Chapter 3 Sugars Lipids Proteins

BIO F111 – General Biology

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Chapter

3

The Molecules of Life


Objectives: To learn

• How (milk) lactose intolerance can be treated?

• Why is it difficult for humans to digest cellulose?

• ‘Puraani jeans aur guitar3’ How is the jeans made puraani by textile companies?


Giant Molecules from Smaller Building Blocks

• Organic compounds are carbon-based.

• Macromolecules are polymers.

• Polymers are made by stringing together many smaller molecules called monomers.

• A dehydration reaction

• links two monomers together and

• removes a molecule of water.

• Hydrolysis does the opposite.


OH H

Short polymer

Dehydration

reaction

Monomer

H2O

Figure 3.4-1

Longer polymer

(a) Building a polymer chain

H2O

Hydrolysis

Figure 3.4-2

Hydrolysis

OH H

(b) Breaking a polymer chain

Large Biological Molecules (Macromolecules)

• There are four categories of large biological molecules found in all living creatures:

1. carbohydrates,

2. lipids,

3. proteins, and3. proteins, and

4. nucleic acids.


Carbohydrates

• Contain C, H, O

• Empirical formula is: CnH2nOn

• Simple sugars are known as monosaccharides


• Simple sugars are known as monosaccharides

• Examples include glucose, galactose, fructose

• Out of the above three, fructose (fruit sugar) is the sweetest

Glucose

C6H12O6

Fructose

C6H12O6

Isomers

Figure 3.5

Isomers

(same formula, different arrangements)

Figure 3.6

In water, many monosaccharides form rings.

(a) Linear and ring structures (b) Abbreviated ringstructure

processed to extract

Starch

broken down into

Glucose

Figure 3.8

Glucose

converted via enzyme to sweeter

Fructose

added to foods ashigh-fructose corn syrup

Functions of Carbohydrates ?


Functions of Carbohydrates

• Provide energy

• Are important components of Nucleic acids

(DNA/RNA)


(DNA/RNA)

• Component of cell membranes

• Maintain cell shape/structure (e.g. Cellulose of

plant cell walls)

Figure 3.0-2

Chapter Thread: Lactose Intolerance

Disaccharides

• Linked by glycosidic bonds b/w monosaccharides

• Examples:

• Sucrose = Glucose + Fructose


• Sucrose = Glucose + Fructose

• Maltose = Glucose + Glucose

• Milk Lactose = Glucose + Galactose

OH H

Glucose Galactose

H2O

Figure 3.7

Lactose

• How can ‘lactose intolerance’ be treated?



• Monosaccharides (Simple sugars) �

Polysaccharides (Complex sugars)


• Common polysaccharides derived from

glucose are: plant starch (linear amylose &

branched amylopectin); plant cellulose

(linear); animal glycogen (branched)

Polysaccharides

• Cellulose

• is the most abundant organic compound on Earth,

• forms cable-like fibrils in the walls that enclose plant cells, and

• cannot be broken by any enzyme produced by • cannot be broken by any enzyme produced by animals.


Spot the difference!

Biostoning of jeans

using the enzyme

‘cellulase’!

Levi Strauss

Cellulase enzyme is

used to

“biostone” jeans

to give

desired colour/texture

in controlled manner.in controlled manner.

The enzyme breaks

down cellulose, releasing

indigo dye in the process.

Next objectives for today

• Why do animals living in cold temperatures

have higher proportions of PUFA (Poly

Unsaturated Fatty Acids) in their body lipids?


• How do fat deposits serve the birds on long

distance flights?

• Why do some athletes take steroids before ‘the

big game’?

Lipids (Fats)

• Large and nonpolar in general

– Do not dissolve in water

• No. of oxygen atoms lesser than in sugars


• Three main types of lipids:

– True fats (e.g., butter)

– Phospholipids (membrane components)

– Steroids (most hormones)

True (Neutral) Fats

• Provide energy & insulation

• Can be stored in a relatively small space


• The building blocks of fats are:

– A glycerol molecule

– Three fatty acids

Fatty acid

Glycerol

(a) A dehydration reaction linking a fatty acid to glycerol

H HO

H2O

Figure 3.11

(b) A fat molecule with a glycerol “head” and threeenergy-rich hydrocarbon fatty acid “tails”

• Saturated fats are usually solid at room

temperature.

– e.g. Most animal fat


• Unsaturated fatty acids have one or more

double bonds between carbons.

– e.g. Most plant and fish fats

How do fat deposits serve the birds

on long distance flights?


• There is more than twice as much energy in a

gram of fat as in a gram of sugar.

• Hydrogenation of vegetable oils produces

saturated fatty acids, sometimes creating

unhealthy ‘trans fats’.


• Trans fatty acids may be produced in the

process of deep frying.

TYPES OF FATS

Saturated Fats Unsaturated Fats

Margarine

Figure 3.12

Margarine

Plant oils Trans fats Omega-3 fats

Phospholipids

• Amphipathic in nature.

• Important component

of cell membranes.


of cell membranes.

Steroids

• Structure contains interlocking rings of

carbon.

• Component of membranes (e.g. cholesterol).


• Component of membranes (e.g. cholesterol).

• Component of hormones (e.g. Testosterone,

estrogen).

Cholesterol can be convertedby the body to

Figure 3.13

Testosterone A type of estrogen

Presence of cholesterol stabilizes

the animal cell membrane.


Alex Rodriguez Mark McGwire

Synthetic anabolic

steroids, prescribed

for cancer/AIDS,

may be abused by

Floyd Landis Ben Johnson

may be abused by

athletes to build

quick muscles.

Thought Question:

Why do animals living in cold temperatures

have higher proportions of PUFA in their

body lipids?

BIO F111



Changing roles of fat…

Objectives

• How could Mr. V.K. Bansal (Bansal Classes) help change the face of Kota (Rajasthan)?

• How could Spiderman stop a fast speeding train in the climax of the movie ‘Spiderman-2’?the climax of the movie ‘Spiderman-2’?


Bansal Sir says:

• “$excess vision can be a detriment. Because if you keep looking too far ahead, it is unlikely that you will be able to tread your present path satisfactorily, let alone relish the journey. I therefore have always restricted my visualizing to a bare minimum. This way, I am freed of needless bother minimum. This way, I am freed of needless bother and am able to focus completely on the task at hand.”

MAJOR TYPES OF PROTEINS

Structural Proteins(provide support)

Storage Proteins(provide amino

acids for growth)

ContractileProteins

(help movement)

Transport Proteins(help transportsubstances)

Enzymes(help chemical

reactions)

Figure 3.15

The Monomers of Proteins: Amino Acids

• All proteins are made by stringing together a common set of 20 kinds of amino acids.

• Every amino acid consists of a central carbon atom bonded to four covalent partners.


The Monomers of Proteins: Amino Acids

• Three of those attachment groups are common to all amino acids:

1. a carboxyl group (−COOH),

2. an amino group (−NH2), and

3. a hydrogen atom.3. a hydrogen atom.

• The variable component of amino acids

• is called the side chain and

• is attached to the fourth bond of the central carbon.


Aminogroup

Carboxylgroup

Figure 3.16-1

(a) The general structure of an amino acid

Sidechain

Hydrophobic Hydrophilic

Figure 3.16-2

Hydrophobicside chain

Hydrophilicside chain

Leucine Serine

(b) Examples of amino acids with hydrophobic and hydrophilicside chains

Structure/Function: Protein Shape

• Cells link amino acids together by dehydration reactions,

• forming peptide bonds, and

• creating long chains of amino acids called polypeptides.

• A functional protein is one or more polypeptide chains precisely twisted, folded, and coiled into a molecule of unique shape.


Carboxylgroup

OH

Aminogroup

H

Sidechain

Amino acid

Dehydration reaction

Sidechain

Figure 3.17-s2

Amino acid

H2O

Sidechain

Sidechain

Peptide bond


• How is it possible to make the huge variety of proteins found in your body from just 20 kinds of amino acids?

• Like the English alphabet used to make different words by varying the sequent of just 26 letters, proteins use 20 different “letters” (amino acids) toproteins use 20 different “letters” (amino acids) tocreate polypeptides hundreds or thousands of amino acids in length.



• The amino acid sequence of each polypeptide determines the three-dimensional structure of the protein.

• A protein’s three-dimensional structure enables the molecule to carry out its specific function.the molecule to carry out its specific function.


One amino acid

(alanine)1

Here you can see how the polypeptidefolds into a compact shape.

Figure 3.18

folds into a compact shape.

129The amino acid sequence of lysozyme

This model allows you to see the details

of the protein’s structure.

Fill in the blank

• The enormous diversity of protein molecules is mostly due to the diversity of _________ on the amino acids.



Forces stabilizing tertiary structure of proteins

Structure determines function3(e.g. Hemoglobin: α2β2)


• Misfolded proteins are associated with many diseases, including some severe nervous system disorders.

• The diseases shown in Figure 3.20 are all caused by prions, misfolded versions of normal brain by prions, misfolded versions of normal brain proteins.


Normalprotein

PrionClustersof prions

Skull

Brain

Prionconvertsnormalproteins

Prionproteinsclumptogether

Figure 3.20

normalproteins

clumptogether

Bovine spongiformencephalopathy(BSE)

Kuru Fatal weight loss indeer, elk, and moose


• A protein’s shape is sensitive to the environment. An unfavorable change in temperature, pH, or some other factor can cause a protein to unravel.


• Denaturation…


Marvel of engineering!

• According to Science News reporter Richard Lipkin, in a January 21, 1995 article - spider silk is so strong and resilient that on the human scale, a web resembling a fishing net could catch a passenger plane in flight!

Hey Spiderman, stop the train!

Video

• Dr. Shibashish Chowdhury talking about the protein folding problem


Documents

Chapter 3 Sugars Lipids Proteins