Biology Cells Overview

Overview of Cells

• Cells serve as the fundamental building blocks of all living organisms.
• Contain protoplasm, consisting of the cell surface membrane, cytoplasm, and nucleus.

Protoplasm Components

• Cell Surface Membrane:

  • Selectively permeable, regulates substance movement in/out.
  • Acts as receptor sites for external stimuli.
  • Composed of proteins and phospholipids; defines cell boundary.

• Cytoplasm:

  • Aqueous medium housing various organelles.

• Nucleus:

  • Houses hereditary material (DNA) organized as chromatin and chromosomes.
  • Surrounded by a nuclear membrane with pores for selective transport.
  • Controls cell activities including growth and division.

• Cell Wall (Plant Cells Only):

  • Rigid structure made of cellulose; provides support and protection.
  • Can undergo lignification and is fully permeable.

Organelles and Their Functions

• Rough Endoplasmic Reticulum (RER):

  • Studded with ribosomes; specializes in protein synthesis and transport.

• Smooth Endoplasmic Reticulum (SER):

  • Lacks ribosomes; involved in lipid and hormone synthesis, detoxification.

• Golgi Apparatus/Body:

  • Stack of membrane-bound sacs; modifies, stores, and packages proteins for secretion.

• Ribosomes:

  • Composed of ribosomal RNA; synthesizes proteins either as secretory or intra-cellular.

• Mitochondria:

  • Double-membrane organelle; produces ATP, essential for energy metabolism.
  • Abundant in energy-demanding cells; can contain thousands in highly active cells.

• Chloroplasts (Plant Cells Only):

  • Double-membrane organelle containing thylakoids with chlorophyll for photosynthesis.
  • Converts sunlight into glucose and stores starch.

• Vacuoles:

  • Fluid-filled organelles; provide structural support to plant cells and store waste and nutrients.

Cell Specialization

• Differentiation:

  • Process where cells develop specialized structures for specific functions.

• Tissues:

  • Composed of similar cells; Simple tissues consist of the same cell type (e.g., muscular tissue).
  • Complex tissues, like blood, include multiple cell types.

• Organs:

  • Consist of various tissues that work collaboratively for specific functions (e.g., stomach integrates gland, muscle, and nerve tissues).

This quiz covers the fundamental concepts of cells, their structure, and the various components of protoplasm. You'll explore the functions of organelles such as the nucleus, cytoplasm, and cell membrane. Test your knowledge on how these cellular structures contribute to the life of living organisms.