chapter 4- chemical composition of the cell

Chemical composition of the cell

Elements• All living and non-living things are made of

subtances called elements• A subtance• Composed of only one kind of atom• Cannot be broken down into simpler

subtances by a chemical reaction• Most common C-carbon, O-oxygen, H-

hydrogen, N-nitrogen.

Elements• It accounts for about 96% of the mass of

human body.• Other elements make up the remaining 4%.• Organic compound-Chemical compounds

that contain the element carbon eg carbohydrates, proteins, lipids and nucleic acids.

• Water is an inorganic compound-composed of hydrogen and oxygen

The importance of Organic compound

Proteins

Carbohydrates

Lipids

Amino acids

Sugars, starch, glycogenand cellulose

Fats, Oils, waxes, Phospholipids and steroils

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2

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So, what are the function of these organic compound???

Food Digestion

What happens to

the food you eat??

Consist largely of Proteins, lipids and

carbohydrates

Complex organic molecules

Small solublemolecules

Digestion1. The process that breaks

down complex food to simpler soluble small molecules

complex small

Starch

glucose

Proteins

Amino acids

Lipids

Glycerol andfatty acids

Energy Synthesizenew protein

Plasma membranecomponent

Nucleic acid nucleotides

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Phosphate group

Pentose sugar Nitrogenous base

2 types of nucleic acids

DNA(deoxyribonucleic acid)

RNA( Ribonucleic acid)

-double stranded polynucleotide-two strands-strands twisted around eachother-double helix

-Contains genetic information-In chloroplast and mitochondria

-Found in cytoplasm,ribosomesand the nucleus-Used for protein synthesis-genetic material for some viruss

The importance of water• Polar molecule• Transport medium• Medium for biochemical reactions• Lubrication• High cohesion

Polar moleculeThe solvent of lifeDissolve many ionic compound eg salt, polar molecules (sugar)

Transport medium• In blood ,lymphatic, excretory and

digestive systems and in vascular tissues of plants.

• Blood plasma is made up of 90% of water• Also contains many biological molecules

eg sugar, amino acid and respiratory gases.

• Waste products are excreted from the body through the urine.

Biochemical reaction• Biochemical reactions take place in the

cell can only occur when there is water• Water used in many digestive reactions• Breaking down the proteins,lipids and

sugars.

Types of carbohydratesMonosaccharides

Disaccharides

Polysaccharides

Monosaccharides Monomers of carbohydrates

Simplest type of carbohydrates

Simple sugars (main source of energy formany cells)

Long chain monosaccharides can combine with Proteins and lipids to form glycoproteins and glycolipids

Reducing sugars and reducing agent

Glucose, fructose ( sweet fruit and honey) and Galactose(milk)

Disaccharides• When 2 monosaccharides combine in

condensation process• What is condensation?• Maltose, Sucrose and Lactose

Glucose + Glucose Maltose + waterCondensation

Hydrolysis

Glucose + Fructose Sucrose + water Condensation

Hydrolysis

Glucose + Galactose Lactose + waterCondensation

Hydrolysis

Maltose- Malt sugar Sucrose – cane sugar

Polysaccharides• Hundreds of monosaccharides can

combine through condensation to form a long chain of molecules.

• Polymers formed by the condensation of glucose monomers.

• Insoluble in water due to large molecular size

• Do not taste sweet and do not crystallise• Starch, glycogen and cellulose

Starch Is the main carbohydrate reserve in plants

Found in plants such as wheat , rice ,potatoes, bread and corn

Glycogen• The main reserve of carbohydrates in

animals and yeast• Human and animals store glycogen mainly

in the liver and muscle cells• Glycogen-----animal starch• The polysaccharide chains are highly

branched• What happens when poly+diluted acid n

enzymmatic reaction????

Polysaccharides + water monosaccharidesHydrolysis

Proteins• Large complex organic molecules• Made up of elements carbon, hydrogen,

oxygen and nitrogen• Some contains sulphur and phosphorus• Foods ( fish, meat, milk, nuts and eggs)

Proteins• Made up of monomers or units called

amino acids.• A dipeptide consists of two molecules of

amino acids that are linked by a peptide bond through condensation.

Amino acid + amino acid dipeptide + watercondensation

hydrolysis

Proteins• Further condensation can form a

polypeptide chain.• There are 20 types of amino acids in living

cells.• Proteins or polypeptides that are broken

down through hydrolysis into amino acids by the digestive enzymes are absorbed into the bloodstream.

Polypeptide + water dipeptides or amino acidsHydrolysis

Proteins structures

Primary structure• The linear sequence of amino acid in a

polypeptide chain• Different types of proteins have different

sequences of amino acids.• The sequences are determined by the

genetic code carried in the DNA in the nucleus

Secondary structure• The polypeptide chain that is

coiled to form an alpha-helix or folded into beta-pleated sheets

• The coiling and folding of polypeptide chain by hydrogen bonds

Tertiary structure• Helix chain or beta-pleated sheets

are folded into 3D shape of polypeptide

• Eg: enzymes,hormones,antibodies and plasma proteins

Quarternary structure• Combination of two or more

tertiary structure polypeptide chains to form one large and complex protein molecule

• For example: haemoglobin