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1009 available questions

Biology · Question 921

According to the lock-and-key model, an enzyme's active site:

  1. Is a rigid structure
  2. Changes shape before substrate binding
  3. Is changed permanently by the substrate
  4. Is changed by the product
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Correct answer: A

Is a rigid structure

The correct answer is Is a rigid structure.

Biology · Question 922

Koshland's induced-fit model proposes that the enzyme's active site:

  1. Changes shape when the substrate binds
  2. Is a rigid structure
  3. Is non-protein in nature
  4. Combines permanently with the substrate
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Correct answer: A

Changes shape when the substrate binds

The correct answer is Changes shape when the substrate binds.

Biology · Question 923

Who first reported the presence of the cell nucleus?

  1. Robert Brown
  2. Robert Hooke
  3. Schleiden
  4. Theodor Schwann
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Correct answer: A

Robert Brown

The correct answer is Robert Brown.

Biology · Question 924

The statement that all living organisms are composed of cells and cell products refers to:

  1. Common origin of cells
  2. Idea of biogenesis
  3. Cell theory
  4. All cells are from other cells
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Correct answer: C

Cell theory

The correct answer is Cell theory.

Biology · Question 925

Which cells continually produce new cells for plant growth and development?

  1. Chlorenchymatous
  2. Meristematic
  3. Parenchymatous
  4. Sclerenchymatous
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Correct answer: B

Meristematic

The correct answer is Meristematic.

Biology · Question 926

Cell fractionation requires which of the following?

  1. Disruption
  2. Spinning
  3. Special media
  4. All of these
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Correct answer: D

All of these

The correct answer is All of these.

Biology · Question 927

Which statement is true for eukaryotic ribosomes?

  1. Have 60S and 40S subunits
  2. Are ribonucleoprotein particles
  3. Require Mg²⁺ for subunit association
  4. All of the statements above
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Correct answer: D

All of the statements above

The correct answer is All of the statements above.

Biology · Question 928

All of the following structures are derived from microtubules except:

  1. Centrioles
  2. Cilia
  3. Flagella
  4. Pseudopodia
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Correct answer: D

Pseudopodia

The correct answer is Pseudopodia.

Biology · Question 929

Centrioles are absent from:

  1. Animal cells
  2. Higher plant cells
  3. Lower plant cells
  4. Microorganisms
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Correct answer: B

Higher plant cells

The correct answer is Higher plant cells.

Biology · Question 930

The chromosome number in normal body cells is:

  1. Diploid
  2. Haploid
  3. Polyploid
  4. Euploid
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Correct answer: A

Diploid

The correct answer is Diploid.