Chapter 2: The Chemical Level of Organization

KEY CONCEPT

• All Matter is made up of atoms• Atoms join together to form

chemicals with different characteristics

• Chemical characteristics determine physiology at the molecular and cellular level

Atomic Particles

• Proton: – positive, 1 mass unit

• Neutron: – neutral, 1 mass unit

• Electron: – negative, low mass

Isotopes

• 2 or more elements with equal numbers of protons but different numbers of neutrons

Elements in the Human Body

Table 2–1

Molecules and Compounds

• Molecules: – atoms joined by strong bonds

• Compounds: – atoms joined by strong or weak bonds

States of Matter

• Solid: – constant volume and shape

• Liquid: – constant volume but change shape

• Gas: – change volume and shape

Chemical reactions & Physiology?

• Energy: – the power to do work

• Work: – a change in mass or distance

Forms of Energy

• Kinetic energy - energy of motion• Potential energy - stored energy• Chemical energy - potential energy

stored in chemical bonds

KEY CONCEPT

• When energy is exchanged, heat is produced, but cells cannot capture it or use it for work

Break Down, Build Up

• Decomposition reaction (catabolism):

AB A + B

• Synthesis reaction (anabolism): A + B AB

• Exchange reaction (reversible): AB A + B

KEY CONCEPT

• Reversible reactions seek equilibrium, balancing opposing reaction rates

• Add or remove reactants:– reaction rates adjust to reach a new

equilibrium

How do enzymes control metabolism?

Figure 2–7

Activation Energy

• Chemical reactions in cells cannot start without help

• Activation energy gets a reaction started

How Enzymes Work

Figure 2–21

KEY CONCEPT

• Most chemical reactions that sustain life cannot occur unless the right enzymes are present

Organic and Inorganic Molecules

• Organic: – molecules based on carbon and

hydrogen

• Inorganic: – molecules not based on carbon and

hydrogen

Why is water so important to life?

Properties of Water (1 of 2)

• Solubility: – water’s ability to dissolve a solute to

make a solution

• Reactivity: – most body chemistry uses or occurs

in water

Properties of Water (2 of 2)

• High heat capacity: – water’s ability to absorb and retain

heat

• Lubrication: – to moisten and reduce friction

KEY CONCEPT

• Most of our body weight is water • Water is the key structural and

functional component of cells and their control mechanisms, the nucleic acids

Electrolytes

• Inorganic ions conduct electricity in solution

• Electrolyte imbalance seriously disturbs vital body functions– Fluid balance– Blood pressure– Muscular contractions

pH

• pH: – the concentration of hydrogen ions

(H+) in a solution

• Neutral pH: – a balance of H+ and OH— – pure water = 7.0

Acids and Bases

• Acid (acidic): pH lower than 7.0 – high H+ concentration,

low OH— concentration

• Base (basic): pH higher than 7.0– low H+ concentration,

high OH— concentration

pH Scale

Figure 2–9

• Has an inverse relationship with H+ concentration: – more H+ ions mean lower pH, less H+

ions mean higher pH

KEY CONCEPT

• pH of body fluids measures free H+ ions in solution

• Excess H+ ions (low pH): – damages cells and tissues, alters proteins– interferes with normal functions

• Excess OH— ions (high pH) also problem

• Normal blood pH – 7.35 to 7.45• Incompatibile with life – 6.8 to 7.8

Acid and Alkaline

• Acidosis: – excess H+ in body fluid (low pH)– Loss of bicarbonate– Blood level < 7.2

• Alkalosis: – excess OH— in body fluid (high pH)– Blood level > 7.5

Nucleic Acids

• Large organic molecules, found in the nucleus, which store and process information at the molecular level

• DNA and RNA

Deoxyribonucleic Acid (DNA)

• Deoxyribonucleic Acid (DNA)– Determines inherited characteristics– Directs protein synthesis– Controls enzyme production– Controls metabolism

• Ribonucleic Acid (RNA)– Codes intermediate steps in protein

synthesis

KEY CONCEPT

• DNA in the cell nucleus contains the information needed to construct all of the proteins in the body

Nucleotides

• Building blocks of DNA• Have 3 molecular parts:

– sugar (deoxyribose)– phosphate group– nitrogenous base (A, G, T, C)

DNA Bases

Figure 2–22b, c

Complementary Bases

• Complementary base pairs:– purines pair with pyrimidines:

• DNA: – adenine (A) and thymine (T) – cytosine (C) and guanine (G)

• RNA: – uracil (U) replaces thymine (T)

Nucleic Acids

• Long chains of nucleotides form RNA and DNA

• RNA and DNA

Figure 2–23

RNA and DNA

• RNA: – Single strand

• DNA: – Double helix – Joined at bases by hydrogen bonds

Forms of RNA

• Messenger RNA (mRNA)• Transfer RNA (tRNA)• Ribosomal RNA (rRNA)

ADP and ATP

• Adenosine diphosphate (ADP): – 2 phosphate groups

• di = 2

• Adenosine triphosphate (ATP): – 3 phosphate groups

• tri = 3

– Energy for muscular contractions

KEY CONCEPT

• Body recycles/renews all chemical components at intervals ranging from minutes to years

• Metabolic turnover lets your body:– Grow– Change– Adapt

SUMMARY (1 of 2)

• Atoms, molecules, and chemical bonds control cellular physiology

• Metabolism and energy work within the cell

• Importance of organic and inorganic nutrients and metabolites

SUMMARY (2 of 2)

• Role of water and solubility in metabolism and cell structure

• Chemistry of acids and bases, pH and buffers

• Structure and function of carbohydrates, lipids, proteins, and nucleic acids