The Fundamental Unit of Life: Cell
Plasma Membrane:
Structure:
Flexible
Semi-Permeable
Function:
Permits entry and exit of materials in cells
Diffusion and Osmosis of certain materials
Cell Wall (Only in Plants):
Structure:
Rigid and Permeable
Non-Living
Function:
Provides strength to the cell and enables the cell to become turgid
Nucleus:
Structure:
Spherical, Double-Membranous, and usually at the centre of the cell
Function:
Controls all metabolic activities of the cell
Helps in transmitting hereditary traits from the parent cell to the offspring.
Cytoplasm:
Structure:
Liquid
Contains all the cell organelles
Function:
Acts as a store of vital chemicals
Site of certain metabolic activities
Endoplasmic Reticulum:
Structure:
Membranous tube network
Connects Plasma Membrane to Nucleus
Function:
Provides a pathway for the distribution of nuclear material
Smooth ER synthesizes lipids, steroids, and cholesterol
It also helps in detoxification. It metabolises various toxic substances
Rough ER has ribosomes that synthesize proteins
Rough ER synthesize digestive enzymes
Difference between RER and SER:
Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum
Has flattened sacs called cisternae Mainly formed of vesicles and tubules
Ribosomes are attached to it Does not contain Ribosomes
Ribosomes:
Structure:
Dense and Spherical particles
Functions:
Synthesis of Proteins
Golgi Apparatus:
Structure:
Set of membrane-bound fluid-filled vesicles and cisternae
Plants have many simpler units of Golgi Bodies called Dictyosomes.
Function:
Storage for various cellular secretions
Involved in the synthesis of Cell Wall, Plasma Membrane and Lysosomes
Lysosomes:
Structure:
Tiny, Spherical, Sac-Like structure
Function:
Help in digestion and protect cells from infection
Digest worn-out cells to make space for new ones
Burst and eat up the cell during breakdown
Mitochondria:
Structure:
Tiny Bodies of cylindrical shape
Double-Membranous and Semi-Autonomous
Function:
Sites of Cellular Respiration
Forms ATP (Adenosine Triphosphate), which is the source of energy
Chloroplasts:
Structure:
Disc-shaped, Double-Membranous and Semi-Autonomous
Function:
Trap solar energy using chlorophyll and make food
Vacuoles:
Structure:
Fluid-filled, Membrane-Bound organelles
Small and many in number (Animal Cell)
Large and occupy most of the cell (Plant Cell)
Function:
Provide turgidity and rigidity to the plant cell
Store toxic metabolic by/end products of plant cell
Types of Cells:
Prokaryotic Cell Eukaryotic Cell
Size is small (1-10mm) Size is large (5-100mm)
Nucleus is absent and replaced by nucleoid Nucleus is present and is surrounded by a
which lacks a membrane nuclear membrane
Nucleolus absent Nucleolus present
Membrane-bound cell organelles are absent Membrane-bound cell organelles are present
Difference between Osmosis and Diffusion:
Osmosis Diffusion
Movement of water molecules(solvent) which Movement of a substance which can be solid,
is a liquid liquid or gas
Requires a semi-permeable membrane Does not require a semi-permeable membrane
3 types of solutions based on their tonicity:
Hypotonic Solution: Isotonic Solution: Hypertonic Solution
The medium surrounding the The medium surrounding the cell has equal The medium surrounding the
cell has a higher water water concentration as the cell. In this case, cell has a lesser water
concentration than the cell. water will continue the flow of movement in concentration than the cell. In
In this case, the cell will gain and outside the cell. It will take in and give out this case, the cell will lose
water by endosmosis. water, making a cycle while keeping the water water by exosmosis.
level the same.
Difference between Mitochondria and Chloroplasts:
Mitochondria Chloroplasts
Occur in cells of plants and animals Occur only in plants
Colourless Green in colour
Rod-like shape Disc-like shape
Liberate energy Trap solar energy to chemical energy
Perform oxidation of food Synthesize food by photosynthesis
Consume O2 and liberate CO2 Consume CO2 and liberate O2
Difference between Cell Wall and Plasma Membrane
Cell Wall Plasma Membrane
Occurs in Plant Cells only Occurs in both Plant and Animal Cells
Non-living and quite thick Living and quite thin
Rigid Flexible
Permeable Semi-Permeable
Formed of cellulose and pectin Formed of lipids, proteins, and carbs
Key Terms:
Osmosis: Movement of water molecules from a region of higher concentration to
a region of lower concentration through a semi-permeable membrane
Diffusion: Movement of a substance from a region of higher concentration to a
region of lower concentration
Protoplasm: The inner contents of the cell, which is constituted of the cytoplasm
and the nucleus
Plasmolysis: Process of shrinkage of the protoplasm of a plant cell and is caused
due to the loss of water through exosmosis when the cell is placed in a hypertonic
solution. In plasmolysis, the plasma membrane eventually detaches from the cell
wall. This shrinkage eventually results in the death of the cell.
Cell Division: Process by which a parent cell divides into daughter cells. It is
necessary for regulating cell growth, development, and repair in multicellular
organisms.
Mitosis: Type of cell division by which a cell replicates its chromosomes and then
segregates them, producing two daughter cells for further cell division.
Meiosis: Type of cell division in sexually reproducing organisms that reduces the
number of chromosomes in the parent cell and produces four gamete cells.
Haploid Cells: Cells that contain only one set of chromosomes. Gametes or sex
cells are the most common type of haploid cells. They are produced by meiosis.
Diploid Cells: Cells that contain two sets of chromosomes. They are produced by
mitosis. The somatic (non-gametic) cells in humans are diploid.
