Explanation

• Prokaryotic cell membranes, such as those found in bacteria, are composed of a thin layer of phospholipids, primarily phosphatidylethanolamine and phosphatidylglycerol, and embedded proteins.
• The phospholipid bilayer forms a semi-permeable membrane that regulates the entry and exit of materials, while the proteins perform various functions such as transport, enzymatic activity, and cell signaling.

Explanation

The heart is the central organ of the blood circulatory system, responsible for pumping blood throughout the body.

It circulates oxygen, nutrients, and waste products via arteries and veins.

Explanation

The hormone that suppresses ovulation is progesterone. 

Progesterone, particularly high levels during pregnancy, prevents ovulation by inhibiting follicular development and providing negative feedback to the hypothalamus, reducing the release of gonadotropin-releasing hormone (GnRH). 

Explanation

The fish heart is a two-chambered organ (one atrium and one ventricle) that only receives deoxygenated blood from the body.

This blood is then pumped to the gills for oxygenation before circulating to the rest of the body.

Explanation

Apoptosis is a programmed and controlled process of cell death, essential for development and removing damaged cells.

It involves a series of biochemical events leading to cell shrinkage, DNA fragmentation, and eventual removal without causing inflammation.

Explanation

Pellicle is a flexible outer covering found in ciliates (like Paramecium) that provides shape and protection.

It is not as rigid as a cell wall and allows movement while maintaining structural integrity.

Explanation

An allele is an alternative form of a gene found at the same position (locus) on homologous chromosomes.

Alleles determine variations in inherited traits, such as flower color or blood type.

Explanation

As a raindrop falls:

• Initially, it accelerates due to gravity.

• As its speed increases, air resistance (a drag force) also increases.

• Eventually, a point is reached where the upward air resistance equals the downward gravitational force.

• At this point, net force = 0, so acceleration stops, and the raindrop continues falling at a constant speed.

This constant speed is called terminal velocity.

Explanation

Sickle cell anemia is caused by a mutation in the gene that codes for the beta-globin chain of hemoglobin,

where valine is substituted for glutamic acid at the sixth position, causing the red blood cells to assume a sickle shape.

Explanation

Human blood is divided into 4 main groups:

1. A
2. B
3. AB
4. O

These groups are determined by the presence or absence of specific antigens on the surface of red blood cells.