Chapter 7, Problem 25A

Summary Introduction

Introduction:

Each cell has different organelle to perform specific tasks. Membrane bound organelle make it possible for different processes to occur simultaneously in a cell. A cell is involved in energy transformations, protein synthesis, food digestion, excretion of wastes and cell division.

Answer to Problem 25A

C. ribosome

Explanation of Solution

Explanation/justification for the correct answer :

C. ribosome- One of the main functions of a cell is to produce proteins. Ribosomes are the sites where proteins are synthesized. They are made of RNA and proteins and are not membrane bound. Nucleolus produces ribosomes. The ribosomes may move freely in the cytoplasm or are attached to endoplasmic reticulum. A cell has many ribosomes to produce a variety of proteins.

Explanation for incorrect answer :

1. chromatin- Within the nucleus is a complex DNA attached to a protein. It is called chromatin. It carries the genetic material of the cell. It does not synthesize proteins. So, this is an incorrect option.
2. Nucleolus- It is a dense structure in nucleus that produces ribosomes. Ribosomes are involved in protein synthesis. So this is an incorrect option.

D. endoplasmic reticulum- It is a membrane system of folded sacs and interconnected channels that act as the site for protein synthesis. Ribosomes are attached to ER at some places and such ER is called rough ER. So, this is an incorrect option.