BIO503 Final Term Past Papers by Qamar

BIO 503 Final Term Subjective

Q1. State fluid mosaic model? 2 Marks

The fluid mosaic model describes the structure of the plasma membrane as a mosaic of components —including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character.

Q2. Saxitoxin? 2 Marks

Saxitoxin is produced by a dinoflagellate also known as "red tide". It blocks voltage-dependent sodium channels.

Q3. Radiation Protection? 2 Marks

Radiation protection, sometimes known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as " The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this".

Q4. Who discovered DNA? And name of scientist discovered the structure of DNA? 2 Marks

In 1953 Watson and Crick determined the structure of DNA.

Q5. Chromatography? 3 Marks

• Analytical methods used to separate molecules.
• It involves a mobile and a stationary phase.
• Mobile phase is what the material to be separated is dissolved in.
• Stationary phase is a porous solid matrix which the mobile phase surrounds.
• Separation occurs because of the differing chemistries each molecule has with both the mobile and stationary phase.

Q6. What are hormones? 3 Marks

Hormones are long-distance chemical signals released by endocrine cells (like the cells of your pituitary gland). They control specific physiological processes, such as growth, development, metabolism, and reproduction. While some hormones are steroid-based, others are proteins. These protein-based hormones are commonly called peptide hormones. For example, insulin is an important peptide hormone that helps regulate blood glucose levels.

Q7. Ionizing radiation? 3 Marks

Ionizing radiation – e.g., radiation emissions from uranium ore, and high frequency waves in the electromagnetic spectrum such as x-rays.

Q8. Name 5 methods to reduce friction? 5 Marks

Friction can be reduced by making the surface smooth by polishing. The friction is due to the roughness of surface. If we make the surfaces smooth by polishing, then friction will be reduced. For example, a slide in the park is polished to make its surface smooth and reduce friction. Due to reduced friction of a polished, smooth slide, children can slide down easily. Friction can be reduced by applying lubricants (like oil or grease) to the rubbing surface. When oil or grease is applied between the moving parts of a machine, a thin layer of oil or grease is formed between the two rubbing surfaces. This layer of oil separates the two rubbing surfaces a little bit due to which their interlocking is reduced to a large extent. This friction is reduced and movement becomes smooth. When oil or grease is applied to the moving parts of a machine, then their surfaces do not rub directly against each other, they rub through a layer of oil and grease. The substance which reduces friction are called lubricants. Friction can be reduced by using wheels to move objects. It is quite difficult to move a heavy suitcase by dragging it on the ground because the sliding friction between the heavy suitcase and the ground is very large. If this heavy suitcase is fitted with small wheels, then it can be pulled very easily. Because when we attach wheels then sliding friction is converted into rolling friction. And rolling friction between the wheels of suitcase and ground is much less. Friction can be reduced by using ball bearing between the moving parts of machine. Ball bearing is a device which consists of a ring of small metal balls. The small metal balls of a ball bearing can roll freely. They are designed to make the moving parts of a machine to roll over each other rather than slide. The ball bearing is introduced between the two surfaces which have to rotate over each other. The axle is fixed on the inner side of a ball bearing and wheel is fixed to the outer side of the ball bearing the ball bearing. They reduce friction by making the two surfaces (axle and wheel) to roll over each other.

Q9. Explain Na+/K+ ATPase? 5 Marks

The Na+/K+ ATPase

The cytosol of animal cells contains a concentration of potassium ions (K+) as much as 20 times higher than that in the extracellular fluid. Conversely, the extracellular fluid contains a concentration of sodium ions (Na+) as much as 10 times greater than that within the cell. These concentration gradients are established by the active transport of both ions. And, in fact, the same transporter, called the Na+/K+ ATPase, does both jobs. It uses the energy from the hydrolysis of ATP to Actively transport 3 Na+ ions out of the cell. For each 2 K+ ions pumped into the cell. This accomplishes several vital functions: It helps establish a net charge across the plasma membrane with the interior of the cell being negatively charged with respect to the exterior. This resting potential prepares nerve and muscle cells for the propagation of action potentials leading to nerve impulses and muscle contraction. The accumulation of sodium ions outside of the cell draws water out of the cell and thus enables it to maintain osmotic balance (otherwise it would swell and burst from the inward diffusion of water). The gradient of sodium ions is harnessed to provide the energy to run several types of indirect pumps. The crucial roles of the Na+/K+ ATPase are reflected in the fact that almost one third of all the energy generated by the mitochondria in animal cells is used just to run this pump.