Posts from the ‘Class IX’ Category

SA2 Science Class IX Question Paper

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OTBA Material for class IX Science/ class XI Biology

CBSE-prepared-OTBA material avialable under Study Material category at home page of this blog.

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Mitochondria: Structure and Functions

mitochondria 2

Mitochondria Structure and Functions

Mitochondria is called the ‘powerhouse of the cell’.
It contains a number of enzymes and proteins that help process carbohydrates and fats obtained from the food we eat to release energy.
This energy is stored in ATP (adenosine triphosphate) molecules that are produced in the mitochondria by the process of oxidative phosphorylation.
Although mitochondria are present in every cell, they are found in high concentrations in the muscle cells that require more energy.
Though the primary function of mitochondria is to produce energy, they also play an important role in the metabolism and synthesis of certain other substances in the body.

Structure:
Mitochondria are present in both plant and animal cells.
They are rod-shaped structures that are enclosed within two membranes – the outer membrane and the inner membrane.
The membranes are made up of phospholipids and proteins.

The space in between the two membranes is called the inter-membrane space which has the same composition as the cytoplasm of the cell.
However, the protein content in this space differs from that in the cytoplasm.
The structure of the various components of mitochondria are as follows:

Outer Membrane

The outer membrane is smooth unlike the inner membrane and has almost the same amount of phospholipids as proteins. It has a large number of special proteins called porins, that allow molecules of 5000 daltons or less in weight to pass through it. The outer membrane is completely permeable to nutrient molecules, ions, ATP and ADP molecules.

Inner Membrane
The inner membrane is more complex in structure than the outer membrane as it contains the complexes of the electron transport chain and the ATP synthetase complex.
It is permeable only to oxygen, carbon dioxide and water. It is made up of a large number of proteins that play an important role in producing ATP, and also helps in regulating transfer of metabolites across the membrane.
The inner membrane has infoldings called the cristae that increase the surface area for the complexes and proteins that aid in the production of ATP, the energy rich molecules.

Matrix
The matrix is a complex mixture of enzymes that are important for the synthesis of ATP molecules, special mitochondrial ribosomes, tRNAs and the mitochondrial DNA. Besides these, it has oxygen, carbon dioxide and other recyclable intermediates.
Although most of the genetic material of a cell is contained within the nucleus, the mitochondria have their own DNA. They have their own machinery for protein synthesis and reproduce by the process of fission like bacteria do.
Due to their independence from the nuclear DNA and similarities with bacteria, it is believed that mitochondria have originated from bacteria by endosymbiosis.

Functions

Functions of mitochondria vary according to the cell type in which they are present.

The most important function of the mitochondria is to produce energy.
The food that we eat is broken into simpler molecules like carbohydrates, fats, etc., in our bodies.
These are sent to the mitochondrion where they are further processed to produce charged molecules that combine with oxygen and produce ATP molecules.
This entire process is known as oxidative phosphorylation.

It is important to maintain proper concentration of calcium ions within the various compartments of the cell.
Mitochondria help the cells to achieve this goal by serving as storage tanks of calcium ions.
They also help in the building of certain parts of the blood, and hormones like testosterone and estrogen.
Mitochondria in the liver cells have enzymes that detoxify ammonia.
They play an important role in the process of programmed cell death. Unwanted and excess cells are pruned away during the development of an organism. The process is known as apoptosis. Abnormal cell death due to mitochondrial dysfunction can affect the function of the organ.

mitochondria  1

Cell Membrane

                                   cellmembrane2

Cell (plasma) membrane. Both prokaryotic and eukaryotic cells are bound by a cell (plasma) membrane. The cell membrane is selectively permeable, allowing certain substances to pass through, but not others. Water, alcohol, and gases readily pass through the cell membrane, but ions, large proteins, and carbohydrates do not. Substances can pass through the cell membrane via one of the processes listed below.

Diffusion and Osmosis

Diffusion

-the process by which molecules spread from areas of high concentratiion, to areas of low concentration. When the molecules are even throughout a space – it is called EQUILIBRIUM

diffusion

Concentration gradient – a difference between concentrations in a space.

Molecules will always move down the concentration gradient, toward areas of lesser concentration. Think of food coloring that spreads out in a glass of water, or air freshener sprayed in a room.

Selectively Permeable – membranes that allow some things through, the cell membrane is selectively permeable, water and oxygen move freely across the cell’s membrane, by diffusion

Osmosis – the diffusion of water (across a membrane)

Water will move in the direction where there is a high concentration of solute (and hence a lower concentration of water.

A simple rule to remember is: salt sucks

Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

 

Type of Solutions

Isotonic Solutions

If the concentration of solute (salt) is equal on both sides, the water will move back in forth but it won’t have any result on the overall amount of water on either side.

ISO” means the same

isotonic

Hypotonic Solutions

The word “HYPO” means less, in this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell.

The cell will gain water and grow larger. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting

In animal cells, the cell may be in danger of bursting, organelles calledCONTRACTILE VACUOLES will pump water out of the cell to prevent this.

hypotonic

Hypertonic Solutions

The word “HYPER” means more, in this case there are more solute (salt) molecules outside the cell, which causes the water to be sucked in that direction.

In plant cells, the central vacuole loses water and the cells shrink, causing wilting.

In animal cells, the cells also shrink.

In both cases, the cell may die.

This is why it is dangerous to drink sea water – its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water.

This is also why “salting fields” was a common tactic during war, it would kill the crops in the field, thus causing food shortages.

hypertonic

Diffusion and Osmosis are both types of PASSIVE TRANSPORT – that is, no energy is required for the molecules to move into or out of the cell.

Sometimes, large molecules cannot cross the plasma membrane, and are “helped” across by carrier proteins – this process is called facilitated diffusion.

CLASS IX ( SOLUTION OF BIOLOGY PART) FA3 EXAM

Section B (Biology)

Q5. Write the name of largest phylum of Animalia kingdom.

Ans. Arthropoda

Q6. Which group of plants is known as “Amphibians of Plantae kingdom” and why?

Ans. Bryophyta, because members of this group live on land as well as in water.

 

Q7. What is the concept of Binomial Nomenclature? Explain and write the rules also.

Ans. Scientific naming of living organisms is known as Binomial Nomenclature. It was given by    Carolous Linnaeus.

Rules: 1. Each scientific name has two epithets, each of them should be underlined separately.

2. Each scientific name should be in ITALICS if printed.

3. First name should be started with Capital letter and Second name should be started

with small letter.

 

Q8.

A. Write the name of kingdom in which bacteria are kept in five kingdom system. Give one example of this kingdom.

Ans. Monera; Mycoplasma

 

B. Write the name of group of plants with naked seeds. Give one example of this group.

Ans. Gymnosperms; Cycas,Pinus etc.

C. Write the names of two scientists who proposed five kingdom system.

Ans. Carl Woose & R H Whittaker

 

Q9. Write the name of phylum of following animals:                                                                                        4

i)Starfish – ECHINODERMATA

ii) Bat –  MAMMALIA OF VERTEBRATA

iii) Hydra – COELENTRATA

iv) Unio- MOLLUSCA

v) Earthworm    – ANNELIDA

vi) Cockroach     – ARTHROPODA

vii) Balanoglossus – PROTOCHORDATA

viii) Sycon – PORIFERA

 

Class IX Science FA 3

Kendriya Vidyalaya, Sikar

Formative Assessment-3

Class IX

MM: 40                                                                                                                                                                Time duration: 90 mins

Section A (Chemistry)

Q1. Calculate the molecular mass of the following Substance :                                                          6X1/2=3

i)  HNO3                                ii) S8                                       iii) K2CO3

iv) C2H5OH                           v) CaCo3                               vi) Al(OH)3

Q2. Write the chemical formula of the following substances :                                                           6X1/2=3

i) Aluminium oxide                          ii) Calcium hydroxide

iii)  Ammonium Sulphate              iv) Ferric chloride

v) Sodium Sulphite                          vi) Zinc Phosphate

Q3. Convert the following masses into moles :

i) 64 gm of Oxygen gas                   ii) 20 gm of water

iii) 34 gm of Ammonia                                    iv) 22 gm of Carbon dioxide

v) 120 gm of Calcium                                       vi) 52 gm of Helium

Q4. Calculate the number of aluminium ions present in 0.05 gm alluminium oxide.

 

Section B (Biology)

Q5. Write the name of largest phylum of Animalia kingdom.                        1

Q6. Which group of plants is known as “Amphibians of Plantae kingdom” and why?                         1+1

Q7. What is the concept of Binomial Nomenclature? Explain and write the rules also.                      1+2

Q8. A. Write the name of kingdom in which bacteria are kept in five kingdom system. Give one example of this kingdom.                                                                                                                                                                                1

B. Write the name of group of plants with naked seeds. Give one example of this group.      1

C. Write the names of two scientists who proposed five kingdom system.                                    1

Q9. Write the name of phylum of following animals:                                                                                        4

i)Starfish                             ii) Bat                     iii) Hydra                                              iv) Unio

v) Earthworm                    vi) Cockroach     vii) Balanoglossus                             viii) Sycon

 

Section C (Physics)

Q10. A lift carries five persons with an average mass of 60 kg to a height of 27 m in 9 secs at a constant speed. What is the power of the lift.                                                                                                                              2

Q11. What is the commercial unit of the energy?                                                                                              1

Q12. A ball of mass 200 gm is thrown vertically upwards with a velocity of 20 m/sec. Calculate its P.E. after 2 secs. (Take g=9.8 m/s2).                                                                                                                                       2

Q13. Define work. What is the work done on a body moving in a circular path? What is the SI unit of work? Define it.                                                                                                                                                                       3

Q14. State law of conservation energy. Prove that the mechanical energy is always constant for a freely falling body.                                                                                                                                                                      3

Q15. Answer in one word or sentence :                                                                                                                 3

  1. Name the physical quantity that defines the rate of doing work.
  2. What is the work done by the moon in rotating around the earth.
  3. Is power a scalar or vector quantity?

. What is the commercial unit of the energy?                                                                                              1

Q12. A ball of mass 200 gm is thrown vertically upwards with a velocity of 20 m/sec. Calculate its P.E. after 2 secs. (Take g=9.8 m/s2).                                                                                                                                       2

Q13. Define work. What is the work done on a body moving in a circular path? What is the SI unit of work? Define it.                                                                                                                                                                       3

Q14. State law of conservation energy. Prove that the mechanical energy is always constant for a freely falling body.                                                                                                                                                                      3

Q15. Answer in one word or sentence :                                                                                                                 3

  1. Name the physical quantity that defines the rate of doing work.
  2. What is the work done by the moon in rotating around the earth.
  3. Is power a scalar or vector quantity?