02-Biomolecules

8/22/2019 02-Biomolecules

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BIOMOLECULES IN CELLS

(Carbohydrates, Lipids, Proteins & Nucleic Acids)


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Carbohydrates Includes sugar, glycogen, starches and cellulose

Represent only 2-3% of the total body weight

In humans and animals, carbohydrates function mainly as asource of chemical energy for generating ATP needed to drivemetabolic reaction

ATP needed to drive metabolic reaction

Composed of C, H & O atom

Most carbohydrates, for each C atom, there are two H and

one O


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Three major groups based on size :

1. Monosaccharides - A monomer of sugar moiety

2. Oligosaccharides A polymer of 2 to 10 sugarmoieties (Dissacharide, Trisaccharide, .)

3. Polysaccharides- A polymer of 10 or moremonosaccharides (Homo & Heteropolysaccharides)

Carbohydrates


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Monosaccharides Smallest carbohydrates or simple

sugars

Example : glucose (blood sugar) &fructose (fruit sugar), galactose,mannose

Important energy sources for many

body cells

Monomer for larger carbohydrates -building blocks of carbohydrates


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Disaccharides Formed when two monosaccharides

join

Examples

Glucose+fructose=Sucrose(table sugar)Glucose+glucose= MaltoseGlucose+galactose= Lactose

Can be split into smaller, simplermolecules through hydrolysis

Artificial sweeteners to limit sugarconsumption for medical reason, avoidcalories that might result in weightgain, mush sweeter than sucrose butfewer calories & do not cause toothdecay


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Polysaccharides Contain many monosaccharides

bound in long chains

Glycogen & starchpolysaccharide of glucose(homopolysaccahrides)

Glycogen is broken down intoglucose molecules which can beused as energy sources

Cellulose plant polysaccharide

Chondroitin sulphate, heparin,chitin, (heteropolysaccahrides)


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Lipids Greasy or oily nonpolar compounds

Substances that dissolve in nonpolar solvents, such as alcohol oracetone, but not in polar solvent such as water

Composed mainly of C, H & O, minor component P & N

Functions

Energy storage

Membrane structure

Protecting against desiccation (drying out).

Insulating against cold.

Absorbing shocks.

Regulating cell activities by hormone actions.

Examples : fats, phospholipids & steroids


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Lipids (Fats) Fats important energy

storage molecules ; theyalso pad & insulate the body

Building blocks of fats areglycerol & fatty acids

Most common type of fatmolecules triglycerides


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Fatty AcidsSaturated & unsaturated fat

Monounsaturated &polyunsaturated

Non Essential Fatty acids- oleicacid, Palmitoliec acid, stearicacid

Essential Fatty Acids- Linoleic,Linolenic & Arachidonic Acid


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Lipids (Phospholipids) One of the fatty acids bound to

glycerol is replaced by a moleculecontaining phosphorus

Hydrophilic (water loving, polar)&hydrophobic (water fearing,nonpolar)


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Lipids (Steroids) Structure differs

considerably fromtriglycerides

Have four rings ofcarbon atoms

Body cell synthesizeother steroids fromcholesterol

HO cholesterol

squalene

sex hormones

glucocorticoid hormones

mineralocorticoid hormones

bile acids

acetic acidisopentenyl

pyrophosphate


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Protein has a large number of important functions in the humanbody

In fact, the human body is about 45% protein.

Its an essential macromolecule without which our bodies would beunable to repair, regulate, or protect themselves.

Large molecules that contain C, H, O & N, some contain S

Normal lean adult body -12-18% protein

Much more complex in structure than carbohydrates or lipids

Have may roles in human body & largely responsible for thestructure of body tissues

Enzymes are protein that speed up most biochemical reactions

Proteins


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Functions of ProteinsProtein has a range of essential functions in the body:1. Required for building and repair of body tissues

(including muscle)

2. Enzymes, hormones, and many immune moleculesare proteins3. Essential body processes such as water balancing,

nutrient transport, and muscle contractions requireprotein to function.

4. Protein is a source of energy.5. Protein helps keep skin, hair, and nails healthy.6. Protein, like most other essential nutrients, is

absolutely crucial for overall good health.


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Protein Structure


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Amino Acids the Building Blocks


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Protein-Primary Structure

Unique sequence of amino acids in a protein

Slight change in primary structure can alter function

Determined by genes

Condensation synthesis reactions form the peptide bonds betweenamino acids


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Protein-Secondary Structure

Repeated folding of proteins polypeptide backbone

stabilized by H bonds between peptide linkages in theproteins backbone

2 types, alpha helix, beta pleated sheets


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Protein-Tertiary Structure

Irregular contortions of a protein due tobonding between R groups

Weak bonds:

H bonding between polar side chains

ionic bonding between charged side chains

hydrophobic and van der Waals interactions

Strong bonds:

disulfide bridges form strong covalent linkages


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Bonds Involved in Protein Structure


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Protein-Quaternary Structure

Results from interactions among 2 or more polypeptides


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Factors That Determine ProteinConformation

Occurs during protein synthesis within cell

Depends on physical conditions of environment

pH, temperature, salinity, etc.

Change in environment may lead to denaturation of protein Denatured protein is biologically inactive

Can renature if primary structure is not lost


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Nucleic Acids : DNA & RNA

First discovered in the nuclei of cells

Large molecules contain C, H, O, N & P

Two types : DNA & RNA


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Nitrogenous Base

DNA contains four different

nitrogenous bases :

1. Adenine (A)

2. Thymine (T)3. Cytosine (C)

4. Guanine (G)

A & G large, double-ringbases called

purines

T & C smaller, single-ringbases calledpyrimidines


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Nucleosides

Pentose Sugar & Phosphate Group

Five-carbon sugar called deoxyribose

attach to each base in DNA

Five carbon sugar ribose attach to eachbase in RNA


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Nucleotides

Both DNA & RNA consist of basic buildingblocks called nucleotides

Nucleic acids are made up of a chain ofrepeating of monomers called nucleotides

Each nucleotide composed of three parts:

1. Nitrogenous base

2. Pentose sugar (monosaccharide)

3. Phosphate group


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Nuceotides in DNA


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DNA

Genetic materials (hereditary information) of humancells & copies of DNA are transferred to nextgeneration

Contain information that determines the structure ofproteins

In human, each gene is a segment of a DNAmolecule

Our genes determine the traits we inherit & bycontrolling protein synthesis they regulate most ofactivities that take place in body cells throughout ourlives


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DNA Structure - Double Helix

DNA has two strands of nucleotides joined together toform a twisted ladder-like structure called a doublehelix

Watson-Crick double helix

Each time DNA is copied, as when living cells divide to

increase their number, the two strands unwind

Each strand serves as template or mold to construct anew strand


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Double Helical DNA- Watson &Crick Model


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RNA

Structurally related to DNA

Relays instructions from the genes to guide each cellsynthesis of proteins from amino acid

Single-stranded, sugar is pentose ribose, pyrimidinebase Uracil (U) instead of thymine (T)

3 types of RNA : mRNA, tRNA & rRNA


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To Summarise -Biomolecules


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Possible Questions

1. Classification of Carbohydrates with examples

2. Classification of Lipids with examples

3. Difference between a fat and oil4. Functions of Carbohydrates, lipids and proteins

5. Structure of Proteins

6. Types of Aminoacids and their biological importance

7. Types of Nucleic acids and their structure and functions

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02-Biomolecules

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