04 Biomolecules 1 AJH

8/13/2019 04 Biomolecules 1 AJH

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Introduction toBiomolecules,

Proteins, andNucleic Acids

Chapter 3, 4.1



Learning Priorities

1. Learn the names and functions of functional

groups.

2. Understand the interconnections between

monomers, polymers, dehydration reactions andhydrolysis reactions.

3. Comprehend the structural features and functional

diversity of proteins.

4. Comprehend the structural features of nucleic acids

and the structural/functional distinctions between

DNA and RNA.



Biomolecules (Biological Macromolecules)



single

covalent

bond

carbon

atom

Organic Moleculescompounds that contain carbon and hydrogen

Carbon

Has 4 electrons in its outer shell

(valence electrons)

Able to form 4 covalent bonds



Functional Groups

• Groups of atoms with specific chemical and physical

properties

• Parts of organic molecules usually involved in chemicalreactions

carbon backbone

funct ional group



Six Prominent Functional Groups





Functional Groups

Test Your Understanding

1. Why do amino groups function as a base?

2. Why do carboxyl groups function as an acid?

3. Not one of the six listed above but importantnevertheless, how would a methyl (CH3)

group function?



Importance of Functional Groups

Estrogen Testosterone



Monomers and Polymers

• Polymers - large molecule (macromolecule, biomolecule)

consisting of many identical or similar units (monomers)

linked together

• Monomer - units that serve as the building blocks (subunits)of polymers

Polymer

(biomolecule)



Biomolecules:Synthesis & Degradation

condensat ion

react ion

(dehydration reaction)

hydrolys is reaction



PROTEINS

Key question: What does this suggest about the structure of proteins?



Key Concepts about Proteins

1. Proteins are polymers of amino acids.• Understand condensation vs hydrolysis reactions

• Recognize functional groups

2. Protein shape depends on amino acid sequence.

• Characterize amino acid side chains• Understand types of chemical interactions

3. Protein functions depend on correct folding intospecific conformations.

• Understand the role of weak interactions in folding

• Recognize why proper folding is crucial to function

4. Proteins are encoded by genes, which cells musttranscribe and translate.



Amino Acids

Non-ionized form

Ionized form

Amino

group

Amino

group

Carboxyl

group

Side chain

Side chain

Carboxyl

group



A m i n

o A c i d R

G r o u p s

Be able to

recognize

which

group eachamino acid

belongs to

based on

funct ional

group at the

end of i ts Rgroup .



Polymerization of Amino Acids

Amino acids polymerize when a bond forms

between the carboxyl group of one amino acid and

the amino group of another

The resulting C-N bond is called a peptide bond

Carboxyl

group

Amino

group

Peptide

bond

What type

of reaction

is this?



Protein = Polypeptide



Protein Shape - Overview

Proteins have 3 - 4 levels of structural organization:



Primary Structure

Primary Structure – sequence of amino acids in a

polypeptide chain

Primary structure determines higher levels of

protein structure…





Secondary

Structures

Stabilized by

hydrogen bonds

(among atoms inprotein backbone)

Common patterns

◦

α-helix◦ β-pleated sheet



van der Waalsattraction leads

to hydrophobic

exclusion

KEY CONCEPT

R groupinteractions

give proteins

unique shapes!

T e

r t i a r y S

t r u c t u r e



Tertiary Structures are Diverse

A tertiary

structure

composed

mostly of

-helices

A tertiary

structure

composed

mostly of

-pleated

sheets

A tertiary

structure

rich in

disulfide

bonds

What enables th ese dif ferent sh apes?



Structure is Related to Function

Protein-Folding Diseases:

• Cystic fibrosis

• Alzheimer’s

• Prion diseases (Mad Cow)

Disulfidebonds form

Ribonuclease protein, denatured (unfolded)

Hydrogenbonds form

Disulfide bonds andhydrogen bonds are broken

Ribonuclease protein, folded





Pro GluGlu5 76

Normalred blood

cells

Sickledred blood

cells

Pro5 76

GluVal

Structure is Related to Function

Normal amino acid sequence Single change in amino acid sequence

(146 amin o acid s)



Summing Up Proteins

#1 – Which is not a function of proteins?A. HormoneB. EnzymeC. Gene

#2 – A protein’s shape depends on its amino acid sequence. A. TrueB. False

#3 – What kind of bond holds together a protein’s primarystructure?

A. Disulfide bondB. Hydrogen bondC. Peptide bond



Proteins areencoded by

genes, whichcells must

transcribe

and translate.

transcription

translation



Nucleic Acids: DNA & RNA

Nucleic acids are

polymers of

nucleotides.



What is a nucleotide?

ID KEY: 3 components

Ribose RNA

Deoxyribose DNA

RNA: A, C, G, and U

DNA: A, C, G, and T



Polymerization of Nucleotides



Nucleic Acid Structure

• Sugar-phosphate backbone

• Bases extend to the side

How is nucleic acid structuresimilar to protein primary

structure?

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04 Biomolecules 1 AJH