Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbon and organic molecules Carbon and its bonds Polymers and monomers - Carbohydrates

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Carbon and organic molecules

• Carbon and its bonds

• Polymers and monomers

- Carbohydrates

- Proteins

- Lipids

- Nucleic acids


• A carbon atom forms four covalent bonds

• C can make chains or rings

Why is carbon so important to molecules of life?

Figure 3.1, top part

Structuralformula

Ball-and-stickmodel

Space-fillingmodel

Methane

The 4 single bonds of carbon point to the corners of a tetrahedron.


• Methane, CH4

Figure 2.8Bx

Arrangement of atoms determines molecular shape.Shape determines function of molecules


• Butane, ball and stick model

Figure 3.1x3


• Cyclohexane, ball and stick model

Figure 3.1x5


• groups of atoms that participate in chemical reactions

• determine the chemical properties of molecules

• Examples: acidity, solubility

What are functional groups and what do they do?

-OH -COOH -NH2 -CH3


What affects solubility in water?

• Molecules with +/- charge are usually hydrophilic or “water-loving”

• Molecules with no charge and non-polar are usually hydrophobic and not soluble in water


• Polymers are long chains of smaller molecular units called monomers

• A huge number of different polymers can be made from a small number of monomers

How do cells make so many different molecules that are needed for life?


• Carbohydrates are a class of molecules

– Monosaccharides: glucose, fructose, ribose

– Disaccharides: maltose, sucrose, lactose

– Polysaccharides: starch, glycogen

CARBOHYDRATES


• are single-unit sugars

• a multiple of CH2O

• fuels for cellular work

Monosaccharides


• Glucose, ball and stick model

Figure 3.4x


disaccharides

Glucose Glucose

Maltose

Figure 3.5

Sucrose

glucose fructose

Dehydration synthesis


• Maltose, ball and stick model

Figure 3.5x


• Sucrose, ball and stick model

Figure 3.6x


• Molecules, including non-sugars, taste sweet because they bind to “sweet” receptors on the tongue

Why is sugar sweet?

Table 3.6


Polysaccharides are long chains of sugar units

• Size: thousands of linked monosaccharides

• purpose: energy storage, structural


• Starch (plants) and glycogen (animals)

• Cellulose (plants) and chitin (insects, fungi)

Figure 3.7

Starch granules in potato tuber cells

Glucosemonomer

STARCH

GLYCOGEN

CELLULOSE

Glycogen granules in muscle tissue

Cellulose fibrils ina plant cell wall

Cellulosemolecules


• Starch Cellulose

Figure 3.7x

= fiber indigestible


• hydrophobic

• composed largely of carbon and hydrogen

• Purposes:

- energy-storage

- insulation, cushioning

- membranes

- signals

Lipids include fats, oils, and steroids.


• Fats are triglycerides

– one glycerol molecule linked to three fatty acids

– fatty acid chains often differ

Fatty acid


• Saturated fats lack double bonds

– solid at room temperature (lard)

• Fatty acids of unsaturated fats contain double bonds– liquid at room temperature (plant oils)

• Trans fats have “wrong way” double bonds

Figure 3.8C


• both polar and nonpolar portions

• major component of cell membranes

Figure 3.9

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Phospholipids


Waxes form waterproof coatings and can prevent organisms from drying out or getting wet

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.


Steroids are often hormones

testosteroneestrogen

Anabolic steroids

Hormone Replacement Therapy


• Cholesterol

• Membranes

• Precursor to Vitamin D, bile salts

Figure 3.9x1

HDL High Density Lipoprotein

LDL Low Density Lipoprotein


• Proteins are involved in – cellular structure

– movement

– nutrition

– defense

– transport

– communication

• Enzymes regulate chemical reactions

Proteins are essential to the structures and activities of life

Figure 3.11


– Their diversity is based on different arrangements of amino acids

composed of 20 kinds of amino acids9 a.a. must be consumed in food

Proteins are the most structurally and functionally diverse of life’s molecules


• Each amino acid contains:

– an amino group

– a carboxyl group

– an R group, which distinguishes each of the 20 different amino acids

Aminogroup

Carboxyl (acid)groupFigure 3.12A


• Each amino acid has specific properties

Leucine (Leu)

Figure 3.12B

Serine (Ser) Cysteine (Cys)

HYDROPHOBIC HYDROPHILIC


• Cells link amino acids together by dehydration synthesis

• Peptide bonds

Amino acid Amino acid Dipeptide

Dehydrationsynthesis

Carboxylgroup

Aminogroup

PEPTIDEBOND

Figure 3.13


• A protein consists of polypeptide chains folded into a unique shape

– shape determines the protein’s function

– A protein loses its function when its polypeptides unravel

A protein’s specific shape determines its function

Figure 3.14A Figure 3.14B


A protein’s primary structure is its amino acid sequence

Secondary structure is polypeptide coiling or folding produced by hydrogen bonding

Figure 3.15, 16

Amino acid

Hydrogen bond

Alpha helix

Pleated sheet

Primarystructure

Secondarystructure


Tertiary structure is the overall shape of a polypeptide

Quaternary structure is the relationship among multiple polypeptides of a protein

Figure 3.17, 18

Polypeptide(single subunitof transthyretin)

Transthyretin, with fouridentical polypeptide subunits

Tertiarystructure

Quaternarystructure


• 2 Nobel prizes - Chemistry and Peace

Linus Pauling contributed to our understanding of protein structure and function

Figure 3.19


• Nucleic acids such as DNA and RNA serve as the blueprints for proteins

• They ultimately control the life of a cell

• DNA sequence is inherited by progeny

Nucleic acids are information-rich polymers of nucleotides


• The monomers of nucleic acids are nucleotides

Phosphategroup

SugarFigure 3.20A

– Each nucleotide is composed of a sugar, phosphate, and nitrogenous base

Nitrogenousbase (A)


• The sugar and phosphate form the backbone for the nucleic acid

Sugar-phosphatebackbone

Nucleotide

Figure 3.20B


• DNA consists of two polynucleotides twisted around each other in a double helix

Figure 3.20C

– The sequence of the four kinds of nitrogenous bases in DNA carries genetic information

Nitrogenousbase (A)

Basepair

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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbon and organic molecules Carbon and its bonds Polymers and monomers - Carbohydrates