Bio Quiz 2

Communication Between Cells

• Cells need: A receptor & a way to process/respond.

• Types of receptors: Transmembrane (surface) & Intracellular (inside).

• Differences: Transmembrane receptors bind extracellular signals, intracellular receptors bind small/nonpolar signals.

• Receptor response: Binding changes receptor shape → triggers a response.

• Specificity: Receptors only bind specific signals.

Energy

• Photosynthesis: Plants store solar energy in sugar.

• Cellular Respiration: Organisms release energy from food molecules.

• Kinetic vs. Potential Energy: Kinetic = movement; Potential = stored energy.

• 1st Law of Thermodynamics: Energy cannot be created/destroyed, only transferred.

• 2nd Law of Thermodynamics: Energy transformations increase entropy (disorder).

• ATP & ADP: ATP = high-energy molecule, ADP = low-energy form.

• Enzymes: Speed up reactions by lowering activation energy.

Photosynthesis

Purpose: Convert solar energy into chemical energy (glucose).

Part I – Light-Dependent Reactions

• Start with: Light & water (H₂O).

• Water molecule: Split into oxygen (O₂), protons, and electrons.

• Oxygen source: Comes from H₂O splitting.

• Chlorophyll absorbs light: Excites electrons → powers ETC.

• Produces: ATP & NADPH (for light-independent reactions).

• Location: Thylakoid membrane (chloroplast).

Part II – Light-Independent Reactions (Calvin Cycle)

• Start with: CO₂ (absorbed from the air).

• End product: Glucose.

• Location: Stroma (chloroplast).

Cellular Respiration (Animals & Plants)

Purpose: Break down glucose for ATP production.

Glycolysis

• Starts with: Glucose.

• Ends with: 2 Pyruvate, NADH.

• ATP produced: 2 ATP.

• Location: Cytoplasm.

Krebs Cycle

• Starts with: Acetyl-CoA (from pyruvate).

• Ends with: CO₂, NADH, FADH₂, ATP.

• Gas released: CO₂.

• ATP produced: 2 ATP.

• Location: Mitochondrial matrix.

Electron Transport Chain (ETC)

• Starts with: NADH & FADH₂.

• Ends with: H₂O & ATP.

• ATP produced: ~34 ATP.

• Location: Inner mitochondrial membrane.

Fermentation (Oxygen NOT present)

• Starts with: Pyruvate.

• Ends with: Lactic acid (animals) or ethanol & CO₂ (plants).

• ATP produced: 2 ATP.

DNA

• 3 subunits: Sugar, phosphate, nitrogenous base.

• Structure: Double helix.

• Backbone: Sugar-phosphate (no info stored).

• 4 Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

• Base-pairing: A-T, C-G.

Genetics

• Genome → Chromosomes → Genes: Genome = all DNA, Chromosomes = DNA strands, Genes = segments coding for proteins.

• Gene expression:

  • Transcription: DNA → mRNA (in nucleus).

  • Translation: mRNA → Protein (in ribosome).

• mRNA modification: Introns removed, exons spliced.

• Introns vs. Exons: Introns = non-coding, Exons = coding.

• Chromosome count: 46 (humans).

• Chromosome # & complexity? No direct relation.

• % of genome as genes? ~1-2%.

• Genetic code: Universal code linking codons (3 bases) to amino acids.

/