The organelle that stores calcium ions in muscle cells is the: MCQ with Answer and Explanation

The organelle that stores calcium ions in muscle cells is the:
A. Golgi apparatus
B. Mitochondria
C. Nucleus
D. Sarcoplasmic reticulum
Answer: Option D
Solution (By JKExamLibrary)
The sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum in muscle cells that stores and releases calcium ions, which trigger muscle contraction. Mitochondria produce ATP, Golgi processes proteins, nucleus controls gene expression.

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Practice More Biology Questions

Question #1
Consider statements about evolution: 1. Evolution is a change in allele frequencies over time. 2. Speciation is the formation of new species. 3. Evolution always leads to more complex organisms. Which are correct?
A. 1 and 3 only
B. 1, 2 and 3
C. 1 and 2 only
D. 2 and 3 only

Correct Answer: Option C


Explanation:
Evolution, at its most fundamental genetic level, is defined as the change in the frequency of alleles within a population over successive generations. Speciation is the evolutionary process by which populations evolve to become distinct, reproductively isolated species. Evolution does not have a predetermined goal or direction towards complexity; it simply results in adaptation to the current environment, which can sometimes lead to simpler forms (like parasites losing complex structures). Thus, statements 1 and 2 are correct.

This question belongs to: Science Biology
Question #2
The pancreas functions as both an exocrine and endocrine gland. Which hormone is secreted by the islets of Langerhans?
A. Insulin
B. Bile
C. Pepsin
D. Gastrin

Correct Answer: Option A


Explanation:
The endocrine part of the pancreas—the islets of Langerhans—contains β-cells that secrete insulin (lowers blood glucose), α-cells secrete glucagon (raises blood glucose), and δ-cells secrete somatostatin. Exocrine pancreas secretes digestive enzymes (trypsin, lipase, amylase). Pepsin is from stomach, bile from liver, gastrin from stomach. Insulin deficiency causes diabetes mellitus.

This question belongs to: Science Biology
Question #3
The process of taking in food through the mouth is called:
A. Egestion
B. Digestion
C. Ingestion
D. Absorption

Correct Answer: Option C


Explanation:
Ingestion is the act of taking food and liquids into the body through the mouth. Digestion is the breakdown, absorption is nutrient uptake, egestion is waste elimination. Ingestion is the first step in nutrition.

This question belongs to: Science Biology