3A_Biomolecules

//Date: 25/3/10//

__HOMEOSTASIS__

__Definition:__ Maintaining equilibrium in a living system, despite changes in external environment.

__Processes which maintain equilibrium:__ - Active transport
 * - Osmosis:** Water molecules move from a region of higher water potential to a region of lower water potential across a semi-permeable membrane, to maintain equilibrium.
 * - Diffusion:** Net movement of molecules from a region of higher concentration to a region of lower concentration across a semi-permeable membrane, to maintain equilibrium.

//Living organisms obtain and process matter and energy// - Plants photosynthesize to make food, by using water and sunlight.

//Energy is stored in the organization of matter// - In cells, energy is produced in mitochondria in the form of ATP (Adenosine triphosphate), using glucose. - In living systems, energy is stored in fats.

//Living things use matter and energy to build and maintain body structures - Mammals produce milk, which contain calcium to build bones. It also contains protein, which help to build muscles.

////Communities of organisms depend on the cycling of matter and the flow of energy// // - Because energy cannot be destroyed, there is a continuous flow of energy from one system to another system. - There is the water cycle and the carbon cycle, which cycle matter and energy.

1. Are we just chemicals?

2. Are we what we eat?//

//3. Why is the carbon molecule suitable for life as we know it?// As carbon has a valency of four, it has 4 electrons free to bond with other atoms, forming macromolecules, with different properties and functions. Carbon is also able to have a double bond with another atom, making it possible to form fats.

//4. Why is the chemistry of water suitable for life?// // It can exist in three states. At 4 degrees celsius and below, instead of contracting, water expands.

This balance is achieved through various biogeochemical cycles and the processes of photosynthesis and cellular respiration//