State the meaning of internal environment.

Identify factors affecting the internal environment.

Explain the necessity to maintain optimal internal environment.

The environment inside an organism.

Internal environment in

plant- filled with air

animal- filled with liquid (interstitial fluid)

Internal environment of a multicellular organisms consist of

interstitial fluid- fills the spaces between the cells and constantly bathes the cells and keeps the cells functioning normally.

blood plasma

Nutrient and waste substances are exchanged between the interstitial fluid and the blood plasma contained in the blood capillaries.

Factor affecting the internal environment.

Physical factors:

• Temperature

•Osmotic pressure

• Concentration of oxygen and carbon dioxide in the bloodstream

Chemical factors:

•Salt level

• Glucose level

• pH

In order for cells of the body to function optimally, the physical factors and the chemical factors within the internal environment must be maintained at a relatively constant level.

Example: Temperature

• For human, the internal environment need to be maintain around 37°C.

• At this temperature, the enzymes give the optimal enzyme activity.

• If the temperature too high, enzymes denatured- so lose ability to function.

• If the temperature too low, enzymes become inactive.

Homeostasis is a process that regulates the chemical and physical parameters in the internal environment so that the conditions are always suitable to meet the needs of cells.

3 functional components pf homeostatic control system:

a receptor- detect a change (stimuli)

a control centre- receive message from receptors and process the information

an effector- receive message from control centre and carry out the appropriate response.

A thermostat in the brain monitors the temperature of the blood.

If the thermostat detect a rise in body temperature above the set point, it sends nerve impulses directing the sweat glands to increase their production sweat.

Thus, lowering body temperature by evaporative cooling.

Negative feedback mechanism prevent small changes from becoming to large.

Other example:

1.Regulate of the blood pH which is 7.4

2.Regulate the amount of sugar in our blood so that it does not fluctuate to much from a concentration 0.1%

In plant, the need for a regulatory system is lesser because:

1.most plant cells are dead at functional maturity, and therefore, chemical reactions do not take place in these cells.

2. plant cells are not bathed in fluid but surrounded by air. Thus, oxygen and carbon dioxide can freely circulated in the intercellular space of plant.

3. plant cells have cell walls that prevent the cells from over-swelling and rupturing when excessive water gets into the cells.

Enables the organism to live in wider range of habitats.

Metabolic activities and physiological processes can still continue even though the external environment fluctuates substantially.

A stable internal environment allows enzymes to function aat an optimal rate.

predict the state of certain cells without predict the state of certain cells without a particular cellular component.a particular cellular component.

Illustrate that most cells are specialised Illustrate that most cells are specialised for the job that they perform. for the job that they perform.

The cellular components of the cell are The cellular components of the cell are completely dependent upon one another completely dependent upon one another for the cell to function at an optimum for the cell to function at an optimum level.level.

For example:For example:

•The nucleus contains information for The nucleus contains information for protein synthesis.protein synthesis.

• This information is relayed to the This information is relayed to the ribosomes, the sites of protein synthesis.ribosomes, the sites of protein synthesis.

• After the process of synthesis is After the process of synthesis is completed, it will be transported through completed, it will be transported through rough endoplasmic reticulum rough endoplasmic reticulum

The protein are enclosed in vesicles The protein are enclosed in vesicles which bud off from rough endoplasmic which bud off from rough endoplasmic reticulum as transport vesicles and reticulum as transport vesicles and transport to Golgi apparatus. transport to Golgi apparatus.

The proteins are processed, modified, The proteins are processed, modified, sorted and repackaged into new vesicles sorted and repackaged into new vesicles during their travel in the Golgi appatarus.during their travel in the Golgi appatarus.

These vesicles bud off from the Golgi These vesicles bud off from the Golgi apparatus and travel to other parts of the apparatus and travel to other parts of the cell or to plasma membrane to be cell or to plasma membrane to be released to the outside of the cell.released to the outside of the cell.

The sequence of events illustrate how The sequence of events illustrate how each cellular component carries out its each cellular component carries out its function in an orderly manner.function in an orderly manner.

The cells as a whole will not be able to The cells as a whole will not be able to function properly if any of its cellular function properly if any of its cellular components loses its ability to function components loses its ability to function normally.normally.

All the system of an organism are able All the system of an organism are able to funtion efficiently because the cellular to funtion efficiently because the cellular components of cells work together and components of cells work together and cooperate harmoniously with one cooperate harmoniously with one another.another.