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Learning objectives

• Functions of mitochondria.

• Locomotion of cells

Extraction of energy from nutrients

• Energy is extracted from foodstuffs.

• Oxygen reacts with carbohydrates, fats and proteins under the influence of enzymes.

• All these reactions occur in mitochondria.

• ATP is formed.

Functional characteristics of ATP

• ATP is a nucleotide composed of:-

1-The nitrogenous base adenine

2-The pentose sugar ribose

3-Three phosphate radicals

Each high energy bonds contains about 12,000 calories of energy per mole of ATP.

When ATP releases its energy, a phosphoric acid radical is split away and ADP is formed.

ATP is called Energy currency of cell as it can be spent and remade continually.

Chemical process in the formation of ATP

• Glycolysis

• Citric acid cycle

• The overall process of formation of ATP is called Chemiosmotic mechanism.

Uses of ATP for cellular function

• ATP is used for 3 major categories of functions:-

1-Transport of substances through multiple membranes of the cell

2-Synthesis of chemical compounds

3-Mechanical work

Locomotion of cells

• 2 types of movements are present:-

1- Ameboid movement

2- Ciliary movement

Types of cells that exhibit ameboidmovement

• WBC

• Fibroblasts

• Germinal cells of skin

• Movement of embryonic cells

Control of ameboid movement

• Chemotaxis- Initiates movement

• Chemotactic substances

• Positive chemotaxis

• Negative chemotaxis

Ciliary movements

• Whiplike movement of cilia

• Occurs in two places in humans:-

1-Respiratory airways

2-Movement of ovum from ovary to uterus

• Cilium has the appearance of a sharp pointed straight or curved hair that projects 2-4 micrometers from the surface of cell.

• Almost 200 cilia on the surface of each epithelial cell inside respiratory passages.

• Cilium is covered by an outcropping of CM.

• It is supported by 11 microtubules – 9 double tubules located around the periphery of the cilium, and 2 single tubules down in the center.

• Each cilium is an outgrowth of a structure that lies immediately beneath the CM, called the basal body of the cilium.

• Flagellum of a sperm is similar to a cilium.

• Difference is that flagellum is much longer and moves in quasi-sinusoidal waves .

• Cilium moves forward with a sudden , rapid whiplike stroke 10-20 times per second, bending sharply where it projects from the surface of the cell.

• Then it moves backwards slowly to its initial position.

• The fluid is continually propelled in direction of fast of fast forward stroke.

Mechanism of ciliary movement

1-Nine double tubules and two single tubules are linked by complex of protein cross linkages to one another.

This whole complex is called axoneme.

2-If membrane is removed and other elements of cilium besides axoneme is destroyed, the cilium can still beat under appropriate conditions.

3-After destruction beating depends on:-

-Availability of ATP

-Appropriate ionic conditions esp Mg and Ca

4-During forward movement, the double tubules on the front edge of the cilium slide outwards towards the tip of cilium and those on back edge remain in place.

5-Multiple protein arms composed of protein Dynein which has ATPase enzymatic activity, project from each double tubule toward an adjacent double tubule.