Carbohydrates, lipids, and proteins

IB Topic 3.2

Pages 56-61

Introduction

Living things are composed of an array of molecules We need to classify them

Certain qualities The more common biochemically important molecules

are:

Molecule Subcomponents

Carbohydrates Monosaccharides

Lipids Glycerol & fatty acids

Proteins (polypeptides) Amino acids

Nucleic acids Nucleotides

Common biochemicals & their structure

Classified as organic or inorganicAll organic molecules contain the element

carbonHowever, not all carbon-containing

molecules are organic Example = carbon dioxide (not organic)

Some of the most important categories …

Category Subcategory Example molecule

Carbohydrates Monosaccharides Glucose, galactose, fructose

Disaccharides Maltose, lactose, sucrose

Polysaccharides Starch, glycogen, cellulose

Proteins Enzymes, antibodies

Lipids Triglycerides, phospholipids

Nucleic Acids DNA, RNA

You should learn to recognize the structures of common molecules

BUT you do not need to draw them (yea!) Wait till organic chemistry …

Open your book to page 57Look at figures 3.2, 3.3, 3.4, and 3.5 Answer question 4

Carbohydrates

Different “sizes” Monosaccharides, disaccharides, polysaccharides

All serve many functions in living organisms Contain only three elements: C, H, O

Hydrogen and oxygen in a 2:1 ratio FYI: many of the carbons in food you eat (carbs)

will be eliminated from your body in carbon dioxide that you breath out

Monosaccharide – simple sugar

Relatively small; taste sweet and soluble in water

Examples: Glucose: made by green leaves using light

energy, our bodies transport it in our blood, respiration (chemical fuel), building block for larger molecules

Galactose Fructose (found in fruits – makes them sweet)

Disaccharides

Made of 2 monosaccharide molecules Examples:

Sucrose (glucose + fructose) Maltose (glucose + glucose) Lactose (galactose + glucose)

Polysaccharides

Built from many monosaccharide molecules connected by glycosidic links

Examples Starch (polymer of glucose) Glycogen (polymer of glucose)

Stores glucose in liver and muscles Cellulose (polymer of glucose)

Component of cell walls

Lipids

Lipids occur in living things as animal fats, plant oils, phospholipids of cell membranes, and steroids

At room temperature, oils are liquid and fats are solid

Contain C, O, and H (like carbs), but proportion of oxygen is much less

Insoluble in water; hydrophobic Can be dissolved in organic solvents (alcohol)

Lipids

Fats and oils are compounds called triglycerides Formed when water is removed between fatty acids and

glycerol

Long hydrocarbon tails

The Role of Lipids

Energy storage Lipids store about twice as much chemical

energy as carbohydrates

If you eat more food than you burn, your body will store much of the excess as fat in adipose tissue

Other important roles of lipids

1. Energy storage Less oxygen atoms/more concentrated source

2. Metabolic water source3. Thermal insulation and buoyancy 4. Water proofing of hair and feathers 5. Electrical insulation

Myelin sheath

Amino Acids, peptides, and proteins

Contain nitrogen, sulphur, hydrogen, carbon and oxygen Amino group: NH2 Carboxyl group: COOH

Amino acids peptides and proteins Polypeptide and protein are used interchangeably

Once the chain is constructed, it takes a specific shape – shape matters with proteins Shape function

Amino acids

Proteins are made from 20 amino acids Also attached is an R group

Differ different chemical characteristics

Most macromolecules are polymers

Carbohydrates, lipids, and proteins are chainlike molecules called polymers Polymer is a long molecule consisting of many

similar or identical building blocks linked by covalent bonds

Monomers

Condensation and hydrolysis

Many organisms rely on food to gain the building block molecules

When animals eat, food is digested (or hydrolyzed) into the building blocks Going from polymers to monomers

These building blocks are transported to body cells and bonded together to form larger molecules

What happens when you eat?

Foods are chemically digested in your alimentary canal

Hydrolyzing enzymes are required Each reaction is called a hydrolysis and

requires a molecule of water as a reactant Think about the word hydrolysis:

Hydro = water Lyse = split

Examples of hydrolysis

Hydrolysis of a disaccharide in two …

Hydrolysis of a triglyceride lipid to …

Hydrolysis of a polypeptide to …

Condensation reactions

Are the reverse of hydrolysis Condensation reactions occur to re-form

larger biochemical molecules Water molecules are products rather than

reactants Also requires a different type of enzyme

Condensation Reaction (or Dehydration Synthesis)

The process of connecting monomers to create a polymer This process requires

energy and is aided by enzymes

Removes water molecules

One monomer provides a hydroxyl group and the other provides a hydrogen

Wrap Up

All organic molecules contain the element _________ Carbohydrates exist as _______, _______, & _______ The smallest carbohydrates are ___________ The subcomponents of other biochemically important

organic molecules are: _____________, which make up proteins _____________, which make up lipids (fats and oils) _____________, which make up nucleic acids (DNA and RNA)

Subcomponents are bonded together by ___________ Larger molecules are split by ____________ Although carbohydrates and lipids are used for energy

storage …

Homework

Due Friday#4-7 page 61