Animal survival Sub topic (a) The need for food

Why is food needed by animals? Cell Growth Cell division Synthesis of new chemicals e.g proteins Movement Repair of damaged cells

Food Groups Type of food Use CarbohydrateProvides energy ProteinNeeded for growth and repair FatsProvides energy and insulation Vitamins/mineralsNeeded for enzyme action

Simple Carbohydrates CREDIT Basic units are simple sugars e.g. glucose Made up of the elements Carbon, hydrogen and oxygen Simple sugars are usually represented as Glucose molecule

Complex Carbohydrates CREDIT Many simple sugars joined together in chains can form more complex carbohydrates e.g. Starch is a long chain of glucose molecules joined together etc

Proteins CREDIT Basic units are amino acids Made up of the elements Carbon, Hydrogen, Oxygen and Nitrogen. Proteins are usually represented as chains of different molecules of amino acids etc Different amino acids

Fats CREDIT Basic unit is one glycerol molecule with 3 fatty acids joined to it Made up of the elements Carbon, Hydrogen, Oxygen Usually represented as the diagram opposite Glycerol 3 fatty acids Fat molecule

Teeth Teeth are used to mechanically breakdown our food into smaller pieces There are four types of teeth Incisors – cutting and biting food Canines – piercing, holding and tearing Premolars – crushing and grinding Molars – crushing and grinding

Animals Carnivores – eat other animals e.g. dogs or cats Herbivores – eat plants e.g. sheep or rabbits Omnivores – eat plants and animals e.g. humans

Incisor Used for biting Canine Used for holding & piercing prey Premolar Used for crushing bones Molar Used for crushing bones Carnivore e.g. dog – eats animals Carnassial teeth Used for slicing and tearing

Herbivore e.g. sheep - eats plants Hard Pad Incisor Used for biting Gap –no canines present Premolar Used for crushing & grinding Molar Used for crushing & grinding

Premolar For crushing food Molar For crushing food Incisor Used for biting Canine Used for biting and tearing food Omnivore e.g. humans – eats plants and animals

Why do we have to digest food? Most of the food we eat consists of complex forms of carbohydrate, protein and fat. We have to breakdown the molecules into their simple basic units into small molecules that can be absorbed through the lining of the small intestine and into the blood We use digestive enzymes to chemically breakdown our food.

Digestion of Carbohydrates Starch Individual glucose molecules

Digestion of Protein Protein Peptide Amino acids

Digestion of Fat Fat molecule Individual Glycerol + 3 Fatty acids

Digestion allows us to breakdown food into its simple sub units. The simple subunits are soluble which allows them to diffuse through the small intestine wall into the bloodstream. The definition of digestion is as follows: Digestion is the breakdown of food from large insoluble molecules to small soluble molecules. Digestion CREDIT

Absorption CREDIT Lining of small intestine starch fatty acids glycerol protein amino acids glucose blood fat

The Alimentary Canal Also referred to as the digestive system. Consists of a muscular tube which runs from the mouth to the anus. Food is broken down (digested) by this system to small soluble molecules and then this food is absorbed into the bloodstream.

1 mouth 2 salivary glands 3 gall bladder 4 liver 5 pancreas 6 small intestine 7 oesophagus 8 stomach 9 large intestine 10 rectum 11 anus

Digestive juices CREDIT Digestive juiceSite of production saliva salivary glands gastric juice stomach lining pancreatic juice pancreas bile liver intestinal juice lining of small intestine

Peristalsis CREDIT Food passes along the alimentary canal by a process called peristalsis. The muscles behind the food contract The muscles in front of the food relax This wave-like motion of contracting and relaxing of muscles allows the food to pass through the oesophagus, the small intestine and the large intestine.

Peristalsis in stomach CREDIT Muscles in the stomach wall churn the food and digestive juices together This mixing helps the digestive juices to start the chemical breakdown of food e.g. pepsin begins to digest protein into peptides

Digestive enzymes As the food passes through the alimentary canal enzymes are produced to digest the food Different enzyme groups breakdown fats, proteins and carbohydrates fats lipase fatty acids + glycerol proteins protease amino acids carbohydrates amylase glucose

Digestive enzymes CREDIT Enzyme group Enzyme Where produced Substrate Product amylasesalivary amylase salivary glands starchmaltose proteasepepsinstomachproteinpeptides lipase pancreasfatsfatty acids + glycerol

Small Intestine Once the food leaves the stomach it passes into the small intestine where digestion is completed. The main function of the small intestine is to absorb this digested food into the blood The small intestine has a very large surface area because It is very long The inner surface is folded and has finger like villi The lining is very thin allowing rapid diffusion

Structure of the small intestine

The small intestine villi

Structure of a villus CREDIT The thin lining of the villus allows rapid diffusion of glucose, amino acids and fatty acids and glycerol The blood capillary absorbs and transports both glucose and amino acids The lacteal absorbs and transports the fatty acids and glycerol Villi provide a large surface area for absorption of the end products of digestion 1 2 3

Villus animation CREDIT G G G G AA FA glycerol

Large intestine Undigested food (mainly fibre from the cellulose cell walls of plants) and a lot of water is passed into the large intestine The large intestine absorbs much of this water The water passes through the lining of the large intestine into the blood The semi solid waste called faeces is stored in the rectum and eliminated through the anus