Molbiol 2011-03-biochem

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Биологические макромолекулы

Белки

Углеводы

Липиды

Нуклеиновые кислоты


Organic Compounds

Molecules unique to living systems contain carbon and hence are organic compounds

They include:

Carbohydrates

Lipids

Proteins

Nucleic Acids


Carbohydrates

Contain carbon, hydrogen, and oxygen

Their major function is to supply a source of cellular food

Examples:

Monosaccharides or simple sugars

Figure 2.14a


Carbohydrates

Disaccharides or double sugars

Figure 2.14b

PLAYPLAY Disaccharides


Carbohydrates

Polysaccharides or polymers of simple sugars

Figure 2.14c

PLAYPLAY Polysaccharides


Lipids

Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates

Examples:

Neutral fats or triglycerides

Phospholipids

Steroids

Eicosanoids

PLAYPLAY Fats


Neutral Fats (Triglycerides)

Composed of three fatty acids bonded to a glycerol molecule

Figure 2.15a


Other Lipids

Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group

Figure 2.15b


Other Lipids

Steroids – flat molecules with four interlocking hydrocarbon rings

Eicosanoids – 20-carbon fatty acids found in cell membranes

Figure 2.15c


Representative Lipids Found in the Body

Neutral fats – found in subcutaneous tissue and around organs

Phospholipids – chief component of cell membranes

Steroids – cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones


Representative Lipids Found in the Body

Fat-soluble vitamins – vitamins A, E, and K

Eicosanoids – prostaglandins, leukotrienes, and thromboxanes

Lipoproteins – transport fatty acids and cholesterol in the bloodstream


Amino Acids

Building blocks of protein, containing an amino group and a carboxyl group

Amino group NH2

Carboxyl groups COOH


Amino Acids

Figure 2.16a–c


Amino Acids

Figure 2.16d, e


Protein

Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds

Figure 2.17


Protein


Figure 2.17

Amino acid Amino acid

Dehydrationsynthesis

HydrolysisDipeptide

Peptide bond

+N

H

H

C

R

H

O

N

H

H

C

R

CC

H

O H2O

H2O

N

H

H

C

R

C

H

O

N

H

C

R

C

H

O

OH OH OH


Protein


Figure 2.17


+N

H

H

C

R

H

O

N

H

H

C

R

CC

H

O

OH OH


Protein


Figure 2.17



+N

H

H

C

R

H

O

N

H

H

C

R

CC

H

O H2O

OH OH


Protein


Figure 2.17



Dipeptide

Peptide bond

+N

H

H

C

R

H

O

N

H

H

C

R

CC

H

O H2O

N

H

H

C

R

C

H

O

N

H

C

R

C

H

O

OH OH OH


Protein


Figure 2.17

Dipeptide

Peptide bond

N

H

H

C

R

C

H

O

N

H

C

R

C

H

O

OH


Protein


Figure 2.17

HydrolysisDipeptide

Peptide bond

H2O

N

H

H

C

R

C

H

O

N

H

C

R

C

H

O

OH


Protein


Figure 2.17

Amino acid Amino acidHydrolysis

Dipeptide

Peptide bond

+N

H

H

C

R

H

O

N

H

H

C

R

CC

H

O

H2O

N

H

H

C

R

C

H

O

N

H

C

R

C

H

O

OH OH OH


Protein


Figure 2.17



HydrolysisDipeptide

Peptide bond

+N

H

H

C

R

H

O

N

H

H

C

R

CC

H

O H2O

H2O

N

H

H

C

R

C

H

O

N

H

C

R

C

H

O

OH OH OH


Structural Levels of Proteins

Primary – amino acid sequence

Secondary – alpha helices or beta pleated sheets

PLAYPLAY Chemistry of Life: Proteins: Secondary Structure

PLAYPLAY Chemistry of Life: Proteins: Primary Structure

PLAYPLAY Chemistry of Life: Introduction to Protein Structure



Tertiary – superimposed folding of secondary structures

Quaternary – polypeptide chains linked together in a specific manner

PLAYPLAY Chemistry of Life: Proteins: Quaternary Structure

PLAYPLAY Chemistry of Life: Proteins: Tertiary Structure



Figure 2.18a–c



Figure 2.18b,d,e


Fibrous and Globular Proteins

Fibrous proteins

Extended and strand-like proteins

Examples: keratin, elastin, collagen, and certain contractile fibers


Fibrous and Globular Proteins

Globular proteins

Compact, spherical proteins with tertiary and quaternary structures

Examples: antibodies, hormones, and enzymes


Protein Denuaturation

Reversible unfolding of proteins due to drops in pH and/or increased temperature

Figure 2.19a


Protein Denuaturation

Irreversibly denatured proteins cannot refold and are formed by extreme pH or temperature changes

Figure 2.19b


Molecular Chaperones (Chaperonins)

Help other proteins to achieve their functional three-dimensional shape

Maintain folding integrity

Assist in translocation of proteins across membranes

Promote the breakdown of damaged or denatured proteins


Characteristics of Enzymes

Most are globular proteins that act as biological catalysts

Holoenzymes consist of an apoenzyme (protein) and a cofactor (usually an ion)

Enzymes are chemically specific



Frequently named for the type of reaction they catalyze

Enzyme names usually end in -ase

Lower activation energy



Figure 2.20


Mechanism of Enzyme Action

Enzyme binds with substrate

Product is formed at a lower activation energy

Product is released

PLAYPLAY How Enzymes Work

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 2.21

Active siteAmino acids

Enzyme (E)Enzyme-substratecomplex (E-S)

Internal rearrangementsleading to catalysis

Dipeptide product (P)

Free enzyme (E)

Substrates (S)

Peptide bond

H2O

+




Substrates (S)

H2O

+





Substrates (S)

H2O

+





Dipeptide product (P)

Free enzyme (E)

Substrates (S)

Peptide bond

H2O

+


Nucleic Acids

Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus

Their structural unit, the nucleotide, is composed of N-containing base, a pentose sugar, and a phosphate group


Nucleic Acids

Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U)

Two major classes – DNA and RNA


Deoxyribonucleic Acid (DNA)

Double-stranded helical molecule found in the nucleus of the cell

Replicates itself before the cell divides, ensuring genetic continuity

Provides instructions for protein synthesis


Structure of DNA

Figure 2.22a


Structure of DNA

Figure 2.22b


Ribonucleic Acid (RNA)

Single-stranded molecule found in both the nucleus and the cytoplasm of a cell

Uses the nitrogenous base uracil instead of thymine

Three varieties of RNA: messenger RNA, transfer RNA, and ribosomal RNA


Adenosine Triphosphate (ATP)

Source of immediately usable energy for the cell

Adenine-containing RNA nucleotide with three phosphate groups


Adenosine Triphosphate (ATP)

Figure 2.23


Solute Solute transported

Contracted smoothmuscle cell

Product made

Relaxed smoothmuscle cell

Reactants

Membraneprotein

P Pi

ATP

PX X

Y

Y

+

(a) Transport work

(b) Mechanical work

(c) Chemical work

Pi

Pi

+ADP


Solute

Membraneprotein

P

ATP

(a) Transport work



Membraneprotein

P Pi

ATP

(a) Transport work

Pi

+ADP



ATP

(b) Mechanical work




ATP

(b) Mechanical work

Pi

+ADP


Reactants

ATP

PX

Y+

(c) Chemical work


Product madeReactants

ATP

PX X

Y

Y

+

(c) Chemical work

Pi

Pi

+ADP




Product made


Reactants

Membraneprotein

P Pi

ATP

PX X

Y

Y

+

(a) Transport work

(b) Mechanical work

(c) Chemical work

Pi

Pi

+ADP


МЕТАБОЛИЗМ


Catabolism provides the building blocks and energy for anabolism.

Figure 5.1


A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell.

Metabolic pathways are determined by enzymes.

Enzymes are encoded by genes.

PLAY Animation: Metabolic Pathways (Overview)


Oxidation-Reduction

Oxidation is the removal of electrons.

Reduction is the gain of electrons.

Redox reaction is an oxidation reaction paired with a reduction reaction.

Figure 5.9


Oxidation-Reduction

In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.

Figure 5.10


The Generation of ATP

ATP is generated by the phosphorylation of ADP.



Substrate-level phosphorylation is the transfer of a high-energy PO4

– to ADP.



Energy released from the transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP by chemiosmosis.



Light causes chlorophyll to give up electrons. Energy released from the transfer of electrons (oxidation) of chlorophyll through a system of carrier molecules is used to generate ATP.

Molbiol 2011-03-biochem

Technology

amino acids figure

c play polysaccharides

types of amino acids

peptide bonds figure

proteins examples

protein macromolecules

spherical proteins

translocation of proteins