Homeostasis and Basic Human Chemistry

Survival Needs

For human survival, several factors must be maintained within appropriate ranges. Too much or too little of these can be harmful.

• Nutrients – sugars (not table sugar), ions, salts

  • Carbs: Main source of energy for cells. Glucose is broken down during cellular respiration to produce ATP, the cell's energy currency.

  • Ions (e.g., sodium, potassium): Transmit electrical signals in nerves and muscles, and maintain fluid balance inside and outside cells.

  • Salts: Dissolve into ions, helping with nerve impulses and muscle contraction.

  • Importance:

    • Energy Production: Without nutrients, cells cannot make ATP.

    • Building Cellular Structures: Nutrients are used to build membranes, proteins, and DNA.

    • Fluid/Electrolyte Balance: Ions and water keep cells from swelling or shrinking.

• Oxygen

  • Needed for cellular respiration, a process that uses glucose and oxygen to make ATP.

  • Without oxygen, cells cannot make enough ATP, leading to cell death.

• Water

  • Makes up most of your body weight.

  • Acts as a solvent for chemical reactions.

  • Helps transport nutrients and waste.

  • Regulates body temperature through sweating and evaporation.

• Normal body temperature

  • Essential for proper metabolic reactions.

  • Too high or too low can disrupt enzyme function and metabolism.

• Appropriate atmospheric pressure

  • Needed for gas exchange in the lungs (oxygen in, carbon dioxide out).

  • Why is Atmospheric Pressure Important?

    • Gas Exchange in the Lung: When you inhale, air moves into your lungs because the pressure inside your lungs becomes lower than the pressure outside (atmospheric pressure).

    • Oxygen Uptake: At high altitudes, atmospheric pressure drops, so less oxygen enters your lungs and blood. This means your cells get less oxygen, which can make you feel tired or sick.

    • Everyday Example: Mountain climbers need extra oxygen because atmospheric pressure is lower at high elevations.

Homeostasis

Homeostasis is the process of maintaining the body's internal environment in a relatively constant state, despite changes in the external environment.

• Definition: The condition of maintaining the body's internal environment in a relative constant state (steady temperature, blood pressure, glucose levels, etc.) within limits.

• Homeostatic Imbalance: Anything that disturbs or alters the balance of the internal environment.

• Homeostasis is a ceaseless process of activities in response to stresses in an attempt to maintain equilibrium.

• Homeostatic Control Mechanisms: Mechanisms that are generally "self-regulating" and serve to maintain the homeostatic "steady state." These mechanisms involve at least three components:

  • Receptor

  • Control center

  • Effector

Negative Feedback

Negative feedback is the most common homeostatic control mechanism, functioning similarly to a thermostat.

• The output shuts off the original effect of the stimulus or reduces its intensity.

• A change in one direction results in a feedback that causes a change or adjustment in the opposite direction.

Positive Feedback

Positive feedback enhances the original stimulus so that the response is accelerated.

• A change in one direction accelerates more change in the same direction.

• Rare in life; Examples include:

  • Blood clotting

  • Labor contractions

  • Orgasm

Basic Chemistry

Energy

Energy is the capacity to do work or put matter into motion.

• Energy does not have mass, nor does it take up space.

• The greater the work done, the more energy it uses up.

Elements

All matter is composed of elements, which are substances that cannot be broken down into simpler substances by ordinary chemical methods.

• Four elements make up 96% of the body:

  • Oxygen

  • Carbon

  • Hydrogen

  • Nitrogen

Atoms

All elements are made up of atoms, which are:

• Unique building blocks for each element

• Smallest particles of an element with properties of that element

• What give each element its particular physical & chemical properties

Combining Matter

Molecules and Compounds

• Most atoms chemically combine with other atoms to form molecules and compounds.

• Molecule: General term for 2 or more atoms bonded together.

  • Molecules with only one type of atom (H2 or O2) are just called molecules.

• Compound: Specific molecule that has 2 or more different kinds of atoms bonded together.

  • Example: C6H12O6 is glucose.

Mixtures

Most matter exists as mixtures: two or more components that are physically intermixed.

• Three basic types of mixtures:

  1. Solution

     • Are homogeneous mixtures, meaning particles are evenly distributed throughout.

     • Solvent: Substance present in greatest amount (usually a liquid, such as water).

     • Solute: Substance dissolved in solvent, present in smaller amounts.

       • Example: Blood sugar – glucose is solute, blood (plasma) is solvent.

     • True solutions are usually transparent.

  2. Colloids

     • Also known as emulsions; are heterogeneous mixtures, meaning particles are not evenly distributed throughout mixture.

     • Can see the solute particles under a microscope, but they do not settle out.

  3. Suspensions

     • Heterogeneous mixtures that contain large, visible solutes that do settle out.

     • Example: Mixture of water and sand.

     • Blood is considered a suspension because if left in a tube, the blood cells will settle out.

Types of Chemical Bonds

Ionic Bonds

• Ions are atoms that have gained or lost electrons and become charged – oppositely charged ions attract.

• Number of protons does not equal number of electrons.

• Ionic bonds involve the transfer of valence shell electrons from one atom to another, resulting in ions:

  • One becomes an anion (negative charge): atom that gained one or more electrons.

  • One becomes a cation (positive charge): atom that lost one or more electrons.

• Attraction of opposite charges results in an ionic bond.

Covalent Bonds

• Formed by sharing of two or more valence shell electrons between two atoms.

• Sharing of 2 electrons results in a single bond.

• Sharing of 4 electrons is a double bond.

• Sharing of 6 electrons is a triple bond.

• Allows each atom to fill its valence shell at least part of the time.

• Two types of covalent bonds:

  • Polar and nonpolar covalent bonds.

Chemical Reactions

• Chemical reactions occur when chemical bonds are formed, rearranged, or broken.

• These reactions can be written in symbolic forms called chemical equations.

• Products: Resulting chemical end products.

• Amounts of reactants and products are shown in balanced equations.

Types of Chemical Reactions

1. Synthesis (combination) reactions: Involve atoms or molecules combining to form larger, more complex molecules.

   • Used in anabolic (building) processes:

2. Decomposition reactions: Involve breakdown of a molecule into smaller molecules or its constituent atoms (reverse of synthesis reactions).

   • Involve catabolic (bond-breaking) reactions:

3. Exchange reactions: Also called displacement reactions, involve both synthesis and decomposition.

   • Bonds are both made and broken:

Energy Flow in Chemical Reactions

• All chemical reactions are either exergonic or endergonic.

• Exergonic reactions: Result in a net release of energy (give off energy).

  • Products have less potential energy than reactants.

  • Catabolic – breaking apart.

• Endergonic reactions: Result in net absorption of energy (use up energy).

  • Products have more potential energy than reactants.

  • Anabolic – make bigger.

Rate of Chemical Reactions

• The speed of chemical reactions can be affected by:

  • Temperature: Increased temperatures usually increase rate of reaction.

  • Particle size: Smaller particles usually increase rate.

  • Catalysts: Increase the rate of reaction without being chemically changed or becoming part of the product.

    • Enzymes are biological catalysts.

Summary Table: Types of Mixtures

Summary Table: Types of Chemical Bonds

Additional info: The notes have been expanded with academic context and examples for clarity and completeness.