 Scientific
study of life.
 Present era is most exciting in biology
 Scientists are trying to solve biological
puzzles like:
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How a single microscopic cell develops into
complex animals and plants?
How plants converts solar energy to chemical
energy of food?
How human mind works?
How various forms of diverse life on earth evolve
from first microbe?
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Evolution makes sense of everything we know about living
organisms.
Organisms living on Earth are modified descendents
of common ancestors
Biology is a quest , on ongoing inquiry about the nature of
life.
Modern biology is as important as it is inspiring
Research breakthroughs in genetics and cell biology are
transforming medicine and agriculture.
Molecular Biology is providing new tools to anthropology
and criminal science(Forensics).
Neuroscience and evolutionary biology are reshaping
psychology and sociology
New models in ecology are helping societies evaluate
environmental issues i-e. causes and biological
consequence of global warming.
That’s how biology weaves into the fabric of our culture
more than before.
This is a better time to explore life.
 New
properties emerge at each level in the
biological hierarchy
 Life can be studied at different levels from
molecules to the entire living planet
 The study of life can be divided into
different levels of biological organization
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Cell is fundamental unit to biology as atom is to
chemistry
All organisms are made of cells.
In the hierarchy of biological organization the cell is
the simplest collection of matter that can live.
Single celled organisms are of diverse form
Complex organisms: Plants and animals are
multicellular;
● Have many kinds of specialized cells
● These cell can be survive on their own
● Tissues and organs can not survive on their own
either.
Cell is a basic unit of structure and function.
 Various
cells functions together or one after
the other. i-e The contraction of muscle cells
move your eyes as you read a sentence.
When you decide to turn the next page,
nerve cells transmit that decision from your
brain to muscle cells of your hand.
 Every thing an organism does occurs
fundamentally at cellular level.
 Life at cellular level arises from structural
order, reinforcing the themes of emergent
properties and correlation between structure
and function. i-e The movement of an animal
cell depends on an intricate interplay of the
structure that make up a cellular skeleton.
 Interaction
of organisms with their
environment. Cells sense and respond to
environmental fluctuations.
 All cells are related by their descent from
earlier cells. However they have been
modified in many different ways during long
evolutionary history of life on earth.
 Although the cells differ substantially from
each other they share certain common
characteristics.
A
eukaryotic cell has membrane-enclosed
organelles, the largest of which is usually the
nucleus
 By comparison, a prokaryotic cell is simpler
and usually smaller, and does not contain a
nucleus or other membrane-enclosed
organelles
 Bacteria and Archaea are prokaryotic;
plants, animals, fungi, and all other forms of
life are eukaryotic
 Theme:
The continuity of life is based on
heritable information in the form of DNA
 Chromosomes contain most of a cell’s
genetic material in the form of DNA
(deoxyribonucleic acid)
 DNA is the substance of genes
 Genes are the units of inheritance that
transmit information from parents to
offspring
 Each
chromosome has one long DNA
molecule
with hundreds or thousands of genes
 DNA is inherited by offspring from their
parents
 DNA controls the development and
maintenance of organisms
 Each DNA molecule is made up of two long
chains arranged in a double helix
 Each link of a chain is one of four kinds of
chemical building blocks called nucleotides
 Genes
control protein production indirectly
 DNA is transcribed into RNA then translated
into a protein
 An organism’s genome is its entire set of
genetic instructions
 The human genome and those of many other
organisms have been sequenced using DNA
sequencing machines.
 Knowledge of a cell’s genes and proteins can
be integrated using a systems approach
 Advances
in systems biology at the cellular
and molecular level depend on “Highthroughput” technology, which yields
enormous amounts of data  Bioinformatics, which is the use of
computational tools to process a large
volume of data
 Interdisciplinary research teams
Cell structure and Function