1 of 8© Boardworks Ltd 2009 Happy 2 nd Birthday Tavis!

1 of 8 © Boardworks Ltd 2009

Happy 2nd Birthday Tavis!


Macromolecules!


You are what you eat

• These macromolecules are the main components of the cells of the body.

• Food comes from other living things that are also made up of cells.

• The digestive system makes the small building blocks of these molecules available to cells for use as energy or as materials for growth and repair.

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You are what you eat!

When food is digested its components enter the blood.

Molecules used for growth and repair become part of the body.

Those used as energy sources are lost as CO2 and H2O.

protein

glucosecarbohydrate

fat fatty acids + glycerol

amino acids


What are cells made from?

Different nutrients are incorporated into each part of a cell:

nucleus: protein

membrane: fats and carbohydrate

cytoplasm: protein and water


Different nutrients


Chemical and physical digestion


Enzymes digest food in the mouth, stomach and small intestine.

Enzymes at work

Enzymes break down large food molecules into smaller ones that can be absorbed by the blood. This is called chemical digestion.

Different types of food are broken down by different enzymes.


Enzymes of digestion


Introduction to lipids

Lipids are a diverse group of compounds that are insoluble in water but soluble in organic solvents such as ethanol.

The most common types of lipid are triglycerides (sometimes known as true fats or neutral fats), but other important lipids include waxes, steroids and cholesterol.

Like carbohydrates, lipids contain carbon, hydrogen and oxygen, but they have a high proportion of hydrogen and a lower proportion of oxygen.


Role of lipids

Lipids are stored in adipose tissue, which has several important roles, including:

The major biological role of lipids is as an energy source. Lipids provide more than twice the amount of energy as carbohydrates – about 38 kJ/g.

heat insulation – in mammals, adipose tissue underneath the skin helps reduce heat loss.

protection – adipose tissue around delicate organs such as the kidneys acts as a cushion against impacts.


The structure of triglycerides


Saturated and unsaturated


The structure of phospholipids


Introducing proteins

Proteins are a diverse group of large and complex polymer molecules, made up of long chains of amino acids.

They have a wide range of biological roles, including:

structural: proteins are the main component of body tissues, such as muscle, skin, ligaments and hair

catalytic: all enzymes are proteins, catalyzing many biochemical reactions

signalling: many hormones and receptors are proteins

immunological: all antibodies are proteins.


The general structure of amino acids

All amino acids have the same general structure: the only difference between each one is the nature of the R group. So the R group defines an amino acid.

aminogroup

carboxylic acid group

R group

The R group represents a side chain from the central “alpha” carbon atom, and can be anything from a simple hydrogen atom to a more complex ring structure.


The 20 naturally occurring amino acids


Peptide bonds and dipeptides


Polypeptides

When more amino acids are added to a dipeptide, a polypeptide chain is formed.

A protein consists of one or more polypeptide chains folded into a highly specific 3D shape.

There are up to four levels of structure in a protein: primary, secondary, tertiary and quaternary. Each of these play an important role in the overall structure and function of the protein.


Globular proteins

Globular proteins usually have a spherical shape caused by tightly folded polypeptide chains.

The chains are usually folded so that hydrophobic groups are on the inside, while the hydrophilic groups are on the outside. This makes many globular proteins soluble in water.

enzymes – such as lipase and DNA polymerase.

hormones – such as estrogen and insulin.

transport proteins – such as hemoglobin, myoglobin and those embedded in membranes.


Introducing carbohydrates

Carbohydrates are a group of substances used as both energy sources and structural materials in organisms.

All carbohydrates contain carbon, hydrogen and oxygen, with the general formula: Cx(H2O)y.

There are three main groups of carbohydrates:

monosaccharides – these are simple sugars, with the general formula (CH20)n, where n can be 3–7

disaccharides – these are “double sugars”, formed from two monosaccharides

polysaccharides – these are large molecules formed from many monosaccharides.


Glucose

The structure of glucose can be represented in different ways:

Glucose is an abundant and very important monosaccharide. It contains six carbon atoms, so it is a hexose sugar. Its general formula is C6H12O6.

Glucose is the major energy source for most cells. It is highly soluble and is the main form in which carbohydrates are transported around the body of animals.

straight chain ring ring (simplified)


Fructose and galactose

Galactose is not as soluble as glucose and has an important role in the production of glycolipids and glycoproteins.

Two other important hexose monosaccharides are fructose and galactose.

fructose galactose

Fructose is very soluble and is the main sugar in fruits and nectar. It is sweeter than glucose.


The formation of disaccharides


Disaccharides

Maltose (malt sugar) is formed from two glucose molecules joined by an alpha 1–4 glycosidic bond.

Sucrose (table sugar) is formed from glucose and fructose joined by an alpha 1–4 glycosidic bond.

Lactose (milk sugar) is formed from galactose and glucose joined by a beta 1–4 glycosidic bond.


What are polysaccharides?

Polysaccharides are polymers containing many monosaccharides linked by glycosidic bonds. Like disaccharides, polysaccharides are formed by condensation reactions.

The major polysaccharides are starch and cellulose in plants, and glycogen in animals.

Polysaccharides are mainly used as an energy store and as structural components of cells.


The structure of starch


Properties and uses of starch

Starch is the major carbohydrate storage molecule in plants.

Starch is produced from glucose made during photosynthesis. It is broken down during respiration to provide energy and is also a source of carbon for producing other molecules.

It is usually stored as intracellular starch grains in organelles called plastids.

Plastids include green chloroplasts (e.g. in leaves) and colorless amyloplasts (e.g. in potatoes).


What is cellulose?

Unlike starch, cellulose is very strong, and prevents cells from bursting when they take in excess water.

Cellulose is another polysaccharide and is the main part of plant cell walls. It is the most abundant organic polymer.

Cellulose consists of long chains of beta glucose molecules joined by beta1–4 glycosidic bonds.

The glucose chains form rope-like microfibrils, which are layered to form a network.


What is glycogen?

Animals do not store carbohydrate as starch but as glycogen.

Glycogen has a similarstructure to amylopectin, containing many alpha 1–6 glycosidic bonds that produce an even more branched structure.

Glycogen is less dense and more soluble than starch, and is broken down more rapidly. This indicates that animals have higher metabolic requirements than plants.

Glycogen is stored as small granules, particularly in muscles and liver.

1 of 8© Boardworks Ltd 2009 Happy 2 nd Birthday Tavis!

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