Chemistry Atoms are the basic units of matter Cells are the basic units of life Cells are made of matter, especially organic matter (contains carbon atoms) The principal categories of organic matter are: – Carbohydrates – Lipids – Proteins – Nucleic acids

pH pH - a measure of the amount of hydrogen ions in a solution. Concentration of hydrogen  [H+]. The relationship between [H+] and pH is: pH=-log [H+]. pH varies between 0 and 14, neutral pH =7= pH of water. The higher the acidity, the higher the concentration of hydrogen ions is. For every unit of pH, the hydrogen concentration in the solution multiplies by This concept of acidity is very important for life

Organic compounds Carbohydrates Lipids Proteins Nucleic acids

Carbohydrates: C6 or C5 ring * C6 ring: common carbohydrates: -1 ring: glucose, fructose, galactose -2 rings: sucrose, lactose, maltose -Many rings: glycogen, starch -Role: Short term energy storage

Carbohydrates: C6 or C5 ring C5 ring: special role In ATP, nucleic acids

Organic compounds Carbohydrates Lipids Proteins Nucleic acids

Lipids Formed by a glycerol backbone and attached fatty-acids Fatty-acids: a string of carbons with hydrogen atoms Molecules hydrophobic and rich in energy  long term energy storage

Figure 2-8 (3 of 6)

Figure 2-8 (2 of 6)

Phospholipids One fatty-acid is replaced by a phosphoric group  property of the molecule changes  amphipatic molecules (like both water and lipids)

Figure Overview

Lipid: Cholesterol Component of cell membrane Base for steroid hormones

Organic compounds Carbohydrates Lipids Proteins Nucleic acids

Proteins Two basic roles: - Structural: building block of the cell (collagen, elastin..) - Enzymatic: control metabolism (enzymes)

Proteins: Primary structure The primary structure of a proteins is its string of amino acids. These a.a. are covalently (strongly) attached There are 20 different amino acids that can potentially be found in the proteins The order of a.a. varies  different sequences

Secondary structure of a protein Folding of the a.a. chain - fold as a alpha helix - or a beta sheet

Tertiary structure of a protein Folding of the chain due to hydrogen bonds formed by the various amino acids ** This folding gives the protein its shape  the shape of a protein gives it its function

Figure 2-16

Figure Overview (1 of 7)

Figure 2-9 (2 of 7)

So what happens when the pH in the cell changes?

The protein changes shape  loose its function  denaturation

Organic compounds Carbohydrates Lipids Proteins Nucleic acids

Nucleic acid DNA RNA ATP Formed by a C5 carbohydrate + phosphate + a base Bases: adenine, cytosine, thymine, guanine and uracil

Figure Overview