An element is a substance that cannot be broken into a simpler substance
E.g.: Iron (Fe)
An atom is the smallest part of a chemical element that can take part in a chemical reaction
A molecule consists of two or more atoms held together by chemical bonds
E.g; H2, CO2
A compound consists of two or more elements chemically bonded together in fixed proportions
E.g: NaCl (Sodium Chloride)- two different elements in 1:1 ratio
A reactant is a substance used up in a chemical reaction
A product is a substance formed in chemical reaction
E.g: C6H12O6 + 6O2 -----> 6CO2 + 6CO2
(Reactant) (Product)
All compounds are molecules, but not all molecules are compounds
E.g: CO2 can be both a compound and a molecule because CO2 has two and more atoms held together by chemical bonds; also, it consists of two or more elements chemically bonded together in fixed proportions.
Electron configuration
Electrons are arranged in shells or energy levels surrounding the nucleus. There is a limit t the numbers of electrons in each shell: 2,8,8
Isotope
An atom has the same numbers of protons and electrons but the different number of neutrons.
The body fights to keep its internal environment when the external environment is acting to change it. This process is call homeostasis
The internal environment is anything having to do inside the body
The external environment is everything around you that can influence you.
Homeostasis is important for our health because our bodies work under certain conditions. If we cannot keep it certain, we can get very sick or even die. So, it is important for all the living organisms including animals, plants, fungi and bacteria.
Body temperature
Too high – proteins/ enzymes (one type of protein) denature change shape/ no longer function. Ps: enzymes are required for every body reaction.
Body temperature
Too low – sweating excessively – loss of body fluids – low blood volume – low blood pressure (in the capillaries) – water leaving capillaries water/ oxygen and glucose – no respiration – shock
High body water
High body pressure – damage walls of blood vessels – hemorrhage/ stroke
High body pressure – strain your heart has to wrote harder to pump blood around the body.
High blood sugar
– water moves into blood by osmosis which is movement of water or other solvent through a cell membrane from a region of low solute concentration to a region of high solute concentration.
Low blood sugar
– less glucose available for respiration
– cells won’t generate energy/ can’t function
Endocrine system
– a set of glands/ organs in the body that secretes hormones in the bloodstream
– to maintain homeostasis
Exocrine gland
– secretes a substance into a tubular structure/ not into the bloodstream
e.g.: sweat gland, salivary blood
Pituitary gland
-secretes hormones that control the secretion of other glands such as the adrenal gland and the thyroid gland
Adrenal gland
-secretes adrenaline into the bloodstream
Thyroid gland
-secretes thyroid hormone (thyroxine)
Adrenaline travels through the bloodstream and controls the function of several organs
-eye -lungs -blood vessels
-heart -muscles -liver
Adrenaline can be secreted very quickly in response to an external stimulus. This is because its secretion is regulated by neurons which travel between the brain and the adrenal gland
Adrenaline is secreted from specialised neurons call chromaffin cells
Electrical impulse is designed to receive messages from other cells and external stimulate.
E.g. : pain, heat, touch etc
Neurons are designed to conduct electrical impulses very quickly. This ensures the secretion of adrenaline happens quickly after the stimulus. They have a very specialised cell structure which facilitates the rapid conduction of electrical impulses
Cell body carries out all normal metabolic functions of cell
Axon terminal sends a message to another neuron
-cause a muscle to contact and secrete
Dendrites is stimulated by environment changes or the activities of other cells
