Cellular Biology Lecture Ch.5-8 Quiz Diagram Review Membrane Dynamics, Transport, Bioenergetics, Respiration, and Photosynthesis

Comprehensive practice flashcards covering cell membrane structure and transport, bioenergetics and enzyme kinetics, cellular respiration stages and yields, and photosynthetic light and dark reactions from Chapters 5 through 8.

Plasma Membrane

A selectively permeable barrier composed of phospholipids, proteins, cholesterol, and carbohydrates that regulates what enters and leaves the cell, providing structure, protection, and maintaining homeostasis.

Fluid Mosaic Model

A structural model describing the cell membrane as a mosaic of diverse components—including phospholipids, proteins, cholesterol, and carbohydrates—that move fluidly within the plane of the membrane.

Phospholipid Bilayer

The structural framework of the plasma membrane, arranged with hydrophilic heads facing the outer and inner aqueous environments and hydrophobic tails pointing inward, forming a basic barrier against substance movement.

Cholesterol (Membrane)

A steroid lipid located between phospholipids that regulates membrane fluidity and stability, preventing the membrane from becoming too rigid at low temperatures or too fluid at high temperatures.

Membrane Carbohydrates

Carbohydrate chains attached to proteins (glycoproteins) or lipids (glycolipids) on the outer surface of the cell membrane that are essential for cell recognition, cellular identity, and communication.

Membrane Proteins

Proteins embedded in or spanning the phospholipid bilayer that function as channels, carriers, pumps, enzymes, and receptors to facilitate transport and cell signaling.

Passive Transport

The movement of substances down their concentration gradient (from an area of high concentration to low concentration) without requiring cellular energy ($\text{ATP}$).

Simple Diffusion

A type of passive transport where small nonpolar molecules move directly across the phospholipid bilayer down their concentration gradient without the assistance of transport proteins.

Facilitated Diffusion

The passive transport of polar or charged molecules down their concentration gradient through specific protein channels or carrier proteins without requiring energy.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of low solute concentration (high water concentration) to a region of high solute concentration (low water concentration).

Hypertonic Solution

An external solution with a higher solute concentration than the cytoplasm of a cell, causing water to flow out of the cell and leading to cell shrinkage (crenation).

Hypotonic Solution

An external solution with a lower solute concentration than the cytoplasm of a cell, causing net water movement into the cell and leading to cellular swelling and potential lysis (bursting).

Isotonic Solution

A solution whose solute concentration equals that of the cell cytoplasm, resulting in equal water movement in and out so that the cell maintains its normal volume.

Active Transport

The movement of substances across a cell membrane against their concentration gradient (from low concentration to high concentration), requiring transport proteins (pumps) and cellular energy ($\text{ATP}$).

Sodium-Potassium Pump

An active transport pump that consumes $\text{ATP}$ to pump $3\,\text{Na}^+$ ions out of the cell and $2\,\text{K}^+$ ions into the cell, maintaining ion balance, membrane potential, and cellular function.

Bulk Transport

The active, $\text{ATP}$-requiring transport of large particles or large quantities of substances across the plasma membrane enclosed within vesicles.

Endocytosis

A form of bulk transport in which the cell takes in external materials by engulfing them and invaginating the plasma membrane to form an intracellular vesicle.

Exocytosis

A form of bulk transport where intracellular vesicles fuse with the plasma membrane to secrete or release materials out of the cell.

Receptor-Mediated Endocytosis

A targeted form of endocytosis in which specific extracellular molecules bind to receptor proteins on the cell surface prior to vesicle formation and internalization.

Metabolism

The totality of all chemical reactions that take place within a living organism or cell.

Kinetic Energy

The form of energy associated with objects or particles in motion, such as the thermal movement of molecules.

Potential Energy

Stored energy, particularly chemical energy stored within the chemical bonds of molecules such as glucose and $\text{ATP}$.

First Law of Thermodynamics

A physical law stating that energy cannot be created or destroyed; it can only be transferred or transformed from one form to another.

Entropy

A thermodynamic measure of the disorder, randomness, or unpredictability within a closed system.

Anabolic Reactions

Metabolic pathways that synthesize larger, complex molecules from smaller subunits, requiring an input of energy (e.g., protein synthesis from amino acids).

Catabolic Reactions

Metabolic pathways that break down large, complex molecules into simpler ones, releasing stored energy (e.g., cellular respiration breaking down glucose).

Exergonic Reaction

A spontaneous chemical reaction that releases free energy, characterized by a negative change in Gibbs free energy ($\Delta G < 0$).

Endergonic Reaction

A non-spontaneous chemical reaction that requires an input of free energy, characterized by a positive change in Gibbs free energy ($\Delta G > 0$).

ATP (Adenosine Triphosphate)

The primary chemical energy currency of the cell, which couples exergonic and endergonic reactions by releasing energy when hydrolyzed into $\text{ADP} + \text{P}_i$.

Enzymes

Biological catalysts, primarily proteins, that increase the rate of specific biochemical reactions by lowering the activation energy without altering $\Delta G$ or being consumed.

Activation Energy

The minimum amount of initial energy required to start a chemical reaction by destabilizing bonds in reactant molecules.

Transition State

The unstable, high-energy intermediate state that reactant molecules must reach at the peak of the activation energy barrier before converting to products.

Induced Fit

The slight conformational change that an enzyme's active site undergoes upon binding its substrate to bind the substrate more securely and catalyze the reaction.

Competitive Inhibition

A regulatory mechanism where an inhibitor molecule structurally mimics the substrate and binds directly to an enzyme's active site, preventing substrate binding.

Feedback Inhibition

A regulatory mechanism in which the high concentration of an end product of a metabolic pathway binds to and inhibits an enzyme earlier in the pathway, preventing overproduction.

Cellular Respiration

A metabolic pathway that systematically breaks down glucose to produce $\text{ATP}$ for the cell, releasing energy stored in chemical bonds.

Oxidation

The loss of one or more electrons from an atom, ion, or molecule during a chemical or redox reaction.

Reduction

The gain of one or more electrons by an atom, ion, or molecule during a chemical or redox reaction.

Substrate-Level Phosphorylation

The direct enzymatic transfer of a phosphate group from a phosphorylated metabolic intermediate to $\text{ADP}$ to form $\text{ATP}$, occurring in glycolysis and the citric acid cycle.

Glycolysis

The anaerobic metabolic breakdown of glucose in the cytoplasm into $2$ molecules of pyruvate, producing a net gain of $2\,\text{ATP}$ and $2\,\text{NADH}$.

Pyruvate Oxidation

The conversion of pyruvate into acetyl-CoA within the mitochondrial matrix, producing $\text{NADH}$ and releasing carbon dioxide ($\text{CO}_2$).

Citric Acid Cycle

A circular series of reactions in the mitochondrial matrix that breaks down acetyl-CoA, producing $2\,\text{ATP}$, $\text{NADH}$, and $\text{FADH}_2$ while releasing $\text{CO}_2$.

Electron Transport Chain (ETC)

A series of protein complexes embedded in the inner mitochondrial membrane that pass electrons from $\text{NADH}$ and $\text{FADH}_2$, using the released energy to pump $\text{H}^+$ ions into the intermembrane space.

Chemiosmosis

The process of synthesizing $\text{ATP}$ using the energy of an electrochemical proton ($\text{H}^+$) gradient across a membrane, driven by the passage of protons through ATP synthase.

Oxygen ($\text{O}_2$ in Aerobic Respiration)

The final electron acceptor in the mitochondrial electron transport chain that combines with electrons and $\text{H}^+$ ions to form water ($\text{H}_2\text{O}$).

ATP Yield of Cellular Respiration

The theoretical amount of $\text{ATP}$ produced per glucose molecule during aerobic cellular respiration, yielding a total of $\sim 30\text{--}32\,\text{ATP}$ ($2$ from glycolysis, $2$ from the citric acid cycle, and $\sim 26\text{--}28$ from oxidative phosphorylation).

Fermentation

An anaerobic process occurring in the cytoplasm when oxygen is unavailable that converts pyruvate into lactic acid or ethanol plus $\text{CO}_2$, yielding $2\,\text{ATP}$ and regenerating $\text{NAD}^+$ for glycolysis.

Photosynthesis

The process by which plants and other photoautotrophs convert light energy into chemical energy stored in sugars, utilizing carbon dioxide and water ($6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$).

Photoautotrophs

Organisms that capture sunlight as an energy source to synthesize organic molecules from inorganic materials through photosynthesis.

Chemoautotrophs

Organisms that produce organic compounds using chemical energy derived from the oxidation of inorganic substances, such as ammonia or hydrogen sulfide, without sunlight.

Thylakoid Membranes

Internal membrane compartments within chloroplasts that contain photosynthetic pigments and serve as the site of the light-dependent reactions.

Stroma

The fluid-filled internal space of the chloroplast surrounding the thylakoid membranes where the Calvin cycle (light-independent reactions) occurs.

Chlorophyll a

The primary photosynthetic pigment in plants that absorbs mainly blue and red wavelengths of visible light and reflects green light, giving plants their green appearance.

Carotenoids

Accessory photosynthetic pigments that absorb additional light wavelengths not captured by chlorophyll and protect plant tissues from damage caused by excess light.

Stomata

Microscopic pores on leaf surfaces that open and close to facilitate gas exchange ($\text{CO}_2$ entry, $\text{O}_2$ release) and regulate water vapor loss.

Light Reactions

The initial stage of photosynthesis taking place in thylakoid membranes that uses light energy to split $\text{H}_2\text{O}$, release $\text{O}_2$, and produce $\text{ATP}$ and $\text{NADPH}$.

Calvin Cycle

The light-independent stage of photosynthesis occurring in the stroma consisting of three phases—carbon fixation, reduction, and RuBP regeneration—that uses $\text{ATP}$, $\text{NADPH}$, and $\text{CO}_2$ to synthesize sugars.

RuBisCO

Ribulose-1,5-bisphosphate carboxylase-oxygenase, the primary enzyme in the Calvin cycle that catalyzes the initial fixation of carbon dioxide ($\text{CO}_2$) into organic molecules.

Carbon Fixation

The enzymatic incorporation of inorganic carbon from carbon dioxide ($\text{CO}_2$) into organic molecules like RuBP during photosynthesis.

Photorespiration

A wasteful process that occurs when RuBisCO binds $\text{O}_2$ instead of $\text{CO}_2$, consuming $\text{ATP}$ and releasing $\text{CO}_2$ without producing sugar, thereby reducing photosynthetic efficiency.

C3 Plants

Plants that fix $\text{CO}_2$ directly using RuBisCO into a 3-carbon compound; common in moderate climates, they are highly susceptible to photorespiration under hot, dry conditions.

C4 Plants

Plants common in hot, high-light environments (e.g., corn) that reduce photorespiration by using PEP carboxylase to initially fix $\text{CO}_2$ into a 4-carbon compound in mesophyll cells before concentrating it around RuBisCO.

CAM Plants

Plants adapted to arid environments (e.g., cacti) that open their stomata to fix $\text{CO}_2$ at night (storing it as malic acid) and run the Calvin cycle during the day with closed stomata to reduce water loss.

PEP Carboxylase

An enzyme found in $C_4$ and CAM plants that initially fixes $\text{CO}_2$ into a 4-carbon organic acid with high affinity for $\text{CO}_2$ and no affinity for oxygen.