[Biology] Membrane (cell membrane and cell wall)

Reading Time: 5 minutes

MEMBRANE

  • A membrane is the outermost boundary of any cell.
  • It is the non-living part of the cell
  • Membrane gives the cell support and shape and serves as a boundary regulating the inflow and outflow of materials from the cell
  • Membrane is of two type
  1. Plasma membrane
  2. Cell wall

PLASMA MEMBRANE:

  • Plasma membrane, also called cell membrane, is the outermost boundary of an animal cell however in most plant cells, it is covered externally by a cell wall.

COMPOSITION OF PLASMA MEMBRANE:

Plasma membrane is mainly composed of lipids and proteins,

  • 60-80% are proteins
  • 20-40% are lipids
  • In addition, carbohydrates are present in minute quantities

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[Biology] Cytoplasm

Reading Time: 12 minutes

PROTOPLASM

  • The living contents of a cell are termed as protoplasm
  • Protoplasm consists of
  1. Cytoplasm
  2. Nucleus

CYTOPLASM:

Cytoplasm is the protoplasm of a cell outside the nucleus

COMPONENTS OF CYTOPLASM:

Cytoplasm has three main components which are

  1. Cytosol
  2. Organelles
  3. Cytoplasmic inclusions

CYTOSOL

  • The soluble part of cytoplasm is the cytosol and forms the ground substance of cytoplasm.
  • Chemically cytosol is 90% water forming a solution containing all the fundamental molecules of life.
  • In cytosol, small molecules and ions may form true solutions and some large molecules form colloidal solutions.
  • Colloidal solution may be a sol (non-viscous) or a gel (viscous). Peripheral parts of the cytoplasm are often gel like.

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[Biology] Nucleus

Reading Time: 5 minutes Nucleus serves as a centre for controlling all the activities of the cell

DISCOVERY:

  • Robert Brown in 1831 was the first individual to observe nucleus.
  • The discovery of nucleus was a revolutionary step which disregarded the concept of cell being an empty compartment bound by thick walls

PLACEMENT:

  • In animal cell, the nucleus occupies a central position.
  • In plant cell, the nucleus is pushed towards the periphery by the central vacuole.

NUCLEI PER CELL:

  • Generally, cells contain a single nucleus and are termed as mono-nucleate cells.
  • Cells containing two or more nuclei are termed as multi-nucleate cells.

VISIBILITY:

  • Nucleus is only visible under the microscope when cell is in non-dividing stage. It contains chromatin material and soluble sap called nucleoplasm.
  • In dividing cell, the nucleus disappears and the chromatin material in it is replaced by chromosomes.

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[Biology] Comparison between (plant & animal cell)+(prokaryotes & eukaryotes)

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PLANT AND ANIMAL CELL

  • Both plant and animal cells are eukaryotic cells.
  • The basic structure of both cells is almost identical.
  • Plant and animal cells are bound by membrane in which the protoplasm is contained.
  • The cytoplasm of each cell consists of membrane-bound organelles that are specialized to carry out specific tasks.
  • The nucleus act as a surveillance center in both animal and plant cells overlooking and controlling all cellular process.
  • Although Plants and animal cells share similarities on various grounds, they are at the same time quite different from one another in various regards.

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[Biology] Biomolecules

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INTRODUCTION

  • All living things are made up of certain chemical compounds that are broadly classified as organic and inorganic compounds.
  • The organic compounds encompass the biological molecules present in the living system.

BIOLOGICAL MOLECULES:

Biological molecules or biomolecules is a broad term used for representing the molecules or ions present in a living system that take part in the chemical processes carried out by the living systems.

BRANCHES:

The study of biological molecules is carried out by correlating Molecular biology with Biochemistry.

MOLECULAR BIOLOGY:

It is the branch of biology in which we study the structure and functions of biological molecules along with molecular synthesis, modifications, mechanisms, and interactions.

BIOCHEMISTRY:

Biochemistry is a sub-discipline which deals with the study of chemical processes occurring within and related to living organisms.

TYPES OF BIOMOLECULES:

There are four main types of biological molecules

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[Biology] Importance of water

Reading Time: 3 minutes

INTRODUCTION

  • Water is the medium of life and is the most abundant compound in all organisms.
  • It is the most important component of the cell, typically forming between 70% to 95% of the mass of the cell.
  • Almost all reactions of the cell occur in the presence of water, taking part in various biochemical processes such as hydrolysis of macromolecules.

The following are some important properties of water holding biochemical significance.

WATER AS A SOLVENT:

  • Due to the polar nature of water, it acts as an excellent solvent for polar molecules and ions
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[Biology] Carbohydrates

Reading Time: 6 minutes A carbohydrate is either sugar or polymer of sugars consisting of carbon, hydrogen, and oxygen.

DEFINITION:


Carbohydrates are polyhydroxy aldehydes or ketones or compounds which yield them upon hydrolysis

EMPIRICAL FORMULA:

The empirical formula for carbohydrates is Cm(H2O)n.

BACKGROUND:

  • The term carbohydrates literally mean “hydrates of carbon”.
  • This name was assigned because, in most of the carbohydrates, the ratio of hydrogen and oxygen is the same as water (2:1).
  • However, there are several non-carbohydrate compounds that appear to be hydrates of carbon i.e. Acetic Acid (C2H4O2).
  • Further, some carbohydrates do not satisfy the empirical formula such as rhamnohexose (C6H12H5).
  • Therefore, carbohydrates cannot always be regarded as hydrates of carbon.

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[Biology] Proteins

Reading Time: 7 minutes

INTRODUCTION

Proteins are polymers of amino acids and are the most abundant organic molecules of the living system constituting about 50% of the cellular dry weight.

AMINO ACIDS:

Amino acids are organic compounds containing two functional groups i.e. amino (-NH2) group and carboxyl (-COOH) group along with a side chain specific to each amino acid.

STRUCTURE OF AMINO ACIDS:

Chemically, an amino acid consists of four components

  1. Carboxylic group (-COOH), which is basic in nature.
  2. Amino group (-NH2), which is acidic in nature.
  3. R side chain which is specific for each amino acid and accounts for the different types of amino acids.
  4. Hydrogen atom linked to the central carbon atom.

If both the carboxyl group and amino groups are attached to the same carbon, the amino acid is termed as α amino acid.

  • There are almost 400 identified amino acids occurring in nature however, only 20 are involved in protein formation in living organisms.
  • These 20 proteins arrange in various combinations to produce different types of proteins in living organism.

PEPTIDE LINKAGE:

The adjacent amino acids in a polypeptide protein chain are linked together via peptide bonds.

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[Biology] Lipids

Reading Time: 5 minutes

INTROUCTION

Lipids are heterogenous group of organic compounds that are relatively insoluble in water and soluble in organic solvents, actually or potentially related to fatty acids and utilized by the living cells

CHEMICAL COMPOSITION

chemically, lipids are esters of fatty acids with alcohol

FATTY ACIDS:

  • Fatty acids are carboxylic acids with a hydrocarbon side chain.

Fatty acids are of two types

  1. When there is no double bond present in the hydrocarbon chain of fatty acids, these fatty acids are termed as saturated fatty acids

  1. When the hydrocarbon side chain of fatty acids contains double bonds, such fatty acids are termed as unsaturated fatty acids.

ALCOHOLS:

Alcohols are a group of organic compounds containing on or more hydroxyl groups attached to a carbon atom.

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[Biology] Nucleic acids

Reading Time: 7 minutes

DEFINITION

Nucleic acids are polymers resulting from the linkage of smaller units called nucleotides.

BACKGROUND:

Nucleic acids were first isolated in 1869, by Fredrich Miescher from the nuclei of pus cells.

NUCLEOTIDES:

Nucleotides are small molecules acting as monomers and join together into a chain forming nucleic acids. Nucleic acids are therefore also known as polynucleotides.

COMPONENTS OF NUCLEOTIDE:

A nucleotide is composed of three components namely

  1. Nitrogen containing base
  2. Pentose sugar (5 carbon monosaccharide)
  3. Phosphate group

NITROGENOUS BASE:

  • The nitrogenous bases found in nucleotides (and hence nucleic acids) are heterocyclic compounds.
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