catalyze the reaction (A) Signup and view all the answers

Stabilizing the transition state too much can increase the efficiency of an enzyme.

False (B) Signup and view all the answers

Besides expression or substrate availability, what other mechanism provides a layer of control over enzyme activity?

regulatory sites Signup and view all the answers

Which of the following is NOT a general characteristic of enzyme binding sites?

They occupy a large portion of the enzyme volume (B) Signup and view all the answers

To react, molecules need to collide with high enough ________ and the correct orientation.

energy Signup and view all the answers

In a Lineweaver-Burk plot, what does the slope of the line represent?

$K_m / V_{max}$ (A) Signup and view all the answers

$V_{max}$ is a constant value published for every enzyme, as it is an intrinsic property of the enzyme itself, independent of experimental conditions.

False (B) Signup and view all the answers

Define the term 'turnover number' ($K_{cat}$) in enzyme kinetics.

The turnover number is the maximal number of substrate molecules converted to product per second by a single active site. Signup and view all the answers

The catalytic efficiency of an enzyme is defined as ______.

$K_{cat} / K_m$ Signup and view all the answers

Which type of reversible enzyme inhibitor binds only to the enzyme-substrate (ES) complex?

Uncompetitive inhibitor (B) Signup and view all the answers

How does a competitive inhibitor affect $K_m$ and $V_{max}$?

Increases $K_m$, no change in $V_{max}$ (C) Signup and view all the answers

Noncompetitive inhibitors impact $K_m$, but do not impact $V_{max}$.

False (B) Signup and view all the answers

Match the type of reversible inhibitor with its effect on $K_m$ and $V_{max}$.

Competitive = Increases $K_m$, no change in $V_{max}$ Uncompetitive = Decreases both $K_m$ and $V_{max}$ Noncompetitive = No change in $K_m$, decreases $V_{max}$ Mixed = Affects $K_m$ and $V_{max}$ differently depending on binding preference Signup and view all the answers

Flashcards

Aldose

Has an aldehyde functional group on its backbone.

Ketose

Has a ketone functional group on its backbone.

Fischer Projection

Vertical lines are dashes (away), horizontal lines are wedges (towards).

Sugar Forms

Sugars can exist in both open-chain (linear) and ring (cyclic) forms and interconvert between the two.