Biology · Science General

Cell Biology and Structure

3,221 Questions

Cell biology focuses on the structure and function of cellular organelles. Key topics include cellular respiration, DNA inheritance, and energy production. These fundamental biology concepts are crucial for medical entrance and state service examinations.

Cell organelles functionsCellular respiration sitesDNA and ribosomesAnimal cell structurePlant cell components

Cell Biology and Structure Questions

Multiple choice

Which enzyme joins Okazaki fragments together?

  1. Helicase

  2. DNA Ligase

  3. DNA polymerase

  4. DNA primase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DNA Ligase is the enzyme responsible for sealing the nicks between Okazaki fragments on the lagging strand. Helicase unwinds the DNA, DNA polymerase synthesizes the new strand, and primase creates the RNA primer.

Multiple choice

What is the role of DNA Polymerase I?

  1. To replace the DNA primer with RNA nucleotides

  2. To join together the Okazaki fragments on the leading strand

  3. To join together the Okazaki fragments on the lagging strand

  4. To replace the RNA primer with DNA nucleotides
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

DNA Polymerase I is specifically responsible for removing the RNA primers used during replication and replacing them with the appropriate DNA nucleotides. DNA Polymerase III is the primary enzyme for elongation.

Multiple choice

Okazaki fragments are built on the [1] strand because this strand is built [2]

  1. [1] Leading strand [2] Continuously

  2. [1] Lagging strand [2] Discontinuously

  3. [1] Lagging strand [2] Continuously

  4. [1] Leading strand [2] Discontinuously
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The lagging strand is synthesized discontinuously in short segments called Okazaki fragments because DNA polymerase can only synthesize in the 5' to 3' direction, which is away from the replication fork.

Multiple choice

The leading strand is the strand of DNA that is replicated...

  1. Discontinuously

  2. Continuously

  3. Using Okazaki fragments

  4. Using DNA Ligase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The leading strand is oriented in the 3' to 5' direction relative to the replication fork, allowing DNA polymerase to synthesize it continuously in the 5' to 3' direction.

Multiple choice

Which of the following best explains the role of DNA primase?

  1. Creates RNA nucleotides to add to DNA

  2. Adds an RNA primer to DNA

  3. Adds a DNA primer to DNA

  4. Creates DNA nucleotides to add to DNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DNA primase is a type of RNA polymerase that synthesizes a short RNA sequence (primer) complementary to the DNA template, which provides the starting point for DNA polymerase III.

Multiple choice

What is the role of single strand binding proteins (SSB) during DNA replication?

  1. Break hydrogen bonds to allow for separation of DNA strands

  2. Allow for supercoiling of the DNA

  3. Stabilize DNA strand + prevent a double helix from reforming

  4. Join the Okazaki fragments together
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Single-strand binding proteins (SSB) bind to the separated DNA strands to prevent them from re-annealing or forming secondary structures, keeping the template accessible for replication.

Multiple choice

Which enzyme unwinds DNA and how does it do this?

  1. DNA Polymerase III by breaking hydrogen bonds

  2. Helicase by breaking hydrogen bonds

  3. DNA Polymerase III by breaking covalent bonds

  4. Helicase by breaking covalent bonds
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Helicase is the enzyme that unwinds the DNA double helix by breaking the hydrogen bonds between the complementary nitrogenous bases.

Multiple choice

What role does DNA gyrase play in DNA replication?

  1. Breaks covalent bonds between DNA nucleotides

  2. Separates nitrogenous bases by breaking hydrogen bonds

  3. Supercoils the DNA in preparation for DNA replication

  4. Relieves strain + prevents supercoiling of separated strands
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

DNA gyrase (a type of topoisomerase) relieves the torsional strain (supercoiling) that builds up ahead of the replication fork as helicase unwinds the DNA.

Multiple choice

DNA replication occurs in the:

  1. Rough Endoplasmic Reticulum

  2. Golgi Apparatus

  3. Nucleus

  4. Cytoplasm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In eukaryotic cells, DNA is stored within the nucleus, and therefore DNA replication takes place inside the nucleus.

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

In 1665, Robert Hooke first observed cells in 

  1. Leaf

  2. Cork

  3. Intestin

  4. Liver
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The first cell was observed and named by Robert Hooke in 1665. He described that it looked like cellula, small rooms which are inhabited by monks hence derived the name 'cell'. The cell he actually saw was the dead cell walls of the plant (cork) under a microscope. Hooke described the characteristics of a cell he observed in his book 'Micrographia'. 

So, the correct answer is 'Cork'

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

Unstained living cells can be best studied by

  1. Phase contrast microscope

  2. Electron microscope

  3. Fluorescent microscope

  4. Polarising microscope
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Phase contrast microscopy is a type of microscopic technique which converts phase shifts in light passing through a transparent specimen to brightness changes in the image. This technique made possible to study living cells without staining.