General Biology: Metabolism, Cellular Respiration, Photosynthesis, Membrane Transport, and Memory

Comprehensive vocabulary flashcards covering principles of metabolism, thermodynamics, learning and memory, photosynthesis, cellular respiration, and membrane transport.

Metabolism

The sum of all chemical reactions and energy transformations occurring within an organism, which functions as an emergent property of life regulated to maintain homeostasis.

Anabolic Pathways

Synthetic metabolic pathways that require energy to make chemical bonds and build complex molecules from simpler ones (for example, protein synthesis from amino acids).

Catabolic Pathways

Metabolic pathways that break chemical bonds and release energy by dismantling complex molecules into simpler compounds (for example, cellular respiration).

First Law of Thermodynamics

The principle of conservation of energy stating that energy cannot be created nor destroyed, but can only be converted from one form to another.

Second Law of Thermodynamics

The thermodynamic law stating that every energy transfer or transformation increases the entropy ($S$) of the universe, with energy frequently lost as heat.

Entropy ($S$)

A quantitative measure of disorder or randomness that reflects the number of possible configurations a system can adopt; in biological processes, it corresponds to heat or energy lost.

Free Energy ($G$)

The usable energy of a system that is available to perform work under cellular conditions.

Exergonic Reaction

A spontaneous chemical reaction that releases energy, characterized by a negative change in free energy ($-\Delta G$) and typically seen in catabolic processes.

Endergonic Reaction

A nonspontaneous chemical reaction that stores energy and requires an input of energy, characterized by a positive change in free energy ($+\Delta G$).

Energy Coupling

The cellular mechanism of pairing an endergonic reaction (which requires energy) with an exergonic reaction (which supplies energy, commonly via ATP hydrolysis).

Adenosine Triphosphate (ATP)

The primary energy molecule of the cell, functioning as a high-energy molecule due to the unstable bond linking its second and third phosphate groups.

Activation Energy ($E_A$)

The initial amount of energy needed to start a chemical reaction, which is lowered by enzymes without altering whether the reaction is spontaneous.

Induced Fit

The conformational shift an enzyme undergoes after binding its specific substrate at the active site, resulting in a tighter fit that facilitates bond making or breaking.

Oxidation

The chemical process involving the donation or loss of an electron ($e^-$) or a hydrogen atom by a molecule.

Reduction

The chemical process involving the acceptance or gain of an electron ($e^-$) or a hydrogen atom, leading to a decrease in net positive electrical charge.

Neuronal Plasticity

The capacity of the nervous system to remodel and modify its synaptic connections after birth in a manner dependent on neural activity.

Short-Term Memory (STM)

A temporary cognitive storage system with a limited capacity and a retention duration of approximately $7\,\text{sec}$, after which irrelevant information is discarded.

Long-Term Memory (LTM)

A permanent cognitive storehouse of infinite capacity and duration that retains important information, which must be retrieved into short-term memory to be actively utilized.

Learning

The active application of knowledge and stored experiences (memories) to decrease the likelihood of experiencing negative outcomes.

Long-Term Potentiation (LTP)

A lasting, activity-dependent increase in synaptic transmission strength driven by physiological changes at synapses, reinforced by organization, chunking, and practice.

Chunking

A cognitive learning strategy that involves organizing sets of related information together to facilitate memory consolidation and long-term potentiation.

Encoding

The cognitive process of transforming processed sensory stimuli into short-term memory and subsequently into long-term memory.

Retrieval

The process of bringing information stored in long-term memory back into short-term memory, an activity that strengthens synaptic connections via long-term potentiation.

Carbon Fixation

The process by which autotrophic organisms convert inorganic carbon from $\text{CO}_2$ into organic carbon-based macromolecules.

Photosynthesis Redox Reaction

The endergonic conversion $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{E} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$, in which $\text{H}_2\text{O}$ is oxidized into $\text{O}_2$ and $\text{CO}_2$ is reduced into glucose ($\text{C}_6\text{H}_{12}\text{O}_6$) using sunlight energy.

Photosystem II (PSII)

A pigment-protein complex in the thylakoid membrane that absorbs photons, excites electrons, transfers them to an electron transport chain, and extracts replacement electrons by oxidizing water ($\text{H}_2\text{O}$).

NADP+ Reductase

The enzyme that catalyzes the transfer of electrons from the photosynthetic electron transport chain to $\text{NADP}^+$, reducing it to $\text{NADPH}$.

Calvin Cycle

A light-independent metabolic pathway in the chloroplast stroma comprising carbon fixation, reduction, and RuBP regeneration phases, which utilizes ATP and NADPH to synthesize G3P.

Rubisco

The enzyme in the chloroplast stroma that catalyzes the initial carbon fixation step by combining $\text{CO}_2$ ($1\text{C}$) with ribulose bisphosphate (RuBP, $5\text{C}$) to form an unstable $6\text{C}$ intermediate.

Glyceraldehyde-3-Phosphate (G3P)

A $3\text{C}$ carbohydrate intermediate generated during the reduction phase of the Calvin cycle, which can either be exported to synthesize glucose ($6\text{C}$) or recycled to regenerate RuBP using ATP.

Glycolysis

A cytoplasm-localized, anaerobic catabolic pathway that breaks down $1\,\text{glucose}$ molecule ($6\text{C}$) into $2\,\text{pyruvate}$ molecules ($3\text{C}$), requiring an initial input of $2\,\text{ATP}$ and producing a total of $4\,\text{ATP}$ and $2\,\text{NADH}$.

Glycolysis Energy Payoff Phase

The exergonic second stage of glycolysis in which two $3\text{C}$ G3P molecules are converted into two $3\text{C}$ pyruvate molecules, yielding $4\,\text{ATP}$ and $2\,\text{NADH}$.

Mitochondrion Structure

The double-membrane eukaryotic organelle consisting of an outer membrane, intermembrane space, folded inner membrane (cristae), matrix, free ribosomes, and circular DNA.

Pyruvate Oxidation

The mitochondrial reaction catalyzed by pyruvate dehydrogenase in which each pyruvate ($3\text{C}$) is converted into acetyl-CoA ($2\text{C}$), yielding $1\,\text{NADH}$ and releasing $1\,\text{CO}_2$ (occurring twice per starting glucose).

Citric Acid Cycle

The mitochondrial matrix pathway wherein acetyl-CoA ($2\text{C}$) joins oxaloacetate ($4\text{C}$) to form citrate ($6\text{C}$); each turn generates $2\,\text{CO}_2$, $1\,\text{ATP}$ (indirectly via GTP), $3\,\text{NADH}$, and $1\,\text{FADH}_2$.

Mitochondrial Electron Transport Chain

A series of electron carriers in the inner mitochondrial membrane that transfer electrons from NADH and $\text{FADH}_2$ to oxygen ($\text{O}_2$), driving the active transport of $\text{H}^+$ from the matrix into the intermembrane space.

ATP Synthase

A protein complex in the inner mitochondrial membrane functioning as a molecular mill that harnesses the exergonic diffusion of $\text{H}^+$ down their electrochemical gradient to synthesize ATP from ADP and inorganic phosphate.

Chemiosmosis

The energy-coupling mechanism that converts the potential energy stored in a transmembrane proton ($\text{H}^+$) gradient into chemical potential energy in the form of ATP.

Maximum ATP Yield of Respiration

The theoretical maximum production of approximately $30$ or $32\,\text{ATP}$ per glucose molecule, including $2\,\text{ATP}$ from glycolysis, $2\,\text{ATP}$ from the citric acid cycle, and approximately $26$ or $28\,\text{ATP}$ from oxidative phosphorylation.

Fluid Mosaic Model

A structural model of biological membranes describing a fluid lipid bilayer in which phospholipids and proteins can move laterally, accompanied by carbohydrates on the exterior surface.

Selective Permeability

The property of the plasma membrane allowing small nonpolar molecules (such as $\text{O}_2$, $\text{CO}_2$, $\text{N}_2$) and very small polar molecules ($\text{H}_2\text{O}$) to diffuse across freely, while completely blocking ions and large molecules without transport proteins.

Dynamic Equilibrium

The stable condition reached during diffusion where solute molecules continue to move randomly across a boundary, but there is no net movement in any direction.

Osmosis

The passive diffusion of water across a selectively permeable membrane from a region of lower solute concentration (higher water concentration) to a region of higher solute concentration (lower water concentration).

Hypertonic Solution

An extracellular solution having a higher solute concentration than the cell's interior, resulting in a net movement of water out of the cell.

Hypotonic Solution

An extracellular solution having a lower solute concentration than the cell's interior, resulting in a net movement of water into the cell.

Facilitated Diffusion

The spontaneous passive transport of specific solutes down their concentration gradient through transmembrane channel or carrier proteins without the expenditure of metabolic energy (ATP).

Sodium-Potassium Pump

An active transport carrier protein that hydrolyzes ATP to export $3\,\text{Na}^+$ ions and import $2\,\text{K}^+$ ions against their concentration gradients, establishing a membrane electrical gradient.

Bulk Transport

An ATP-requiring mode of active transport that moves large quantities of molecules across the cell boundary via vesicles without directly crossing the phospholipid bilayer.

Exocytosis

The bulk transport process in which secretory vesicles fuse with the plasma membrane, releasing their contents outside the cell and contributing new lipids to plasma membrane growth.

Endocytosis

The bulk transport process in which external materials are internalized by invagination of the plasma membrane to form vesicles inside the cell.