Introduction to Biochemistry, Homeostasis, Mitosis, Inflammation, Fever, and Infection – Study Notes for Anatomy & Physiology

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Introduction

This study guide covers foundational concepts in biochemistry, homeostasis, cell biology, and the physiological processes of inflammation, fever, and infection. These topics are essential for understanding the structure and function of the human body in health and disease.

Homeostasis and Survival Needs

Definition and Importance

Homeostasis is the maintenance of relatively stable internal conditions despite continuous changes in the external environment. It is vital for the survival and proper functioning of the body.

Survival Needs: Nutrients, oxygen, water, normal body temperature, and appropriate atmospheric pressure are essential for maintaining homeostasis.
Disruption of homeostasis can lead to disease or dysfunction.

Feedback Mechanisms

Negative Feedback: The most common feedback mechanism. The response reduces or shuts off the original stimulus, helping to maintain balance. Example: Regulation of body temperature.
Positive Feedback: The response enhances or exaggerates the original stimulus, often leading to a cascade or amplifying effect. Example: Blood clotting, labor contractions.

Maslow's Hierarchy of Needs (Additional info)

Physiological needs (food, water, rest) form the base of the hierarchy and are essential for survival before higher-level needs can be addressed.

Basic Chemistry for Anatomy & Physiology

Atoms, Molecules, and Compounds

Element: A substance that cannot be broken down into simpler substances; made up of atoms with specific properties.
Molecule: Two or more atoms bonded together (e.g., O2).
Compound: A molecule containing two or more different kinds of atoms (e.g., H2O, CO2).

Mixtures: Solutions, Colloids, and Suspensions

Solution: Homogeneous mixture; solute particles are evenly distributed and do not settle out (e.g., saline solution).
Colloid: Heterogeneous mixture; particles are not evenly distributed, cloudy but do not settle (e.g., cytoplasm).
Suspension: Heterogeneous mixture with large, visible solutes that settle out (e.g., blood cells in plasma).

Type	Particle Size	Settling	Example
Solution	Small	No	Saline
Colloid	Intermediate	No	Cytoplasm
Suspension	Large	Yes	Blood

Chemical Reactions

Synthesis (Anabolic): Atoms or molecules combine to form a larger, more complex molecule.
Decomposition (Catabolic): Breakdown of a molecule into smaller components.
Exchange: Involves both synthesis and decomposition.
Reversible Reactions: Can proceed in both directions.

Factors Affecting Chemical Reactions

Temperature (higher temperature increases reaction rate)
Concentration of reactants
Particle size (smaller particles react faster)
Catalysts: Substances that increase the rate of reaction without being consumed. Enzymes are biological catalysts.

ATP: The Energy Currency

Adenosine Triphosphate (ATP): The primary energy carrier in cells, produced during cellular respiration.
ATP breaks down to ADP and AMP, releasing energy for cellular processes.

Water and Salts in Homeostasis

Water: Most abundant molecule in cells (60-80%), excellent solvent, regulates temperature, and participates in chemical reactions.
Salts: Compounds that dissociate into ions (electrolytes) in water. Important ions include Na+, K+, Ca2+, Cl-, Fe.

Acids, Bases, and pH

Acid: Releases H+ ions in solution.
Base: Accepts H+ ions or releases OH-.
pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (alkaline), with 7 being neutral.
pH is calculated as

Biological Macromolecules

Carbohydrates

Include sugars (saccharides) and starches; contain C, H, O.
Main source of energy (ATP production).
Monosaccharides: Smallest unit (e.g., glucose).

Lipids

Contain C, H, O (sometimes P); include triglycerides, phospholipids, steroids.
Triglycerides: Main form of stored energy.
Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.
Steroids: Four interlocking hydrocarbon rings; cholesterol is the basis for all steroids.

Proteins

Contain C, H, O, N, S, and sometimes P.
Made of amino acids; perform a wide variety of functions (enzymes, structure, transport).

Nucleic Acids

Contain C, H, O, N, P; largest molecules in the body.
Made of nucleotides (adenine, guanine, cytosine, thymine, uracil).
Two types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Store and transmit genetic information.

Cellular Transport Mechanisms

Passive Transport

No energy required; substances move down their concentration gradient.
Simple Diffusion: Movement of molecules from high to low concentration.
Facilitated Diffusion: Uses carrier or channel proteins.
Osmosis: Diffusion of water across a semipermeable membrane.

Osmolarity and Tonicity

Isotonic: Same osmolarity as the cell; no net water movement.
Hypertonic: Higher osmolarity than the cell; water leaves the cell (crenation).
Hypotonic: Lower osmolarity than the cell; water enters the cell (lysis).

Solution Type	Effect on Cell
Isotonic	No change
Hypertonic	Cell shrinks (crenation)
Hypotonic	Cell swells and may burst (lysis)

Active Transport

Requires energy (ATP); moves substances against their concentration gradient.
Primary Active Transport: Direct use of ATP (e.g., Na+-K+ pump).
Secondary Active Transport: Uses energy from the movement of another substance.
Vesicular Transport: Movement of large particles via vesicles (endocytosis, exocytosis).

Resting Membrane Potential

Established by the Na+-K+ pump and differential permeability of the plasma membrane.
More Na+ outside and more K+ inside the cell.
Typical resting membrane potential: -70 to -90 mV.

Cell Cycle and Mitosis

Cell Cycle

Series of changes a cell undergoes from formation to reproduction.
Interphase: Cell grows and carries out normal functions; DNA is duplicated in S-phase.
Mitosis: Division of the nucleus into two genetically identical daughter cells.

Protein Synthesis

Genetic Code and RNA Types

Gene: Segment of DNA coding for a polypeptide.
mRNA (Messenger RNA): Carries genetic code from DNA to ribosomes.
rRNA (Ribosomal RNA): Forms part of the ribosome.
tRNA (Transfer RNA): Brings amino acids to the ribosome.

Steps of Protein Synthesis

Transcription: DNA information is copied into mRNA in the nucleus.
Translation: mRNA is decoded at the ribosome to assemble a polypeptide chain.

Inflammation and Fever

Inflammation

Occurs in response to tissue injury; aims to prevent infection, initiate healing, and limit further damage.
Acute Inflammation: Lasts minutes to days; characterized by vasodilation, increased capillary permeability, and diapedesis (movement of white blood cells).
Chronic Inflammation: Lasts days to years; involves macrophages, lymphocytes, and plasma cells, leading to tissue destruction and repair.

Systemic Manifestations

Fever: Caused by pyrogens acting on the hypothalamus; increases body temperature to enhance immune response.
Leucocytosis: Increased white blood cell count.
Acute-phase Reactants: Proteins such as C-reactive protein and fibrinogen increase in plasma.

Infection

Chain of Infection

Process includes colonization, infection, and spread.
Septicaemia: Presence of bacteria in the blood due to failure of defense mechanisms; can lead to widespread vasodilation and shock.

References

Marieb, E.N. & Hoehn, K. (2023). Human Anatomy & Physiology, Global Edition (12th ed.). Pearson Education Inc.
Craft, J.A., Gordon, C.J., Huether, S.E., McCance, K.L., Brashers, V.L., & List, S.L. (2022). Understanding Pathophysiology (4th ANZ ed.). Elsevier Australia.
Perry, J., Douglas, C., Rebeiro, G., & Waters, D. (Eds.). (2020). Potter and Perry's Fundamentals of Nursing (6th ANZ ed.). Elsevier Australia.