Unit-1
➢ Cell Structure and Function
Structure of cell
1. Cell: Basic Unit of Life
• Definition: Structural and functional unit of life
• Types: Prokaryotic (no nucleus, bacteria)
Eukaryotic (has nucleus, plants & animals)
2. Cell Membrane (Plasma Membrane)
• Structure: Phospholipid bilayer with proteins
• Functions:
o Controls entry/exit of substances
o Selectively permeable
o Communication (receptors)
3. Cell Wall (Only in Plants, Fungi, Bacteria)
• Made of:
o Cellulose (plants)
o Chitin (fungi)
, o Peptidoglycan (bacteria)
• Function:
o Protection & shape
o Prevents bursting from water intake
4. Nucleus (Control Center)
The nucleus is the control centre of eukaryotic cells, composed of a double membrane called
the nuclear envelope with pores, the jelly-like nucleoplasm, and chromatin (DNA and proteins).
Its main functions are to store genetic material, control cellular activities like growth and
metabolism, and regulate gene expression, cell division, and the synthesis of ribosomal RNA
(rRNA) in the nucleolus
Structure of the nucleus
• Nuclear envelope: A double membrane that encloses the nucleus, separating it from
the cytoplasm. It is studded with nuclear pores.
• Nuclear pores: Channels in the nuclear envelope that control the movement of
molecules, such as proteins and RNA, between the nucleus and the cytoplasm.
• Nucleoplasm: The gel-like substance filling the nucleus, in which the chromatin and
nucleolus are suspended. It provides a medium for chemical reactions.
• Chromatin: A complex of DNA and proteins (primarily histones). It condenses to form
visible chromosomes during cell division.
• Nucleolus: A dense, non-membranous structure within the nucleus where ribosomal
RNA (rRNA) is synthesized and assembled with proteins to form ribosomes.
• Nuclear matrix: A network of protein filaments that provides structural support within
the nucleus.
• Functions:
o Controls cell activities
, o Stores genetic info
o Site of RNA synthesis
5. Cytoplasm
• Jelly-like fluid between nucleus and membrane
• Function:
o Holds organelles in place
o Site of metabolic reactions
6. Cell Organelles (Only in Eukaryotes)
a) Mitochondria
• Powerhouse
• ATP production (energy)
• Has its own DNA
b) Ribosomes
• Site of protein synthesis
• Found free or on RER
c) Endoplasmic Reticulum (ER)
• Rough ER (RER): Has ribosomes → protein transport
• Smooth ER (SER): Lipid synthesis, detoxification
d) Golgi Apparatus
• Modifies, sorts & packages proteins
• Forms lysosomes
e) Lysosomes
• Digestive enzymes
• Removes waste or damaged organelles
f) Vacuoles
• Storage of water, waste, nutrients
• Large in plant cells
What is Genetic Engineering?
• Genetic engineering is the process of modifying the genetic material (DNA or RNA)
of an organism to achieve desired traits or produce specific biological products.
➢ Cell Structure and Function
Structure of cell
1. Cell: Basic Unit of Life
• Definition: Structural and functional unit of life
• Types: Prokaryotic (no nucleus, bacteria)
Eukaryotic (has nucleus, plants & animals)
2. Cell Membrane (Plasma Membrane)
• Structure: Phospholipid bilayer with proteins
• Functions:
o Controls entry/exit of substances
o Selectively permeable
o Communication (receptors)
3. Cell Wall (Only in Plants, Fungi, Bacteria)
• Made of:
o Cellulose (plants)
o Chitin (fungi)
, o Peptidoglycan (bacteria)
• Function:
o Protection & shape
o Prevents bursting from water intake
4. Nucleus (Control Center)
The nucleus is the control centre of eukaryotic cells, composed of a double membrane called
the nuclear envelope with pores, the jelly-like nucleoplasm, and chromatin (DNA and proteins).
Its main functions are to store genetic material, control cellular activities like growth and
metabolism, and regulate gene expression, cell division, and the synthesis of ribosomal RNA
(rRNA) in the nucleolus
Structure of the nucleus
• Nuclear envelope: A double membrane that encloses the nucleus, separating it from
the cytoplasm. It is studded with nuclear pores.
• Nuclear pores: Channels in the nuclear envelope that control the movement of
molecules, such as proteins and RNA, between the nucleus and the cytoplasm.
• Nucleoplasm: The gel-like substance filling the nucleus, in which the chromatin and
nucleolus are suspended. It provides a medium for chemical reactions.
• Chromatin: A complex of DNA and proteins (primarily histones). It condenses to form
visible chromosomes during cell division.
• Nucleolus: A dense, non-membranous structure within the nucleus where ribosomal
RNA (rRNA) is synthesized and assembled with proteins to form ribosomes.
• Nuclear matrix: A network of protein filaments that provides structural support within
the nucleus.
• Functions:
o Controls cell activities
, o Stores genetic info
o Site of RNA synthesis
5. Cytoplasm
• Jelly-like fluid between nucleus and membrane
• Function:
o Holds organelles in place
o Site of metabolic reactions
6. Cell Organelles (Only in Eukaryotes)
a) Mitochondria
• Powerhouse
• ATP production (energy)
• Has its own DNA
b) Ribosomes
• Site of protein synthesis
• Found free or on RER
c) Endoplasmic Reticulum (ER)
• Rough ER (RER): Has ribosomes → protein transport
• Smooth ER (SER): Lipid synthesis, detoxification
d) Golgi Apparatus
• Modifies, sorts & packages proteins
• Forms lysosomes
e) Lysosomes
• Digestive enzymes
• Removes waste or damaged organelles
f) Vacuoles
• Storage of water, waste, nutrients
• Large in plant cells
What is Genetic Engineering?
• Genetic engineering is the process of modifying the genetic material (DNA or RNA)
of an organism to achieve desired traits or produce specific biological products.
