The Fundamental Unit Of Life

Question 1

Who discovered cell and when was it discovered?

Answer 1

Rober Hooke in 1665.

Question 2

How was the cell discovered?

Answer 2

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.

Question 3

Who were the two biologist who discovered the cell theory and when was it discovered?

Answer 3

Scheilden in 1838 and Schewann in 1839.

Question 4

Who expanded the cell theory and when was it expanded?

Answer 4

Virchow in 1855

Question 5

Who discovered the free living cells in the pond water and when was it discovered?

Answer 5

Leuweenhoek in 1674

Question 6

Who discovered the nucleus and when was it discovered?

Answer 6

Robert Brown in 1831

Question 7

Who discovered the Protoplasm and when was it discovered?

Answer 7

Purkinje in 1839

Question 8

What is a plasma membrane or cell membrane?

Answer 8

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.

Question 9

Define diffusion

Answer 9

Substances like carbon dioxide and oxygen can move across the cell membrane by the process of diffusion.

Question 10

In what ways diffusion plays an important role?

Answer 10

Diffusion plays an important role in the gaseous exchange between the cell and between the cell and its external environment

Question 11

Define osmosis?

Answer 11

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.

Question 12

Define hypotonic solution.

Answer 12

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.

Question 13

Define isotonic solution.

Answer 13

If the medium has exactly same water concentration as the cell, there will be no net movement through the cell membrane.

Question 14

Define hypertonic solution.

Answer 14

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.

Question 15

What is plasma membrane made up of?

Answer 15

Plasma membrane is flexible and is made up of organic molecules called lipids and proteins.

Question 16

Define endocytosis.

Answer 16

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.

Question 17

What is a cell wall? define its functions.

Answer 17

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.

Question 18

Define plasmolysis.

Answer 18

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.

Question 19

Define nuclear membrane and its functions.

Answer 19

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

Question 20

What are chromosomes?

Answer 20

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

Question 21

Define DNA(deoxyribo nucleic acid)

Answer 21

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.

Question 22

What is chromatin material?

Answer 22

It is visible as entangled mass of thread like structures, whenever the cells about to divide it gets organised into chromosomes

Question 23

Define nucleoid?

Answer 23

Undefined nuclear region containing only nucleic acid is called a nucleoid

Question 24

Who are prokaryotes?

Answer 24

Organisms whose cells lack nuclear membrane

Question 25

Who are eukaryotes?

Answer 25

Organisms with cell having a nuclear membrane

Question 26

Difference between prokaryotic cells and Eukaryotic cells

Answer 26

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

Question 27

What is cytoplasm?

Answer 27

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

Question 28

What are endoplasmic reticulum?

Answer 28

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

Question 29

What is rough endoplasmic reticulum and what are its functions?

Answer 29

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

Question 30

What are the functions of smooth endoplasmic reticulum?

Answer 30

It helps in the manufacture of fat molecules or lipids important for cell functioning. It helps in detoxifying many poisons and drugs

Question 31

Define membrane biogenesis.

Answer 31

Building the cell membrane with the help of lipids and proteins is called membrane biogenesis.

Question 32

What are the functions of Endoplasmic reticulum?

Answer 32

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.

Question 33

Who first described Golgi apparatus?

Answer 33

Camillo Golgi

Question 34

Describe cisterns.

Answer 34

System of membrane bound vesicles arranged approximately parallel to each other in stacks are called cisterns.

Question 35

What is the function of Golgi apparatus?

Answer 35

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

Question 36

What are lysosomes and what are its functions?

Answer 36

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.

Question 37

How are lysosomes able to break down Complex substances into simpler substance?

Answer 37

Lysosomes are able to break Complex substances into simple substances because they contain powerful digestive enzymes capable of breaking down all organic material

Question 38

Why are lysosomes known as suicidal bags?

Answer 38

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

Question 39

What is mitochondria and what are its functions?

Answer 39

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.

Question 40

Define ATP(Adenosine Triphosphate)

Answer 40

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

Question 41

What are two types of plastids?

Answer 41

Chromoplast and leucoplast

Question 42

What are chloroplasts?

Answer 42

Chromoplast containing the pigment chlorophyll, they are important in plants for photosynthesis, they also contain various yellow or orange pigments in addition to chlorophyll

Question 43

What are leucoplasts?

Answer 43

They are primarily organelles in which materials such as starch, oil, and protein granules are stored

Question 44

Define stroma

Answer 44

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

Question 45

What are Vacuoles?

Answer 45

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.

Question 46

What are the functions of vacuole?

Answer 46

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.

Question 47

Why a cell is known as the fundamental structural unit of Living Organism?

Answer 47

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.

Question 48

Define cell division

Answer 48

The process by which new cells are made is known as cell division.

Question 49

What are the two main types of cell division?

Answer 49

Mitosis and meiosis

Question 50

Define mitosis and what are its functions?

Answer 50

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.

Question 51

Define meiosis and what are its function?

Answer 51

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.