Cell Biology: Membrane Dynamics, Cellular Respiration, and Photosynthesis

Comprehensive vocabulary flashcards covering membrane structure, transport mechanisms, thermodynamics, enzyme kinetics, cellular respiration, fermentation, and photosynthesis.

Selectively Permeable

The property of a biological membrane that allows some substances to cross it more easily than others.

Amphipathic molecules

Molecules that contain both hydrophilic and hydrophobic regions, such as phospholipids whose hydrophilic heads face water and hydrophobic tails face each other.

Fluid mosaic model

A structural model stating that a cell membrane is a fluid structure with a 'mosaic' of various proteins randomly distributed within it.

Cholesterol (in cell membranes)

A lipid embedded in animal cell membranes that maintains fluidity at different temperatures by restraining phospholipid movement at warm temperatures and preventing tight packing at cool temperatures.

Peripheral proteins

Membrane proteins that are bound to the surface of the membrane.

Integral proteins

Membrane proteins that are embedded directly within the membrane.

Diffusion

The passive movement of a substance from an area of high concentration to an area of low concentration, such as the diffusion of oxygen and carbon dioxide.

Osmosis

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

Facilitated diffusion

Passive transport of charged or polar solutes across the plasma membrane with the help of transport proteins.

Aquaporins

Channel proteins that specifically facilitate the transport of water across the cell membrane.

Carrier proteins

Transport proteins that bind to molecules and change their shape to shuttle them across the membrane.

Tonicity

The ability of a surrounding solution to cause a cell to gain or lose water, depending on the concentration of solutes that cannot cross the membrane.

Isotonic solution

A surrounding solution whose solute concentration is equal to that inside the cell, resulting in no net water movement.

Hypertonic solution

A surrounding solution whose solute concentration is greater than that inside the cell, causing the cell to lose water.

Hypotonic solution

A surrounding solution whose solute concentration is less than that inside the cell, causing the cell to gain water.

Osmoregulation

An adaptation for life involving the control of solute concentrations and water balance, such as through the use of a contractile vacuole.

Active transport

A method of membrane transport that requires energy ($\text{ATP}$) and transport proteins to move solutes against their concentration gradients.

Exocytosis

A bulk transport process in which transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell.

Endocytosis

A bulk transport process requiring energy wherein the cell takes in macromolecules by forming vesicles derived from the plasma membrane.

Phagocytosis

A form of endocytosis commonly referred to as 'cellular eating.'

Pinocytosis

A form of endocytosis commonly referred to as 'cellular drinking.'

Metabolism

The sum of all the chemical reactions occurring inside the body.

Catabolic pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds, such as in cellular respiration.

Anabolic pathways

Metabolic pathways that consume energy to build complex molecules from simpler ones, such as in photosynthesis.

Bioenergetics

The study of how energy flows through living organisms.

Chemical energy

A form of potential energy available for release in a chemical reaction.

First law of thermodynamics

The principle stating that energy can be transferred and transformed, but it cannot be created or destroyed.

Second law of thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe.

Entropy

A measure of molecular disorder or randomness.

Exergonic reaction

A chemical reaction that proceeds with a net release of energy and is associated with catabolism.

Endergonic reaction

A chemical reaction that absorbs energy from its surroundings and is associated with anabolism.

Activation energy

The initial free energy of activation needed to start a chemical reaction.

Enzymes

Biological catalysts made of proteins that speed up the rate of a chemical reaction without being consumed, accomplished by reducing activation energy.

Active site

The specific catalytic pocket or region on an enzyme where the substrate binds.

Cofactors

Inorganic, non-protein enzyme helpers, typically metal ions like zinc and copper.

Coenzymes

Organic, non-protein enzyme helpers, such as vitamins.

Competitive inhibitor

A substance that reduces enzyme activity by binding directly to the active site, competing directly with the substrate.

Non-competitive inhibitor

A substance that impedes enzyme reactions by binding to another part of the enzyme, thereby altering its shape.

Fermentation

A catabolic process that involves the partial degradation of sugars occurring without the consumption of oxygen.

Aerobic respiration

A catabolic pathway that consumes organic molecules and oxygen ($O_2$) to produce $ATP$.

Anaerobic respiration

A catabolic pathway that consumes organic molecules and an inorganic compound other than oxygen (such as sulfate) as the final electron acceptor in an electron transport chain to yield $ATP$.

Oxidation

A redox process in which a substance loses electrons ('OIL').

Reduction

A redox process in which a substance gains electrons ('RIG').

Dehydrogenation

A redox reaction during cellular respiration in which glucose loses hydrogen atoms to become oxidized to $CO_2$, and oxygen gains hydrogen atoms to become reduced to $H_2O$.

Substrate-level phosphorylation

The enzyme-catalyzed mode of $ATP$ synthesis occurring directly during glycolysis and the citric acid cycle by adding an inorganic phosphate to $ADP$.

Oxidative phosphorylation

The production of $ATP$ using energy derived from the electron transport chain and chemiosmosis.

Glycolysis

A metabolic pathway occurring in the cytoplasm (with or without $O_2$) that splits one glucose molecule ($C_6H_{12}O_6$) into two pyruvate molecules ($C_3H_6O_3$), producing a net gain of $2\text{ ATP}$ and $2\text{ NADH}$.

Pyruvate oxidation

The transition stage in the mitochondrion where pyruvate is oxidized to acetyl CoA, producing $2\text{ acetyl CoA}$, $2\text{ CO}_2$, and $2\text{ NADH}$ per glucose molecule.

Citric acid cycle

Also called the Krebs cycle; a series of reactions in the mitochondrial matrix that completes the breakdown of pyruvate by combining acetyl CoA with oxaloacetate, yielding $2\text{ ATP}$, $6\text{ NADH}$, $2\text{ FADH}_2$, and $4\text{ CO}_2$ per glucose molecule.

Electron transport chain

A sequence of carrier proteins in the inner mitochondrial membrane (cristae) that transfers electrons from $NADH$ and $FADH_2$ to oxygen ($O_2$) as the final electron acceptor, directly generating no $ATP$.

Chemiosmosis

An energy-coupling mechanism that uses energy stored in a proton-motive force ($H^+$ gradient) to drive $ATP$ synthesis through $ATP$ synthase.

ATP synthase

A protein complex that catalyzes the phosphorylation of $ADP$ to $ATP$ as hydrogen ions move down their concentration gradient across the inner membrane.

Alcohol fermentation

A two-step fermentation pathway where pyruvate is converted to ethanol, releasing $CO_2$ and regenerating $NAD^+$ (utilized by yeast in brewing, winemaking, and baking).

Lactic acid fermentation

A fermentation pathway where pyruvate is reduced directly by $NADH$ to form lactate and $NAD^+$ (utilized by fungi/bacteria to produce cheese and yogurt, and by human muscle cells when $O_2$ is scarce).

Beta oxidation

The metabolic catabolic pathway that breaks down fatty acids into simpler units to be used as fuel in cellular respiration.

Biosynthesis

Anabolic pathways responsible for constructing large, complex molecules from smaller molecules derived from food digestion or intermediates of cellular respiration.

Autotrophs

Self-feeders (producers) that sustain themselves without eating anything derived from other living beings, such as plants, algae, and some prokaryotes.

Heterotrophs

Consumers that obtain their organic material from other organisms, either living or dead (e.g., humans and animals).

Mesophyll

The interior green tissue of a leaf where chloroplasts are mainly concentrated, typically containing $30$ to $40$ chloroplasts per cell.

Thylakoids

Microscopic sacs inside chloroplasts containing chlorophyll within their membranes, enclosing an internal compartment called the thylakoid space, and organized into stacks called grana.

Stroma

The dense fluid within the chloroplast surrounded by the inner and outer membrane, encompassing the thylakoids.

Stomata

Microscopic pores on the surface of leaves through which carbon dioxide ($CO_2$) enters and oxygen ($O_2$) exits.

Photosynthesis reaction

The redox reaction summarized by the chemical equation: $6\text{ CO}_2 + 12\text{ H}_2O + \text{Light energy} \rightarrow C_6H_{12}O_6 + 6\text{ O}_2 + 6\text{ H}_2O$.