Chapter 1 - Fundamental Unit Of Life

Question 1

What is a cell?

Answer 1

The basic functional and structural unit of life.

Question 2

Discovery of cell

Answer 2

In 1665, Robert Hooke observed the honeycomb like structures in a thin slice of cork (non-living) under a self designed primitive microscope.

Question 3

Discovery of free living cells in pond water for the first time was done by

Answer 3

Leeuwenhoek in 1674 by his own microscope.

Question 4

Discovery of the nucleus of the cell was done by

Answer 4

Robert Brown 1831

Question 5

Who coined the term “protoplasm” for the fluid substance of the cell?

Answer 5

Purkinje in 1839

Question 6

The Cell Theory was given by

Answer 6

Schleiden (1838) and Schwann (1839) two German biologists.

Question 7

Cell theory states

Answer 7

The cell is the basic functional and structural part of living things.
All things are made up of cells.

Question 8

Cell theory was further expanded by

Answer 8

Virchow (1855) by suggesting that “All cells arise from pre existing cells”
Omnis Cellula e Cellula

Question 9

Discovery of Electron Microscope in 1940, enabled us to

Answer 9

Observe and understand the complex structure of the cell and its various organelles.

Question 10

The 3 basic features present in every cell is

Answer 10

Plasma membrane
Nucleus
Cytoplasm

Question 11

Plasma membrane

Answer 11

It is the outermost covering of the cell that separates the contents of the cell from its external environment.

Question 12

Hypotonic Solution

Answer 12

If the medium surrounding the cell has a higher water concentration than the cell, meaning that the outside solution is very dilute, the cell will gain water by osmosis. The cell swells up.

Question 13

Importance of Plasma membrane

Answer 13

The plasma membrane allows or permits the entry and exit of some materials in and out of the cell. It also prevents movement of some other materials. Therefore it is known as a selectively-permeable membrane.

Question 14

Diffusion

Answer 14

The spontaneous movement of a substance from a region of high concentration to a region where its concentration is low.

Question 15

Importance of Diffusion

Answer 15

Diffusion plays an important role in gaseous exchange between the cells as well as the cell and its external environment.

Question 16

The plasma membrane is flexible and is made up of organic molecules called

Answer 16

Phospholipids made up of lipids and proteins

Question 17

Endocytosis

Answer 17

The process by which a cell engulfs material into the cell due to the flexibility of the cell membrane.

Question 18

Hypotonic Solution

Answer 18

If the medium surrounding the cell has a higher water concentration than the cell, meaning that the outside solution is very dilute, the cell will gain water by osmosis. Such a solution is called as

Question 19

Isotonic Solution

Answer 19

If the medium has exactly the same water concentration as the cell, there will be no net movement of water across the cell membrane. The cell remains the same size.

Question 20

Hypertonic Solution

Answer 20

If the medium has a lower concentration of water than the cell,meaning that it is a very concentrated solution, the cell will lose water by osmosis. The cell shrinks.

Question 21

Applications of osmosis

Answer 21

Unicellular freshwater organisms and most plant cells tend to gain water through osmosis.

Question 22

The plasma membrane is flexible and is made up of organic molecules called

Answer 22

Phospholipids

Question 23

Endocytosis

Answer 23

The process by which a cell engulfs material into the cell due to the flexibility of the cell membrane.

Question 24

Cellulose

Answer 24

It is a complex substance and provides structural strength to plants.

Question 25

Plasmolysis

Answer 25

When a living plant cell loses water through osmosis there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.

Question 26

Importance of Cell wall

Answer 26

Cell walls permit the cells of plants, fungi and bacteria to withstand very dilute (hypotonic) external media without bursting. It is semi-permeable

Question 27

How does the cell wall save the Cell from bursting?

Answer 27

In hypotonic solutions the cells tend to take up water by osmosis. The cell swells, building up pressure against the cell wall. The wall exerts an equal pressure against the swollen cell. In this condition the cell is said to be turgid.

Question 28

The nucleus has a double layered covering called

Answer 28

It has pores which allow the transfer of material from inside the nucleus to its outside.

Question 29

Chromosomes

Answer 29

"Rod-shaped" structures seen in the nucleus "only when the cell is about to divide."

Question 30

What do Chromosomes contain?

Answer 30

Chromosomes contain information for inheritance of features from parents to next generation in the form of DNA

Question 31

DNA and RNA stand for

Answer 31

Deoxyribonucleic Acid and Ribonucleic acid

Question 32

Chromosomes are composed of

Answer 32

DNA and proteins

Question 33

Functional segments of DNA are called

Answer 33

Genes

Question 34

In a cell which is not dividing, this DNA is present as

Answer 34

Part of Chromatin

Question 35

Chromatin

Answer 35

Chromatin material is visible as entangled mass of thread-like structures.

Question 36

Role of Nucleus

Answer 36

1. It plays a central role in cellular reproduction, the process by which a single cell divides and forms two new cells. 2. It determines the way the cell will develop and what form it will exhibit at maturity, by directing the chemical activities of the cell.

Question 37

Such organisms, whose cells lack a nuclear membrane(nucleoid), are called

Answer 37

"Prokaryotes" | Pro = primitive or primary; karyote ≈ karyon= nucleus

Question 38

Prokaryotic cell vs Eukaryotic cell

Answer 38

``` Prokaryotic Cell: - single-celled organism - lacks a membrane-bound nucleus - No cell organelles Eukaryotic Cell: - contains a nucleus and other organelles enclosed within membranes ```

Question 39

The significance of membranes can be illustrated with the example of

Answer 39

Viruses lack any membranes and hence don't show characteristics of life until they enter a living body and use its cell machinery to multiply.

Question 40

Cell Organelles

Answer 40

specialized cell structures characterized as very small/responsible for specific cell activity

Question 41

Endoplasmic Reticulum (ER)

Answer 41

It is a large network of membrane-bound tubes and sheets. It looks like long tubules or round or oblong bags (vesicles).

Question 42

The ER membrane is similar in structure to the

Answer 42

Plasma Membrane

Question 43

Rough Endoplasmic Reticulum

Answer 43

RER looks rough under a microscope because it has particles called ribosomes attached to its surface. Manufacturing of Protein with the help of ribosomes.

Question 44

Protein manufacturing at RER

Answer 44

The ribosomes, which are present in all active cells, are the sites of protein manufacture. The manufactured proteins are then sent to various places in the cell depending on need,using the ER.

Question 45

Smooth Endoplasmic Reticulum (SER)

Answer 45

The region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface. Smooth Endoplasmic Reticulum (SER) The SER helps in the manufacture of fat molecules, or lipids,important for cell function.

Question 46

Membrane biogenesis

Answer 46

In this process, some of these proteins and lipids synthesised by SER help in building the cell membrane.

Question 47

More functions of SER

Answer 47

1. Some other proteins and lipids synthesised by it function as enzymes and hormones. 2. It also plays a crucial role in detoxifying many poisons and drugs

Question 48

Functions of ER

Answer 48

Although the ER varies greatly in appearance in different cells, it always forms a network system. Thus, one function of the ER is to serve as channels for the transport of materials (especially proteins) between various regions of the cytoplasm or between the cytoplasm and the nucleus.

Question 49

The ER also functions as a "cytoplasmic network" providing

Answer 49

a surface for some of biochemical activities of the cell

Question 50

Golgi apparatus

Answer 50

A system of membranes that modifies and packages proteins for export by the cell.

Question 51

It consists of a system of membrane-bound vesicles arranged approximately parallel to each other in stacks called

Answer 51

"Cisterns" These membranes often have connections with the membranes of ER and therefore constitute another portion of a complex cellular membrane system.

Question 52

What is Division of Labour?

Answer 52

It is the breakdown of workload to smaller and more specific tasks that helps individual cells function more efficiently.

Question 53

What is concentration gradient?

Answer 53

The difference in the concentrations of the molecules in the two areas is called the concentration gradient.

Question 54

Cytosol

Answer 54

The fluid in the cytoplasm which holds the organelles in the cell. The cytosol, being a fluid, allows for biological reactions and mechanisms to occur, and for transport of substances between organelles