General Biology Midterm Exam Review

A comprehensive vocabulary review of core biological concepts, including scientific method, basic chemistry, macromolecules, cytology, cell membrane transport, bioenergetics, cellular respiration, photosynthesis, and cell communication.

Hypothesis

A testable explanation for an observation.

Inductive Reasoning

A type of logical thinking that moves from specific observations to a general conclusion.

Deductive Reasoning

A type of logical thinking that moves from a general idea to a specific prediction.

Peer Review

The formal evaluation process wherein other scientists evaluate scientific work.

Atomic Number

The number of protons in an atom's nucleus.

Mass Number

The total number of protons plus neutrons in an atom.

Covalent Bond

A chemical bond formed when atoms share electrons.

Ionic Bond

A chemical bond formed when electrons are transferred from one atom to another.

Hydrogen Bond

A weak attraction between partially charged molecules or regions.

Acid

A substance that increases the concentration of $H^+$ in a solution, lowering the pH below $7$.

Base

A substance that decreases or binds $H^+$, resulting in a higher pH above $7$.

Buffer

A substance that helps resist changes in pH.

Carbohydrates

Macromolecules composed of sugars whose main function is providing energy.

Lipids

Macromolecules composed of fatty acids, glycerol, and other lipid structures that function in long-term energy storage, membrane structure, and signaling.

Proteins

Macromolecules composed of amino acids that serve as enzymes, transport structures, receptors, and support cellular structure.

Nucleic Acids

Macromolecules composed of nucleotides that store and help use genetic information.

Dehydration Synthesis

A reaction that builds and joins molecules together by removing water.

Hydrolysis

A reaction that breaks molecules apart by adding water.

Primary Structure

The unique sequence of amino acids in a polypeptide chain.

Secondary Structure

Localized foldings in a polypeptide chain consisting of $\alpha$-helices and $\beta$-sheets.

Tertiary Structure

The overall three-dimensional shape of a polypeptide chain.

Quaternary Structure

The structure resulting from the assembly of multiple polypeptide chains.

Cell Theory

The biological principle stating that all living things are made of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells.

Prokaryotic Cell

A simple type of cell lacking a membrane-bound nucleus and membrane-bound organelles, characteristic of bacteria and archaea.

Eukaryotic Cell

A complex cell type containing a membrane-bound nucleus and membrane-bound organelles, characteristic of animals, plants, fungi, and protists.

Surface Area-to-Volume Ratio

A physical constraint that decreases as a cell grows larger, making material exchange across the membrane less efficient and limiting maximum cell size.

Nucleolus

A specialized region inside the nucleus responsible for producing and assembling ribosomal subunits.

Ribosomes

Cellular complexes that carry out protein synthesis.

Mitochondria

Eukaryotic organelles that serve as the primary site of cellular respiration and ATP production.

Lysosomes

Organelles containing digestive enzymes involved in breaking down biological materials.

Peroxisomes

Organelles involved in oxidation reactions and the breakdown of specific molecules.

Rough ER

A region of the endoplasmic reticulum studded with ribosomes that is involved in protein synthesis and processing.

Smooth ER

A region of the endoplasmic reticulum lacking ribosomes that synthesizes lipids and steroid hormones, detoxifies chemicals, and stores $Ca^{2+}$.

Golgi Apparatus

An organelle that modifies, sorts, and packages proteins and lipids, acting as the distribution center of the cell.

Cytoskeleton

A network that provides structural support and organization to the cell, composed of microfilaments (actin), intermediate filaments (fibrous proteins), and microtubules (tubulin).

Total Magnification

The product of the ocular lens magnification multiplied by the objective lens magnification ($\text{Ocular lens} \times \text{Objective lens}$).

Fluid Mosaic Model

The structural model describing the plasma membrane as a fluid combination of phospholipids, proteins, and carbohydrates.

Amphipathic

Possessing both a hydrophilic (water-attracted) region and a hydrophobic (water-avoiding) region, as found in phospholipids.

Passive Transport

The movement of substances across a membrane down their concentration gradient (from high to low concentration) without expending cellular energy.

Simple Diffusion

The unassisted movement of small, nonpolar molecules (such as $O_2$ and $CO_2$) directly through the phospholipid bilayer from high to low concentration.

Facilitated Diffusion

The passive movement of molecules down their concentration gradient aided by a membrane transport protein, requiring no ATP.

Osmosis

The diffusion of water molecules across a selectively permeable membrane.

Hypertonic Solution

An extracellular solution with a higher solute concentration than the cytoplasm, causing water to exit the cell.

Hypotonic Solution

An extracellular solution with a lower solute concentration than the cytoplasm, causing water to enter the cell.

Isotonic Solution

A solution that has an equal solute concentration relative to the cell, resulting in no net movement of water.

Active Transport

The transport of substances against their concentration gradient (from low to high concentration), requiring cellular energy usually in the form of ATP.

Sodium-Potassium Pump

An active transport carrier mechanism that expels $3\text{ Na}^+$ out of the cell while importing $2\text{ K}^+$ into the cell.

Metabolism

The totality of an organism's chemical reactions.

First Law of Thermodynamics

The physical law stating that energy cannot be created or destroyed; it can only be transferred or transformed.

Exergonic Reaction

A spontaneous chemical reaction that releases free energy.

Endergonic Reaction

A nonspontaneous chemical reaction that requires an input of energy to proceed.

ATP (Adenosine Triphosphate)

The primary energy-transfer molecule in cells that powers cellular work by coupling exergonic reactions to endergonic reactions.

Enzymes

Biological catalysts that speed up chemical reactions by lowering the activation energy without being consumed or altering overall free energy changes.

Substrate

The specific reactant molecule upon which an enzyme acts.

Active Site

The specific region of an enzyme where the substrate binds.

Catalase

An enzyme that accelerates the breakdown of hydrogen peroxide into water and oxygen ($2H_2O_2 \rightarrow 2H_2O + O_2$).

Cellular Respiration

The catabolic process that transfers energy from glucose into ATP, summarized as $\text{Glucose} + O_2 \rightarrow CO_2 + H_2O + \text{ATP}$.

Glycolysis

The initial stage of cellular respiration wherein glucose is split into $2$ pyruvate, yielding a net gain of $2\text{ ATP}$ and $2\text{ NADH}$.

Pyruvate Processing

The second stage of cellular respiration that converts pyruvate into Acetyl-CoA, yielding $\text{NADH}$ and releasing $CO_2$.

Citric Acid Cycle

The third stage of cellular respiration that processes Acetyl-CoA to produce $\text{NADH}$, $\text{FADH}_2$, ATP/GTP, and waste $CO_2$.

Chemiosmosis

The process wherein energy stored in a proton gradient across a membrane powers ATP synthesis.

Fermentation

An anaerobic pathway utilized when oxygen is absent whose primary function is regenerating $\text{NAD}^+$ to keep glycolysis running.

Photosynthesis

The endergonic process occurring in chloroplasts that converts carbon dioxide and water into glucose and oxygen using light energy ($6CO_2 + 6H_2O + \text{energy} \rightarrow C_6H_{12}O_6 + 6O_2$).

Light-Dependent Reactions

The photosynthetic reactions occurring in thylakoids where chlorophyll and photosystems (PSII and PSI) absorb light to generate a proton gradient, producing ATP and NADPH.

Calvin Cycle

The light-independent pathway of photosynthesis that uses ATP and NADPH to reduce $CO_2$ into sugars through three phases: carbon fixation, reduction, and regeneration.

Ligand

A signaling molecule that specifically binds to a receptor protein.

Ligand-Gated Ion Channel

A membrane receptor that opens or closes a gate in response to the binding of a specific ligand, allowing ions to pass through.

G-Protein-Coupled Receptor (GPCR)

A cell-surface receptor that acts as a middleman between an extracellular signal and internal cell signaling pathways via G proteins.

Intracellular Receptor

A receptor located inside the cell that binds signaling molecules capable of crossing the plasma membrane.

Second Messengers

Small, non-protein intracellular signaling molecules that relay and amplify signals received by cell-surface receptors.

Apoptosis

A controlled, programmed mechanism of cell death essential for normal biological regulation.