BIOLOGY 1 Marks Question

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.

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.

1. Basal body.
2. Axoneme.

Ostrich's Egg.

Carotene.

Presence of cell wall.

Fluid Mosaic Model.

Carotene.

Mycoplasma, Bacteria, Human RBC Ostrich egg.

Proteins 52% and lipids 40%.

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

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

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

Certain cell organelles function in coordination. Because of this they are taken as part of the endomembrane system.

Since the functions of mitochondria and chloroplasts are not coordinated by the other components (ER, lysosomes, etc.) of the endomembrane system, they do not form part of endomembrane system.

Fimbriae and pili.

Semipermeability is the property of cell membrane, by which it allows certain molecules to pass across and does not allow certain other molecules to pass across.

The centrioles form the basal body of cilia or flagella, and spindle fibres that give rise to spindle apparatus during cell division in animal cells.

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

Tonoplast is the single-membrane boundary of sap vacuoles in plant cells.

An elaborate network of filamentous proteinaceous structures present in the cytoplasm is called the cytoskeleton.

Cell is defined as the structural and functional unit of life.

Based on the position of the centromere, a chromosome may be:

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

1. Robert Brown.
2. Fleming.

It is the site of synthesis of lipid-like steroidal hormones.

Microbodies are the single membrane-bound minute vesicles containing various enzymes in the cytoplasm of plant and animal cells, e.g., peroxisomes, glyoxysomes, etc.

Inclusion bodies are the structures in prokaryotic cells in which reserve food materials are stored, but are not bounded by a membrane.E.g. cyanophycean granules, glycogen granules, phosphate granules.

The two types of glycocalyx are:

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

Lipid synthesis.

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

Tubulin.

Ribosomes.

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

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

Cytoplasma.

Cell Theory (Malthias Scheiden, 1868; Schwann, 1839; and Rudolf Virchow, 1855) Cell theory as understood today is:

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

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

Lipid synthesis.

These enzymes are hydrolases (like lipases, proteases and carbohydrases) which function optimally at acidic pH.

Unicellular organisms are capable of:

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

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

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

Chitin.

• 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.

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.

It is the site of active ribosomal RNA synthesis.

Lysosome.

Because there is no boundary membrane for the nucleolus.

• 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.

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

Nostoc.

Pleuro-pneumonia like organisms.

Mitochondria and chloroplasts.

• 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.

(a) Two (Doublets) (b) Three (Triplets).

Since mitochondria possess a single circular DNA molecule, a few RNA molecules, 70 S ribosomes and other components needed for protein synthesis, they are called semiautonomous organelles.

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

Lysosomes.

Red blood cells.

When the transportation of substance takes place against concentration gradient it is called active transport.

1. Robert Brown.
2. Flemming.

A telocentric chromosome has a terminal centromere.

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

1. Osmosis.
2. Active transport.

Ribosome.

The metacentric chromosome has middle centromere forming two equal arms of the chromosome.

Chromoplasts.

Chloroplasts.