BIOLOGY 1 Marks Question

3. In prokaryotes, there are no membrane bound organelles.

Solution:

Membrane-bound organelles are organelles surrounded by a double membrane. Nucleus, mitochondria, chloroplasts, etc., are examples of such organelles. These cell organelles are absent from prokaryotes.

1. Only eukaryotic cells have nuclei. They are absent from prokaryotes.
2. Cell walls are only present in plant cells. They are absent from all animal cells.
3. All cells arise from pre-existing cells.

3. pre-existing cells.

Solution:

According to the biogenic theory, new cells can only arise from pre-existing cells. Only complete cells, in favorable conditions, can give rise to new cells.

1. Robert Brown discovered the cell.

Solution:

Robert Brown did not discover the cell. The cell was discovered by Robert Hook.

1. Basal body.
2. Axoneme.

1. Kinetochores are the disc-shaped structures on either side of a centromere.
2. SER is the major site of synthesis of lipids and lipid-like steroidal hormones.

1. A metacentric chromosome has the centromeres right in the middle, with two equal arms.
2. 70 S ribosomes.

1. All living organisms are composed of cells and products of cells.
2. All cells arise from pre-existing cells.

• 'S'(called Svedberg unit), stands for the sedimentation coefficient.
• It measures the density and size of ribosomes.

1. Independent existence.
2. Performing the essential functions of life.

1. Mitochondria.
2. These cell organelles multiply by fission.

1. They form spindle fibres that give rise to spindle E apparatus.
2. They form the basal body of cilia or flagella.

1. Human/ mammalian erythrocytes.
2. Sieve tube cells of phloem.

1. Red Blood Cells (RBC).
2. Nerve cell or haque comezometro.

1. 60 S, 40 S.
2. 50 S, 30 S.

• Acrocentric chromosome has the centromere close to its end.
• Telocentric chromosome has a terminal centromeres (at its tip).

1. Osmosis.
2. Active transport.

1. Anton Von Leeuwenhoek ord.
2. Robert Hooke.

• A polysome is a chain of ribosomes, which are attached to a single strand of mRNA.
• The ribosomes of a polysome translate the mRNA into polypeptides.

• Outermost layer-Glycocalyx.
• Innermost layer-Plasma membrane.

• Nuclear pores are the openings found in the nuclear envelope, formed by the fusion of its two membranes.
• They help in exchange of proteins, RNAs, ribosomes between the nucleoplasm and blad cytoplasm.

1. Robert Brown.
2. Fleming.

• Filament, Hook and Basal body.
• Filament is the longest.

1. Telocentric
2. Acrocentric
3. Metacentric or
4. Sub-metacentric.

1. Robert Brown.
2. Flemming.

• There are nine equally spaced doublets of peripheral fibrils in a cilium/ flagellum.
• There is also a pair of centrally located microtubules; hence the arrangement of microtubules in a cilium flagellum, is called (9 + 2) arrangement.

• Slime layer- it is a loose sheath.
• Capsule- it is thick and tough and gives resistance to antibiotics.

1. Transport of molecules across it.
2. Forms the boundary for protoplasm (delimits it from the environment).

• 23 pairs/ 46 chromosomes.
• About 2.2 meters.

E.g. cyanophycean granules, glycogen granules, phosphate granules.