Chemistry and the body

Chemistry and the body

What chemicals are found in the body?What chemical reactions happen in the

body- and why?Where do the chemicals come from?

Chemical bonds can be formed or broken

1. Synthesis: A + B AB (also known as condensation) glucose + galactose lactose (+ water)

1. Decomposition: AB A + BStarch plus water maltose

3. Exchange: AB +CD AC + BDHCl + NaOH NaCl + H2O

Why do chemical reactions happen inside the body?

• To build large molecules (anabolism)• To break down molecules and use the

products in other reactions (catabolism)• To store energy• To release energy to use for cellular work• Metabolism: sum of all these reactions

Chemical reactions don’t just happen

• In the body, most reactions require biological• catalysts (enzymes)

• Enzymes make the reaction happen more quickly

• Catalysts do NOT make reactions occur that • would not happen otherwise- the reactions• just occur more quickly

• Enzymes themselves are not changed or used• up in the reactions

What chemicals are important for living things?

Organic- contain carbon and hydrogen

Inorganic- everything else

Water- essential to all life on Earth

• Solvent properties (hydrogen bonds)

• Can absorb and distribute heat in the body (what does “warm-blooded” really mean?)

• Transport medium

• Participates in many chemical reactions in thebody

Ionic compounds dissolve in water

Some electrolytes form acids and bases in water.These can be very damaging to tissues.Buffers minimize pH changes.

Organic molecules and macromolecules

• Carbohydrates– sugars

• Lipids– Triglycerides, phospholipids, sterols, prostaglandins

• Proteins– Amino acids

• Nucleic acids– Nucleotides– Triphosphates– See Table 2.6 for summary

Carbohydrates are made of sugars

• Monosaccharides• Disaccharides• Polysaccharides• Oligosaccharides• Primary energy

source• Can be structural

(cellulose)

Lipids are more diverse in structure and function

Triglycerides: energy storage and insulation

Phospholipids: cell membranes“phospholipid bilayer”

Steroids:Building blocks for certain hormonesAlso support cell membranes

Proteins• Made up of amino acids (any combination of• 20 different amino acids)

• Extremely diverse in size and structure

• Functions:• structure• cell receptors• many specialized functions (hemoglobin,

antibodies)• enzymes• Protein structure is complex

Form follows function• Proteins can change

their shape and revert to their original shape

• Proteins can be “denatured”: change in temperature or pH can denature (destroy) a protein

• Protein function can be blocked

How do we know what a protein will look like?

• Amino acid sequence• One or more polypeptide chains• Amino acid sequence is determined by DNA

sequence (gene)

Nucleic acids

• Comprised of nucleotides

• DNA, RNA• DNA stores genetic

information in the nucleus

• RNA “uses” genetic information in DNA to make polypeptides

RNA DNA

Comparison of DNA and RNAFeature DNA RNA

Nucleotides A, C, G, T A, C, G, U

Sugars deoxyribose ribose

Number of strands of nucleotides

Two (double helix) One (structure varies)

Function Stores genetic information Protein synthesis

Location in cell Nucleus (formed there and stays there)

Formed in nucleus, functions in cytoplasm

High-energy compounds

• ATP (adenosine triphosphate)

• Provides energy for chemical reactions in cells

How do these molecules “behave” in the watery inside of a cell?

• Ionic compounds dissolve into ions• Polar molecules react with water but don’t fall

apart (“hydrophilic”)• Nonpolar molecules separate from water

(“hydrophobic”)• Cell membranes are made of phospholipids• Implications?

Summary• Metabolism is the series of chemical

reactions by which cells capture, store and use energy to perform body functions and maintain homeostasis.

• Cells utilize/produce many essential substances:water, oxygen, carbon dioxide, salts, ions, organic molecules, and macromolecules.

• That’s why we eat food.