1. THE HUMAN BODY Part A: Digestion and Nutrition

2. V.C.E. BIOLOGY UNIT 1 Autotrophs are producers

3. Requirements of Living Things Energy – all life requires a source of energy Oxygen – organisms require oxygen for cellular respiration Water – required for growth, maintenance and repair Nutrients – required for growth, maintenance and repair Waste removal – many harmful by-products result from the cells chemical processes Reproduction – organisms need to replace themselves

4. Autotrophs and Heterotrophs Autotrophs are organisms that are able to make their own organic molecules they need from simple inorganic molecules – they are self feeders. Heterotrophs are unable to synthesise their own organic molecules, they must eat other living things.

5. Autotrophs Most autotrophs are plants that create organic molecules (glucose) through a process known as photosynthesis which occurs in specialised cell organelles called chloroplasts. Some bacteria are able to produce organic molecules from inorganic molecules in a process called chemosynthesis.

6. Photosynthesis Plants make the organic material, glucose, from simple inorganic molecules, carbon dioxide and water, in the presence of light energy and chlorophyll. This allows for the conversion of light energy into stored chemical energy for use by the plant. 6CO 2 + 12H 2 0  C 6 H 12 O 6 + 6H 2 0 + 6O 2 chlorophyll Light energy

7. Photosynthesis/Cellular Respiration Autotrophs use energy twenty four hours a day – using oxygen to break down glucose to release the energy and produce water and carbon dioxide. By day this is balanced by the photosynthesise that occurs – using carbon dioxide and water to produce glucose and oxygen. At low light levels the plant must take up oxygen for cellular respiration, but at higher light levels the plant produces excess oxygen through photosynthesis.

8. Structural Adaptations Plants have evolved many adaptations to collect light more efficiently. Obviously leaves at the end of stems and branches allows the plant to collect more light than merely growing along the ground. Dorsiventral leaves – one side has all the chlorophyll containing cells the other has none or few. Isobilateral leaves – hang vertically reducing heat absorption, but chlorophyll is present on both sides of the leaf

9. Other Nutritional Requirements Plants need other nutrients also. Just like animals they need to be able to make lipid based membranes and nitrogen based proteins and hormones. Nitrogen is abundant on Earth, but mostly found in the atmosphere in a form that organisms can’t use. Many plants have formed symbiotic relationships with bacteria that live in the roots and convert the nitrogen into a useable form.

10. Other Nutritional Requirements Mineral Salts. Plants need elements such as nitrogen, phosphorous, potassium, sulfur, calcium and magnesium in large quantities for making proteins and many cell processes. These are called the macronutrients. They also need micronutrients such as iron, boron and zinc in small amounts. These are drawn up from the soil by the roots

11. V.C.E. BIOLOGY UNIT 1 Heterotrophs are consumers

12. Nutritional Requirements Carbohydrates – an immediate source of energy and can be used to store energy as glycogen. Lipids – also an energy source and store (adipose cells) important for membranes, hormones and vitamins. Proteins – cells need amino acids to make proteins. There are nine essential amino acids that must be in an animals diet. Vitamins – vitamins are a diverse group of organic compounds which are used in a broad range of chemical processes in the cell. Minerals – these are the mineral salts or metal salts that are important for making new cells, particularly blood cells and to aid other processes.

13. Digestion Food must be digested by heterotrophs. Chemical digestion is the use of chemicals called enzymes to break large molecules into smaller ones for absorption into the blood vessels Physical digestion is the use of teeth, specialised bones, tongue and muscles to mechanically break down large chunks of food into smaller chunks – increasing the surface area to volume ration for the enzymes to work.

14. Digestive Systems The simplest heterotrophs absorb their nutrients from their surroundings by diffusion. As organisms become more complex they need to eat food, digest it and send the chemicals around the body for each cell to use. Therefore systems of specialised organs evolved. Each system suits the organisms diet. Systems contain features for mechanical digestion, a one way flow, sequential release of enzymes, improved surface areas for uptake of nutrients and efficient excretion of wastes.

15. Mammalian Digestive Systems There is much variation between mammals, however, they all contain: A mouth cavity (may have teeth and tongue) – initial physical and chemical digestion (uptake of glucose) Oesphagus – physical digestion Stomach – physical digestion and chemical digestion (break down of fats and proteins) Small Intestine (villi and microvilli) – chemical digestion – major site of absorption of lipids, proteins and carbohydrates Large Intestine – final chemical digestion (salts absorbed) and uptake of water Rectum – excretes waste material.

16. Energy Storage All animals will feast when food is plentiful and store the excess energy for times of famine as this is a natural cycle. Humans have broken free of this cycle and need to be sure that they do not regularly eat more energy than they are using or they will store excess energy – which may cause medical concerns. Animals store excess energy as fat because it is lighter than carbohydrates (50%), contains more ATP (25%) and can therefore yield more energy for the animal. Excess energy is initially stored in the liver and high energy use areas as glycogen (cho), but if there is more excess then lipids are deposited in adipose tissue around organs and about the body.