Bio 178 Lecture 4The Chemical Building Blocks of Life

Outline

• Macromolecules

• Proteins

• Nucleic Acids

• Lipids (Mon)

• Carbohydrates (Mon)

Reading

• Chapter 3

Quiz Material

• Questions on P 60

• Chapter 3 Quizzes on Text Website (www.mhhe.com/raven7)

Chemistry of Carbon - Organic Molecules

• Biological molecules are composed primarily of C atoms bonded to H, O, N, & S.• Hydrocarbons - Store a lot of energy!

Functional Groups• The part of a molecule responsible for its chemical properties.

• Organic moleculesHave a C based core with attached functional groups.

Functional Groups

Macromolecules

Types

Carbohydrates, lipids, proteins, & nucleic acids.

Polymer

A long chain of similar molecules.

Making and Breaking Macromolecules

• Dehydration synthesis

• Hydrolysis

ProteinsComposition

Polymers of amino acids.

Amino Acids

Carboxyl Group

Amino Group Functional groups can be polar, non-polar, electrically charged, aromatic, or have unique properties.

Protein Synthesis

Protein StructureBonds that stabilize Protein Structure

• Hydrogen bond

• Disulfide bridge

• Ionic bond

Fig. 3.7b(TE Art)

C C S

CO

ON

N

C

H

HCCS

H

H

Disulfidebridge

2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Levels of Protein Structure

• Primary

• Secondary

• Motifs

• Tertiary

• Domains

• Quaternary

Primary Structure

• Unique aa seq of a protein• Determined by genetic information

Secondary Structure of a Protein

Coiling or folding of the polypeptide chain as the result of hydrogen bonds at regular intervals along the polypeptide backbone

Motifs (Supersecondary structure)A distinctive, usually recurrent structural element (secondary protein structures) such as a simple protein motif consisting of two alpha helices.

Examples:

• turn

•

• barrel

Tertiary Structure

• The overall 3D shape of the polypeptide chain. Hydrophobic regions will be on the inside.

• Due to interactions between the R groups.

• Stability of tertiary structure is determined by how well non-polar R groups (will be different sizes) fit into the protein interior.

Domains• Portion of a polypeptide chain that folds independently of the rest of the polypeptide chain (can be excised and still fold correctly).

• Domains often have different functions within the protein (eg. DNA binding region).

Quaternary StructureThe spacial arrangement of the polypeptide chains (subunits) when a protein is composed of 2 or more polypeptide chains.

Protein FoldingChaperone Proteins

• Enable new proteins to fold correctly.

• Example - heat shock proteins.

• Scientific evidence suggests that the primary function of chaperones is to prevent protein aggregation (of incompletely folded proteins).

Chaperone Proteins and Disease

• Can chaperones prevent protein misfolding diseases?

• Why do these defense mechanisms fail in patients with these diseases?

Human Brain with Spongiform Encephalopathy

Normal (Good) PrPC Prion (Bad) PrPSc

Normal Protein Folding is Critical to Function

Protein DenaturationA change in the shape of the protein.

Caused by a change in temperature or polarity of the protein’s environment.

Protein Functions

Function Class Examples Use

Enzyme catalysis

Enzymes ProteasesBreak down

protein

Defense Immunoglobulins AntibodiesMark foreign substances

TransportLong distance transporters

Hemoglobin

Transport O2 and CO2

TransportShort distance transporters

Proton pump

Transports protons across

membranes

Function Class Examples Use

Support Fibers CollagenForms

cartilage

Motion MuscleActin & Myosin

Muscle Contraction

Regulation

Hormones InsulinGlucose

Transport

Storage Ion BindingFerritin

Calmodulin

Stores IronBinds

Calcium

Protein Functions

Fig. 3.4

Structural Proteins

Nucleic AcidsCompositionPolymers of nucleotides (5-C sugar, phosphate group, & nitrogenous base).

Types

• DNA (deoxyribonucleic acid)

• RNA (ribonucleic acid)

Functions

DNA - Genetic instructions. Occurs in the nucleus.

RNA - Direct protein synthesis. Made in the nucleus, travels to the cytoplasm.

A Nucleotide is a monomer of a nucleic acid

Nitrogenous Bases