Macromolecules Carbohydrates, Proteins, Lipids, Nucleic Acids.
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Transcript of Macromolecules Carbohydrates, Proteins, Lipids, Nucleic Acids.
Macromolecules
Carbohydrates, Proteins, Lipids, Nucleic Acids
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
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
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
Carbohydrates
• Carbohydrates include sugars and starches
• Carbohydrates consist mostly of carbon, hydrogen and oxygen
Carbohydrates
• General formula: (CH2O)n
• Contain hydroxyl groups and one carbonyl group
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
Glucose
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
Carbohydrates
• There are three classes of carbohydrates, based on the number of sugar units:
1) Monosaccharides
2) Disaccharides
3) Polysaccharides
• Monosaccharides are the monomer forms
• Glucose is a monomer
• Disaccharides consist of two monomers
• Maltose and sucrose are disaccharides
Dehydration synthesis
• Disaccharides form by dehydration synthesis (condensation reaction)
• Dehydration reaction forms glycosidic linkages (usually 1-4 or 1-6)
Disaccharides
• Sucrose: glucose and fructose
• Lactose: glucose and galactose
• Maltose: glucose and glucose
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
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
glycogen
amylose amylopectin
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
• Cellulose
• Chitin
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
Proteins
• Contain C, H, N, O and sometimes P and S
• Made of long chains of amino acids joined with peptide bonds
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)
Amino Acids
• Side chain (R) can be:1. neutral-nonpolar (hydrophobic) 2. neutral-polar (hydrophilic)3. basic (hydrophilic)4. acidic (hydrophilic)
Examples
• Polar: cysteine
• Nonpolar: alanine
Examples
• Basic: lysine (lys)
• Acidic: glutamic acid (glu)
• Polypeptide bond formation
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
Protein Structure
I. Primary Structure: sequence of amino acids unique to each protein
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)
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)
Protein Structure
IV. Quaternary Structure
•2 or more polypeptide chains (subunits) come together to form a functional protein
e.g. hemoglobin has four chains
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
Protein Function
• There are seven different functions for proteins:– Structural
– Storage
– Transport
– Hormonal
– Contractile
– Antibodies
– Enzymes
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
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
Lipids
• There are four types of lipids:– Fats– Phospholipids– Waxes– Sterols/steroids
Fats
• The most common energy-storing molecules
• Large lipid made of two smaller molecules: glycerol and fatty acids joined by an ester linkage
Fats
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
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
Triglycerides
• The majority of fat in organisms consists of molecules of triglycerides which are composed of three fatty acid molecules combined with glycerol
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
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)
Phospholipids
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
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
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
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
Structure of Nucleic acids• Nitrogen bases are:
– Guanine– Adenosine
– Cytosine– Thymine (DNA)– Uracil (RNA)
Purines: double rings
Pyrimidines: single ring
Nucleic acids
• The sugars are:– Deoxyribose in DNA– Ribose in RNA
Nucleotides
• Nucleotides are formed by condensation reactions between a nitrogenous base, a pentose sugar and a phosphate group
Polynucleotides (nucleic acids)
• Are formed by covalent bonds between nucleotide monomers (3′– 5′)
• Phosphodiester linkages form a backbone of alternating phosphates and sugar
Polynuceotides• Nitrogenous bases stick out from the
backbone but not straight out
• The bases can form hydrogen bonds
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
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′
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
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
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
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