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  • Lipid bilayer + embedded proteins
  • Selectively permeable - controls movement of substances
  • Phospholipid bilayer
==> Hydrophilic head - water soluble
==> Hydrophobic tails - water insoluble
  • Bilayer - Two layers
  • Basic structure of cell membranes

Membrane Transport

 Based on the permeability a membrane is said to be:
1. Permeable: If a substance passes readily through the membrane
2. Impermeable: If a substance does not pass through the membrane
3. Selectively permeable: If the membrane allows some of the substances
to pass through but does not allow all the substances to pass through it.

 Substances are transported across the membrane either by:
1. Passive Transport or 2. Active Transport

 1. Passive Transport

  • Cross membrane with no energy
  • movement from high concentration to low


 Diffusion

  • Diffusion is the movement of molecules from an area of high concentration to an area of low concentration


 Osmosis
  • Osmosis is the passage of water across a membrane from an area of high concentration to an area of low concentration


 2. Active Transport
  • Requires chemical energy to cross(ATP)
  • Movement from low concentration to high

Evolution of Cell Theory

  • Robert Hooke (1665) Discovered cell
  • Robert Brown (1833) discovered nucleus in a cell
  • Scleiden & Schwann (1839) proposed cell theory
  • Virchow (1855) Cell arise from pre-existing cells



Cell Theory

  • Cells are structural & functional units of life
  • All organisms are made up of cells
  • All cells arise from pre-existing cells only
More Importance things to remember cell theory
  • Nucleic acid is the genetic material in all cells
  • Cells interact with each other which results in the organism's function
  • Basic chemical composition is more/less same in all cells



  • A cell is a structural and functional unit of all living organisms
  • Cell is the building block of all living organisms
  • It is microscopic
  • All living things are made up of cells


 Discovery Of Cells


  • Anton van Leewenhoek (1632-1723) The study of cell is impossible without microscope. studied the structure of bacteria, protozoa, red blood cells under the simple microscope that was designed by him.
  • Robert Hooke (1665) the empty honey-comb like structures viewed in a thin section of bottle cork. The word cell was first coined by Robert hook
  • Schleiden (1838) the German botanist proposed that all plants are made up of plant cells
  • Theodore Schwann (1839) - The anatomist Theodore Schwann studied and concluded that all animals are also composed of cells.
  • Rudolf Virchow (1858) - Cell theory was again rewritten
  • Robert Brown (1831) discovered the presence of nucleus in the cells of orchid roots. This was an important discovery.
  • Purkinje (1840) - He coined the term protoplasm for the slimy substance that is found inside the cells.
  • The invention of electron microscope in the year 1932 more and more information about the become available to us.


  • Tables can be classified according to their purpose and characteristics used.


Tables may be classified as follows:

1. Simple or one-way table 
2. Two way table
3. Manifold table

1. Simple or one-way table

  • A simple or one-way table is the simplest table which contains data of one characteristic only.
  • A simple table is easy to construct and simple to follow.
  • For example, the blank table given below may be used to show the number of adults in different occupations in a locality



2. Two way table

  • A table, which contains data on two characteristics, is called a two way table.
  • Either stub or caption is divided into two co-ordinate parts
  • For example the caption may be further divided in respect of ‘ sex’ . This subdivision is shown in two-way table, which now contains two characteristics namely, occupation and sex



3. Manifold table

  • More and more complex tables can be formed by including other characteristics.
  • For example, we may further classify the caption sub-headings in the above table in respect of “marital status”, “ religion” and “socio-economic status” etc. A table ,which has more than two characteristics of data is considered as a manifold table. For instance , table shown below shows three characteristics namely, occupation, sex and marital status.


General Rules For Tabulation


  • Each Table must have a number and title
  • A table should neither be too larger or too small
  • One purpose for one table
  • Large number may be approximated
  • Unites of measurement under each column heading
  • Space or break for large column tables
  • Compared value get near
  • In tables with many columns it will be useful o label the columns with numbers or alphabets for reference in the text
  • Stubs should be arranged in some logical orders
  • Miscellaneous use one column
  • Use double or thick line for headings


Tabulation is the process of grouped data in the form of a table so that it is easily understood and an investigator is quickly able to locate the desired information.

Aim Of Tabulation

  • To present voluminous heterogeneous statistical data
  • Easy to check for any errors
  • It presents facts in minimum possible space
  • Comparison of data




Parts Of Table

1. Table number For easy reference and identification
2. Title of the table The title should be placed centrally on the top of a table just below the table number (or just after table number in the same line)
3. Head note Its Optimal. give information like unites of measurements, scientific notation etc.
4. Captions or column headings  They may have main heading and sub-headings and are usually written in lower case
5. Stubs  The heading of horizontal rows are stubs
6. Body of the table  Important part of the table and consists of the cells in which numerical values
7. Footnotes Last part of the table. explains the specific feature of the data content 


Sampling Method


  • Sampling is simply the process of learning about the population on the basis of a sample drawn from it
  • Two types of sampling methods
1) Random or probability samples 
2) Non random samples


1. Random Sampling

In this method every item in the universe has an equal chance of being selected
There are 3 types of random sampling methods
i)   Simple random sampling
ii)  Stratified sampling
iii) Cluster sampling

i) Simple random sampling


  • In this method of sampling every unit of the population has an equal opportunity of being selected in the sample


ii)  Stratified sampling

  • In this method of sampling a finite population is divided into certain strata or groups on the basis of certain characteristics


iii) Cluster sampling

  • In this method of sampling the whole population divided into number of relatively small clusters or groups
  • Then some of the clusters are randomly selected


2) Non random samples


  • Non-random sampling methods are those which do not provide every item in the universe with a known chance of being included in the sample
  • The selection process is partially subjective
  • The choice of sample items depend upon the exclusively on the judgement of the investigater