final review

Cell Theory

All organisms are composed of cells, cells are the basic unit of life, and all cells come from pre-existing cells.

Prokaryotic cells

Cells without a nucleus, usually smaller, and lack membrane-bound organelles.

Eukaryotic cells

Cells with a true nucleus and membrane-bound organelles.

Three domains of life

Bacteria, Archaea, and Eukarya.

Model organisms

Organisms like E. coli, yeast, fruit flies used for studying cellular processes.

Light microscopy

Uses visible light to view cells up to ~1000x magnification.

Electron microscopy

Uses electrons for high-resolution images; includes SEM and TEM.

Hydrogen bond

Weak bond between a hydrogen atom and an electronegative atom (e.g., O, N).

Covalent bond

Strong chemical bond formed by sharing electrons.

Van der Waals interactions

Weak attractions between molecules or parts of molecules.

Carbohydrates

Macromolecules made of sugar monomers; used for energy and structure.

Lipids

Hydrophobic molecules including fats, phospholipids, and steroids.

Proteins

Polymers of amino acids with structural and catalytic roles.

Nucleic acids

DNA and RNA, store and transmit genetic information.

Plasma membrane

Selective barrier composed of a phospholipid bilayer with proteins.

Fluid mosaic model

Describes membrane as fluid and dynamic with proteins embedded.

Cholesterol in membrane

Modulates fluidity and stability of the membrane.

Simple diffusion

Movement of molecules from high to low concentration without energy.

Facilitated diffusion

Passive transport with help of membrane proteins.

Active transport

Movement of molecules against gradient using ATP.

Endocytosis

Process where cells internalize molecules by engulfing them.

Exocytosis

Vesicle fusion with membrane to release contents outside the cell.

CFTR channel

Chloride channel defective in cystic fibrosis patients.

Glycolysis

Breakdown of glucose into pyruvate; occurs in cytoplasm.

Pyruvate oxidation

Converts pyruvate to acetyl-CoA in mitochondria.

Citric acid cycle

Cycle producing NADH, FADH₂, and CO₂ from acetyl-CoA.

Electron transport chain

Series of proteins that create a proton gradient to make ATP.

ATP synthase

Enzyme that synthesizes ATP using proton motive force.

Fermentation

Anaerobic pathway regenerating NAD⁺ to allow glycolysis to continue.

Extracellular matrix (ECM)

Network of proteins and polysaccharides outside cells for support.

Collagen

Most abundant ECM protein providing tensile strength.

Fibronectin

ECM glycoprotein that binds integrins and collagen.

Integrins

Transmembrane receptors connecting ECM to cytoskeleton.

Tight junctions

Prevent leakage of molecules between epithelial cells.

Adherens junctions

Connect actin filaments between neighboring cells.

Desmosomes

Anchor intermediate filaments; provide strong cell-cell adhesion.

Gap junctions

Channels allowing communication between adjacent animal cells.

Rough ER

Membrane-bound organelle with ribosomes, site of protein synthesis.

Smooth ER

Lipid synthesis and detoxification.

Golgi apparatus

Modifies, sorts, and packages proteins and lipids.

Clathrin

Protein forming coated pits in receptor-mediated endocytosis.

Phagocytosis

Engulfment of large particles by cells.

LDL receptor

Binds low-density lipoprotein particles for cholesterol uptake.

Familial hypercholesterolemia

Genetic disorder caused by faulty LDL receptors.

Cytoskeleton

Network of protein filaments for structure and movement.

Actin filaments

Thin filaments involved in cell shape and movement.

Microtubules

Hollow tubes guiding intracellular transport and cell division.

Intermediate filaments

Rope-like structures for mechanical strength.

Kinesin

Motor protein that moves along microtubules toward + end.

Dynein

Motor protein that moves toward − end of microtubules.

Cilia and flagella

Microtubule-based structures for cell motility.

Lamellipodia

Sheet-like projections for cell crawling.

Filopodia

Spike-like extensions involved in sensing environment.

DNA

Double-helix molecule storing genetic information.

RNA

Single-stranded molecule involved in protein synthesis.

Gene

Sequence of DNA coding for a functional product.

Mutation

Change in DNA sequence.

Transposons

Mobile DNA elements that can change position.

Euchromatin

Less condensed, transcriptionally active chromatin.

Heterochromatin

Highly condensed, transcriptionally inactive chromatin.

Histones

Proteins around which DNA wraps to form nucleosomes.

Telomeres

Repeated DNA sequences at chromosome ends.

Telomerase

Enzyme that extends telomeres using RNA template.

End-replication problem

Inability to fully replicate 3' end of lagging strand.

Transcription

DNA → RNA; initiated by RNA polymerase at promoter.

Promoter

DNA sequence where transcription starts.

Enhancer

DNA element increasing transcription from a distance.

Transcription factors

Proteins that regulate gene transcription.

RNA splicing

Removal of introns and joining of exons.

5’ cap

Modified guanine nucleotide added to mRNA for stability.

Poly-A tail

Stretch of adenine added to mRNA for export and stability.

Translation

mRNA → protein using ribosomes and tRNA.

Codon

Three-nucleotide sequence in mRNA coding for an amino acid.

Anticodon

Three-nucleotide sequence on tRNA complementary to mRNA codon.

Ribosome

Molecular machine that synthesizes proteins.

RNA interference (RNAi)

Post-transcriptional gene silencing by small RNAs.

CRISPR-Cas9

Genome editing tool using guide RNA and nuclease.

Epigenetics

Heritable changes in gene expression without DNA sequence change.

Nucleus

Organelle containing DNA and site of RNA synthesis.

Nuclear envelope

Double membrane surrounding the nucleus.

Nuclear pores

Protein complexes allowing transport in and out of nucleus.

Nucleolus

Site of ribosomal RNA synthesis.

Nuclear localization signal (NLS)

Sequence directing proteins to the nucleus.

Nuclear export signal (NES)

Sequence directing proteins out of the nucleus.

Importin

Transport protein that imports cargo with NLS.

Exportin

Transport protein that exports cargo with NES.

Replicative senescence

Cell division halts due to telomere shortening.

Werner syndrome

Premature aging disorder linked to telomere maintenance failure.

Reverse transcriptase

Enzyme that synthesizes DNA from RNA template (e.g. telomerase).

Population doubling

One complete cycle of cell replication in culture.

TTAGGG

Human telomere repeat sequence.

Rap1

Protein that binds telomeres to protect chromosome ends.

In situ hybridization

Technique to visualize specific DNA/RNA sequences in cells.

Mitochondria

Powerhouse organelle for ATP production.

Peroxisome

Organelle that breaks down fatty acids and detoxifies.

Autophagy

Cellular self-digestion process.

Proteasome

Complex that degrades unneeded or damaged proteins.

Signal peptide

Sequence directing newly made proteins to specific locations.

Endomembrane system

Includes ER, Golgi, vesicles, lysosomes, and membrane.

Secretory vesicle

Transports proteins to the cell surface.