Bodies of organisms are made of tiny units called Cells. Cell have outer
boundary called cell membrane [made up of lipids and
proteins], most cells have
a nucleus and inside the cell membrane or plasma membrane
is present cytoplasm.
Nucleus, cytoplasm and membrane are basic components of
Types of cell components:
Endoplasmic reticulum is of two types Rough
ER – it has ribosome attached to it. Ribosome
manufactures proteins. Smooth ER has a role in
manufacturing lipids. ER also serves as a transport channel
between various regions of cytoplasm or cytoplasm and
In vertebrates, SER detoxifies poisons and drugs.
Golgi body helps in formation of lysosomes [contain
digestive enzymes which digest wastes, foreign bodies or even
damaged cell organelles and the cell itself – hence called suicide
It helps in making complex sugars from simple sugars
and stores, packages products in vesicles.
Nucleus contains chromatin material, during
division of cell it gets organized into chromosomes. These
contain information to be inherited by the next generation
in form of DNA.
Functional units of DNA are genes. DNA contains
information necessary for organizing and constructing cells.
A single large Vacuole is present in plant cells and
multiple small vacuoles in animal cells. Vacuoles store
liquids or solid contents.
Centrioles are seen only in animal cells. Plastids
are found only in plant cell.
Green plastids called chloroplasts carry chlorophyll. White
plastids are called leucoplasts; they store starch, oil and
proteins. They have their own DNA and ribosome.
Membranes are porous and allow nutrients and substances to
move in or out. Hence it’s selectively permeable. Diffusion
plays an important role in exchange of gases. Water is moved
by osmosis [Solvent moves from dilute to concentrated
solution]. Food is taken in by endocytosis. Cytoplasm and
nucleus are called protoplasm.
Plant and Animal Cells:
bacterial cells have cell wall [made of cellulose]
outside the membrane. No
cell wall in animal cells. Because of cell walls plant
cells can withstand much
greater variations in surrounding medium than animal
and hence do not show any characteristics of life till
they enter a host and
use its cell machinery to multiply. They have few
biochemical mechanisms on
their own; they enter the host and use his processes for
their work. They have
either DNA or RNA not both. RNA acts genetic material
only in viruses.
Facts of Cellular Respiration:
involves using oxygen [aerobic] to break down food
[glucose] into energy;
carbon dioxide and water are released.
this process takes
place in absence of oxygen [in yeast] then alcohol,
carbon dioxide and energy
are formed. This is anaerobic respiration.
Yeast [single celled organisms] is used in making wine
They convert sugar to alcohol; this process is called fermentation
by Louis Pasteur].
conversion of milk into curd. Bio fertilizers are
organisms that enrich the
quality of soil.
rapidly and produces carbon dioxide by respiration this
causes bubbles of gas
that fill the dough and increase its volume. So it’s
used in making bread,
pastries and cakes.
made from fungi and bacteria. However antibiotics
don’t work against viral
infections. Antibiotic like penicillin stops
creation of a cell wall in
bacteria but as humans don’t create a cell wall it has
no effect on humans.
Viruses don’t follow these pathways and hence viral
infections don’t have
benzoate [can be
metabolized by body], sodium metabisulphide, salts of
propanoic, sorbic acid
and edible oils are some common preservatives. Sugar
reduces moisture content
and so microbes can’t grow.
than sugar; used in cold drinks, cold foods], sucralose
[550x; used by diabetic patients to sweeten food; is
excreted in urine],
alitame are artificial sweeteners.
progress from lower to higher forms. But evolution seems
to have given birth to
complex designs even when simpler designs continue to