Macromolecules Carbohydrates, Proteins, Lipids, Nucleic Acids.

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Macromolecules Carbohydrates, Proteins, Lipids, Nucleic Acids

Transcript of Macromolecules Carbohydrates, Proteins, Lipids, Nucleic Acids.

Page 1: Macromolecules Carbohydrates, Proteins, Lipids, Nucleic Acids.

Macromolecules

Carbohydrates, Proteins, Lipids, Nucleic Acids

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Organic molecules

• Organic molecules contain carbon• Carbon is a unique and important element • Carbon is able to form strong, stable

covalent bonds (electrons are shared) forming single, double or triple bonds

• Organic compounds form the structure of living cells

• Carbohydrates, lipids and proteins, nucleic acids are examples

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Inorganic compounds

• Are not generally part of the structure of living things

• Inorganic substances are found in the form of ions such as sodium and calcium

• Water is an essential inorganic compound

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Complex molecules

• Many organic molecules are very complex

• Cells make these complex molecules by joining smaller molecules together into chains known as polymers

• Polymers are large molecules made up of small identical or similar molecules strung together. (like beads in a necklace)

• Each small molecules is called a monomer

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Carbohydrates

• Carbohydrates include sugars and starches

• Carbohydrates consist mostly of carbon, hydrogen and oxygen

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Carbohydrates

• General formula: (CH2O)n

• Contain hydroxyl groups and one carbonyl group

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Monosaccharides

• Pentoses: 5 carbons with 5 functional groups

• Hexoses:6 carbons with 6 functional groups

• Both will form ring structures as OH reacts with another functional group

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Glucose

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Glucose

• The most important molecule for providing energy for the cell in cellular respiration

• Produced in photosynthesis

• Important in the synthesis of amino acids and nucleic acids

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Carbohydrates

• There are three classes of carbohydrates, based on the number of sugar units:

1) Monosaccharides

2) Disaccharides

3) Polysaccharides

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• Monosaccharides are the monomer forms

• Glucose is a monomer

• Disaccharides consist of two monomers

• Maltose and sucrose are disaccharides

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Dehydration synthesis

• Disaccharides form by dehydration synthesis (condensation reaction)

• Dehydration reaction forms glycosidic linkages (usually 1-4 or 1-6)

 

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Disaccharides

• Sucrose: glucose and fructose

• Lactose: glucose and galactose

• Maltose: glucose and glucose

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Polysaccharides

• Polysaccharides are large carbohydrate molecules that are polymers of 100 - 1000s of monosaccharides

• They can be branched with 1-4 and 1-6 linkages on one sugar

• Insoluble in water (more branches = less soluble)

• Examples: starch, glycogen, cellulose

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Storage Polysaccharides

• Plant starch– Amylose – long chain of 1-4 glucoses– Amylopectin – long chain of 1-4 glucoses with

branches 1-6 linkages (1 every 20 – 25 glucose)

• Animal “starch” – Glycogen – made of α-glucose– more highly branched than amylopectin

(1 every 6 -10 glucose)– Stored mainly in liver and muscle cells

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glycogen

amylose amylopectin

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Structural Polysaccharides

• Cellulose: – plant cell walls– Composed of β-glucose– Long chains of 1-4 linkages– Indigestible by humans

• Chitin: – insect exoskeletons, fungal cell walls– Monomer is glucosamine

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• Cellulose

• Chitin

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Proteins• Are the building blocks for cellular growth

and repair

• Build enzymes, hormones and bodily fluids

• Make antibodies to fight diseases

• Are very diverse in function:– Enzymes– Hormones– Insulin– Keratin

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Proteins

• Contain C, H, N, O and sometimes P and S

• Made of long chains of amino acids joined with peptide bonds

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Amino Acids

• There are 20 different kinds

• 8 are essential (must be consumed since the body cannot make them)

• Differ only in the side chain (R)

• Have 2 active functional groups (carboxyl and amino)

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Amino Acids

• Side chain (R) can be:1. neutral-nonpolar (hydrophobic) 2. neutral-polar (hydrophilic)3. basic (hydrophilic)4. acidic (hydrophilic)

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Examples

• Polar: cysteine

• Nonpolar: alanine

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Examples

• Basic: lysine (lys)

• Acidic: glutamic acid (glu)

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Protein structure

• Proteins can be very large molecules

(as many as1000 amino acid monomers)

• Proteins are formed by dehydration synthesis

• The bonds that form are called peptide bonds

• Molecules with many amino acids are called polypeptides

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Protein Structure

I. Primary Structure: sequence of amino acids unique to each protein

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Protein Structure

II. Secondary Structure: amino acids interact with neighbours to form hydrogen bonds, chains fold into sheets or wrap into coils (α-helix or β-pleated sheets)

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Protein Structure

III. Tertiary structure

•Additional, less regular contortoins due to side group interactions

•Hydrophilic, hydrophobic, acid/base

•H-bonds, ionic bonds, covalent bonds (disulfide bridges)

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Protein Structure

IV. Quaternary Structure

•2 or more polypeptide chains (subunits) come together to form a functional protein

e.g. hemoglobin has four chains

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Protein Structure

• Protein structure is stable and function is normal as long as its natural environment remains constant

• If pH, salt concentration, temperature or other conditions change, the protein can become denatured

• Bonds are broken

• Denatured protein may not function

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Protein Function

• There are seven different functions for proteins:– Structural

– Storage

– Transport

– Hormonal

– Contractile

– Antibodies

– Enzymes

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Lipids

• Includes fats, phospholipids, waxes and steroids

• Serve as long term storage of energy

• Made up of two types of molecules:– Fatty acids – Glycerol

• Fatty acids are long hydrocarbon chains with a caboxyl group at one end

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Lipids

• Consist mainly of O, C and H atoms linked by nonpolar covalent bonds

• They are insoluble in water but soluble in other nonpolar substances

• Used for storing energy, building membranes and other cell parts as well as chemical signalling molecules

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Lipids

• There are four types of lipids:– Fats– Phospholipids– Waxes– Sterols/steroids

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Fats

• The most common energy-storing molecules

• Large lipid made of two smaller molecules: glycerol and fatty acids joined by an ester linkage

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Fats

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Fats

• Glycerol is an alcohol with three carbons, each bearing a hydroxyl group

• A fatty acid consists of a hydrocarbon chain with about 16 – 18 carbon atoms and carboxyl group on one end

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Fatty acids• Fats with the maximum number od

hydrogen atoms are said to be saturated

• They have no double bonds

• Are linear (straight)

• Fatty acids with double bonds are said to be unsaturated

• They are bent

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Triglycerides

• The majority of fat in organisms consists of molecules of triglycerides which are composed of three fatty acid molecules combined with glycerol

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Triglycerides

• If the fatty acids are saturated then it is a saturated fat which are solid at room temperature e.g. butter and lard

• If the fatty acids are unsaturated then it is a polyunsaturated fat which is liquid at room temperature

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Phospholipids

• A major component of cell membranes

• Structurally similar to fats but they contain a phosphate group and have only two fatty acids instead of three

• The phosphate group can be thought of as a polar head (hydrophilic)and the fatty acids as long nonpolar tails (hydrophobic)

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Phospholipids

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Waxes

• Contain long-chain fatty acids linked to alcohols or carbon rings

• They are more hydrophobic than fats and this makes them effective natural coatings for fruits and leaves, feathers

bee wax

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Sterols/Steroids

• A component of cell membranes

• Contain four fused hydrocarbon rings and several different functional groups

• All steroids have the same ring pattern: three 6-sided ringsand one 5-sided ring

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Sterols/Steroids

• Sterols are hydrophobic

• Cholesterol is a common substance in animal cell membranes and is used as a starting material for making other steroids including sex hormones

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Nucleic acids

• DNA and RNA are polymers of nucleic acids

• Nucleotides are made of three subunits:– A nitrogen base– A pentose sugar– A phosphate group

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Structure of Nucleic acids• Nitrogen bases are:

– Guanine– Adenosine

– Cytosine– Thymine (DNA)– Uracil (RNA)

Purines: double rings

Pyrimidines: single ring

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Nucleic acids

• The sugars are:– Deoxyribose in DNA– Ribose in RNA

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Nucleotides

• Nucleotides are formed by condensation reactions between a nitrogenous base, a pentose sugar and a phosphate group

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Polynucleotides (nucleic acids)

• Are formed by covalent bonds between nucleotide monomers (3′– 5′)

• Phosphodiester linkages form a backbone of alternating phosphates and sugar

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Polynuceotides• Nitrogenous bases stick out from the

backbone but not straight out

• The bases can form hydrogen bonds

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Nucleic acid formation

• The ability to form hydrogen bonds determines the structure and function of nucleic acids

• Bases in 2 neighbouring nucleic acid chains will pair up with H-bonds

• This gives the double stranded helical form of DNA

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Nucleic acid formation

• Because the bases don’t stick out straight, the 2 chains must be anti-parallel to fit together

• One chain must be 3′– 5′ and theother 5′– 3′

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Nucleotides as Energy Transformation Intermediates

• ATP (adenosine triphosphate)– Provides energy

• NAD+ (nicatinamide adenine dinucleotide)– Used in cellular respiration

• FAD+ (flavin adenine dinucleotide )– Used in cellular respiration

• NADP+ – Used in photosynthesis

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ATP• Adenosine triphosphate is the energy

providing molecule in the cell

• ATP is a monomer

• Adenine plus 3 phosphate groups attached to a ribose sugar

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ATP cycle• Energy released by cellular catabolism is

used to phosphorylate ADP regenerating ATP

• Energy stored in ATP is released to do cellular work when ATP is hydrolyzed

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ATP hydrolysis• The 3 phosphate groups are negatively

charged due to ionized hydroxyl groups

• Like charges cause repulsion

• Bonds between the phosphate groups are unstable and can be hydrolyzed

• Water hydrolyzes the terminal phosphate bond

• One molecule of inorganic phosphate, ADP and energy is released