Comprehensive Biology: Cell Membranes, Enzymes, Respiration, Photosynthesis, DNA, Protein Synthesis, Genetics, Cell Signaling, Evolution, Data Skills, IB Command Terms

Structure of phospholipid

Hydrophilic phosphate head + hydrophobic fatty acid tails.

Function of phospholipid bilayer

Controls movement of substances into and out of cell.

Why is membrane selectively permeable?

Only certain substances can cross.

Small nonpolar molecules that diffuse easily

O₂ and CO₂.

Diffusion definition

Passive movement from high to low concentration.

Osmosis definition

Movement of water through partially permeable membrane from low solute to high solute concentration.

Facilitated diffusion

Passive transport using channel/carrier proteins.

Active transport definition

Movement against concentration gradient using ATP.

Protein used in active transport

Carrier protein/pump.

Endocytosis definition

Cell takes in material using vesicles.

Exocytosis definition

Cell releases material using vesicles.

Hypertonic solution effect

Cell loses water.

Hypotonic solution effect

Cell gains water.

Isotonic solution effect

No net water movement.

Function of cholesterol in membrane

Maintains membrane fluidity and stability.

Problem: damaged membrane

Loss of homeostasis.

Enzyme definition

Biological catalyst that lowers activation energy.

Active site

Region where substrate binds.

Lock-and-key model

Substrate fits exactly into active site.

Induced-fit model

Active site changes shape slightly to fit substrate.

Factors affecting enzyme activity

Temperature, pH, substrate concentration.

Effect of high temperature on enzymes

Denaturation.

Denaturation definition

Permanent change in enzyme shape.

Product of enzyme-substrate reaction

Products released; enzyme unchanged.

Competitive inhibition

Inhibitor competes for active site.

Non-competitive inhibition

Inhibitor binds elsewhere changing active site shape.

Problem: enzyme denatured

Metabolic reactions slow or stop.

Purpose of respiration

Produce ATP for cellular work.

Aerobic respiration equation

Glucose + oxygen → carbon dioxide + water + ATP.

Glycolysis location

Cytoplasm.

Glycolysis products

2 pyruvate + 2 ATP + 2 NADH.

Krebs cycle location

Mitochondrial matrix.

Electron transport chain location

Inner mitochondrial membrane.

Final electron acceptor

Oxygen.

Product formed when oxygen accepts electrons

Water.

ATP yield of aerobic respiration

~36-38 ATP.

Anaerobic respiration in humans

Lactic acid fermentation.

Anaerobic respiration in yeast

Alcoholic fermentation.

Product of alcoholic fermentation

Ethanol + CO₂.

Why is aerobic respiration more efficient?

Produces much more ATP.

Problem without oxygen

ETC stops.

Photosynthesis equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Organelle for photosynthesis

Chloroplast.

Pigment used

Chlorophyll.

Light-dependent reactions location

Thylakoid membrane.

Calvin cycle location

Stroma.

Product of light-dependent reactions

ATP + NADPH + O₂.

Purpose of photolysis

Splits water to provide electrons.

Calvin cycle function

Produces carbohydrates using CO₂.

Enzyme used in carbon fixation

RuBisCO.

Limiting factors of photosynthesis

Light intensity, CO₂ concentration, temperature.

Problem with low light

Reduced ATP and NADPH production.

DNA replication purpose

Produce identical DNA molecules.

Semi-conservative replication

Each DNA molecule contains one old strand and one new strand.

Helicase function

Breaks hydrogen bonds and unwinds DNA.

DNA polymerase function

Adds nucleotides in 5' → 3' direction.

Ligase function

Joins Okazaki fragments.

Leading strand

Synthesized continuously.

Lagging strand

Synthesized discontinuously.

Okazaki fragments

Short DNA fragments on lagging strand.

Complementary base pairing

A-T and C-G.

Product of DNA replication

2 identical DNA molecules.

Problem: mutation

Altered genetic sequence.

Transcription definition

Production of mRNA from DNA.

Translation definition

Production of protein from mRNA.

Location of transcription

Nucleus.

Location of translation

Ribosome.

RNA polymerase function

Synthesizes mRNA.

Codon definition

3-base sequence on mRNA.

Anticodon definition

Complementary 3-base sequence on tRNA.

Start codon

AUG.

Stop codons

UAA, UAG, UGA.

Product of translation

Polypeptide/protein.

Peptide bond

Bond between amino acids.

Mutation effect on proteins

Can alter amino acid sequence.

Gene definition

DNA sequence coding for a protein.

Allele definition

Alternative form of a gene.

Homozygous definition

Two identical alleles.

Heterozygous definition

Two different alleles.

Dominant allele

Expressed if present.

Recessive allele

Only expressed when homozygous.

Genotype definition

Genetic makeup.

Phenotype definition

Observable characteristics.

Punnett square purpose

Predict offspring genotypes.

Meiosis purpose

Produce haploid gametes.

Crossing over definition

Exchange of DNA between homologous chromosomes.

Independent assortment

Random orientation of chromosomes.

Variation sources

Mutation, meiosis, fertilization.

Problem: nondisjunction

Abnormal chromosome number.

Chemical signaling definition

Communication between cells using molecules.

Ligand definition

Signaling molecule.

Receptor definition

Protein that binds signaling molecule.

Endocrine signaling

Hormones travel in bloodstream.

Synaptic signaling

Neurotransmitters cross synapse.

Reception step

Ligand binds receptor.

Transduction step

Signal cascade amplifies message.

Response step

Cell changes activity.

Second messenger examples

cAMP and calcium ions.

Protein kinase function

Phosphorylates proteins.

Example hormone

Insulin.