Biology

Maintaining a balance
Pp1
Key Ideas- page 7
If a variably deviates too far from the normal steady state, death can occur.
All metabolic reactions in living organisms are catalyzed by enzymes
Enzymes are protein molecules, each with an active site and being specific in its action.
The rate of reaction of an enzyme depends on a number of different factors.
Key Ideas- page 12
Tissue fluid and plasma form the internal environment of body cells.
This internal environment is relatively stable
Two-way exchange occurs between extracellular and intracellular fluids.
Homeostasis is the condition of a relatively stable internal environment.
Homeostasis can be disrupted by agents such as disease and trauma.
Most body systems play various roles in homeostasis.
Maintaining homeostasis is a two-stage process; sensors detect change of a variable from the desired value and effectors act to counteract the change detected. Such systems are called negative feedback systems.
Key Ideas- page 16
The nervous control system is made up of the central nervous system and the peripheral nervous system.
Nerve cells or neurons are the basic structure of nervous tissue.
Neurons transmit nerve impulses.
In the nervous system, the passage of a nerve impulse along one neuron involves electrical changes, while the transmission from cell to cell involves diffusion of chemical substances.
Special glands, called endocrine glands, produce chemicals called hormones which are secreted directly into the blood stream.
Key Ideas- page 35
Organisms have structural, behavioral and physiological adaptations that equip them to survive in their habitat.
Extremes of environmental temperature can overwhelm the homeostatic mechanisms for body temperature control in an organism.
Some animals go into torpor/ hibernate to survive sub-zero temperatures.
There is less temperature variation in aquatic environments then in terrestrial environments.
If the water in cells freezes, the cells are killed.
Animals that remain at cold latitudes during winter have adaptations that prevent cells from freezing.
Key ideas- page 38
Plants maintain their temperature within an optimal range.
Many plant characteristics facilitate heat loss, others minimize heat uptake
Ice formation between plant cells facilitates plant survival in sub-zero temperatures.

Pp2
Key Ideas- page 46
In mammals, blood is an important transporting tissue
The blood of mammals is made up of several different components
Donated blood may be used as whole blood or may be separated into various components for specialized use.
Key Ideas- page 70
The composition of blood varies as it circulates the body
Fluid and other materials move through the capillary walls into the adjacent tissues
The liver plays a major role in the storage and conversion of organic compounds.
Carbon dioxide; a waste product of metabolism, must be removed from cells for the maintenance of an appropriate pH in tissues.
Nitrogenous waste is excreted as ammonia, uric acid and urea.
Lymphatic vessels return leaked tissue fluid to the blood circulating system.
The shortage of donor blood has stimulated research into the development of artificial or synthetic blood.
Key Ideas- page 63
Oxygen is essential for the production of high levels of ATP required for the metabolic functions of individuals.
As the blood moves around the body, gases move in and out of the blood from regions of high concentration to regions of low concentration.
The extent of the association of haemoglobin with oxygen for transport around the bloodstream of affected by a number of factors.
Key Ideas- page 54 Arteries are thick-walled vessels that transport blood away from the heart.
Veins are relatively thin-walled vessels that transport blood to the heart.
The walls or arteries and veins each have a three-layer structure.
Arteries and veins are connected by networks of very thin-walled vessels called