Cell Chemistry and Macromolecules – Practice Flashcards

A set of 100 question-and-answer flashcards covering key concepts from BIOB10 Week 1 Lecture 2 on cell chemistry and macromolecules.

What did Jacques Monod famously claim about biochemical truths across species?

Anything found to be true in E. coli must also be true in elephants.

Which four elements make up about 99 % of the atoms in humans?

Hydrogen, carbon, nitrogen, and oxygen.

What part of an atom determines its chemical properties?

The number of electrons in the outermost shell.

Where are protons and neutrons located within an atom?

In the nucleus.

Define a molecule in biological context.

Two or more atoms in a definite arrangement held together by chemical bonds.

What is a biomolecule?

A molecule made by living organisms, typically centered around carbon.

How many other atoms can carbon bond to?

Up to four.

Why is carbon particularly suited to serve as the backbone of biomolecules?

Its size and electronic structure allow versatile bonding with up to four atoms.

When atoms share electrons to fill their outer shells, what type of bond is formed?

A covalent bond.

What distinguishes a polar covalent bond from a non-polar covalent bond?

Unequal versus equal sharing of electrons, leading to partial charges only in polar bonds.

In a polar covalent bond, what name is given to the atom that more strongly attracts the shared electrons?

The electronegative atom.

Give an example of a non-polar molecule common in cells.

Hydrocarbons consisting only of carbon and hydrogen.

Name the four major types of noncovalent interactions important in cells.

Ionic bonds, hydrogen bonds, van der Waals attractions, and hydrophobic interactions.

What causes ionic bonds?

Electrical attraction between atoms bearing full opposite charges after electron transfer.

How do hydrogen bonds contribute to DNA structure?

They hold the two strands of the double helix together between complementary bases.

What are van der Waals attractions?

Weak, nonspecific interactions between atoms in close proximity due to transient dipoles.

Why are hydrophobic interactions not considered true bonds?

They arise from the tendency of non-polar molecules to avoid water rather than from direct attractive forces.

What is the simplest group of biological molecules composed solely of carbon and hydrogen?

Hydrocarbons.

What are functional groups?

Specific groupings of atoms that behave as a unit and alter the properties of biomolecules.

List three ways functional groups affect a biomolecule’s properties.

Introduce electronegative atoms, increase polarity or reactivity, and confer positive or negative charge.

Name six common functional groups in biology.

Methyl, hydroxyl, carboxyl, amino, phosphate, and carbonyl.

What is a monomer?

A small building block that can be joined to form a polymer.

What reaction joins monomers into polymers, and what is removed?

Condensation reaction; water is removed.

What reaction breaks polymers into monomers, and what is consumed?

Hydrolysis reaction; water is added.

Identify the four classes of macromolecules.

Carbohydrates, lipids, proteins, and nucleic acids.

What is the general chemical formula for carbohydrates?

(CH₂O)ₙ.

When the carbonyl group of a monosaccharide is at the end of the molecule, what type of sugar is it?

An aldose.

What is a ketose?

A sugar whose carbonyl group is in an internal position.

In aqueous solution, how do sugars with five or more carbons usually exist?

As closed ring structures.

What is the difference between α-glucose and β-glucose?

Orientation of the hydroxyl on carbon 1: below versus above the ring plane.

What term describes molecules like glucose and galactose that share a formula but differ in spatial arrangement?

Isomers.

Through what type of covalent linkage are two monosaccharides joined?

A glycosidic (C-O-C) bond.

What is sucrose an example of?

A disaccharide used for energy storage.

What are oligosaccharides commonly attached to in cells?

Lipids or proteins, forming glycolipids and glycoproteins.

Give two structural polysaccharides.

Cellulose and chitin.

Name two storage polysaccharides.

Starch and glycogen.

What distinguishes lipids from other biomolecules in terms of solubility?

They are non-polar and dissolve in organic solvents but not in water.

What three categories of lipids have key cellular functions?

Fats (triacylglycerols), steroids, and phospholipids/glycolipids.

What components form a triacylglycerol molecule?

One glycerol and three fatty acids linked by ester bonds.

Define saturated fatty acid.

A fatty acid with no carbon–carbon double bonds.

What is an unsaturated fatty acid?

A fatty acid containing one or more double bonds.

How many hydrocarbon rings characterize a steroid nucleus?

Four.

Which steroid is a crucial component of animal plasma membranes?

Cholesterol.

Are plant cell membranes typically cholesterol-free?

Yes, plants lack cholesterol in their membranes.

What is the basic structure of a phospholipid?

Glycerol, two fatty acids, a phosphate, and a polar head group.

Why are phospholipids described as amphipathic?

They possess both hydrophilic and hydrophobic regions.

What major cellular structure self-assembles from phospholipids?

The lipid bilayer of membranes.

What sugar is found in DNA nucleotides?

Deoxyribose.

Which sugar is present in RNA nucleotides?

Ribose.

What covalent bond links nucleotides together in nucleic acids?

A phosphodiester bond between the 3′ hydroxyl and 5′ phosphate.

Name the two classes of nitrogenous bases.

Purines and pyrimidines.

Which base pairs with adenine in DNA?

Thymine.

Guanine pairs with which base in DNA?

Cytosine.

How many hydrogen bonds connect G-C pairs?

Three.

State three additional functions of nucleotides besides building nucleic acids.

Carrying chemical energy (e.g., ATP), forming parts of coenzymes, and acting as intracellular signaling molecules.

Approximately how many different proteins are made in each mammalian cell?

About 10,000.

What type of biomolecule accelerates chemical reactions in cells?

Enzymes (proteins).

Give two examples of protein-mediated signaling molecules.

Kinases and phosphatases.

What are the two functional groups present in every amino acid?

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

What carbon atom links the amino and carboxyl groups in an amino acid?

The alpha carbon.

Define R group in amino acids.

The variable side chain that imparts specific properties.

Name the four categories of amino acid side chains.

Polar charged, polar uncharged, non-polar, and special (e.g., sulfhydryl).

Which amino acid can form disulfide bonds?

Cysteine.

What bond joins amino acids in proteins?

A peptide bond.

According to the second law of thermodynamics, what happens to entropy in isolated systems?

It increases.

How do cells generate order without violating the second law?

They couple order-producing reactions to heat-releasing reactions that increase environmental entropy.

Distinguish catabolic and anabolic pathways.

Catabolic pathways break down molecules to release energy; anabolic pathways build molecules using energy.

In metabolic pathways, what remains unchanged during each reaction?

The enzyme (catalyst).

What is the active site of an enzyme?

The region where substrate binds and the reaction occurs.

Define activation energy.

The energy barrier that must be overcome for a reaction to proceed.

Can enzymes make energetically unfavorable reactions occur alone?

No, they only speed favorable reactions.

What symbol indicates a reaction’s free energy change?

ΔG (delta G).

When is a reaction considered energetically favorable?

When ΔG is negative (ΔG < 0).

How does the cell drive an energetically unfavorable reaction?

By coupling it to a favorable reaction with a larger negative ΔG.

What is ΔG°?

The standard free energy change measured under standard conditions.

Name two main activated carrier molecules produced by glucose oxidation.

ATP and NADH.

How do carrier molecules resemble money in cellular metabolism?

They store energy or chemical groups to “pay” for unfavorable reactions.

What type of bond in ATP stores readily releasable energy?

Phosphoanhydride bond.

During ATP hydrolysis, which products are released?

ADP and inorganic phosphate (Pi).

In reaction coupling, what is typically the first step involving ATP?

Transfer of a phosphate to create a high-energy intermediate.

What is the net result of coupling glutamic acid with NH₃ using ATP?

Formation of glutamine, ADP, and Pi.

Why are oxidation reactions in cells performed in many small steps?

To capture usable energy efficiently rather than release it all as heat.

What process converts glucose to pyruvate while generating ATP and NADH?

Glycolysis.

Which two sequential steps in glycolysis illustrate reaction coupling?

Oxidation of glyceraldehyde 3-phosphate (step 6) followed by substrate-level phosphorylation (step 7).

What is the overall ΔG for steps 6 and 7 combined in glycolysis?

Favorable –12.5 kJ/mol.

During step 6 of glycolysis, which carrier molecule is reduced?

NAD⁺ to NADH.

In step 7 of glycolysis, what molecule donates a phosphate to ADP to form ATP?

1,3-Bisphosphoglycerate.

What macromolecule stores glucose residues for later energy use in animals?

Glycogen.

Which storage molecule performs a similar role in plants as glycogen does in animals?

Starch.

What term describes the spontaneous clustering of non-polar molecules in water?

The hydrophobic effect (hydrophobic interactions).

Why are polar side chains often located on the exterior of soluble proteins?

They form hydrogen bonds with water, enhancing solubility.

What property allows enzymes to be highly specific for their substrates?

Complementary shape and chemical interactions at the active site.

What type of interaction stabilizes α-helices and β-sheets in proteins?

Hydrogen bonds between backbone atoms.

How can the free energy released by ATP hydrolysis be quantified?

Approximately –30.5 kJ/mol under standard conditions.

What is a coenzyme?

A small organic molecule that works with an enzyme to facilitate catalysis, often nucleotide-derived.

Give an example of a purine base.

Adenine (or guanine).

Cytosine, thymine, and uracil belong to which class of bases?

Pyrimidines.

Which lipid class provides precursors for steroid hormones?

Cholesterol (steroids).

What feature of van der Waals interactions makes them universally present between atoms?

They arise from transient induced dipoles due to electron motion.

In cellular metabolism, what is the ultimate fate of most energy released by catabolic reactions?

It is dissipated as heat, increasing entropy of the surroundings.