Chemistry Of Cells

Chemistry of the Cell for Middle School Life Science

Four Important Cellular Macromolecules Carbohydrates – fuel for cell functions Lipids – stored energy and membrane structure Nucleic Acids – genetic information Proteins – many cell functions

Carbohydrates Fuel for cell functions Made up of saccharides (sugars) Glucose, Sucrose, Dextrose, Maltose, Lactose, Fructose, Cellulose, etc.

Carbohydrates Monosaccharides - simple sugars made up of 3 to 6 carbons - a monosaccharide is either a triose, tetrose, pentose or hexose. Disaccharides - 2 monosaccharides covalently linked. Polysaccharides - polymers consisting of chains of monosaccharide or disaccharide units. Base Structure:

Monosaccharides The free ends of a straight monosaccharide chain often bond to form a cyclic molecular structure simple sugars made up of 3 to 6 carbons.

Disaccharides Maltose is made when starch is broken down – it is simply two linked glucoses. Cellobiose is formed when cellulose is broken down for energy Disaccharides - 2 monosaccharides covalently linked.

Disaccharides Other common disaccharides include: Sucrose (common table sugar) formed from glucose & fructose bonding together. Lactose (milk sugar) composed of galactose & glucose

Polysaccharides - plant Cellulose (found in plant roots, seed, fruits and tubers) consists of long linear chains of glucose. Cellulose provides strength and rigidity to plant cell walls and is not digestible by most organisms (dietary fiber). Plants store glucose as amylose or amylopectin, (commonly called starch). Amylose is a glucose polymer. Amylose often has 300 – 600 linked glucose molecules

Glycogen is the glucose storage polymer in animals. The highly branched structure permits rapid release of glucose from glycogen stores, e.g., in muscle during exercise. The ability to rapidly mobilize glucose is more essential to animals than to plants. Polysaccharides - animal

Lipids Formed from fatty acids Non-polar (hydrophobic) compounds Functions: Triglycerides - stored energy Phospholipid bilayer – cell membranes Steroids – cholesterol, testosterone, estrogen, bile acids, Vitamin D

Fatty Acids Most fatty acids , the simplest lipids, are non-polar and thus repel water. If every carbon atom in a fatty acid chain is joined to another carbon atom by a single bond (and 2 H atoms), it is said to be saturated . If a pair of carbon atoms is joined by a double bond, it is said to be unsaturated .

Stored Energy Lipids Triglycerides are the main form of lipid used to store energy in the body. They have a glycerol backbone with three fatty acid tails. When lipids are metabolized (broken down for use), they produce LOTS of energy

Cell Membrane Lipids Phospholipids have a phosphate group plus two fatty acid tails. Hydrophobic tails hover together while the polar heads align to form a cell membrane. Cell membrane lipids are amphipathic , having a non-polar (hydrophobic) end and a polar (hydrophilic) end.

Steroids Steroids have a four fused carbon rings and a short branched hydrocarbon tail. Cholesterol is a steroid found in membranes, and is the precursor for synthesis of hormones (testosterone, estrogen, etc.), bile acids and vitamin D.

Nucleic Acids d eoxyribo n ucleic a cid (DNA) r ibo n ucleic a cid (RNA) Store, carry, and aid in the transmission of genetic information Made from (chains) of nucleotides Each nucleotide has three parts: Phosphate group Nitrogen base 5-carbon sugar (Ribose or Deoxyribose )

DNA Deoxyribonucleic acid Double-stranded helix Has the sugar Deoxyribose Forms chromosomes Uses four nucleotide bases Adenine Thymine Cytosine Guanine

RNA Ribonucleic acid single stranded (usually) Has the sugar Ribose Transcribes DNA to make proteins Four nucleotide bases Adenine Uracil Guanine Cytosine

Proteins Made from amino acids Seven major functions: Storage : iron, amino acid storage (seeds, milk & egg whites) Structural proteins : support and shape (collagen in hair/nails, microtubules/microfilaments) Signaling : membrane receptor proteins & chemical messengers Contractile : cell movement (cilia/flagella/pseudopodia, muscle) Defensive : against foreign substance and disease-causing organisms (antibodies) Enzymes : biological catalysts Transport: hemoglobin

Proteins Made from amino acids

Proteins Each is made from a specific sequences of amino acids joined together by peptide bonds The sequence of amino acids will determine the physical structure (how it folds) of the protein A single substitution may result in a protein that is not folded properly (sickle-cell anemia)

Proteins Proteins have many different functions, often dictated by shape, which is determined by the amino acid sequence that affects folding Examples: hemoglobin, flagella, membrane receptors, hair

Summary Carbohydrates Fuel for cell functions Formed from simple “sugars” or saccharides Glucose, Sucrose, Dextrose, Maltose, Lactose, Fructose, Cellulose, Amylose Lipids Formed from fatty acids Mainly non-polar (hydrophobic) compounds Functions: Triglycerides - stored energy Phospholipid bilayer – cell membranes Steroids – cholesterol, testosterone, estrogen, bile acids, Vitamin D Nucleic Acids Store, carry, and aid in the transmission of genetic information DNA & RNA - made from (chains of) nucleotides Each nucleotide has three parts: Phosphate group Nitrogen 5-carbon sugar (Ribose or Deoxyribose) Proteins Made from amino acids Seven major functions (S3CDET): Storage, Structure, Signaling, Contractile, Defensive, Enzymes and Transport

Chemistry Of Cells

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