22 Biology -- Cell Biology

Describe the structure and function of mitochondria.

1 Answers

Structure of Mitochondria:

1. Double membrane: Mitochondria have two membranes—an outer membrane and an inner membrane—that enclose the organelle.

2. Inner membrane folds: The inner membrane contains numerous folds called cristae, which increase the surface area available for chemical reactions.

3. Matrix: The innermost compartment of the mitochondria is called the matrix, which is enclosed by the inner membrane and contains a gel-like substance.

4. DNA: Mitochondria have their own DNA, known as mitochondrial DNA (mtDNA), which is separate from the cell's nuclear DNA.

Function of Mitochondria:

1. Energy production: Mitochondria are often referred to as the "powerhouses" of the cell because their main function is to generate energy in the form of adenosine triphosphate (ATP) through cellular respiration.

2. ATP production: Mitochondria perform aerobic respiration, using oxygen and nutrients from the cell to produce ATP through processes like the Krebs cycle and oxidative phosphorylation.

3. Oxygen utilization: Mitochondria are responsible for consuming oxygen during the process of oxidative phosphorylation, where electrons are transferred along the electron transport chain to generate ATP.

4. Metabolism regulation: Mitochondria play a vital role in regulating cellular metabolism by controlling the breakdown of various molecules, such as carbohydrates and fatty acids, to produce energy.

5. Calcium homeostasis: Mitochondria help maintain cellular calcium levels by taking up and releasing calcium ions, which are crucial for several cellular processes, including signaling and muscle contraction.

6. Apoptosis regulation: Mitochondria are involved in programmed cell death, known as apoptosis. They release certain molecules that trigger the apoptosis pathway, playing a critical role in cell survival and development.

7. Heat production: In certain specialized cells, mitochondria can generate heat instead of ATP through a process called thermogenesis. This is particularly important for maintaining body temperature in organisms such as hibernating animals and newborn infants.

Define suicidal bag. Why is Lysosome called so?

Suicidal bag also known as lysosome is a cell organelle which are sphere shaped sacs filled with hydrolytic enzymes that have the capability to break down many types of biomolecules including the useful cells and materials that can derail the functioning of the cell . It mostly occurs in ageing, dead and diseased cells.

Lysosome is called as suicidal bag because it helps in the self-destruction of its cell, tissue or organs by releasing the lysosomal enzymes caused by rupturing of their...

why golgi body or golgi complex known as traffic police of cell?

In golgi complex, various substances like proteins, lipids, sterols, polysacchharids ect are chemically modified, to condensed and finally packed in secretion vesicles and transported to their final destination through the secretory path way and pass out from the cell through exocytosis. thus it is known as traffic police of cell.

Differentiate between RER and SER

RER	SER
RER stands for Rough Endoplasmic Reticulum.	SER stands for Soft Endoplasmic Reticulum.
Ribosomes attach to the outer surface of their membrane.	They don't bear ribosomes on their membrane.
They are mainly formed of cisternae and few tubules.	They are formed of vesicles and steroids.
They involve in synthesis of proteins and enzymes.	They involve in synthesis of glycogen, lipid and steroids.
They help in formation of lysosomes.	They help in formation of sphaerosomes.
They...

Which chemical gives rigidity to the cell wall?

Generally, cell wall is composed of cellulose which is one of its strongest layer. However, decomposition of additional amount of lignin on the cellulose forms the secondary cell wall which is primarily responsible for providing the rigidity to the cell. Hence, lignin is the chemical that gives rigidity to the cell wall.

Differentiate between heterochromatin and euchromatin.

Heterochromatin	Euchromatin
It is the darkly stained region of chromatin.	It is the lightly stained region of chromatin.
It remains tightly coiled and condensed during interphase.	It remains loosely coiled and diffused during interphase.
It is supposed to be metabolically and genetically inert.	It is supposed to be metabolically and genetically active.
It possess small amount of DNA and large amount of RNA.	It contains relatively large amount of DNA.

Differentiate between cytoplasm and nucleoplasm.

Cytoplasm	Nucleoplasm
It is found between cell-membrane and the nucleus.	It is found inside the nucleus.
Various types of cell organelles and cell inclusions are present in cytoplasm.	Only nucleoli and chromatin fibers are found in Nucleoplasm.
It helps in glycolysis, biosynthesis of proteins and exchange of materials between cell organelles	It helps in formation of spindle proteins during cell division and acts as nuclear skeleton.
Cyclosis occurs	Cyclosis doesn't occur.

What is Cyclosis? Why is it important?

The streaming movement of cytoplasm within the eukaryotic cell is called Cyclosis.

Cyclosis is important because of following reasons:

It helps in movement of cell organelles and cell inculsions.
It helps in distribution of materials inside the cell.
It helps in formation of pseudopodia in Amoeba and leucocytes.

What are cell inculsions?

Cell inculsions are non living, metabolically inactive substances present in cytoplasm. They are also called as deutoplasmic bodies or ergastic bodies. For eg: Carbohydrates, proteins, essential oils, latex, mineral crystals, cellulose, inulin, fats, oils, pigment, enzymes etc. They may also be produced as a by product of various metabolic activities inside the cell.

Compare: Chloroplast, Chromoplasts and leucoplasts.

Chloroplasts	Chromoplasts	Leucoplasts
It is green plastid.	It is coloured plastid.	It is colourless plastid.
It contains grana.	It lacks grana.	It lacks grana.
It bears chlorophyll pigment.	It bears carotenoids (carotene and xanthophyll) pigments.	It lacks pigments.
It is involved in synthesis of food.	It is involved in synthesis of phospholipids	It is involved in storage of food materials
It is found in green parts of plants such as leaves, unripe fruit, young stems	It is found...

What are F1 particles? Mention it's importance.

The small tennis racket like structure present in the cristae in the inner membrane of mitochondria are called F₁ particles. They are also called elementary particles or oxysomes.

In the head of F1 particles, enzyme ATPase or ATP synthase is present which controls the synthesis of ATP, so these are the functional unit of mitochondria Al's called as ATP particles

Name two semi-autonomous cell organelles. Why are they called so?

Mitochondria and Plastids are the two semi-autonomous cell organelles.

They are called semi-autonomous cell organelles because they have got all the requirements for the synthesis of proteins and enzymes for their functioning like:

I) 70S type of ribosomes

ii)Self replicating DNA molecules which can form RNA

iii) ATP molecules to provide energy.

However, they are not fully autonomous and some activities are performed by nuclear DNA.

What do you mean by active transport?

If the passage of substances across the selectively permeable plasma membrane requires the energy then it is called active transport.The energy required for active transport is obtained from ATP in the cell. For eg: Salt intake by plants take place through active transport.

What is plasmodesmata? Mention it's importance

Plasmodesmata are the gaps formed during the development of primary and secondary cell wall. They are important as they act as a cytoplasmic bridges or junctions between two adjacent cells and help in transfer of materials.

Name two types of proteins as reported in fluid mosaic model

The two types of proteins in fluid mosaic model are:

I) Extrinsic or peripheral proteins : They are the proteins that lie outside the outer and inner surface of Phospholipid bilayer.

ii) Intrinsic or internal proteins: They are partially or completely embedded over Phospholipid bilayer

Show your familiarity with phagocytosis, pinocytosis and exocytosis

Phagocytosis: It is the process of intake of large sized solid food particles by cell. It is also called as cell eating process.

Pinocytosis: It is the process of large sized liquid nutrients by cell. It is also called as cell drinking process.

Exocytosis: It is the process of expelling large sized materials outside the cell. It is also called as cell vomiting process.

Who termed protoplasm as the "physical basis of life" and why?

Huxley defined protoplasm as "physical basis of life" because it is the fundamental substance in all organisms. Protoplasm is endowed with life and as protoplasm does cell ceases to function and dies.

Differentiate between prokaryotic cells and eukaryotic cells

characters	prokaryotic cells	eukaryotic cells
envelope system	single envelope system	two envelop system
cell organelles	membrane-bound cell organelles are absent	membrane-bound cell organelles are present
cell wall	if present consists of murein	if present consists of cellulose hemicellulose and pectin
size of cell	usually smaller	comparatively larger
cell division	mostly amitosis	mitosis and meiosis

Differentiate between mitochondria and chloroplast

mitochondria	chloroplast
it is the site of aerobic respiration	it is the site of photosynthesis
thylakoids are absent	thylakoids are present
chlorophyll is absent	chlorophyll is present
cristae are present	cristae are absent
it is light-independent cell organelle	it is light-independent cell organelle

Why are mitochondria called the powerhouse of a cell?

Mitochondria are called the powerhouse of a cell as they release energy in the form of ATP (adenosine triphosphate).

Name the site for :protein synthesisphotosynthesis

protein synthesis= ribosomes
photosynthesis= chloroplasts

Define cellular totipotency.

cellular totipotency is the capacity of development of a whole body of organism from the living nucleated vegetative cell.

List out limitations of sandwich model

They are:

it could not explain the active and bulk transport of materials through the cell membrane
it couldn't explain the transport of solute and solvent through the cell membrane
lipid: protein ratio does not favor this method
it does not explain the functional specificity and variability in the biomembranes.

Describe the modern cell theory. Mention the exceptions of cell theory .

Cell

The modern cell theory states;

a.) Cells are the basic unit of both structure and function of living organisms.

b.) The body of an organism is made up of cell and their products.

c.) Every cell is made up of a small mass of protoplasm (nucleus, cell- organelles and plasma membrane with or without cell wall. )

d.) New cells arise from the division of pre-existing cells.

e.) Growth of an organism takes place through cell division and cell growth.

f.) Life passes from one generation to the next in...

Why mitochondria is known as semi-autonomous structure of cell?

Mitochondria is double membranous, semi autonomous structure which is the power house of the cell. It is a membrane bound cellular structure found in most of the eukaryotic cells.

Mitochondria is semi autonomous because of following reasons;

1. It has it's own DNA which can replicate independent of the nuclear DNA.

2. It also has it's own ribosome which helps in protein synthesis.

As mentioned above , mitochondria can synthesize protein, enzymes and other material on it's own due to it's DNA and...

Mention different types of cell wall.

These are the different types of cell wall :-

1. Plant Cell Wall (Cellulosic cell wall)

(Image of plant cell wall)

https://images.app.goo.gl/xecscFUZsfhK67JM9

2. Bacterial Cell Wall (Muramic cell wall)

(Image of bacterial cell wall)

https://images.app.goo.gl/Kjf3ZLduYvJX1w4dA

3. Fungal Cell Wall (Chitinous cell wall)

(Image of fungal cell wall)

https://images.app.goo.gl/TDEvW1pBr7uPgZvGA

4. Algal Cell Wall

(Image of Algal Cell Wall)

https://images.app.goo.gl/JLtMap73Qm8CMCn9A

5. Archaeal Cell Wall

(Image...

What is cell coat? What is its main function?

The secretion of any cell which gets incorporated into the cell surface and protects the cell from external environment, also is itself renewed periodically is referred to as a cell coat. The functions of the cell coat include :

1. To protect the cell membrane,

2. To aid the diffusion process,

3. To help in cell recognition during cell communication.

Is cell membrane selectively permeable or semi permeable? Why?

What is histocompatibility?

What are the types of Ribosomes?

The type of ribosome is determined by the speed with which they sediment in a centrifuge.

Two basic types of ribosomes are:

1. 70S ribosome

Subunits: 30S and 50S

2. 80S ribosome

Subunits: 40S and 60S

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