Lecture 1
Biology 115, Human Biology
Basic Biological Principles, Chemical Biology

T. Irving 01/07/97; Revised A. Howard 01/16/00

Why do we study Human Biology?

• To understand our bodies
• To become knowledgeable citizens

What is Human Biology?

Study of:

• How our bodies work
  Physiology & Genetics
• How Humans fit in with the rest of the Biological World Evolution & Ecology
• Humans are part of the Biosphere
  • Biosphere = global ecosystem
  • All organisms belong to ecosystems
  • Humans are the result of an evolutionary process
  • Humans form part of the Animal Kingdom
  • Other Kingdoms are plants, Fungi, protists, and monera
  • Humans are Vertebrates

Like all animals:

• Humans reproduce and grow
• Humans are highly organized
• Guiding principle in organization is to attain homeostasis

Humans are a product of their cultural heritage

• All animals show some sort of "animal behavior"
• Human behavior is particularly complex
• How humans interact with biosphere and each other strongly influenced by cultural, religious customs and practices as well as their economic activity

Energy Flow

• Ecosystems can be described in terms of energy flows
• Humans have unprecedented ability to modify their ecosystems
• Creates complex environmental, legal and ethical issues

Scientific Method:

• General question
• Considering known data, formulate a specific hypothesis
• Do a controlled experiment
• Is the hypothesis supported?
• Experiments must be repeatable
• The results of several experiments can be summarized in terms of theories or concepts
• Theories and concepts must stand the test of time

A Specific Example

• Can an artificial sweetener cause cancer?
• Specific hypothesis:
• Ingestion of sweetener S lead to a statistically significant increase in the prevalence of bladder cancer in a rat model

   

Hypotheses have yes or no answers generally

Experiment:

• Collect data relating % sweetener in diet to bladder cancer incidence in a genetically identical strain of laboratory rats
• If cancer incidence IS significantly greater than control group, then hypothesis IS supported
• If cancer incidence IS NOT significantly greater than control group, then hypothesis IS NOT supported

"Significance" is a statistical concept.

• "Significantly different" is not synonymous with "greatly different".
• It means that the data says that a hypothesis is true or false with a given level of uncertainty, typically 5 or 1%.
• This is the chance that when you decide something is true, that it is actually false.

   

Chemistry of Life

Elements & Atoms

• Atoms have structure
• Protons, neutrons, etc.
• The number of protons determines the number of electrons
• Number of electrons determines an element's chemical properties.

Molecules & compounds are formed by the interaction of atoms via their electron clouds

• Ionic Compounds
• Covalent compounds
• Polar molecules
• Hydrogen bonds
  • -structure of water
  • -proteins
  • -hold the two helices of DNA together.

Acids & Bases

• A solution is acidic or basic depending on the [H⁺]
• pH 0 to 14, acid -> base

Organic Compounds

• Organic compounds consist mainly of carbon atoms.
• Carbon can form very complex molecules and typically associated with living things.

Proteins, Carbohydrates, Lipids and Nucleic Acids

• Are biological macromolecules
• Macro means large
• Monomers -> polymers
• Formed by process of synthesis
• Broken down by hydrolysis
• Both processes may or may not require energy

Proteins

• Amino acids link together to form polypeptides
• Proteins have primary, secondary, tertiary and quaternary levels of structure
• The three-dimensional tertiary or quaternary structure is essential for enzymes (which are proteins) to function

Carbohydrates

• Many different types of sugars
• Most made up of 6 carbon monomers (hexose sugars)
• 5 carbon sugars important component of DNA.
• Sugar monomers link end to end to form long chain polysaccharides
• These chains may be branched; e.g. glycogen or animal starch

Lipids

• Fats and oils are relatively small compounds that are all very similar structurally
• Energy rich
• Main component biological membranes

Nucleic acids

• Consist of a nitrogenous base, phosphate group and a pentose (5 carbon) sugar
• Nitrogenous bases are adenine, guanine, cytosine, thymine in DNA
• Uracil substitutes for thymine in RNA

Nucleotides (base + sugar + phosphate) assemble into long chain polymers by linking sugars via a phosphate group.

• In DNA the backbones form the double helix stabilized by hydrogen bonding
• interaction between the bases
• RNA is single stranded but may be folded

	DNA	RNA
Sugar	deoxyribose	ribose
Bases	adenine	adenine
	guanine	guanine
	thymine	uracil
	cytosine	cytosine
Strands	double	single
Structure	helical	not helical

ATP is the "Universal energy currency"

• ATP is like a nucleotide but has two additional high-energy phosphates
• Is formed by the process of "cellular respiration"