Chapter 4: Cellular Metabolism and Proteins

Anaerobic Metabolism of Glucose

Anaerobic metabolism refers to the breakdown of glucose without oxygen, producing less ATP compared to aerobic metabolism.

• ATP Yield: Anaerobic metabolism of one glucose molecule yields 2 ATP.

• Pros: Rapid energy production, useful in low-oxygen conditions.

• Cons: Low ATP yield, accumulation of lactic acid.

Proteins and Amino Acids

Proteins are polymers of amino acids and serve structural, enzymatic, and regulatory roles in cells.

• Amino Acids: Building blocks of proteins, each with a unique side chain.

• Roles of DNA and RNA: DNA stores genetic information; RNA translates this information into proteins.

• Transcription: The process of copying DNA into messenger RNA (mRNA).

• Translation: The process where ribosomes synthesize proteins using mRNA as a template.

• Types of RNA: mRNA (messenger), tRNA (transfer), and rRNA (ribosomal) each play distinct roles in protein synthesis.

Chapter 5: Membrane Transport and Homeostasis

Osmosis and Tonicity

Osmosis is the movement of water across a semipermeable membrane. Tonicity describes the effect of a solution on cell volume.

• Isosmotic: Solutions with equal osmotic pressure.

• Hyperosmotic: Solution with higher osmotic pressure than another.

• Hyposmotic: Solution with lower osmotic pressure than another.

• Hypertonic: Causes cell to shrink (water leaves cell).

• Hypotonic: Causes cell to swell (water enters cell).

• Isotonic: No net change in cell volume.

Membrane Permeability and Equilibrium

Permeating solutes can cross the membrane; non-permeating solutes cannot. This affects water movement and equilibrium.

• Equilibrium: Achieved when solute and water concentrations are balanced across the membrane.

Transport Proteins, Enzymes, and Receptors

These membrane proteins facilitate movement of substances and signal transduction.

• Transport Proteins: Enable facilitated diffusion and active transport.

• Enzymes: Catalyze reactions at the membrane.

• Receptors: Bind signaling molecules and initiate cellular responses.

Types of Membrane Transport

Cells use various mechanisms to move substances across membranes.

• Diffusion: Passive movement of molecules from high to low concentration.

• Simple Diffusion: Direct movement through the lipid bilayer.

• Facilitated Diffusion: Movement via transport proteins.

• Osmosis: Diffusion of water.

• Primary Active Transport: Uses ATP to move substances against their gradient.

• Secondary Active Transport: Uses energy from another gradient.

• Carrier-Mediated Transport: Involves specific carrier proteins.

Channel vs. Carrier Proteins

• Channel Proteins: Form pores for rapid movement; selective for specific ions.

• Carrier Proteins: Bind and transport molecules; slower, but highly specific.

Properties of Diffusion

• 7 Characteristics: Rate depends on concentration gradient, temperature, molecular size, membrane surface area, membrane permeability, distance, and electrical charge.

• 2 Properties of Simple Diffusion: No energy required; moves down concentration gradient.

Vesicular Transport

Vesicular transport moves large particles or fluids via membrane-bound vesicles.

• Phagocytosis: Cell engulfs large particles.

• Endocytosis: Cell takes in substances by forming vesicles.

• Exocytosis: Cell expels substances via vesicles.

• Transcellular Transport: Movement through the cell, crossing both apical and basolateral membranes.

• Transepithelial Transport: Movement across epithelial layers.

Electrochemical Gradients

Gradients of ions like Na+ and K+ are crucial for cell function.

• Depolarization: Membrane potential becomes less negative.

• Repolarization: Membrane potential returns to resting state.

• Hyperpolarization: Membrane potential becomes more negative.

Chapter 6: Communication, Integration, and Homeostasis

Cell Communication

Cells communicate using chemical and electrical signals, which can be local or long-distance.

• Signal Molecules: Only cells with specific receptors respond.

• Signal Pathways: Four common features: signal molecule, receptor, intracellular signal pathway, and response.

• Lipophilic vs. Lipophobic Molecules: Lipophilic molecules cross membranes easily; lipophobic require membrane receptors.

• Signal Transduction: Conversion of a signal from one form to another.

• Second Messenger System: Intracellular molecules relay signals from receptors.

• Signal Cascade and Amplification: One signal molecule can trigger a large cellular response.

Membrane Receptors

Membrane receptors are classified into four categories, each with distinct mechanisms.

• Categories: Channel-linked, enzyme-linked, G protein-coupled, and intracellular receptors.

• Saturation, Specificity, Competition: Receptors can be saturated, are specific for certain ligands, and may compete for binding.

• Adrenergic Receptors: Bind adrenaline/noradrenaline; different types have different ligand affinities.

• Upregulation/Downregulation: Cells can increase or decrease receptor numbers in response to signals.

Signal Termination and Transduction Targets

• Signal Termination: Signals are terminated by degradation, removal, or receptor inactivation.

• Transduction Targets: Signal transduction can regulate gene expression, enzyme activity, or ion channel function.

Homeostasis and Control Systems

Homeostasis is maintained by variables and control systems, including the nervous and endocrine systems.

• Cannon's 4 Postulates: Describe principles of homeostatic regulation.

• Long-Distance Pathways: Hormones and nerves maintain homeostasis across the body.

• Nervous vs. Endocrine System: Nervous system is fast and specific; endocrine is slower and widespread.

Chapter 7: Introduction to the Endocrine System

Hormones and Chemical Messengers

Hormones are chemical messengers secreted by endocrine glands to regulate physiological processes.

• Definition: Hormones travel through blood to target organs.

• Pheromones: Chemical signals released outside the body to affect other organisms.

• Half-Life: Time required for hormone concentration to decrease by half.

• Degradation: Hormones are broken down by enzymes or excreted.

Steroid vs. Protein/Amino Acid Hormones

• Steroid Hormones: Derived from cholesterol; lipid-soluble; act on intracellular receptors.

• Protein/Amino Acid Hormones: Water-soluble; act on membrane receptors.

Hormone Synthesis and Release

• Precursors: Specific amino acids or cholesterol are used to synthesize hormones.

• Trophic Hormones: Stimulate the release of other hormones.

• Release Control: Feedback mechanisms regulate hormone secretion.

Pituitary Gland and Portal System

• Anterior vs. Posterior Pituitary: Anterior releases hormones via blood; posterior stores and releases neurohormones.

• Hypothalamic-Hypophyseal Portal System: Connects hypothalamus to anterior pituitary for hormone transport.

Feedback Systems

• Short Loop Feedback: Pituitary hormone inhibits hypothalamic release.

• Long Loop Feedback: Target gland hormone inhibits both pituitary and hypothalamic release.

Hormone Interactions

• Synergism: Combined effect greater than sum of individual effects.

• Permissiveness: One hormone enables another to act.

• Antagonism: One hormone opposes the action of another.

Pathologies

• Hypersecretion: Excess hormone production.

• Hyposecretion: Insufficient hormone production.

• Primary Pathology: Problem in the target gland.

• Secondary Pathology: Problem in the pituitary or hypothalamus.