Chapter 3 Life’s Chemistry

Carbon- life on earth – major molecule that make up living systems Bonds with four other atoms – variety of shapes and functions. Living cells use C to make complicated molecules. Organic molecule- hydrocarbons. The function of carbon molecule changes – functional groups added to carbon skeleton. Functional groups- atoms or groups of atoms which add functions by combining O,P,S & N to large carbon skeletons.

Major Organic Molecules (Life depends) Molecules that contain carbon in combination with hydrogen. Four major groups: carbohydrates lipids proteins nucleic acids How do humans acquire these molecules? Cells use molecules – to maintain life

Polymers: large biologically important molecules are constructed by bonding smaller molecules (monomers) Dehydration synthesis – the process of building polymers Hydrolysis - the process of breaking down polymers Polymers expand properties of monomers

1. Carbohydrates contain C, H & O [1:2:1] function to store energy & provide support building blocks (monomers) are monosaccharides ] Eg. Sugar & starch

Carbon forms – infinite variety of molecules Functional groups- molecules that add function to other molecules Major molecules- carbohydrates, lipids, proteins and nucleic acids Large biological molecules- polymers-different properties than the unit monomers Polymers – made through dehydration synthesis and recycled through hydrolysis.

Monosaccharides simple sugars containing carbons. C, H, O ratio is 1:2:1

Disaccharides simple sugars composed of 2 monosaccharides linked together by dehydration synthesis. Other common disaccharides: maltose (seed sugar) & lactose (milk sugar).

Oligosaccharides Moderately sized- for identification and forming complex structures. Glycoproteins, glycolipds- on cell suface- immunity protecting animal’s body from infection Polysaccharides complex carbohydrates made up of hundreds of monomers linked by dehydration synthesis.

Eg. Cellulose, chitin, starch and glycogen. Differ by orientation of bond that link monomers.

Carbohydrates- formula (CH2O)n. Most common – GLUCOSE Oligosaccharides- identity molecules. Polymers of glucose form complex carbohydrates such as starch. Changing the arrangement of monomers and modifying glucose produce different characteristics for starch, cellulose and chitin.

2. Lipids contain C, H, O [  C >>  O] do not dissolve in water but in organic solvents Vital to life Hydrophobic-major component of membrane Within cells form compartments, separating one aqueous environment from another

Triglycerides (fats) composed of glycerol linked to 3 fatty acid chains by dehydration synthesis. Fatty acids – long hydrocarbons up to 36 carbon atoms with an acidic functional group. Fatty acids can be saturated or unsaturated function to cushion organs, as insulation & in long-term energy storage (adipose tissue). Combine to form more complex lipids.

Phospholipids lipid bonded to a phosphate group major component of cell membranes Enzymes replace one of the fatty acids in a TG with phosphate.

Sterols lipids that have 4 interconnected carbon rings Ex. Vitamin D, cortisone, estrogen & cholesterol Cholesterol-vital for cells- maintain fluidity of cell membranes Synthesized in liver

Waxes fatty acids combined with hydrocarbons help waterproof fur, feathers, leaves & fruits Jojoba oil- shampoos – liquid wax.

Attaching fatty acids to glycerol- produce-fats (TG) or membrane components (PL). Sterols – lipids- based on an interconnecting ring structure. Eg: cholesterol and sex hormones. Cholesterol- vital to cells.

3. Proteins contain C, H, O, N, (S) monomers are amino acids Differ from carbohydrates and lipids. Proteins- control all life’s activities. Proteins – blood to clot, muscles to contract, oxygen to reach tissues. Enzymes – poteins- allow biochemical reactions to proceed fast- sustain life. Structural proteins – bone and hair.

Amino acid: central C tom bonded to 4 different functional components.

Proteins have a 3-dimensional shape (conformation) : primary (1 o ) structure - amino acid sequence of polypeptide chain secondary (2 o ) structure - coiling & folding produced by hydrogen bonds tertiary (3 o ) structure - shape created by interactions between R groups quarternary (4 o ) structure - shape created by interactions between two or more polypeptides A change to the shape of a protein causes denaturation.

Examples: antibodies hemoglobin insulin & glucagon keratin fibrin & thrombin spider silk (strongest natural fiber known) enzymes (maltase, pepsin, lipase)

Enzyme mechanism of action Enzymes can be used to join substrates or break apart substrates. The shape of the enzymes active site is critical to proper functioning.

Proteins- provide majority of life’s function. 20 aa forms the basis of all proteins Final conformation of a protein- levels of interactions between components of polypeptide. Changes in temp, pH or ions in environment of a protein will denature the shape and function.

4. Nucleic Acids contain C, H, O, N, P monomers are nucleotides

DNA (deoxyribonucleic acid) 5-carbon sugar is deoxyribose nitrogenous bases are A, G, C & T double-stranded helix held together by hydrogen bonds is the genetic material

RNA (ribonucleic acid) 5-carbon sugar is ribose nitrogenous bases are A, G, C & U single-stranded enables information in DNA to be expressed

Nucleis acids- polymers of nucleotides. Nucleotides- A, C, T, G and U. DNA & RNA use different bases. DNA stores information in the sequence of its nucleotides. Genetic code- same all life on Earth. Gene- sequence of nucleotides- having information for an entire protein. ATP- key energy carrier.