SLCC Biology Test 2

What are proteins made of?

Amino acids joined into polypeptide chains.

What determines a protein’s function?

Its shape and chemical properties.

What is a ligand?

A molecule that binds to a protein.

What is a binding site?

The place on a protein where a ligand binds.

What builds proteins?

Ribosomes.

What four things attach to an amino acid’s central carbon?

An amino group, carboxyl group, hydrogen, and R group.

What makes amino acids different from one another?

Their R groups, or side chains.

What is a peptide bond?

A covalent bond joining one amino acid’s carboxyl group to another’s amino group.

What reaction joins amino acids and releases water?

Dehydration synthesis.

What reaction breaks peptide bonds using water?

Hydrolysis.

What is a polypeptide?

A chain of amino acids.

What is an essential amino acid?

One that must come from food because the body cannot make enough of it.

What is primary structure?

The amino acid sequence.

What is secondary structure?

Local folds: alpha-helices and beta-sheets.

What stabilizes alpha-helices and beta-sheets?

Hydrogen bonds between parts of the peptide backbone.

What is tertiary structure?

The overall three-dimensional shape of one polypeptide.

What is quaternary structure?

Multiple polypeptide subunits assembled together.

What forms a disulfide bond?

A covalent sulfur–sulfur bond between two cysteine side chains.

What interaction occurs between oppositely charged side chains?

An ionic interaction.

What interaction occurs between nonpolar side chains such as Ala and Val?

A hydrophobic interaction.

Where are hydrophilic side chains usually found in a globular protein in water?

On the exterior, facing water.

What side chains usually face the lipid tails in a transmembrane region?

Nonpolar, hydrophobic side chains.

What is phosphorylation?

Adding a phosphate group, which can change protein activity.

What is denaturation?

Loss of normal protein folding, generally without breaking the amino acid sequence.

What can change a protein’s shape?

Temperature, pH, chemical exposure, ligand binding, or modifications such as phosphorylation.

Front: Question

Back: Answer

What is metabolism?

All chemical reactions occurring in a cell.

What is a metabolic pathway?

A linked series of reactions that produces a final product.

What is anabolism?

Building complex molecules; requires energy.

What is catabolism?

Breaking complex molecules down; generally releases energy overall.

What is an enzyme?

A biological catalyst, usually a protein.

How do enzymes speed reactions?

They lower activation energy.

What is activation energy?

The initial energy barrier a reaction must overcome.

Do enzymes change a reaction’s overall energy change or equilibrium?

No—they change how quickly equilibrium is reached.

Are enzymes used up by their reactions?

No—they can be reused.

What is a substrate?

A reactant that an enzyme binds and acts on.

Where does a substrate bind?

The enzyme’s active site.

What is induced fit?

The enzyme adjusts its shape when a substrate binds.

What is a competitive inhibitor?

A molecule that competes with the substrate for the active site.

What is an allosteric inhibitor?

A molecule that binds elsewhere and reduces enzyme activity.

What is an allosteric activator?

A molecule that binds elsewhere and increases enzyme activity.

In your course’s terminology, what is a cofactor?

An inorganic enzyme helper, such as a metal ion.

What is a coenzyme?

An organic enzyme helper, often derived from a vitamin.

What is feedback inhibition?

A pathway’s end product inhibits an earlier enzyme.

What usually happens when an enzyme gets too hot?

It may denature and lose activity.

How can pH affect enzymes?

It changes side-chain charges and can disrupt binding, catalysis, or folding.

Memory cue: Anabolism assembles; catabolism cuts apart; enzymes lower the hurdle.

Chapter 9: Lipids, membranes, and organelles

Front: Question

Back: Answer

What is a triglyceride made of?

One glycerol and three fatty acids.

What is a fatty acid?

A hydrocarbon chain with a carboxyl group at one end.

What makes a fatty acid saturated?

No carbon–carbon double bonds in its chain.

What makes a fatty acid unsaturated?

One or more carbon–carbon double bonds.

What does a cis double bond do to a fatty acid?

Creates a kink, reducing tight packing.

What identifies a steroid?

Four fused carbon rings.

What is a phospholipid’s basic structure?

A hydrophilic head and usually two hydrophobic tails.

What does amphipathic mean?

Having both hydrophilic and hydrophobic regions.

How do phospholipids arrange in a bilayer?

Heads face water on both sides; tails face inward.

What does the fluid mosaic model describe?

A membrane containing a moving mixture of lipids, proteins, and attached carbohydrates.

What increases membrane fluidity: saturated or cis-unsaturated tails?

Cis-unsaturated tails.

What does cholesterol do in membranes?

Buffers fluidity against temperature changes.

What is a transmembrane protein?

A protein that spans the entire membrane.

What is a peripheral membrane protein?

A protein associated with a membrane surface without spanning the bilayer.

What are glycoproteins and glycolipids?

Proteins and lipids with attached carbohydrates.

What do exterior membrane carbohydrates help with?

Cell recognition and attachment.

What does rough ER do?

Helps fold, modify, and transport proteins; also makes phospholipids.

What makes rough ER look rough?

Attached ribosomes.

What does smooth ER do?

Makes lipids and steroids, handles carbohydrate metabolism, detoxifies chemicals, and stores calcium.

What does the Golgi apparatus do?

Modifies, sorts, tags, and packages proteins and lipids; makes certain carbohydrates.

Which Golgi face receives materials?

Cis face.

Which Golgi face sends materials?

Trans face.

What do lysosomes do?

Digest macromolecules, worn-out components, and engulfed pathogens.

What is a vesicle?

A small membrane-covered sac that holds or transports material.

Are mitochondria and chloroplasts part of the endomembrane system?

No.

Are all proteins made by rough-ER-bound ribosomes?

No—free ribosomes also make proteins.

Memory cue: Ribosomes build; rough ER processes; Golgi packages; lysosomes digest.

Chapter 10: Membrane transport

Front: Question

Back: Answer

What does selectively permeable mean?

Allows some substances to cross while restricting others.

What is a solute?

A dissolved substance.

What is a solvent?

The substance doing the dissolving.

What is a concentration gradient?

A difference in concentration between areas.

What direction is down a concentration gradient?

High → low concentration.

What is simple diffusion?

Movement directly through the bilayer, down a gradient, without a transport protein.

What is facilitated diffusion?

Movement down a gradient through a channel or carrier.

Does facilitated diffusion require cellular energy?

No.

What happens to oxygen when its concentration is higher outside a cell?

It diffuses into the cell.

What is osmosis?

Net movement of water across a selectively permeable membrane.

What is an aquaporin?

A water channel protein.

What is dynamic equilibrium?

Movement continues, but there is no net movement in either direction.

Where does water move in basic tonicity problems?

Toward the side with more nonpenetrating solute.

What happens to an animal cell in a hypotonic solution?

Water enters; it swells and may burst.

What happens to a cell in a hypertonic solution?

Water leaves; it shrinks.

What happens in an isotonic solution?

Water enters and leaves equally; no net size change.