Sneak-Preview 2025 – Biochemistry Review

40 question-and-answer flashcards summarizing the key biochemical concepts, metabolic states, functional groups, amino acids, protein structure, enzyme kinetics, and study tips presented in the Sneak-Preview 2025 lecture notes.

How many Calories per gram do carbohydrates provide?

4 Cal/g

What polysaccharide is the storage form of glucose in humans?

Glycogen

Which dietary fuel is the most energy-dense?

Triglycerides (fats) at 9 Cal/g

How many Calories per gram do proteins provide?

4 Cal/g

Which two functional groups combine to form a peptide bond?

An amino (-NH₂) group and a carboxyl (-COOH) group

What is oxidation in metabolic terms?

Loss of electrons from a dietary component with capture of that energy for the body

Which hormone rises in the fed (post-meal) state?

Insulin

What process stores excess glucose as glycogen in liver and muscle?

Glycogenesis

Which hormones dominate in the basal (post-overnight fast) state?

Low insulin, high glucagon

Name the liver pathway that breaks down glycogen to maintain blood glucose during fasting.

Glycogenolysis

What alternative fuel is generated from fats in the liver during fasting?

Ketone bodies (ketogenesis)

During the starved state, which tissues release fatty acids for energy?

Adipose tissue (triglyceride mobilization)

In prolonged starvation, what fuel does the brain primarily use?

Ketone bodies

Write the Henderson–Hasselbalch equation.

pH = pKa + log([acceptor]/[donor])

A one-unit drop in pH corresponds to what change in [H⁺]?

Ten-fold increase in hydrogen-ion concentration

Which buffer pair maintains blood pH against metabolic CO₂ acid load?

Carbonic acid (H₂CO₃) / Bicarbonate (HCO₃⁻)

What type of functional group is –CH₂OH?

Alcohol

What functional group contains a carbonyl carbon double-bonded to oxygen and single-bonded to OH?

Carboxylic acid

Which sulfur-containing group can form disulfide bonds between cysteines?

Sulfhydryl (-SH) leading to disulfide (-S-S-)

What reaction type forms esters from an acid and an alcohol?

Dehydration (condensation) with loss of H₂O

How many standard (proteinogenic) amino acids are there?

20

Which amino acid can form disulfide bridges?

Cysteine

Which amino acid disrupts an α-helix due to its rigid ring?

Proline

Name the three amino acids that can be phosphorylated.

Serine, Threonine, Tyrosine

At pH below an ionizable group’s pKa, is the group protonated or deprotonated?

Protonated

Define the primary structure of a protein.

The linear sequence of amino acids

What type of secondary structure is stabilized by intra-chain hydrogen bonds and can be disrupted by proline?

α-Helix

Which secondary structure can involve both intra- and inter-chain hydrogen bonds?

β-Sheet (β-pleated sheet)

What forces primarily drive tertiary protein structure?

Hydrophobic interactions among side chains

How many polypeptide chains does hemoglobin contain?

Four (quaternary structure)

Relative to myoglobin, does hemoglobin have higher or lower affinity for O₂?

Lower affinity

What is the role of an enzyme’s active site?

Binds substrate and lowers activation energy to catalyze the reaction

Which type of amino-acid side chains most often participate in hydrogen bonding within an active site?

Polar R groups

Define Km in Michaelis–Menten kinetics.

Substrate concentration at which reaction velocity is half of Vmax; inversely related to enzyme-substrate affinity

If Km is low, what is the enzyme’s affinity for its substrate?

High affinity

In competitive inhibition, how are Vmax and Km affected?

Vmax unchanged; Km increases

In non-competitive inhibition, how are Vmax and Km affected?

Vmax decreases; Km unchanged

Where does a competitive inhibitor bind?

At the enzyme’s active site

Where does a non-competitive inhibitor bind?

At a site other than the active site (allosteric site)

On a Lineweaver–Burk plot, which value remains constant with competitive inhibition?

Y-intercept (1/Vmax), meaning Vmax is unchanged

On a Lineweaver–Burk plot, which value remains constant with non-competitive inhibition?

X-intercept (-1/Km), meaning Km is unchanged

Which side-chain pKa (~6) allows histidine to act as a physiological buffer?

Imidazole ring of histidine

What classroom advice was emphasized for an online biochemistry course?

Stay on schedule with weekly lectures/quizzes and review bolded material