Comprehensive Biology: DNA, Cell Structure, and Metabolic Processes

DNA

Double-stranded nucleic acid storing genetic information

Nucleotide

Phosphate + deoxyribose + nitrogenous base

Antiparallel

DNA strands run 5′→3′ and 3′→5′

Complementary base pairing

A-T, C-G via hydrogen bonds

Sugar-phosphate backbone

Held by covalent bonds

Semi-conservative replication

One original + one new strand

Helicase

Breaks hydrogen bonds

DNA polymerase III

Adds nucleotides (5′→3′)

Leading strand

Continuous synthesis

Lagging strand

Discontinuous synthesis

Okazaki fragments

Short DNA segments

DNA ligase

Joins fragments

Transcription

DNA → mRNA (nucleus)

RNA polymerase

Synthesizes RNA

Translation

mRNA → polypeptide (ribosome)

Codon

mRNA triplet

Anticodon

tRNA triplet

Protein

Polymer of amino acids

Peptide bond

Covalent bond between amino acids

Primary structure

Amino acid sequence

Secondary structure

α-helix / β-pleated sheet

Tertiary structure

3D folding

Quaternary structure

Multiple polypeptides

Enzyme

Biological catalyst

Active site

Region substrate binds

Induced fit

Active site changes shape

Activation energy

Energy needed to start reaction

Denaturation

Loss of structure → loss of function

Prokaryote

No nucleus or membrane-bound organelles

Eukaryote

Nucleus + organelles

Organelle

Specialized cell structure

Mitochondrion

Site of aerobic respiration

Endosymbiotic theory

Mitochondria evolved from bacteria

Fluid mosaic model

Proteins embedded in phospholipid bilayer

Phospholipid

Hydrophilic head + hydrophobic tails

Diffusion

Passive, high → low concentration

Facilitated diffusion

Passive, uses proteins

Active transport

Against gradient, uses ATP

Osmosis

Diffusion of water

Cell respiration

Controlled release of energy → ATP

Glycolysis

Cytoplasm, glucose → pyruvate

Link reaction

Pyruvate → acetyl-CoA

Krebs cycle

Produces reduced coenzymes

ETC

Inner mitochondrial membrane

Chemiosmosis

ATP via proton gradient

ATP synthase

Enzyme that makes ATP

Meiosis

Produces haploid cells

Meiosis I

Separates homologous chromosomes

Meiosis II

Separates sister chromatids

Crossing over

Exchange of DNA

Independent assortment

Random chromosome alignment

Gene

DNA sequence coding for trait

Allele

Alternative form of a gene

Genotype

Genetic makeup

Phenotype

Observable trait

Dominant

Expressed when present

Recessive

Expressed only when homozygous

Linked genes

Same chromosome

Recombination

New allele combinations

Hydrogen bonds

Bases

Covalent bonds

Backbone / peptide bonds

Polymerase

Adds, ligase joins

ATP use

Active transport

Inner mitochondrial membrane

ETC

Same chromosome

Linked genes