Cell Biology Review: Cells, Organelles, and Macromolecules (Lecture Notes)

Vocabulary flashcards covering key terms and definitions from the lecture notes on cells, organelles, and macromolecules.

Surface area to volume ratio

Small cells maximize surface area relative to volume to enable efficient diffusion and exchange of materials.

Factors affecting diffusion rate

Concentration gradient, temperature, particle size, and properties of the surrounding medium influence diffusion speed.

Plasma membrane (cell membrane)

Phospholipid bilayer that encloses the cell and regulates transport and communication with the environment.

Cytoplasm

Stuff inside the cell membrane excluding the nucleus; includes cytosol and organelles involved in metabolism.

DNA

Genetic material of the cell; in prokaryotes it is typically circular and in the nucleoid region, in eukaryotes linear DNA housed in the nucleus.

Ribosomes

Ribonucleoprotein particles that synthesize proteins; ~70S in prokaryotes and ~80S in eukaryotes.

Prokaryotic cell

Lacks a nucleus and membrane-bound organelles; typically smaller with circular DNA and 70S ribosomes.

Eukaryotic cell

Has a nucleus and membrane-bound organelles; linear DNA and 80S ribosomes.

Peptidoglycan

Polymer forming the bacterial cell wall, providing rigidity and shape.

Plant cell wall (cellulose-based)

Rigid layer outside the plasma membrane made of cellulose; provides structure and support.

Chloroplast

Organelle responsible for photosynthesis; contains chlorophyll and its own DNA, ribosomes, and thylakoid membranes.

Central vacuole

Large plant cell organelle that stores water and maintains turgor pressure.

Nuclear envelope

Double membrane surrounding the nucleus with nuclear pores to regulate transport.

Nucleolus

Region within the nucleus where rRNA is synthesized and ribosome assembly begins.

Free ribosomes

Ribosomes that float in the cytosol and synthesize cytosolic and organelle-targeted proteins.

Bound (membrane-bound) ribosomes

Ribosomes attached to the rough endoplasmic reticulum and synthesize proteins for secretion or membranes.

Rough endoplasmic reticulum (RER)

ER studded with ribosomes; synthesizes secreted and membrane proteins.

Smooth endoplasmic reticulum (SER)

ER lacking ribosomes; synthesizes lipids and detoxifies compounds.

RER vs SER abundance

Secretory cells have more RER; detoxifying and lipid-synthesizing cells have more SER.

Glycosylation

Attachment of carbohydrate groups to proteins or lipids, forming glycoproteins and glycolipids.

Mitochondrion

Powerhouse of the cell; produces ATP; contains its own DNA and ribosomes and a double membrane.

Similarity: circular DNA

Mitochondria and chloroplasts contain circular DNA separate from the nuclear genome.

Dynactin complex

Protein complex that activates dynein and links cargo to dynein for transport along microtubules.

9+2 microtubule structure

Axoneme structure of cilia and flagella: nine doublets around two central microtubules.

Extracellular matrix (ECM)

Network outside the cell that provides structural support and biochemical signals.

Integrins

Transmembrane receptors that mediate adhesion to the ECM and signaling to the cell interior.

Cadherin

Calcium-dependent cell–cell adhesion molecules that link cells via the cytoskeleton.

Plasmodesmata

Channels through plant cell walls that connect adjacent plant cells' cytoplasm.

Gap junctions

Intercellular channels formed by connexins that allow passage of small molecules between animal cells.

Dehydration synthesis (condensation)

Reaction that forms polymers by removing water; requires energy.

Hydrolysis

Reaction that breaks polymers into monomers by adding water; catalyzed by enzymes.

Starch

Plant storage polysaccharide with α-1,4/α-1,6 glycosidic bonds; branched and digestible by humans.

Cellulose

Structural plant polysaccharide with β-1,4 glycosidic bonds; linear and not digestible by humans.

Macromolecule structure → function

The 3D structure and chemical properties of a macromolecule determine its role in biology.

Nucleotide

Monomer of nucleic acids; consists of a sugar, phosphate group, and a nitrogenous base.

Base-pairing hydrogen bonds

Hydrogen bonds between complementary bases (A–T with 2; G–C with 3 in DNA; A–U in RNA).

Peptide bond

Covalent bond linking amino acids through a dehydration synthesis reaction.

Primary structure

Linear sequence of amino acids in a polypeptide.

Tertiary structure

Three-dimensional folding of a protein's polypeptide, stabilized by various bonds and interactions.

Homeostasis

Maintenance of stable internal conditions (pH, temperature, ion concentrations) essential for enzyme activity.

Lipids

Nonpolar, hydrophobic biomolecules (fats, oils, phospholipids, steroids) with energy storage and membrane roles.

Triglyceride

Glycerol backbone esterified to three fatty acids; primary form of stored fat.

Saturated fatty acids

Fatty acids with no carbon–carbon double bonds; straight chains, typically solid at room temperature.

Unsaturated fatty acids

Fatty acids with one or more carbon–carbon double bonds; kinked chains, typically liquid at room temperature.

Phospholipid

Amphipathic lipid with a hydrophilic head and hydrophobic tails; forms bilayers in water.

Why phospholipids form membranes

Amphipathic nature drives formation of lipid bilayers, unlike triglycerides which are nonpolar energy storage molecules.