notes for leaving cert biology - food
Note by eimearkelly3, updated more than 1 year ago
Created by eimearkelly3 over 10 years ago

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Nutrition is the way in which an organism obtains its food

A nutrient is any substance that is important in sustaining life (the major nutrients are proteins, carbohydrates, lipids, vitamins, minerals, and water). They are chemical substances present in food that are use by organisms to maintain metabolism and the continuity of life.

Nutrients are used as a source of energy to make chemicals needed for cell or metabolic reactions as the raw materials for the growth and repair of stuructures in an organism.


Common elements Carbon Hydrogen Oxygen Nitrogen Phosphorous Sulfur

Dissolved salts Sodium Magnesium Chlorine Potassium Calcium

Trace elements Iron Copper Zinc

*with the exception of C, H, O, the above elements are referred to as minerals

Compounds made from carbon are said to be organic compounds

Biomolecules / biochemicals are substances made by living things that have important metabolic roles. They are organic compounds that contain carbon, hydrogen, and other elements.

Carbohydrates Lipids (fats and oils) Proteins Vitamins

ELEMENTS: C,H,OFORMULA:   Cx(H2O)y (where x and y are the same number i.e. there is always twice as much hydrogen as oxygen in a carbohydrate e.g. C6H12O6 (glucose)SOURCES: bread, rice, potatoes, pasta

monosaccharides disaccharides polysaccharides

MONOSACCHARIDESSingle sugar units (ring of carbon atoms)Sweet & soluble in waterEnergy providers5 carbon sugars- pentoses (e.g.ribose, deoxyribose)6 carbon sugars - hexoses (e.g. glucose --> main molecule from which organisms get their energy - fruit,sweets), fructose (sweeter than glucose - fruit) and galactose.

DISACCHARIDESTwo monosaccharides joined togetherSweet & soluble in waterEnergy providerse.g. sucrose (table sugar - glucose + fructose)       maltose (found in germinating seeds - glucose + glucose)       lactose (found in milk - glucose + galactose)

POLYSACCHARIDESMany monosaccharides linked togetherNot sweet & insoluble in waterFood storage / structural supporte.g. starch (amylose)--> carbohydrate stored by plants                                    composed of branched and unbranched chains of glucose molecules                                    food storage in plants                                    easily digested (glucose molecules arranged in a line)                                    rice, potatoes, flour, bread, pasta       cellulose --> structural carbohydrate in plants (cell wall)                          composed of long chains of glucose molecules bonded together                          more cross bonding between chains than starch as it is not readily broken                                     down it acts as a source of fibre in animal diets.   chitin --> strong polysaccharide in the exoskeleton of arthropods (crabs, beetles, lobsters, and                  the cell walls of fungi                 offers structural support       glycogen--> polysaccharide stored by animals                         many glucose molecules, more branched than starch                         stored predominantly in muscle and liver cells

ELEMENTS: C,H,ORATIO: No set ratio (very little oxygen)e.g. C200H4O11

FAT: Lipids that are solid at room temperature (20 degrees)OIL: Lipids that are liquid at room temperature (20 degrees)

Triglyceride: A lipid with 3 fatty acids linked to a glycerol, acts as the fat and oil energy reserves of plants and animals. (smallest lipid)

Phospholipid: Fat-like substances where one of the fatty acids is replaced by a phosphate group or has a phosphate group attached to it. (major component of cell membranes).

SOURCES: meat, milk, butter, chesse, plant oils, margarine.

STRUCTURAL ROLE phospholipids --> cell membranes under the skin --> heat insulation and energy store (adipose tissue) protective layer around the internal organs e.g. kidneys protective wax cuticle on the outside of plants e.g. holly

METABOLIC ROLE energy storage --> contains more than 2x energy for the same mass of carbohydrate or protein. energy source  --> realeased during respiration storage of fat soluble vitamins e.g. vitamin D some lipids function as hormones e.g. oestrogen

ELEMENTS: C, H, O, N (P/S sometimes)COMPOSED OF: Amino acids, linked in chains folds and branches. The bond between amino acids is called a peptide bond.

A peptide has a small number of amino acidsA polypeptide has more than 20 amino acidsA protein is a long polypeptide (at least 200 amino acids)

Each protein has a specific 3 dimensional, functional shape.


The arrangement and sequence of amino acids determines the type of protein produced.Fibrous proteinsLong chains in parellel form (little/ no folding) strong and tough e.g. collagen, myosin, keratin.Globular proteinsTightly folded amino acid chains giving a spherical shape e.g. enzymes

Protein synthesis takes place within the ribosomes of the cell.

Structural role Keratin --> protein found in hair, finger nails, toenails, and the outer dead layer of skin. Myosin --> major protein involved in the contraction of skeletal and cardiac muscle. Collagen --> Major protein in cnonective tissue (elasticity of skin).

Metabolic role Many proteins function as enzymes (biological catalysts). Many proteins act as hormones, they are chemical messengers in th blood that help regulate many metabolic activities.

Vitamins are organic compunds needed in small quantities in the diet to ensure a good standard of health. They are complex, carbon-based substances that the body cannot make.

VITAMIN C (WATER SOLUBLE --> ASCORBIC ACID) Common sources: vegetables, fruit (espcially citrus fruits such as ornages and lemons) Required by the body to assist with the absorption of iron from the gut and also to maintain strong connective tissue and for the growth and maintenance of bones and teeth. Deficiency of vitamin C can result in scurvy. Symptoms of scurvy include: internal bleeding, easy bruising, bleeding gums, loose teeth, poor healing.

VITAMIN D (FAT SOLUBLE --> CALCIFEROL) Good sources: milk, eggs, liver, fish liver oils, produced by the skin when exposed to U.V. light Required by the body for the absorption of calcium and phosphorous from the gut and also to ensure healthy bone formation and maintenance. Deficiency of Vitamin D can result in a disease called rickets (in children) and osteomalacia (in adults) Symptoms include: late teething and walking, deformed legs and arms, and weak bones.

ENERGY TRANSFER REACTIONSAll the reactions in an organism can be referred to as its matabolism. Metabolism can be divided into anabolism, and catabolism.ANABOLISMSmaller molecules are converted into larger ones (requires energy) e.g. protein synthesis/ photosynthesisCATABOLISMComplex molecules are broken down into simpler ones (release of energy) e.g. digestion/respiration.

Minerals are soluble inorganic salts that contain elements essential for a healthy metabolism. They are neeed in minute quantities by the body to maintain a healthy body.Plants obtain their minerals by abosorbing them from soil water.Animals obtain their minerals through their diet.

Plant mineral requirementsCALCIUM --> required for the formation of the middle lamella, located between the cells to 'glue' them together.MAGNESIUM --> required for the production of chlorophyll

Animal mineral requirementsCALCIUM --> required for the healthy formation of teeth and bones.IRON --> required for the formation of haemoglobin

WATER Component of the cell's cytoplasm and also of the body's fluids. Universal solvent --> an ideal transport medium for many soluble substances Plays a role in a number of metabolic processes e.g. photosynthesis and respiration. Enables dissolved substances to move through cell membranes. Controls the shape of the cell, the red blood cells are biconcave in shape and as such is extremely efficient at carrying oxygen, its shape is determined by the correct level of water in the cell. Good absorber of heat energy. A great deal of heat is required to increase temperature. As water is a temperature-stable medium it is ideally suited for metabolism and for homeostasis. Participates in chemical reactions: Condensation reactions: where smaller molecules join to form larger molecules with the loss of a water molecule

Hydrolysis reactions: where a molecule gains water and is broken down to form smaller molecules.

Photosynthesis: where water is borken down to supply hydrogens and electronsRespiration: where water is formed as an end product.


SOURCES: Meat, fish, eggs, nuts, peas & beans, milk

Food + Experiments


Lipids (Fats+oils)


Vitamins, Minerals + Water

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