Comprehensive Biology Flashcards: Enzymes, Cell Division, and Membrane Transport

Vocabulary practice flashcards covering enzyme structure and function, stages of meiosis and mitosis, cell cycle regulation, and cellular membrane transport mechanisms.

Proteins

Organic compounds composed of amino acids linked together by peptide bonds.

Amino acids

The building blocks of proteins composed of a central carbon atom, an amine group ($NH_2$), a carboxyl group ($COOH$), and a specific R group.

Primary protein structure

The linear sequence of a chain of amino acids that makes up a protein.

Secondary protein structure

The local folding of a polypeptide chain into helices ($\alpha$-helices) or sheets ($\beta$-pleated sheets).

Tertiary protein structure

The three-dimensional folding pattern of a protein resulting from side chain interactions.

Quaternary protein structure

A protein structure consisting of more than one amino acid chain.

Enzymes

Proteins that help catalyze chemical reactions, usually bearing names ending with the suffix -ase.

Active site

The region of an enzyme that contains binding sites to orient substrates and a catalytic site to reduce chemical activation energy.

Lock and Key Model

A model of enzyme action where the substrate fits into the enzyme's active site like a key into a lock.

Induced Fit Model

A model of enzyme action where the enzyme changes its shape slightly as the substrate binds to the active site.

Oxidation

The loss of electrons during a redox reaction, where the electron-losing compound acts as a reducing agent.

Reduction

The gain of electrons during a redox reaction, where the electron-gaining compound acts as an oxidizing agent.

Meiosis

A type of cell division consisting of two successive divisions that reduces the chromosome number of the daughter cells by half.

Meiosis I

The reduction division phase of meiosis where paired homologous chromosomes separate across four distinct stages.

Meiosis II

The equational division phase of meiosis where sister chromatids separate, resulting in four mature haploid sex cells.

Leptotene

The first stage of Prophase I where replicated chromosomes condense, similar to the early prophase stage in mitosis.

Zygotene

The second stage of Prophase I characterized by synapsis and the formation of tetrads and synaptonemal complexes.

Pachytene

The third stage of Prophase I during which genetic crossing over occurs between homologous chromosomes.

Diplotene

The stage of Prophase I where the synaptonemal complex dissociates and chiasmata become visible as the nuclear envelope begins to disintegrate.

Diakinesis

The final stage of Prophase I where spindle fibers form and begin attaching to tetrads while the nuclear membrane fragments.

Metaphase I

The stage of Meiosis I where the nuclear membrane is completely disintegrated and attached spindle fibers move tetrads to the metaphase plate.

Anaphase I

The stage of Meiosis I where homologous chromosomes separate and move from the center of the cell toward opposite poles.

Cell specialization

The process, also known as cell differentiation, by which genetic cells change into distinct cell types to perform specific functions.

Cell modification

Adaptations or changes acquired by a cell after cell division that aid the cell in various beneficial ways.

Cell cycle

An ordered series of events that occurs in a cell from one division to the next.

Interphase

The non-dividing and longest stage of the cell cycle during which the cell grows and copies its chromosomes in preparation for division.

$G_1$ Phase

The first gap phase of interphase where the cell increases in volume, duplicates organelles, and prepares necessary chemicals for DNA synthesis.

$G_1$ Checkpoint

Also known as the restriction point in yeast, a cell cycle checkpoint that verifies cell size, nutrient sufficiency, and DNA damage before committing to divide.

S Phase

The synthesis phase of interphase during which genetic material is replicated and histones are actively synthesized.

$G_2$ Phase

The second gap phase of interphase where energy is replenished, tubulin dimers are produced, and mitotic spindle formation begins.

$G_2$ Checkpoint

The checkpoint that ensures all DNA is completely and correctly replicated without damage before the cell enters M phase.

$G_0$ Phase

A resting or non-dividing phase where cells are not actively preparing to divide until triggered by external signals.

Mitosis

Nuclear cell division, also called karyokinesis, consisting of Prophase, Metaphase, Anaphase, and Telophase to produce two identical daughter cells.

Prophase (Mitosis)

The first phase of mitosis where chromatin condenses into chromosomes, centrioles duplicate, and the nuclear envelope breaks down.

Metaphase (Mitosis)

The phase of mitosis where chromosomes align along the metaphase plate with spindle fibers fully attached to centromeres.

Anaphase (Mitosis)

The phase of mitosis where sister chromatids separate and move toward opposite poles as individual daughter chromosomes.

Telophase (Mitosis)

The final stage of mitosis where chromosomes reach opposite poles, nuclear membranes reform around them, and cytokinesis begins.

M Checkpoint

The spindle checkpoint occurring during metaphase that checks the proper attachment of spindle fibers to kinetochores.

Fluid Mosaic Model

The model of plasma membrane structure proposed by Singer and Nicolson in 1972, composed of a phospholipid bilayer, proteins, carbohydrates, and cholesterol.

Membrane transport

The movement of particles, ions, or molecules across or through a membranous barrier.

Passive transport

The movement of molecules down a concentration gradient from high to low concentration without requiring energy (ATP).

Simple diffusion

The direct movement of small, uncharged, or lipid-soluble solute molecules through a membrane from high to low concentration.

Osmosis

The diffusion of solvent molecules through a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.

Hypertonic solution

A solution with a higher solute concentration than the cell interior, causing water to exit the cell and leading to plasmolysis or crenation.

Hypotonic solution

A solution with a lower solute concentration than the cell interior, causing water to enter the cell and leading to swelling or hemolysis.

Isotonic solution

A solution with a solute concentration equal to that of the cell interior, resulting in no net movement of water.

Facilitated diffusion

The movement of molecules across a membrane from high to low concentration assisted by transport proteins such as channels or carriers.

Channel proteins

Membrane proteins that form pores or passageways for ions or small molecules, such as aquaporins for water transport.

Carrier proteins

Transport proteins that undergo a conformational change upon binding specific molecules like glucose or amino acids to move them across the membrane.

Active transport

The movement of molecules across a membrane against a concentration gradient (from low to high concentration) requiring ATP energy.

Primary active transport

Active transport that directly utilizes energy from ATP to pump ions, such as the sodium-potassium pump.

Secondary active transport

Transport that uses potential energy from electrochemical gradients established by ion pumps, also known as cotransport.

Symporter

A transporter protein involved in secondary active transport that moves two different substrates across the membrane in the same direction.

Antiporter

A transporter protein involved in secondary active transport that moves substrates across the membrane in opposite directions.

Bulk transport

The transport mechanism responsible for moving large materials into or out of cells by way of membrane-bound vesicles.

Endocytosis

A cellular bulk transport process in which substances from outside the cell are engulfed into vesicles formed by the cell membrane.

Phagocytosis

A form of endocytosis known as cell-eating in which a cell engulfs large particles using pseudopodia and encloses them in a phagosome.

Pinocytosis

A non-specific form of endocytosis known as cell-drinking where the cell membrane encloses and gulps extracellular fluid containing dissolved molecules.

Receptor-mediated endocytosis

A specific endocytic process where membrane receptor proteins bind target molecules before engulfing them in a vesicle.

Exocytosis

The process where intracellular secretory vesicles fuse with the plasma membrane to release contents into the extracellular space.