The Fundamental Unit Of Life Flashcards
Who discovered cell and when was it discovered?
Rober Hooke in 1665.
How was the cell discovered?
Robert Hooke examined a thin slice of cork in a self made microscope, it resembled as the structure of a honeycomb and small boxes can be seen these boxes were named as cell, a latin word for small room.
Who were the two biologist who discovered the cell theory and when was it discovered?
Scheilden in 1838 and Schewann in 1839.
Who expanded the cell theory and when was it expanded?
Virchow in 1855
Who discovered the free living cells in the pond water and when was it discovered?
Leuweenhoek in 1674
Who discovered the nucleus and when was it discovered?
Robert Brown in 1831
Who discovered the Protoplasm and when was it discovered?
Purkinje in 1839
What is a plasma membrane or cell membrane?
It is the outermost covering of a cell it separates the contents of a cell from external environment it allows only specific materials to go in or come out of the cell.
Define diffusion
Substances like carbon dioxide and oxygen can move across the cell membrane by the process of diffusion.
In what ways diffusion plays an important role?
Diffusion plays an important role in the gaseous exchange between the cell and between the cell and its external environment
Define osmosis?
The movement of water molecules through such a selectively permeable membrane is called osmosis. It is a net diffusion of water across a selectively permeable membrane toward a higher solute concentration.
Define hypotonic solution.
If the medium surrounding the cell has higher water concentration, meaning that the outside solution is very dilute the cell will gain water by osmosis.
Define isotonic solution.
If the medium has exactly same water concentration as the cell, there will be no net movement through the cell membrane.
Define hypertonic solution.
If the medium surrounding the cell has a lower water concentration than the cell, meaning that the solution is very concentrated the cell will lose water by osmosis.
What is plasma membrane made up of?
Plasma membrane is flexible and is made up of organic molecules called lipids and proteins.
Define endocytosis.
The flexibility of cell membrane enables the cell to engulf in food and other material from its external environment this process is known as endocytosis.
What is a cell wall? define its functions.
Plant cell have another rigid outer covering known as cell wall. This cell wall is mainly composed of cellulose. Cellulose is a complex substance which provides structural strength to the plants.
Define plasmolysis.
When are living plant cell loses water through osmosis there is a shrinkage or contraction of the contents of the cell away from the cell wall.
Define nuclear membrane and its functions.
The nucleus has a double layered covering called the nuclear membrane it has pores which allows a transfer of material from inside the nucleus to the cytoplasm
What are chromosomes?
They are rod shaped structures that can only be seen when the cells about to divide, they contain information for Inheritance of characters from parents to next generation in the form of DNA molecules, chromosomes are composed of DNA and proteins
Define DNA(deoxyribo nucleic acid)
DNA molecules contain information necessary for constructing and organising cells. Functional segments of DNA are called genes. In a Cell which is not dividing this DNA is present as a part of chromatin material.
What is chromatin material?
It is visible as entangled mass of thread like structures, whenever the cells about to divide it gets organised into chromosomes
Define nucleoid?
Undefined nuclear region containing only nucleic acid is called a nucleoid
Who are prokaryotes?
Organisms whose cells lack nuclear membrane
Who are eukaryotes?
Organisms with cell having a nuclear membrane
Difference between prokaryotic cells and Eukaryotic cells
Prokaryotic cell
1) size is generally small from 1 to 10 micrometre
2) nuclear region is not well defined and is known as nucleoid
3) chromosomes are single
4) membrane bound cell organelles are absent
Eukaryotic cell
1) size is generally large from 5 to 100 micrometer
2) nuclear region is well defined and surrounded by nuclear membrane
3) more than one chromosomes
4) membrane bound cell organelles are present
What is cytoplasm?
Cytoplasm is the fluid content present inside the plasma membrane, it also contains many specialized cell organelles, each of these cell organelles performs a specific function for the cell
What are endoplasmic reticulum?
It is a large network of membrane bound tubes and sheets, they look like long tubules or round or oblong bag, its membrane is similar to that of plasma membrane, endoplasmic reticulum are of two types rough endoplasmic reticulum and smooth endoplasmic reticulum
What is rough endoplasmic reticulum and what are its functions?
Rough endoplasmic reticulum looks rough under the microscope because it has particles called ribosomes attached to its surface, the ribosomes which are present in all active cells are the sites of protein manufacture, the manufactured protein is then sent to various parts depending on the need using the endoplasmic reticulum
What are the functions of smooth endoplasmic reticulum?
It helps in the manufacture of fat molecules or lipids important for cell functioning.
It helps in detoxifying many poisons and drugs
Define membrane biogenesis.
Building the cell membrane with the help of lipids and proteins is called membrane biogenesis.
What are the functions of Endoplasmic reticulum?
1) It serves as channels for transport of material between various regions of cytoplasm or between the cytoplasm and the nucleus.
2) It also functions as cytoplasmic framework providing a surface for biochemical activities.
Who first described Golgi apparatus?
Camillo Golgi
Describe cisterns.
System of membrane bound vesicles arranged approximately parallel to each other in stacks are called cisterns.
What is the function of Golgi apparatus?
1) the material synthesised near the endoplasmic reticulum is packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus
2) its functions include the storage, modification and packaging of products in vesicle.
3) it is also involved in the formation of lysosomes
What are lysosomes and what are its functions?
Lysosomes are membrane boundary sacks filled with digestive enzymes, these enzymes are made by rough endoplasmic reticulum, lysosomes are a kind of waste disposal system for the cell, they help to clean the cell by digesting any foreign material as well as worn out cell organelles.
How are lysosomes able to break down Complex substances into simpler substance?
Lysosomes are able to break Complex substances into simple substances because they contain powerful digestive enzymes capable of breaking down all organic material
Why are lysosomes known as suicidal bags?
Lysosomes are known as suicidal bags because during the disturbance in the cellular metabolism meaning when the cell get damage lysosomes may burst and the enzymes digest their own cell
What is mitochondria and what are its functions?
Mitochondria is the powerhouse of the cell. It has two membrane, the outer membrane is porous whereas the inner membrane is deeply folded, these deep folds increase the surface area for ATP generating chemical reactions. The energy required for chemical activities needed for life is released by mitochondria in the form of ATP molecules.
Define ATP(Adenosine Triphosphate)
It is known as the energy currency of the cell, the body uses energy stored in ATP for making new chemical compounds and for mechanical work
What are two types of plastids?
Chromoplast and leucoplast
What are chloroplasts?
Chromoplast containing the pigment chlorophyll, they are important in plants for photosynthesis, they also contain various yellow or orange pigments in addition to chlorophyll
What are leucoplasts?
They are primarily organelles in which materials such as starch, oil, and protein granules are stored
Define stroma
Internal organisation of chloroplast consist of numerous membrane layers embed in a material called stroma, these are similar to mitochondria in external structure like mitochondria plastids also have their own DNA and ribosomes
What are Vacuoles?
They are the storage sacs for liquid or solid contents. They are small sized in animals and large sized in plants, the central vacuole in some plants may occupy 50-90% of the cell volume.
What are the functions of vacuole?
In plant cells vacuoles are full of cell sap which provides turgidity and rigidity to the cell.
These include amino acids, sugars, various organic acids and some proteins.
They also play an important role in expelling excess water and some wastes from the cell.
Why a cell is known as the fundamental structural unit of Living Organism?
This is because each cell acquires its structure and ability to function because of the organisation of its membrane and organelles in specific ways, it has basic structural organisation, it helps the cell to perform certain task such as respiration, obtaining nutrition, clearing of waste material, and creating of new protein.
Define cell division
The process by which new cells are made is known as cell division.
What are the two main types of cell division?
Mitosis and meiosis
Define mitosis and what are its functions?
In this type of division most cell divide for growth, each cell called the mother cell divides to form two new identical daughter cells, these daughter cells have the same number of chromosomes as the mother cell, they help in the growth and repair of tissues in organisms, this type of division includes only one division.
Define meiosis and what are its function?
It involves two consecutive divisions, when a cell divided by meiosis it produces 4 new cells instead of just 2, the new cells only have half number of chromosomes then that of the mother cell.
