Four Classes of Biological Molecules Carbohydrates Sugars and their polymers Nucleic acids and nucleotides DNA, RNA, ATP Lipids Various hydrophobic molecules Proteins and amino acids

Carbohydrates: CH2O Monosaccharides: glucose, fructose, many others Disaccharides: sucrose, lactose Polysaccharides: starch, cellulose, glycogen, agar, chitin, xanthan gum

A nucleotide: a monomer of DNA http://www.emc.maricopa.edu/faculty/farabee/BIOBK/nucleotide.gif

Nucleic acids are the polymers made from nucleotides. DNA tRNA http://www.biochem.uwo.ca/meds/medna/IMG/tRNA.GIF

Lipids Hydrophobic Contain mostly C and H, and only some O. Fats, oils and waxes Contain more chemical energy per gram Why do we eat fatty foods? Survival mechanism; we evolved that way. Insulation Protection; cushions internal organs

Lipid Building blocks: Fatty Acids

Saturated fats – contain as many H’s as possible (saturated). Unsaturated fats contain one or more double bonds. Monounsaturated fats Polyunsaturated fats The more saturated the fat or the longer the carbon chains, the harder the fat is at room temperature. Beef suet vs. vegetable oil

Amphipathic molecules Amphipathic molecules “ both feeling” one end is hydrophobic one end is hydrophilic Detergent molecules are like this Polar end mixes with water Hydrophobic end mixes with grease Substitute a phosphate group for one fatty acid chain of a triglyceride: phospholipid

Hydrophilic portions associated with water. Hydrophobic portions avoid water by associating with each other.

Phospholipids are amphipathic Hydrophilic “head” group Hydrophobic “tails”

Steroid are lipids Cholesterol is an important part of your cells, but too much in your blood vessels is BAD.

Steroids Lipids with a different structure Based on cholesterol In food and made by the liver Vitamin D, steroid hormones, and bile salts Includes “anabolic steroids”, source of controversy in the sports world

Hormones are messenger molecules your body makes. “Steroid hormones” are chemically related to cholesterol.

A lipid polymer: a biodegradable plastic made by bacteria.

Inclusions of PHB in a bacterial cell

Proteins Contain C, H,O and N (nitrogen) Made up of 20 different amino acids Amino group – NH2 Makes it a base Carboxyl (acid) group – COOH Makes it an acid Side chain or R group Linked by peptide bonds

Peptide Bond: joins two amino acids together. Many amino acids joined: polypeptide or protein.

Proteins: important and abundant Proteins make up structural and functional molecules within the body. Enzymes: the tools of the cell. About 50% of the dry weight of cells Structure of protein is directly determined from the DNA sequence.

Proteins: 4 levels of organization Primary structure The particular amino acids and their order Secondary structure – folding in alpha helices or beta sheets Tertiary structure The 3D shape of the protein, critical for function Quaternary structure Multiple proteins work together (hemoglobin)

Primary and secondary structure http://www.mdx.ac.uk/www/lifesciences/alex/images/0321_1.gif

Tertiary and quaternary structures http://www.chembio.uoguelph.ca/educmat/phy456/gif/myoglob.gif http://www.chemsoc.org/exemplarchem/entries/2004/durham_mcdowall/images/1a3n-4-struct.png

The 3D shape of a protein is critical for its function. If a protein is subjected to high or low temperatures, changes in pH or ion concentration the protein denatures, or changes shape and becomes nonfunctional.

From molecules to cells We study the 4 classes of biological molecules because that’s what cells are made of. Cells take in these molecules, digest them Convert them polymers into monomers Rebuild polymers according to directions in cell’s DNA As we study the cell, note what the cells are made of.

Cell Theory All organisms are composed of one or more cells Cells are alive, and are the basic living unit of organization of all organisms All cells come from other cells

Every cell has three main parts: Plasma (cell) membrane – a boundary that separates inside of cell from external environment. A set of genetic instructions In eukaryotes this is in the Nucleus; in prokaryotes there is no membrane, stays in a section of the cell is called the nucleoid. A cell body - the cytoplasm; gel-like substance within the cell membrane.

Cells are measured in micrometers or microns. Eukaryotic cells are bigger and more complex than prokaryotic cells. Advantages of being made of cells: Specialization Surface area A multicellular organism can survive the loss of single cells.

Plasma Membrane The plasma membrane does more than just separate the outside of a cell from the inside; it controls what enters and leaves the cell, and much of the activity within the cell. Most of the cell membrane is made of a phospholipid bilayer. Amphipathic molecule – phosphate heads on the outside and inside, and fatty acid tails in the middle.

The membrane is selectively permeable – it allows fat soluble substances to pass through (such as steroid hormones) and some other small, uncharged molecules. Cholesterol is a large molecule, and helps to stabilize the membrane in animals. Plants use phytosterol.

Fluid mosaic model - proteins float like icebergs in a sea of phospholipids. Proteins can be integral proteins – go all the way through the membrane, or may be peripheral proteins -bound to the inside or outside membrane.

Integral Proteins can be channels or transporters. Peripheral proteins can be receptors, or can be cell identity markers or recognition proteins that identify a cell as “self” (like UPC codes). These are often glycoproteins. They may also mark worn out red blood cells or cells that have been infected with a virus.

All cells have a plasma membrane Some cells, such as bacterial, fungal and plant cells, also have a cell wall. The organelles in a eukaryotic cell all have membranes around them. These membranes are very similar to the plasma membrane: lipid bilayer with proteins floating in it.

Cytoplasm refers to cytosol plus organelles and inclusions. cytosol - contains proteins, enzymes, nutrients, ions, and other small molecules organelles -“little organs” - highly organized structures with characteristic shapes that are specialized for specific cellular activities. inclusions - are temporary structures in the cytoplasm that contain secretions and storage products of the cell.