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FUNDAMENTAL UNIT OF LIFE (CELLS)

Plant cells Cells cells are the structural and functional unit of life
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Such organisms are called unicellular organisms;
for example, Amoeba, Paramecium, and bacteria
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Such organisms are called
multicellular organisms
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The smallest cell Mycoplasma is around 0
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whereas the largest cell is an ostrich egg which is around 125 mm in diameter
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Plasma membrane protector the cell and separates its contents from the external
environment also allows selective entry and exit of molecules
Location -


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Structure
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Function
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• It controls the selective entry and the exit of different molecules
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Permeability refers to the ability of a substance to allow molecules of gases or liquids to
pass through it
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Selectively-permeable: The substance allows certain specific molecules to pass through it
Permeable: The substance allows all molecules to pass through it
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The process continues until the concentration is
equal or at equilibrium
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It is the movement of water from a region of
high water concentration to a region of low water concentration through a
selectively-permeable membrane until equilibrium is achieved
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The three types
of solutions are as follows:

Hypotonic Solution The concentration of water is
higher in this solution than the
concentration of water in the cell
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Cell swells in size

Isotonic solution The concentration of water
in this solution is equal to the
concentration of water in the cell
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Water moves outside the cell
Cells shrinks in size

Cell Wall
Location It is an additional layer in plant cells outside the plasma membrane
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It is a rigid layer
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It protects plant cells from any physical injury
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But the cell wall exerts pressure on the plasma membrane and
help it retain its structure for longer,

When in hypertonic situations, cells lose water and the contents of the cytoplasm shrink; this
process is known as plasmolysis

Nucleus
Location It is embedded in the cytoplasm
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It is double-membraned; there
are pores in the membrane
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• It stores genes that are responsible for the transfer of characteristics from parent to
offspring
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Parts of the Nucleus
Nuclear Membrane It is a double membrane separating the nucleus from the cytoplasm
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Nuclear Pore It is a protein channel
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Nucleolus • It is a round body or region found inside the nucleus
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Chromatin It is a thread-like structure that carries genes
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Chromatin, Chromosomes, Genes, and DNA
Chromatin contains the information for inheritance of characteristics from the parent to the
offspring
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Chromosomes are the condensed version of chromatins
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In
humans, there are 46 chromosomes
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DNA contains all the information required for constructing and organising a cell
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The functional segments of the DNA are called genes
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It is composed mainly of water and salts
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It contains organelles
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Structure -

It is made up of organic molecules - lipids and proteins
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Function Producers proteins and lipids
Transport proteins and lipids to other organelles
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RER is covered with ribosomes
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They look rough under the microscope
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The RER is responsible for protein production
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It is responsible for lipid production
It also helps detoxify poison and drugs in many animals
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They transport proteins and
lipids to the plasma membrane of the cell in order to build the membrane
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Golgi Apparatus
Location It is found near the endoplasmic reticulum and the nucleus
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Structure It is made up of membrane

bound vesicles or flattened sacs that are arranged parallelly to one another in stacks called
cisternae
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It forms the lysosomes
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simple sugars
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Structure They are membrane-bound sacs filled with digestive proteins made by the RER
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They are known as the suicide bags because when the cell is damaged, the lysosome bursts
and the enzymes digest the cell, effectively killing it

Mitochondria
Location Multiple mitochondria are located
in the cytoplasm
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The outer membrane is porous, while the inner
membrane is folded many times
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Mitochondria contain their own DNA and ribosomes to produce their own proteins
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• ATP is used as a form of energy for all of the cell's processes
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Plastid
Location Multiple plastids are found
in the cytoplasm
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Structure A plastid has a double membrane
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A plastid has its own DNA and ribosomes
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Chloroplasts ('chloro-green, 'plasts' - plastid) are found in the cells of the leaves and other
green parts of a plant
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Chromoplasts ('chromo-colour, 'plasts'-plastid) are found in the cells of flowers, leaves, roots,
and fruits of a plant
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• Leucoplasts ('leuco' - white, 'plasts' - plastid) are found in non-photosynthetic parts of a
plant such as roots
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They store starch, oils, and protein in the roots of
the plant
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Structure There are multiple vacuoles in animal
cells that are small
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The vacuole of plant cells contains amino acids, sugars, organic acids,
and some proteins
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In plant cells, it provides support to the
cell

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