© 2011 pearson education, inc. biochemistry week 5 - 7 oapb dr. thornton

© 2011 Pearson Education, Inc.

BioChemistry

Week 5 - 7

OAPB

Dr. Thornton


Carbon’s Place in the Living World

• Carbon is a central element to life

• Most biological molecules are built on a carbon framework.


Glucose

• Simple sugar

• Most important energy source for our bodies

• Contains several –OH groups

Can you identify the C and the –OH?


Why Is Carbon Central to Life?

• The complexity of living things is facilitated by carbon’s linkage capacity.

• Carbon has great bonding capacity due to its structure.



Carbon’s outer shell has only four of the eight electrons necessary for maximum stability in

most elements.

+ or -??

Go toPAGE 43

in text


Carbon Bonds



Carbon atoms are thus able to form stable, covalent bonds with a wide variety of atoms,

including other carbon atoms.

BUILD THIS MOLECULE


3.2 Functional Groups


Functional Groups

Remember carbon is a central element to life because most biological molecules are built

on a carbon framework

Groups of atoms known as functional groups can give special properties to carbon-based

molecules


Functional Groups

• For example, the addition of an –OH group to a hydrocarbon molecule always results in the formation of an alcohol.

Methanol Ethanol

IsopropalDRAW THEIRFORMULAS


Little Activity

Add 50ml of H2O to 50 ml of 95% Isopropyl Alcohol (C3H6OH)

WHAT HAPPENED?


Functional GroupsGroup Structural Formula Found in

Carboxyl (–COOH)

Hydroxyl (–OH)

Amino (–NH2)

fatty acids, amino acids

alcohols, carbohydrates

amino acids

DNA, ATPPhosphate (–PO4)

Functional Groups

Functional groups often impart an electrical charge or polarity onto molecules, thus

affecting their bonding capacity.

Identify Charges and polar areas


3.3 Carbohydrates


Carbohydrates

Carbohydrates are formed from the building blocks or monomers of simple sugars, such as

glucose.


These monomers can be linked to form larger carbohydrate polymers, which are known as

polysaccharides or complex carbohydrates.

Carbohydrates


Complex Carbohydrates

Four polysaccharides are critical in the living world:

Starch (energy storage in plants)

Glycogen (stored energy in animals)

Cellulose (make-up of plant cell walls)

Chitin (make-up of exoskeletons)


Four Complex Carbohydrates (1)

Starch is the nutrient storage form of

carbohydrates in plants.

Starch

Structure

Function

Example

Serves as a form of carbohydrate storage in many plants

Starch granules within cells of a rawpotato slice



Glycogen is the nutrient storage form of

carbohydrates in animals.

Glycogen

Serves as a form ofcarbohydrate storage in animals

Glycogen granules(black dots) withina liver cell



Cellulose is a rigid, structural carbohydrate found in the cells walls

of many organisms.

Cellulose

Provides structuralsupport for plantsand other organisms

Cellulose fibers within the cell wallof a marine algaecell



Chitin is a tough carbohydrate that forms the

external skeleton of arthropods.

Makes up a largeportion of the outer“skin” or cuticle ofarthropods

Chitin

The chitinous cuticleof a tick


3.4 Lipids


Lipids

The defining characteristic of all lipids is that they do not readily dissolve in water (think fats)

Glycerin (pg 34 of text)


LipidsLipids do not possess the monomers-to-polymers structure seen in other biological molecules; no

one structural element is common to all lipids (grrrrr)


Lipids

Among the most important lipids are the triglycerides, composed of a glyceride and three fatty acids.

Most of the fats that human beings consume are triglycerides.

© 2011 Pearson Education, Inc. Figure 3.8

The Triglyceride Tristearin

fatty acidsglycerol


Saturated Fatty Acids

(Pg 51 of text)


Monosaturated Fatty Acids


Polyunsaturated Fatty Acids


Phospholipids

• A third class of lipids is the phospholipids

• Each is composed of two fatty acids, glycerol, and a phosphate group.


Phospholipids

The material forming the outer membrane of cells is largely composed of phospholipids.


(a) Phospholipid structure

variablegroup

phosphategroup

glycerol

polar head nonpolar tails

(b) Phospholipid orientation

oil (nonpolar)

water (polar)

“like attracts like”

nonpolar hydrophobic tails(fatty acids) exposed to oil

polar hydrophilic heads exposed to water

—

Figure 3.12

Phospholipids


Waxes

A fourth class of lipids is the waxes, each of which is composed of a single fatty acid

linked to a long-chain alcohol


Waxes

• Waxes have an important “sealing” function in the living world.

• Almost all plant surfaces exposed to air, for example, have a protective covering made largely of wax.

© 2011 Pearson Education, Inc. Figure 3.13

Waxes


3.5 Proteins


Proteins

• Proteins are an extremely diverse group of biological molecules composed of the monomers called amino acids.


Proteins

• Sequences of amino acids are strung together to produce polypeptide chains, which then fold up into working proteins.

• Important groups of proteins include enzymes, which hasten chemical reactions, and structural proteins, which make up such structures as hair.


Enzymes

Hormones

Protective

Toxins

Transport

Contractile

Structural

Storage Stores nutrients

Movement

Move other molecules

Chemical messengers

Quicken chemical reactions

Mechanical support

Communication

Healing; defense against invader

Defense, predation

Cell signaling

Sucrase: Positions sucrose (tablesugar) in such a way that it can bebroken down into component partsof glucose and fructose.

Growth hormone: Stimulates growthof bones

Hemoglobin: Transports oxygenthrough blood

Myosin and actin: Allow musclesto contract

Fibrinogen: Stops bleeding Antibodies: Combat microbialinvaders

Keratin: Hair, Collagen: Cartilage

Ovalbumin: Egg white, used asnutrient for embryos

Bacterial diphtheria toxin

Glycoprotein: Receptors on cellsurface

Types of Proteins

Type Role Examples

Table 3.4

Table 3.4


Levels of Protein Structure

• The primary structure of a protein is its amino acid sequence; this sequence determines a protein’s secondary structure—the form a protein assumes after having folded up.


The linkage of several amino acids . . .

. . . produces a polypeptide chain like this:

A typical protein wouldconsist of hundreds ofamino acids

Figure 3.16


Levels of Protein Structure

• The larger-scale three-dimensional shape that a protein assumes is its tertiary structure, and the way two or more polypeptide chains come together to form a protein results in that protein’s quaternary structure.

• The activities of proteins are determined by their final folded shapes.


Four Levels of Structure in Proteins

(a) Primary structure

The primary structure of any protein is simplyits sequence of amino acids. This sequencedetermines everything else about theprotein's final shape.

(b) Secondary structure

Structural motifs, such as the corkscrew-likealpha helix, beta pleated sheets, and the lessorganized "random coils" are parts of manypolypeptide chains, forming their secondarystructure.

(c) Tertiary structure

These motifs may persist through a set oflarger-scale turns that make up the tertiarystructure of the molecule.

(d) Quaternary structure

Several polypeptide chains may be linkedtogether in a given protein, in this casehemoglobin, with their configuration formingits quaternary structure.

amino acid sequence

beta pleatedsheet

alpha helix

random coil

foldedpolypeptidechain

two or morepolypeptidechains

Figure 3.18


Lipoproteins

• Lipoproteins are biological molecules that are combinations of lipids and proteins.

• High-density and low-density lipoproteins (HDLs and LDLs, respectively), which transport cholesterol in human beings, are important determinants of human heart disease.


Glycoproteins

• Glycoproteins are combinations of carbohydrates and proteins.

• The signal-receiving receptors found on cell surfaces often are glycoproteins.


Animation 3.5: Proteins

Proteins

PLAYPLAY


3.6 Nucleic Acids


Nucleic Acids

• Nucleic acids are polymers composed of nucleotides.


Nucleotides

• The nucleic acid DNA (deoxyribonucleic acid) is composed of nucleotides that contain a sugar (deoxyribose), a phosphate group, and one of four nitrogen-containing bases.


(a) Nucleotides are the building blocks of DNA.

Nucleotide nitrogenousbase

sugar(deoxyribose)

phosphategroup

(b) A computer-generated model of DNA

DNAdouble helix

The outer “rails”of the doublehelix arecomposed ofsugar and phosphate components ofthe molecule

DNA consists of twostrands of nucleotideslinked by hydrogenbonds

The rungs consistof bases hydrogen-bonded together

Figure 3.19


Nucleic Acids

• DNA is a repository of genetic information.

• The sequence of its bases encodes the information for the production of the huge array of proteins produced by living things.


Nucleic Acids

• A second nucleic acid is RNA (ribonucleic acid), which transports the information encoded in DNA to the sites of protein synthesis—structures called ribosomes—and which helps make up the structure of ribosomes.

© 2011 Pearson Education, Inc. Table 3.5

Summary Table of Biological Molecules

Type of Molecule Subgroups Examples and Roles

Carbohydrates

Proteins

Lipids

Nucleic acids

Ribonucleic acid (RNA)

Deoxyribonucleic acid (DNA)

Glycoproteins: protein-sugar molecule

Lipoproteins: protein-lipid molecule

Structural

Enzymes: chemically active

Phospholipids: polar head, nonpolar tails

Steroids: four-ring structure

Fatty acids: components of triglycerides

Triglycerides: 3 fatty acids and glycerol

Polysaccharides

Monosaccharides

Disaccharides

Glucose: energy source

Sucrose: energy source

Glycogen: storage form of glucose

Starch: carbohydrate storage in plants; used byanimals in nutrition

Cellulose: plant cell walls, structure; fiber inanimal digestion

DNA contains information for the production ofproteins

Chitin: external skeleton of anthropods

Fats, oils (butter, corn oil): food, energy, storage,insulation

Sucrase: breaks down sugar

Table 3.5

One variety of RNA carries DNA’s information tothe sites of protein production, the ribosomes;another variety of RNA helps make up ribosomes.

Cell surface receptors

HDLs, LDLs: transport of lipids

Keratin: hair

Cell membrane structure

Cholesterol: fat digestion, hormone precursor, cellmembrane component

Stearic acid: food, energy sources

© 2011 pearson education, inc. biochemistry week 5 - 7 oapb dr. thornton

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