Bio Exam 2 LOs- Cell Membrane, Transport, Energetics, and Enzymes

Vocabulary practice flashcards covering cell membranes, transport mechanisms, energetics, thermodynamics, and enzyme kinetics from Biology Exam 2 learning objectives.

Saturated Lipid Composition

A membrane lipid composition that results in less fluidity and lower permeability.

Unsaturated Lipid Composition

A membrane lipid composition that results in greater fluidity and higher permeability.

Diffusion

The movement of a substance down its concentration gradient (from high to low concentration) across the lipid bilayer.

Osmosis

The movement of water across a membrane due to differences in solute concentration.

Hypertonic Solution

A condition relative to the outside of the cell where the inner solution has more solutes, causing water to move into the cell and leading to cell swelling.

Hypotonic Solution

A condition where the inner solution has less solutes relative to the outside, causing water to move out of the cell and leading to cell shrinkage.

Isotonic Solution

A condition where solute concentrations are equal on both sides of the membrane, resulting in no net water movement.

Facilitated Diffusion

The passive transportation of ions and molecules down their electrochemical gradient using a transmembrane protein.

Passive Transport

Transmembrane protein-mediated movement (via channels or carriers) that does not require an input of energy.

Active Transport

Transmembrane protein-mediated movement via pumps (ATP-driven or gradient-driven) that requires an input of energy.

Channels

Transmembrane proteins involved in passive transport that create an openable or closable tunnel specific to one molecule or ion.

Carriers

Transmembrane proteins involved in passive transport that bind to a solute (ion or molecule) and change shape to carry it across the membrane.

ATP-driven Pumps

Active transport proteins that utilize ATP hydrolysis (losing one phosphate group) to move an ion or molecule against its concentration gradient, such as the $\text{Na}^+/\text{K}^+$ ATPase pump.

Gradient-driven Pumps

Active transport proteins that move two or more ions/molecules, using potential energy from a passive transport process moving one substance with its gradient to move another against its gradient.

ATP (Adenosine Triphosphate)

The primary cellular energy source that powers transport pumps and provides energy for nonspontaneous reactions.

Coupled Reactions

A process in which energy released by an exergonic (spontaneous) reaction drives an endergonic (nonspontaneous) reaction.

Free Energy

The usable energy in a chemical system available to do work.

Exergonic Reaction

A spontaneous chemical reaction that results in a decrease in free energy.

Endergonic Reaction

A nonspontaneous chemical reaction that requires energy input and results in an increase in free energy.

Entropy

A measure of randomness or disorder in a system, represented as $\Delta S$.

Enthalpy

The amount of potential energy (heat) contained within chemical bonds, represented as $\Delta H$.

Exothermic Reaction

A reaction that releases energy, characterized by a negative change in enthalpy ($-\Delta H$).

Endothermic Reaction

A reaction that absorbs energy, characterized by a positive change in enthalpy ($+\Delta H$).

Active Site

The specific region of an enzyme where amino acid residues actively bind to the substrate, featuring a unique shape specific to one substrate.

Substrate Saturation

The state where reaction rate levels off as substrate concentration increases because all enzyme active sites are fully occupied.

Reaction Profile Diagram

A plot of free energy over the course of a chemical reaction, showing energy levels of reactants, activation energy ($E_a$), peak energy at the transition state, and products.

Exergonic vs. Endergonic Profiles

Graphs demonstrating free energy changes, where an exergonic reaction shows a net decrease in free energy and an endergonic reaction shows a net increase in free energy.

Structures of fats

primarily consist of glycerol and fatty acids, forming triglycerides, phospholipids, and steroids, which are essential for cellular functions and energy storage.

Glycerol (3-carbon alcohol molecule) in fats

Each carbon is attached to a hydroxyl (OH) group, the carbon backbone is held together by single covalent C-C and C-H bonds

Double bonds in fatty acids (fats)

occur between carbon atoms, resulting in kinks in the fatty acid chains that affect the fluidity and melting points of fats. UNSATURATED

amphipathic

hydrophobic and hydrophilic regions within a molecule

Are fats amphipathic?

No, mostly hydrophobic

Are steroids amphipathic?

Sometimes, depends on R-group

Are phospholipids amphipathic?

Yes, head vs tail

Fats

Steroids basic structure

four fused rings, three 6-carbon rings, one 5-carbon ring, possible r-groups

Steroid

phospholipd head

polar, contains PO4-, hydrohilic

phospholipid tail

fatty acid, hydrophobic

phospholipid

Fatty acid tails - saturated

• bond = single

• shape = straight

• packing = tight

• fluidity = low

fatty acid tails - trans

• bond = at least one double

• shape = straight

• packing = tight

• fluidity = low

• similar to saturated

• hydrogen atoms sit on opposite sides

fatty acid tails - cis

• bond = at least one double

• shape = bent

• packing = loose

• fluidity = high

• hydrogen atoms sit on same side

Trans

Cis

vesicles

water molecules impact how phospholipids spontaneously form bilayers in water.

Number of bonds to determine if a lipid is saturated?

Single

Number of bonds to determine if a lipid is unsaturated?

Double

Function of fats

energy processing + storage

Function of steroids

membrane structure, cell signaling (hormones), gene regulation

function of phospholipids

membrane structure + all membrane functions (proteins, etc.)