Bio 211 Exam 1

Why did eukaryotic cells evolve internal membrane systems?

They compartmentalize reactions and allow controlled import, transport, and processing.

What is the cell theory?

All living things are made of cells; cells are the basic unit of life; cells arise from cells.

Key difference: prokaryotes vs. eukaryotes?

Eukaryotes have a nucleus and membrane-bound organelles; prokaryotes lack both.

Where is bacterial DNA located?

In the cytosol/nucleoid region; it is not enclosed by a nucleus.

Are plants prokaryotic or eukaryotic?

Eukaryotic.

What are the three cytoskeleton filament classes?

Microfilaments, intermediate filaments, and microtubules.

Main function of microfilaments?

Cell shape, movement, and contraction.

Main function of intermediate filaments?

Mechanical strength and structural support.

Main function of microtubules?

Cell organization, intracellular transport, and chromosome movement.

What is one advantage of multicellularity?

Specialized cells can perform different functions, increasing organismal complexity.

What makes a cell a living entity?

It maintains homeostasis, uses energy, grows, responds, reproduces, and carries genetic information.

What supports common ancestry of all cells?

All cells share fundamental features such as DNA, ribosomes, and similar genetic mechanisms.

Why are internal membranes useful for organelles?

They create specialized compartments with distinct conditions and functions.

What membranes surround the nucleus and mitochondria?

Both are surrounded by double membranes.

What is the endosymbiotic theory?

Mitochondria and chloroplasts evolved from bacteria engulfed by ancestral eukaryotic cells.

Evidence supporting endosymbiotic theory?

Mitochondria have their own DNA and double membranes, among other bacterial-like features.

What is the main characteristic of cancer cells?

Uncontrolled cell division and proliferation.

How can imperfect DNA replication create multiple cancer populations?

Mutations accumulate, producing genetically different cell populations that can be selected.

What does an atomic nucleus contain?

Protons and neutrons.

What determines an element's identity?

The number of protons in its nucleus.

What determines whether an atom is an isotope?

Its number of neutrons.

What can make a nucleus radioactive?

An unstable neutron-to-proton balance.

What are the two major energy-storage molecules in cells?

Fatty acids and polysaccharides can both store energy.

Why are hydrogen bonds biologically important?

They are weak individually but collectively provide molecular specificity.

How many electrons does helium need to gain or lose?

None; helium already has a full outer shell.

How many electrons does oxygen gain to fill its outer shell?

Two electrons.

How many electrons does carbon gain or lose to fill its outer shell?

Four; carbon usually shares electrons instead.

How many electrons does sodium lose to fill its outer shell?

One electron.

How many electrons does chlorine gain to fill its outer shell?

One electron.

Why is helium relatively unreactive?

Its outer electron shell is already completely filled.

Why does sodium chloride form an ionic interaction?

Sodium loses one electron and chlorine gains one.

Why is carbon ideal as a biological backbone?

It forms four covalent bonds and stable chains, rings, and diverse structures.

Why is water an excellent solvent?

Its polarity lets it interact with and surround charged or polar substances.

Covalent vs. non-covalent interactions?

Covalent bonds share electrons; non-covalent interactions do not.

Why does water dissolve NaCl?

Water's partial charges stabilize Na+ and Cl- ions and separate them.

What reaction forms a peptide bond?

Condensation: amino acid + amino acid → dipeptide + H2O.

What reaction breaks a peptide bond?

Hydrolysis: peptide + H2O → smaller peptide/amino acids.

What does amphipathic mean?

A molecule has both hydrophilic and hydrophobic regions.

How do amphipathic molecules behave in water?

Hydrophilic regions face water; hydrophobic regions avoid it.

Is DNA charged in a cell?

Yes. Its phosphate backbone gives DNA an overall negative charge.

what is the difference between a strong acid vs. a weak acid?

Strong acids dissociate extensively; weak acids dissociate only partially.

What is a hydronium ion?

H3O+, formed when a proton associates with water.

What determines pH?

Hydrogen ion concentration: pH = −log[H+].

What is the Henderson-Hasselbalch equation?

pH = pKa + log([A−]/[HA]).

Definition of an acid?

A substance that donates a proton (H+).

Definition of a base?

A substance that accepts a proton (H+).

What is pKa?

The pH at which an acid is 50% protonated and 50% deprotonated.

Why is pKa important for biological molecules?

It predicts protonation state at cellular pH.

What does a buffer do?

It resists changes in pH by accepting or donating H+.

Which amino acid groups can ionize?

The amino group, carboxyl group, and ionizable R groups.

What are the main functions of carbohydrates?

Energy storage, energy supply, structural support, and cell recognition.

Aldose vs. ketose?

An aldose has an aldehyde group; a ketose has a ketone group.

What distinguishes α-D-glucose from β-D-glucose?

They differ in the orientation of the anomeric OH group.

What are the building blocks of proteins?

Amino acids.

How many standard amino acids build human proteins?

20 standard amino acids.

What are the main amino acid categories?

Nonpolar, uncharged polar, acidic, and basic.

General structure of an amino acid?

Central carbon bonded to amino group, carboxyl group, H, and R group.

What determines an amino acid's identity?

Its specific R group.

How do polypeptides form higher-order structure?

amino acid side chains and backbone groups drive folding.

Polypeptide vs. protein?

A polypeptide is an amino acid chain; a protein is a functional folded structure.

What forms protein secondary structure?

Hydrogen bonds between backbone groups form α-helices and β-sheets.

What stabilizes tertiary structure?

Hydrophobic, ionic, H-bond, van der Waals, and disulfide interactions.

What is quaternary protein structure?

The arrangement and interaction of multiple polypeptide subunits.

How are α-helices stabilized?

Backbone hydrogen bonds form along the same polypeptide chain.

How are β-sheets stabilized?

Backbone hydrogen bonds form between neighboring strands.

What is a protein domain?

A modular region of a protein that can often fold and function independently.

Monoclonal vs. autoantibodies?

Monoclonal antibodies come from one clone; autoantibodies target the body's own molecules.

Why can antibodies be used in experiments?

They bind specific target molecules, allowing detection or measurement.

What is self-assembly?

Spontaneous organization of molecules into ordered structures.

What is the function of molecular chaperones?

They assist protein folding and help prevent or reverse misfolding.

Hsp70 vs. Hsp60?

Hsp70 assists folding during/after synthesis; Hsp60 provides a chamber for folding.

How does ATP help chaperones?

ATP binding and hydrolysis regulate chaperone conformational cycles.

What is ubiquitin?

A small protein attached to target proteins to mark them for degradation.

How is ubiquitin attached to proteins?

E1 activates ubiquitin; E2 carries it; E3 ligase transfers it to the target.

What does the proteasome do?

Recognizes ubiquitinated proteins, unfolds them, and degrades them into peptides.

What does the proteasome structure look like?

A barrel-like proteolytic core capped by regulatory complexes.

What is a prion?

An infectious misfolded protein that can induce abnormal folding of normal proteins.

Why are amyloids unusual protein aggregates?

They form highly ordered, stable fibrillar structures rich in β-sheets.

What is a protein aggregation disease?

A disease involving accumulation of abnormally folded or aggregated proteins.

What is the first law of thermodynamics?

Energy cannot be created or destroyed; it can only be transferred or transformed.

What is the second law of thermodynamics?

Energy transfers increase overall entropy in an isolated system.

What is Gibbs free energy?

The energy available to drive useful work at constant temperature and pressure.

How is ΔG calculated?

ΔG = Gproducts − Greactants.

What does negative ΔG mean?

The reaction is energetically favorable/spontaneous.

What does positive ΔG mean?

The reaction is energetically unfavorable and requires energy input.

What does ΔG sign and magnitude tell you?

Sign indicates favorability; magnitude indicates the driving force.

What is an enzyme?

A biological catalyst that speeds chemical reactions without being consumed.

Important enzyme properties?

Specificity, catalytic activity, regulation, and lower activation energy.

How do enzymes catalyze reactions?

They stabilize the transition state and lower activation energy.

Catalyst vs. enzyme?

Both speed reactions by lowering activation energy; enzymes are biological catalysts.

How does activation energy relate to ΔG?

Activation energy controls reaction rate; ΔG determines overall reaction favorability.

What does induced fit describe?

Substrate binding changes enzyme shape, optimizing interactions for catalysis.

What is the Michaelis-Menten equation?

v = Vmax[S]/(Km + [S]).

What does Vmax represent?

The maximum reaction velocity when enzyme active sites are saturated.

What does Km represent?

The substrate concentration at which v = ½Vmax.

Why determine Km and Vmax?

They describe enzyme activity and help compare enzyme-substrate interactions.

What is an allosteric enzyme?

An enzyme regulated when molecules bind at sites other than the active site.

Competitive inhibitor: effect on Km and Vmax?

Km increases; Vmax remains unchanged.

Noncompetitive inhibitor: effect on Km and Vmax?

Vmax decreases; Km is unchanged in the ideal case.

What happens when [S] ≪ Km?

v ≈ (Vmax/Km)[S]; velocity is approximately proportional to [S].