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Key Concepts in Biology Communication

Apr 9, 2025

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Miss Esteric Biology: OCR Module 5 - Communication, Homeostasis, and Energy

Introduction

  • Comprehensive lecture covering OCR Module 5.
  • Topics include communication, homeostasis, and energy.
  • Resources like flashcards for key terms are available for further study.

Homeostasis

  • Definition: Maintenance of a constant internal environment through physiological control systems.
  • Key controlled factors: Body temperature, blood pH, blood glucose, and blood water potential.
  • Feedback Loops:
    • Negative Feedback: Common, involves mechanisms to return conditions to set limits when deviations are detected.
    • Positive Feedback: Rare, amplifies deviations from set limits (e.g., childbirth and oxytocin release).

Thermoregulation

  • Importance: Ensures enzymes operate at optimal temperature for metabolic reactions.
  • Ectotherms: Rely more on behavioral changes (e.g., basking) to regulate temperature.
  • Endotherms: Use nervous system and hormones for temperature regulation.
    • Involves physiological changes like sweating, vasodilation, and shivering.

Excretion

  • Metabolic reactions create waste products that must be removed (excretion).
  • Key Waste Products:
    • Carbon dioxide (from respiration) excreted by lungs.
    • Nitrogenous waste (urea from amino acids) excreted by kidneys.

The Liver

  • Functions: Urea formation, detoxification, glycogen storage.
  • Structure: Hepatocytes, lobules, sinusoids, kupffer cells.
  • Blood Supply: Hepatic artery, hepatic portal vein, hepatic vein.

The Kidney and Nephrons

  • Function: Filter blood, excrete urea, regulate blood water potential.
  • Structure:
    • Cortex, medulla, pelvis.
    • Nephron components: Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct.
  • Processes:
    • Ultrafiltration: Occurs in Bowman's capsule.
    • Selective Reabsorption: Glucose reabsorbed in proximal convoluted tubule via co-transport.
    • Loop of Henle: Maintains a sodium ion gradient to facilitate water reabsorption.
    • Osmoregulation: Involves ADH and aquaporins to regulate blood water potential.

Neurons and Nervous System

  • Types of Neurons: Sensory, relay, motor.
  • Action Potential: Depolarization due to sodium ion influx; follows 'All or Nothing' principle.
  • Synapses: Neurotransmitters diffuse across synaptic cleft to transmit impulses.

Hormonal Communication

  • Endocrine System: Glands secrete hormones transported in blood to target organs.
  • Steroid vs Non-steroid Hormones: Lipid-soluble vs water-soluble mechanisms.

The Adrenal Glands

  • Adrenal Cortex: Secretes cortisol, aldosterone, androgens.
  • Adrenal Medulla: Secretes adrenaline and noradrenaline affecting heart rate and blood pressure.

The Pancreas

  • Exocrine Functions: Secretes digestive enzymes.
  • Endocrine Functions: Insulin and glucagon regulate blood glucose levels.

Plant Responses

  • Defense Mechanisms: Physical and chemical defenses against herbivores.
  • Tropisms: Growth responses to stimuli like light and gravity.

Plant Hormones

  • Types: Auxins, gibberellins, abscisic acid, ethylene.
  • Roles: Control growth, seed germination, fruit ripening.

Animal Responses

  • Nervous System: Peripheral and central systems, autonomic and somatic control.
  • Brain Structure: Cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland.
  • Reflexes: Simple pathways for automatic responses to stimuli.

Photosynthesis

  • Structure of Chloroplasts: Stroma, thylakoid membranes, granum.
  • Photosynthetic Pigments: Chlorophyll varieties absorb different wavelengths.
  • Reactions:
    • Light-Dependent Reactions: Involve photosystems and electron transport chains.
    • Light-Independent Reactions: Calvin cycle produces glucose using ATP and reduced NADP.

Respiration

  • Aerobic vs Anaerobic:
    • Glycolysis: Occurs in cytoplasm, produces pyruvate and ATP.
    • Link Reaction and Krebs Cycle: Occur in mitochondria, generate reduced coenzymes for oxidative phosphorylation.
    • Oxidative Phosphorylation: Produces ATP using electron transport chain and chemiosmosis.
    • Anaerobic Respiration: Produces lactate or ethanol, less efficient.

Respiratory Substrates

  • Types: Carbohydrates, lipids, proteins.
  • RQ Values: Indicate type of substrate being respired.

This notes summary captures the key points and main ideas discussed in the lecture on OCR Module 5. Use it as a reference for studying and revisiting essential concepts.

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