BIOL Exam 2

What term describes a molecule, such as a phospholipid, that possesses both hydrophilic and hydrophobic regions?

Amphipathic

Which functional group forms the polar, hydrophilic head of a phospholipid?

Phosphate functional group

What molecular shape characteristic of individual lipids favors the formation of a single-layer sphere known as a micelle?

A wedge shape with a bulky phosphate head.

How does the molecular shape of phospholipids forming a liposome or bilayer sheet differ from those forming micelles?

W

Which functional group constitutes the polar, hydrophilic end of a cholesterol molecule?

Hydroxyl group (—OH)

How does cholesterol influence the structure and property of the cell membrane?

Its amphipathic structure allows it to pack tightly between phospholipids to regulate membrane fluidity.

How are integral membrane proteins positioned relative to the lipid bilayer?

They are embedded directly within or span across the lipid bilayer

How do peripheral membrane proteins differ from integral membrane proteins in their membrane association?

They are attached to the surface of the membrane rather than embedded in the hydrophobic core.

What cellular function do membrane anchor proteins perform?

They stabilize the cell by attaching it to the extracellular matrix or internal cytoskeleton.

Which type of membrane protein recognizes and binds external signaling molecules?

Receptor protein

Where are hydrophobic amino acid residues positioned on a transmembrane channel protein?

On the external protein surface that contacts the hydrophobic interior of the phospholipid bilayer

Why is a hydrophilic channel required in the center of a transmembrane channel protein?

To allow polar and charged substances to bypass the nonpolar membrane core.

Which class of molecules crosses the phospholipid bilayer most easily via simple diffusion?

Small, nonpolar molecules such as O2, CO2, and N2

Why are small inorganic ions like Na+, K+, and Cl- virtually impermeable to the lipid bilayer?

Their charge prevents them from entering and crossing the nonpolar hydrophobic core of the bilayer

How does facilitated diffusion differ from simple diffusion regarding required membrane components?

Facilitated diffusion requires membrane transport proteins, whereas simple diffusion occurs directly through the lipid bilayer.

How does a carrier protein transport molecules across the plasma membrane during facilitated diffusion?

It undergoes a conformational change upon binding the molecule to transport it across the membrane.

Why is protein-mediated transport capable of saturation, whereas simple diffusion is not?

Because the finite number of transport proteins can become fully occupied at high substrate concentrations.

What source of energy directly powers primary active transport?

ATP Hydrolysis

How does the Na+/K+ ATPase pump move sodium and potassium ions relative to their concentration gradients?

It pumps both sodium Na+ and potassium K+ ions against their respective concentration gradients from low to high concentration.

What energy source drives secondary active transport across a cell membrane?

An electrochemical concentration gradient previously established by primary active transport.

How do symporter proteins move two different substances across the membrane in secondary active transport?

They move both substances in the same direction across the membrane.

How do antiporterr proteins move two different substances across the membrane in secondary active transport?

They move the two substances in opposite directions across the membrane.

is chemical energy classified as kinetic energy or potential energy?

it’s classified as potential

Why is a concentration gradient considered a form of potential energy?

It stores energy due to the difference in position and concentration of particles across a space.

Do weak chemical bonds have high or low potential energy?

High potential energy

Why do fuel molecules like carbohydrates hold high chemical energy?

They contain relatively weak and less stable bonds that release energy when broken.

Why does CO2 have lower potential energy compared to starch?

CO2 contains very stable, strong bonds that store less available potential energy.

What specific type of biological molecule is ATP?

ATP is nucleotide composed of adenine, ribose and three phosphate groups.

Which specific part of the ATP molecule stores high potential energy?

The high potential energy is stored in the bonds linking the phosphate groups.

What chemical reaction breaks down ATP to release energy for cell work?

ATP hydrolysis breaks down ATP to release energy.

What are the chemical products of ATP hydrolysis?

The products are ADP, an inorganic phosphate group, and released energy.

Metabolic processes that break down complex molecules are called_______ pathways?

Catabolic

Metabolic processes that synthesize complex molecules and require ATP are called______ pathways.

Anabolic

What type of chemical reaction releases free energy into its surroundings?

An exergonic reaction releases free energy.

What type of chemical reaction requires an input of free energy to proceed?

An endergonic reaction requires an input of energy.

Name two cellular activities powered by the energy released from ATP.

Two examples are muscle contraction and active transport pumping.

Why do the phosphate bonds in ATP contain high potential energy?

The negatively charged phosphate groups repel each other, making the bonds weak and unstable.

What is an open system in thermodynamics?

A system that exchanges both matter and energy with its surroundings.

What does the First law of Thermodynamics state?

Energy cannot be created or destroyed, only transferred or transformed.

What does the Second Law of Thermodynamics state?

The total entropy, or disorder, of a reacting system must increase during a reaction.

What is entropy?

A measure of disorder or randomness in a system.

How does enthalpy change over the course of a typical spontaneous reaction?

Enthalpy decreases because reactants have more potential energy than products.

• Reactants start with a high potential energy but then decreases over the course of a reaction.

How does entropy change over the course of a typical spontaneous reaction?

Entropy increases because products have more disorder than reactants