Chapter 3: Cell Structures and Their Functions

Vocabulary flashcards covering key cell structures, organelles, DNA/gene expression, and cell processes from the lecture notes.

Cell

The smallest unit of life; carries out metabolism, energy use, synthesis, communication, and reproduction.

Cytoplasm

The jelly-like substance that surrounds and holds the cell’s organelles.

Plasma membrane

The cell membrane; outer boundary that encloses the cytoplasm and regulates movement of substances into and out of the cell.

Fluid-mosaic model

Model describing the cell membrane as a fluid, dynamic bilayer with proteins, cholesterol, and carbohydrates.

Phospholipid bilayer

Two-layer arrangement forming the core of the cell membrane; hydrophilic heads face water, hydrophobic tails face the interior.

Polar head

Hydrophilic region of a phospholipid that interacts with water.

Nonpolar tail

Hydrophobic region of a phospholipid facing the interior of the membrane.

Intracellular

Inside the cell.

Extracellular

Outside the cell.

Nucleus

Large organelle near the cell’s center that houses chromosomes; bounded by the nuclear envelope with pores.

Nuclear envelope

Double membrane surrounding the nucleus with nuclear pores for transport.

Nuclear pore

Openings in the nuclear envelope that allow substances to pass into and out of the nucleus.

Chromatin

Loosely coiled DNA-protein complex inside the nucleus when not dividing.

Chromosome

Tightly coiled DNA-protein structure visible during cell division.

Nucleolus

Diffuse region inside the nucleus where ribosomal subunits begin to form.

Ribosome

Organelle that synthesizes proteins; free or attached to the endoplasmic reticulum.

Endoplasmic reticulum

Network of membranes; rough ER has ribosomes and synthesizes proteins; smooth ER lacks ribosomes and is involved in lipid synthesis, detoxification, and calcium storage.

Rough ER

ER with attached ribosomes; site of protein synthesis.

Smooth ER

ER lacking ribosomes; site of lipid synthesis, detoxification, and calcium storage.

Golgi apparatus

Stacks of membranes that modify, package, and distribute proteins and lipids from the ER; forms vesicles.

Vesicle

Membrane-bound sac used for transport within or outside the cell.

Lysosome

Membrane-bound vesicle with digestive enzymes that break down materials inside the cell.

Peroxisome

Small membrane-bound vesicle containing enzymes that break down fatty acids and hydrogen peroxide.

Mitochondrion

Organelle producing most of the cell’s ATP via aerobic metabolism; features cristae and a matrix.

Cristae

Folds of the inner mitochondrial membrane that increase surface area.

Mitochondrial matrix

Fluid inside the inner membrane containing enzymes and mitochondrial DNA.

mtDNA

Mitochondrial DNA; circular DNA within mitochondria.

Cytoskeleton

Internal framework of protein filaments (microtubules, microfilaments, intermediate filaments) that supports the cell and moves organelles.

Microtubule

Hollow protein tubes; provide support, aid in cell division, and form cilia/flagella.

Microfilament

Small-diameter filaments that support cell shape and enable movement; actin in muscle contraction.

Intermediate filament

Filaments providing mechanical support; keratin is a common example.

Keratin

A type of intermediate filament protein associated with skin cells.

Centriole

Paired organelles in the centrosome; involved in mitosis.

Cilia

Short projections that move materials across the cell surface; composed of microtubules.

Flagellum

Long, whip-like projection; usually one per cell; propels sperm.

Microvilli

Tiny extensions increasing surface area; found on absorptive surfaces like intestine and kidney; supported by actin filaments.

DNA

Deoxyribonucleic acid; stores genetic information and directs protein synthesis; double helix composed of nucleotides.

Nucleotide

Monomer of DNA/RNA; consists of a sugar, phosphate group, and nitrogenous base.

Gene

A sequence of nucleotides that provides instructions to make a specific protein.

Transcription

Process in the nucleus copying DNA into messenger RNA (mRNA).

Translation

Process in the cytoplasm where mRNA is used with tRNA to synthesize a protein at the ribosome.

mRNA

Messenger RNA; carries genetic information from DNA to ribosomes for protein synthesis.

tRNA

Transfer RNA; carries specific amino acids to the ribosome and matches anticodons to codons during protein synthesis.

Codon

Three-nucleotide sequence on mRNA that codes for an amino acid.

Anticodon

Three-nucleotide sequence on tRNA that pairs with a codon on mRNA.

Interphase

Nondividing phase of the cell cycle during which DNA is replicated.

Mitosis

Division of the nucleus into two nuclei; includes prophase, metaphase, anaphase, and telophase.

Prophase

Chromatin condenses into visible chromosomes; spindle forms; nuclear membrane dissolves.

Metaphase

Chromosomes align at the cell equator under spindle influence.

Anaphase

Sister chromatids separate and move to opposite poles; centromeres split.

Telophase

Nuclei form around separated chromosomes; chromosomes de-condense; cytoplasm divides.

Cytokinesis

Division of the cytoplasm, producing two separate daughter cells.

Differentiation

Process by which cells develop specialized structures and functions; active vs inactive portions of DNA.

Apoptosis

Programmed cell death; regulates cell numbers and removes unwanted tissue.

Aging (cellular aging)

Cellular aging due to factors like cellular clock, death genes, DNA damage, free radicals, and mitochondrial damage.

Tumor

Abnormal proliferation of cells; can be benign or malignant; cancer may metastasize.