This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Mitochondrial Structure and Function – 1”.
1. Mitochondria is the organ for ______
a) Cellular respiration
b) Cellular digestion
c) Cellular death
d) Cellular motility
Explanation: Mitochondria is a bean shaped organ in the cell cytoplasm. Its major role is cellular respiration. It utilizes oxygen and carbohydrate to release carbon dioxide and energy in the form of ATP. Cellular respiratory processes such as Kreb’s cycle and oxidative phosphorylation takes place in mitochondria.
2. The protruding invaginated sheets inside mitochondria is known as _____
d) Cellular Digestion
Explanation: The structure of mitochondria under the microscope is bean shaped with inner and outer mitochondrial membranes surrounding it. The inner membrane invaginates inside to produce finger-like protrusions known as the Cristae.
3. The inner boundary membrane and inner cristal membrane are joined by ____
a) Mitochondrial junctions
b) Membrane junctions
c) Cristae junctions
d) Tubule junctions
Explanation: The inner boundary membrane and internal cristal membranes in the mitochondria are joined to one another by narrow tubular connections known as cristae junctions. The cristae are internal protrusions that hold the respiratory mechanism important for cellular respiration.
4. Which part of mitochondria has almost 70-75% protein content?
a) Outer membrane
b) Inner membrane
c) Both outer and inner membrane
d) Intermembrane space
Explanation: The outer membrane of mitochondria is composed of approximately 50% lipid by weight and contains a mixture of different enzymes. The inner membrane contains more than 100 different polypeptides and has a very high protein to lipid ratio. The protein content exceeds 70% by weight.
5. Which part of mitochondria is responsible for the degradation of many enzymes?
a) Mitochondrial matrix
c) Inner membrane
d) Outer membrane
Explanation: The outer membrane of mitochondria is composed of approximately 50% lipid by weight and contains a mixture of different enzymes. It is involved in diverse activities such as enzyme degradation. The oxidation of epinephrine, degradation of tryptophan and elongation of fatty acid takes place in outer mitochondrial membrane.
6. In the inner membrane of mitochondria, there is one protein molecule for approximately every _______
a) 15 phospholipids
b) 25 phospholipids
c) 5 phospholipids
d) 10 phospholipids
Explanation: The inner membrane contains more than 100 different polypeptides and has a very high protein to lipid ratio. The protein content exceeds 70% by weight. This corresponds to about one protein molecule for every 15 phospholipids.
7. Cardiolipin present in inner mitochondrial membrane plays a role in ___________
a) Formation of the respiratory mechanisms
b) Activation of proteins involved in Glycolysis
c) Activation of proteins involved in electron oxidation
d) Activation of proteins
Explanation: The inner membrane of mitochondria is virtually devoid of cholesterol and rich in unusual phospholipid and cardiolipins, which is the characteristics of bacterial membrane, from which the inner mitochondrial membrane has presumable evolved. Cardiolipin plays a role in facilitating the activity of several large protein complexes involved in lector transport and ATP synthesis.
8. Porins are present in ____________
a) Inner membrane
b) Outer membrane
c) Both inner and outer membrane
d) Intermembrane space
Explanation: Porins are integral proteins that have relatively large internal channel surrounded by a barrel of Beta strands. The porins of outer mitochondrial membrane are dynamic structures that are more permeable to molecules such as ATP, NAD and Coenzyme A. The inner mitochondrial membrane is highly impermeable and all molecules and ions require special membrane transporters to gain entrance.
9. The mitochondrial DNA in humans encode for how many poplypeptides?
Explanation: The mitochondria possess their own genetic material and the machinery to manufacture their own RNAs and proteins. The mitochondrial DNA encodes a small number of polypeptides which are 13 in humans. These are tightly integrated in the inner mitochondrial membrane along with polypeptides encoded by nuclear genes.
10. Human mitochondrial DNA encodes for ____________
a) 2 rRNAs
b) 3 rRNAs
c) 1 rRNA
d) 4 rRNAs
Explanation: The mitochondria possess their own genetic material and the machinery to manufacture their own RNAs and proteins. In humans, the mitochondrial DNA encodes for 2 ribosomal RNAs (rRNAs).
11. Human mitochondrial DNA encodes for _________
a) 21 tRNAs
b) 31 tRNAs
c) 22 tRNA
d) 24 tRNAs
Explanation: The mitochondria possess their own genetic material and the machinery to manufacture their own RNAs and proteins. In humans, the mitochondrial DNA encodes for 2 ribosomal RNAs (rRNAs) and also 22 transfer RNAs (tRNAs) that are used in protein synthesis within the organelle.
12. The mitochondrial RNA polymerase is made up of _____________
a) 1 subunit
b) 2 subunits
c) 3 subunits
d) multiple subunits
Explanation: Mitochondrial RNA polymerase helps in the synthesis of proteins from mitochondrial RNA. The mitochondrial RNA polymerase is unlike the multi-subunit RNA polymerase enzyme of prokaryotic and eukaryotic cell and contains only a single subunit similar to certain bacterial viruses.
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