AP Biology

Discuss the following with your group and be prepared to discuss

with the class

1. Why is the shape of a molecule important?

2. How is a covalent bond different from ionic?

3. How are hydrogen bonds different from covalent?

We are beginning our first Unit today: Bio-Molecules

Right now, the test is set for Tuesday, Sept 17th

Functional groups-parts of organic molecules that are

involved in chemical reactions

They give organic molecules distinctive properties

hydroxyl amino

carbonyl (ketones and aldehydes) sulfhydryl

carboxyl phosphate

H2O

HO

HO H

H HHO

Polymers- long molecules built by linking repeating

building blocks in a chain monomers

building blocks repeated small units

covalent bonds

H2O

HO

HO H

H HHO

How to build a larger Bio-molecule

Dehydration Synthesis (also called Condensation Reaction)

joins monomers by “taking” H2O out one monomer donates OH–

other monomer donates H+ together these form H2O

requires energy & enzymes

enzymeThis is an example of an

Anabolic, endergonic

reaction.

H2O

HO H

HO H HO H

How to break down a larger molecule

Hydrolysis (also called Digestion)

use H2O to breakdown polymers reverse of dehydration synthesis takes off one monomer at a time

H2O is split into H+ and OH–

H+ & OH– attach to ends

requires enzymes releases energy enzyme

This is an example of an

Catabolic, exergonic

reaction.

Bio-Molecules Large organic molecules formed by

smaller molecules bonding together macromolecules

4 major classes of macromolecules: carbohydrates lipids proteins nucleic acids

AP Biology 2008-2009

ProteinsMultipurpose

molecules

Proteins

Various functions: enzymes (speed up metabolism) structure physical stability and movement

(keratin-hair/nails/skin, collagen-bones/cartilage/tendons, myosin-muscles)

transport (hemoglobin- in red blood cells, proteins in cell membranes)

cell communication/regulatory signals (insulin & other hormones) receptors

defense (antibodies/recognize foreign invaders)

storage (hold amino acids for later use)

- Most structurally & functionally diverse group

Amino acids

central carbon Two functional groups:

carboxyl group (acid) amino group

R group (side chain) variable group that is

different for each amino acid gives unique chemical

properties to each amino acid like 20 different letters of an

alphabet can make many words (proteins)

—N—H

HC—OH

||O

R

|—C—

|

HProtein monomer (building block)

Peptide Bonds – Linking of Amino Acids

Effect of different R groups:Nonpolar amino acids

nonpolar & hydrophobic

Effect of different R groups:Polar amino acids

polar or charged & hydrophilic

Building proteins Peptide bonds

covalent bond between NH2 (amino) of one amino acid & COOH (carboxyl) of another

C–N bond

peptidebond

dehydration synthesisH2O

Building proteins Polypeptide chains have direction

N-terminus = NH2 end C-terminus = COOH end repeated sequence (N-C-C) is the

polypeptide backbone

Protein structure & function

hemoglobin

Function depends on structure 3-D structure

twisted, folded, coiled into unique shape

collagen

pepsin

Primary (1°) structure Order of amino acids in chain

amino acid sequence determined by genes (DNA)

slight change in amino acid sequence can affect protein’s structure & its function even just one amino acid change

can make all the difference!

(Example of structure determining function) Sickle Cell Anemia

What type of mutation is

this?

Secondary (2°) structure “Local folding”

folding along short sections of polypeptide interactions between

adjacent amino acids H bonds

weak bonds between R groups

forms sections of 3-D structure helix pleated sheet

Tertiary (3°) structure “Whole molecule folding”

interactions between distant amino acids and R groups

Quaternary (4°) structure More than one polypeptide chain bonded

together

collagen = skin & tendons hemoglobin

Protein denaturation Unfolding a protein

conditions that disrupt H bonds and ionic bonds temperature pH salinity

alter 2° & 3° structure alter 3-D shape

destroys functionality some proteins can return to their functional shape

after being denatured, many cannot

Enzymes a type of protein that acts as a catalyst, speeding

up chemical reactions

H2O

Substrate(sucrose)

Fructose

Glucose

Some enzymes require other atoms or molecules in order to

function:

-Cofactors: inorganic ions, such as iron, copper, or zinc that bind to

enzymes in order to help break down specific substances.

-Coenzymes: organic molecules that are required by certain enzymes to

carry out catabolic reactions.