Chapter 2 : Cell Structure & Cell Organisation

INTERNAL ENVIRONMENT

INTERNAL ENVIRONMENT

environment inside the organisms, i.e. fluid surrounding the cells

External Environment

physical place where it lives in and where it interacts with other

organisms

Tissue Fluid / Interstitial Fluid

• Fluid surrounding the cells

Tissue Fluid / Interstitial Fluid

• Fills the narrow spaces between the cells

• bathes the cells• keeps the cells

functioning normally

Formation of interstitial fluid

FACTORS AFFECTING INTERNAL ENVIRONMENT

Temperature

Osmotic pressure

pH value

Glucose level 37⁰C

≈ 7.4

90mg per 100 cm-3

Maintenance Optimal Temperature

Temperature is maintained at 37ºC

Too High DENATURE

Too LowINACTIVE

Maintenance of Optimal pH

pH of human tissue fluid is 7.4

If the pH changes, enzymes will be denatured and lose the ability to function

HOMEOSTASIS

HOMEOSTASIS

Maintenance of a steady state in the internal environment

The steady state is the optimum level for all body functions

Organ systems interact with one another to maintain a stable internal environment

HOMEOSTASIS MAINTAINED :

BLOOD PH TEMPERATURE

OSMOTIC PRESSURE BLOOD GLUCOSE

integumentary, nervous and endocrine system nervous & endocrine system

endocrine system, kidney & ADH hormone endocrine system, glucagon & insulin

normal condition normal condition

Receptor detects stimulus & start corrective mechanism

Receptor detects stimulus & start corrective mechanism

Stimulus (above normal)

Stimulus (below normal)

Negative feedback

Negative feedback

Glucose Level

Osmoregulation

pH

• Above / below pH 7.4• Involves the following systems:

a) Respiratory systemb) Excretory systemc) Circulatory system

• Maintain optimal pH by monitoring the concentrations of ions & salts in the blood

THE UNIQUENESS OF THE CELL

Organelle missing Predicted state of the cell

Nucleus •All cell activities stop•Cell does not live long•The cell dies

Mitochondrion • No energy for cell activities• The cell dies

Ribosome • Cell is unable to synthesise enzymes (proteins)• Cell growth stops• Cell is unable to repair itself• Finally, the cell dies

Endoplasmic reticulum (RER & SER)

• Less enzymes produced• Synthesis and transport of proteins & glycerol stop

Golgi Body • Proteins produced become defective• Cell is unable to produce certain types of proteins