Biology Review Lecture – Core Vocabulary

Photosynthesis

• Overall equation: 6CO*2 + 6H*2O + \text{light energy} \;\longrightarrow\; C*6H*{12}O*6 + 6O*2
• Two major stages
  • **Light-dependent reactions** (in thylakoid membrane)
  • Inputs: light, H*2O, ADP, P*i, NADP^+
  • Outputs: ATP, NADPH, O_2
  • Purpose: convert light energy \u2192 chemical energy, release oxygen, pump H^+ to build gradient
  • **Calvin Cycle / Light-independent reactions** (in stroma)
  • Inputs: CO_2, ATP, NADPH
  • Output: glucose (C*6H*{12}O_6)
  • Overall purpose: carbon fixation & reduction \u2192 carbohydrate synthesis
• Stoma vs. Stroma
  • **Stoma** (no \u201cr\u201d): microscopic pore on leaf underside \u2192 gas exchange ( CO*2\leftrightarrow O*2 + water vapor)
  • **Stroma** (with \u201cr\u201d): fluid interior of chloroplast where Calvin cycle occurs
• In sunlight (15-min graph described)
  • O*2 \u2191, CO*2 \u2193 \u2192 photosynthesis predominates
• In darkness
  • O*2 \u2193, CO*2 \u2191 \u2192 only respiration continues

Cellular Respiration (Aerobic)

• Overall equation (36-ATP version used in lecture):
  C*6H*{12}O*6 + 6O*2 \longrightarrow 6CO*2 + 6H*2O + 36\,ATP
• Three major stages
  1. **Glycolysis** (cytoplasm)
  • Anaerobic; ancient pathway; yield: 2ATP + 2NADH
  • End product: pyruvic acid \u2192 (with O_2) acetyl-CoA
  1. **Krebs / Citric Acid Cycle** (mitochondrial matrix)
  • Yield per glucose: 2ATP + 8NADH + 2FADH*2 + 6CO*2
  1. **Electron Transport Chain & Chemiosmosis** (inner mito. membrane)
  • NADH/FADH2 donate high-energy e\u207b
  • e\u207b energy pumps H^+ against gradient
  • H^+ flows through **ATP synthase** \u2192 \approx 32ATP
  • Final e\u207b acceptor: O*2 \u2192 H*2O
  • Net yield \u2248 36ATP / glucose ( 2 + 2 + 32 )

Fermentation (Anaerobic Options)

• Trigger: lack of oxygen prevents pyruvate \u2192 acetyl-CoA
• Goal: regenerate NAD^+ so glycolysis can continue (still yields 2 ATP)
• Human muscle: pyruvate \u2192 **lactic acid** (burn during sprint)
• Yeast: pyruvate \u2192 **ethanol + CO_2** (brewing; ethanol toxic to yeast)

Bioenergetics & Thermodynamics

• First Law of Thermodynamics: **Energy cannot be created or destroyed; only converted**
• Entropy: measure of **disorder** in a system; tends to increase
• Energy forms
  • **Kinetic energy**: energy of motion (TRUE)
  • **Potential energy**: stored energy (teacher\u2019s slip \u201cprofessional\u201d)
• Cellular energy currency: **ATP (adenosine triphosphate)**

Enzymes & Catalysis

• Enzymes = **proteins** (NOT carbohydrates)
• Function: **speed up reactions by lowering activation energy**
• Catalyzed reaction faster than uncatalyzed (TRUE)
• Activation energy \u2260 \u201cinitiation energy\u201d (FALSE statement in lecture)
• **Competitive inhibition**
  • Inhibitor resembles substrate & binds active site
  • Example: morphine vs. naloxone on opioid receptor; naloxone displaces morphine without activating receptor \u2192 medical reversal

Diffusion & Membrane Transport

• Diffusion: **movement of molecules from high \u2192 low concentration** (down gradient)

Cell Cycle & Mitosis

• Interphase = G*1 (growth) + S (DNA synthesis) + G*2 (prep)
  • DNA replication occurs in **S phase**
  • Normal cell \u201cdaily life\u201d happens throughout Interphase
• Mitosis sequence: **Prophase \u2192 Metaphase \u2192 Anaphase \u2192 Telophase**
  • First phase: **Prophase**
• **Cytokinesis**
  • Division of cytoplasm; follows telophase; *not* part of mitosis itself
  • Animal cells: **cleavage furrow**
  • Plant cells: **cell plate formation**
• DNA must replicate **before** any cell division (mitosis or meiosis) to prevent daughter cells with half DNA
• Binary fission: simple prokaryotic division, replicate DNA then split
• Improper regulation of eukaryotic division \u2192 **cancer**

Meiosis & Genetic Variation

• Purpose: **reduction division** \u2192 haploid gametes (23 chromosomes)
  • Without meiosis, chromosome number would **double each generation** (TRUE)
• Diploid (2n): 46 chromosomes; Haploid (n): 23 chromosomes
• Key terminology
  • **Homologous chromosomes**: nearly identical pairs (one maternal, one paternal)
  • **Sister chromatids**: duplicated copies of a single chromosome joined at centromere
• Events
  • **Prophase I**
  • Homologous chromosomes **pair (synapsis)**
  • **Crossing over** occurs \u2192 new allele combinations
  • **Metaphase I**: **independent assortment** (random orientation of homologous pairs)
• Sources of genetic variability
  1. Crossing over (new recombinant chromosomes)
  2. Independent assortment ( 2^{23} \;\approx\; 8\times10^6 gamete combos)
  3. Random fertilization ( combines two gametes \u2192 \approx 7\times10^{13} possible zygotes )
• Meiosis vs. Mitosis occurrence
  • **Mitosis**: somatic (body) cells (TRUE)
  • **Meiosis**: germ/sex cells only; NOT somatic (FALSE statement corrected)

Quick True / False & Fact Check Review

• Kinetic energy = energy of motion \u2192 **True**
• Catalyzed reaction faster than uncatalyzed \u2192 **True**
• Enzymes are carbohydrates that slow reactions \u2192 **False** (they are proteins that speed them)
• Activation energy called \u201cinitiation energy\u201d \u2192 **False**
• Mitosis & meiosis both in somatic cells \u2192 **False**
• Without meiosis, chromosome number doubles each generation \u2192 **True**

Practical / Graph & Lab Reminders

• Plant respiration lab: plotting \u201ctime vs. O*2 ppm\u201d & \u201ctime vs. CO*2 ppm\u201d
• Interpreting slopes indicates dominant metabolic process (photosynthesis vs. respiration)
• Expect exam images: cartoon or micrograph of mitotic stages; must identify phases & answer associated questions (e.g., \u201cWhich phase is