Chapter 3, Problem 1RQ

Describe the general functions of the following in a eukaryotic cell: the plasma membrane, cytoplasm, DNA, ribosomes, organelles, and cytoskeleton.

Summary Introduction

To describe: The general functions of plasma membrane, cytoplasm, DNA, ribosomes, organelles, and cytoskeleton in eukaryotic cell.

Introduction: Cells are the smallest structural, functional, and biological unit of all living organisms. They are modified in different ways to carry out various functions. They are divided into two types, namely prokaryotic and eukaryotic cell. Prokaryotes are single-celled organisms, and eukaryotes are mostly multicellular organisms. Protists and fungi are eukaryotes that are single-celled organisms. Plants and animals are the eukaryotes that are multi-celled organisms.

Explanation of Solution

Functions of plasma membrane:

Plasma membrane, also called cell membrane is the semi-permeable biological membrane that surrounds the entire cellular organelles. They contain lipid bilayer with transmembrane proteins attached with it. They basically protect the cell from foreign particles. It regulates the membrane transport into or out of the cell.

Functions of cytoplasm:

The cell contains cell membrane, nucleus, and cytoplasm. Cytoplasm combines with all the outside materials of nucleus, and it is enclosed by the cell membrane. The cytoplasm encloses the cellular organelles like ribosome, endoplasmic reticulum, centrosome, lysosome, and Golgi apparatus. Various cellular activities continue within the cytoplasm.

Functions of DNA:

Nucleic acids are the major organic molecules of all living organisms. Nucleic acids are made of three major components, such as nitrogenous base, pentose sugar, and phosphate group. The two major nucleic acids are deoxyribonucleic acid (DNA), ribonucleic acid (RNA). DNA carries the genetic information from one generation to next generation. DNA controls the synthesis of RNA in the cell.

Functions of ribosomes:

It is a non-membranous structure found in the cytoplasm of the cell. It is the core organelle for protein synthesis. It can be found free or attached with the rough endoplasmic reticulum.

Functions of organelles:

The eukaryotic cells have many membrane bound cell organelles. They are present in the cytoplasm of the eukaryotic cell. Golgi complex, endoplasmic reticulum, lysosomes, vacuoles, peroxisomes, chloroplast, and mitochondria are the cell organelles that are present in the eukaryotic cells. Endoplasmic reticulum is mainly classified into smooth endoplasmic reticulum and rough endoplasmic reticulum.

The functions of various organelles are given as follows:

1. a.      Nucleus: It is a membrane-bound organelle, covered by nuclear envelope. Nucleus contains nucleolus and chromatin material. Chromatin material consists of DNA and proteins.
2. b.      Nucleolus: It is a core region in the nucleus where components of ribosome assemble.
3. c.       Rough ER: It is a network of membranous sacs and tubes; its external surface is attached with the ribosome. It helps in protein processing and secretion. Also, the addition of carbohydrate with protein occurs to produce glycoprotein, which helps in production of new membrane within the cell.
4. d.      Smooth ER: It is a network of membranous sacs and tubes but not attached with the ribosome. It helps in detoxification and lipid synthesis. It helps in folding of protein and transferring of synthesized protein.
5. e.       Peroxisome: It is a specialized single membrane-bound vesicle found in the cytoplasm of the cell. It produces hydrogen peroxide as a by-product and converts it to water.
6. f.        Centrosome:  The formation of microtubules initiate at the centrosome. It contains a pair of centrioles.
7. g.      Mitochondrion: It is double membrane-bound organelles. It is important for the cellular respiration and energy generation in the form of ATP. Two phospholipid bilayer membranes enclosed with mitochondria possess a great role in functioning of mitochondria. It is also called as the “power house” of the cell.
8. h.      Lysosome: It is a single membrane-bound organelle. It is the storage unit of hydrolytic enzymes. Breakdown of indigested substance and cell organelles are recycled here.
9. i.        Golgi apparatus: It is a single membrane-bound organelle stack of flattened membranous sac. It is the active unit of modification, sorting, and secretion of cell products.

Functions of cytoskeleton:

Cytoskeleton is a complex network with interlinking filaments and tubules that extend through the cytoplasm. Cytoskeletal proteins help in maintaining the shape and internal organization of a cell. It provides mechanical support for cell division and cell movement with the help of three components namely microtubules, actin filaments, and intermediate filament. Expect the intermediate filaments, both the microtubules and actin filaments are involve in the cellular motility. Tubulin and actin proteins are cytoskeletal proteins that help in cell division process. Apart from this, tubulin helps in the movement of vesicles and actin protein helps in muscle contraction.