Lecture Notes: Plasma Membrane, Transport, Gene Expression, and Cell Division

Vocabulary flashcards covering key concepts from plasma membrane structure and function, transport mechanisms, cellular organelles, genetic language (DNA/RNA) and transcription/translation, and the cell cycle with mitosis.

Fluid mosaic model

A dynamic plasma membrane model with a bilayer fluid matrix of phospholipids and embedded proteins, not a rigid solid.

Phospholipid bilayer

Two layers of phospholipids forming the basic structure of the plasma membrane, with hydrophilic heads outward and hydrophobic tails inward.

Integral protein

A protein that is part of the membrane structure, embedded within or spanning the bilayer.

Transmembrane protein

An integral protein that crosses the entire membrane from outside to inside (ECF to ICF).

Peripheral protein

A membrane-associated protein located on the inner or outer surface, not spanning the membrane.

Glycoprotein

An integral membrane protein with carbohydrate chains; often involved in cell recognition.

Glycocalyx

A sugar-rich coating on the outside of a cell formed by glycoproteins and glycolipids.

Ion channel

A transmembrane channel protein that allows specific ions to pass through the membrane.

Carrier protein

A transporter that binds a molecule on one side, changes shape, and releases it on the other side.

Receptor protein

A membrane protein that binds a signaling molecule (ligand) to trigger a cellular response.

Ligand

A molecule that binds to a receptor to initiate a signaling event.

Enzyme (membrane protein)

A protein that catalyzes a chemical reaction at or near the membrane.

Substrate

The molecule that binds to an enzyme’s active site to undergo a reaction.

Linker protein

Structural proteins that glue membrane components together, providing support.

Cell identity markers

Molecules (often glycoproteins) that help identify a cell as self or non-self.

Aquaporin

A membrane channel that specifically facilitates water movement.

Selective permeability

Property of the membrane to allow some substances to cross while restricting others.

Osmosis

Diffusion of water across a selectively permeable membrane, often via aquaporins.

Diffusion

Passive movement of solutes from high to low concentration along the concentration gradient.

Concentration gradient

A difference in solute concentration between two regions that drives diffusion.

Facilitated diffusion

Passive transport that requires a membrane protein (channel or carrier) but no energy input.

Channel mediated facilitated diffusion

Facilitated diffusion that uses a specific ion channel to move ions down their gradient.

Carrier mediated facilitated diffusion

Facilitated diffusion where a carrier protein transports a molecule across the membrane.

Potassium channel

A specific ion channel for potassium ions involved in electrical signaling.

Glucose transporter

A carrier protein that moves glucose into or out of the cell via facilitated diffusion.

Vesicle

A small spherical membrane-bound compartment that transports substances into, within, or out of the cell.

Endocytosis

Process of taking in material by vesicle formation at the plasma membrane (endo = inside).

Exocytosis

Process of expelling material from the cell via vesicle fusion with the plasma membrane (exo = outside).

Transcytosis

Transport of material across a cell by vesicles: in on one side, through the cell, and out the other side.

Cytoplasm

The interior of the cell excluding the nucleus; contains cytosol and organelles.

Cytosol

The intracellular fluid portion of the cytoplasm.

Cytoskeleton

A network of protein filaments (microfilaments, intermediate filaments, microtubules) that provide structure and transport.

Microfilaments

Thin actin filaments involved in cell movement and shape changes.

Intermediate filaments

Cytoskeletal elements providing mechanical support and integrity.

Microtubules

Hollow tubules of tubulin that organize cell structure and enable chromosome movement during division.

Centrosome

Microtubule organizing center; contains a pair of centrioles in animal cells.

Centriole

A cylindrical cell structure within the centrosome composed of microtubules; important for spindle formation.

Cilia

Short, hair-like projections on the cell surface that move fluids across the cell surface.

Flagellum

Long, whip-like structure that propels certain cells.

Microvilli

Small, finger-like projections that increase the cell surface area for absorption.

Ribosome

Ribonucleoprotein machines that synthesize proteins; composed of two subunits.

Rough endoplasmic reticulum (RER)

ER studded with ribosomes that synthesizes and folds proteins.

Smooth endoplasmic reticulum (SER)

ER involved in lipid synthesis and detoxification; lacks ribosomes.

Golgi apparatus

Organelle that packages, modifies, and sorts proteins into vesicles for delivery.

Lysosome

Organelle with enzymes that digest waste and worn-out cell components.

Peroxisome

Organelle that breaks down fatty acids and neutralizes toxins; produces harmless byproducts.

Mitochondrion

Powerhouse of the cell; generates ATP through cellular respiration.

Nucleus

Membrane-bound organelle containing DNA; contains the nuclear envelope and pores.

Gene

A DNA sequence that encodes a functional product (protein or RNA).

DNA

Deoxyribonucleic acid; double-stranded, with deoxyribose sugar and bases A, T, G, C.

RNA

Ribonucleic acid; typically single-stranded, with ribose sugar and bases A, U, G, C.

Transcription

Process of copying DNA into RNA within the nucleus.

Translation

Process of converting RNA into a protein at the ribosome in the cytoplasm.

Messenger RNA (mRNA)

RNA that carries genetic instructions from DNA to the ribosome for protein synthesis.

Transfer RNA (tRNA)

RNA that brings amino acids to the ribosome during translation.

Ribosomal RNA (rRNA)

RNA component of ribosomes that helps assemble amino acids into proteins.

Codon

A triplet of RNA bases that codes for a specific amino acid.

Start codon

AUG; signals the beginning of translation.

Stop codon

Codons that signal termination of translation (e.g., UAA, UAG, UGA).

Complementary base pairing

A pairs with T (DNA) or U (RNA); G pairs with C; governs nucleic acid pairing.

Chromatin

Uncondensed DNA-protein complex in the nucleus; becomes chromosome during cell division.

Chromosome

Condensed X-shaped form of DNA visible during cell division.

Histone

Protein around which DNA winds to form chromatin; spool-like in structure.

Interphase

Cell cycle phase when the cell grows and duplicates organelles and DNA (G1, S, G2).

G0

A non-dividing, quiescent state in which cells are not preparing to divide.

G1

Growth phase; duplicates organelles and cytosol in preparation for DNA replication.

S phase

DNA synthesis phase; chromosomes are replicated.

G2

Second growth phase; duplicates enzymes and proteins needed for division.

Prophase

First mitotic phase; chromosomes condense and the spindle forms.

Metaphase

Mitotic phase where chromosomes align along the cell's equator.

Anaphase

Mitotic phase in which sister chromatids separate and move to opposite poles.

Telophase

Mitotic phase where nuclei reform around separated chromosomes; beginning of cytokinesis.

Cytokinesis

Division of the cytoplasm resulting in two separate daughter cells.