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Class XI biology paper

11th bio 1


OTBA Material for class IX Science/ class XI Biology

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


Definitions related with Human Excretory System

• Anuria refers to a total stop of urine production frequently caused by circulatory failure with anoxic damage of the tubular system.
• (Renal plasma) Clearance is a cleaning index for blood plasma passing the kidneys. The efficacy of this cleaning process is directly proportional to the excretion rate for the substance, and inversely proportional to its plasma concentration.
• Diuresis is an increased urine flow (ie, volume of urine produced per time unit).
• Excretion fraction (EF) for a substance is the fraction of its glomerular filtration rate, which passes to and is excreted in the urine.
• ¬Extraction fraction (E) for a substance is the fraction extracted by glomerular filtration from the total amount of substance delivered to the kidney during one passage of the arterial blood plasma.
• Free water clearance is the difference between urine flow and osmolar clearance (see below). The free water clearance is an indicator of the excretion of solute-free water by the kidneys. Excess water is excreted compared to solutes, when free-water clearance is positive. Excess solutes are excreted compared to water, when free-water clearance is negative. – Free water clearance is an estimate of the renal capacity for excretion of solute-free water.
• Glomerular filtration is due to a hydrostatic/colloid osmotic pressure gradient – the Starling forces.
• Glomerular filtration fraction (GFF) is the fraction of the plasma flowing to the kidneys that is ultrafiltered (GFR/RPF). GFF is normally 0.20 or 1/5. – The GFF is reduced during acute glomerulonephritis.
• Glomerulonephritis is an autoimmune injury of the glomeruli of both kidneys.
• Glomerular filtration rate (GFR) is the volume of glomerular filtrate produced per min.
• Glomerular propulsion pressure in the blood of the glomerular capillaries is the hydrostatic minus the colloid osmotic pressure of the blood (ie, 2-3 kPa in a healthy resting person).
• Glomerulo-tubular balance refers to the simultaneous increase in NaCl and water reabsorption in the proximal tubules as a result of an increase in GFR and filtration rate of NaCl. An almost constant fraction of salt and water is thus reabsorbed regardless of the size of GFR.
• Nephron: A nephron consists of a glomerulus, a proximal tubule forming several coils (pars convoluta) before ending in a straight segment (pars recta), the thin part of the Henle loop and a distal tubule also with a pars recta and a pars convoluta.
• The nephrotic syndrome refers to a serious increase in the permeability of the glomerular barrier to albumin, resulting in a marked loss of albumin in the urine. The albuminuria (more than 3 g per day) causes hypoalbuminaemia and generalized oedema.
• Net ultrafiltration pressure is the pressure gradient governing the glomerular filtration – the net result of the so-called Starling forces (see Fig. 25-7).
• Osmolar clearance is the plasma volume cleared of osmoles (solutes) each minute. – Osmolar clearance is also defined as the fictive urine flow that would have rendered the urine isosmolar with plasma. – Osmolar clearance is the difference between the urine flow and the free water clearance, and osmolar clearance estimates the renal capacity to excrete solutes.
• Osmolarity is the amount of osmotically active particles dissolved in a litre of solution.
• Proximal tubule consists of the proximal convoluted tubule and pars recta.
• Renal threshold for glucose is the blood glucose concentration at which the glucose can be first detected in the urine (appearance threshold) or at which the reabsorption capacities of all tubules are saturated (saturation threshold).
• Renal ultrafiltrate is also compared to plasma water, because it is composed like plasma minus proteins. The fraction of one litre of plasma that is pure water is typically 0.94. Thus, the concentration of many substances in the ultrafiltrate, Cfiltr, is equal to Cp/0.94.
• Single effect gradient is a transepithelial concentration gradient between the tubular fluid and the medullary interstitial fluid established at each level of the thick ascending limb by active NaCl reabsorption.
• Tmax refers to the maximal net transfer rate of substance by tubular secretion or reabsorption.
• Tubular passage fraction. The fraction of the amount ultrafiltered of substance passing a cross section of the nephron is the passage fraction. The passage fraction for inulin does not vary at all throughout the nephron. The passage fraction for inulin is one and remains so.
• Tubular reabsorption fraction. The reabsorption fraction is the reverse of the passage fraction (1 minus the passage fraction).
• Tubular reabsorption (active or passive) is the net movement of water and solute from the tubular lumen to the tubule cells and often further on into the peritubular capillary network.
• Tubular secretion (active or passive) represents the net addition

Sample Paper Class XI Biology III unit test

Sample paper
Unit Test III Class XI Subject : Biology
Max Marks 40 Duration 90 Mins.

1. What is meant by Tidal Volume? Give its value also for a normal adult human. (½+½)
2. Which blood group is Universal Donor? Which antigens are present in this blood group? (½+½)
3. Write the name of :-
1. Enzyme present in saliva.
2. Secretion of small intestine
3. Movement of human gut
4. End product of digestion of fat.

4. Explain the mechanism of Breathing in detail. (4)
5. Give a well labelled diagram to show duct system between Pancreas, Liver, Gall bladder and Small Intestine. (4)
6. Explain structure of the Heart with the help of suitable diagram. (4)
7. Write a note on Erythroblastosis foetalis. (4)
8. Explain sigmoid growth curve with the help of suitable diagram. Also label it’s all stages. (5)
9. Give details of ECG and ANGINA. (3+2=5)
10. Explain following terms :- (1×10=10)
1. Diphyodont
2. Heterophyodont
3. Total lung capacity
4. IRV
5. Dental formula
6. Cardiac cycle
7. Chyme
8. Differentiation
9. CAD
10. Diarrhoea


Our Digestive System

digestive sys

Your Digestive System

The story we’re about to tell is of stormy seas, acid rains, and dry, desert-like conditions. It’s an arduous journey that traverses long distances and can take several days. It’s one in which nothing comes through unchanged. It’s the story of your digestive system whose purpose is turn the food you eat into something useful — for your body!

Down the Hatch
It all starts with that first bite of pizza. Your teeth tear off that big piece of crust. Your saliva glands start spewing out spit like fountains. Your molars grind your pizza crust, pepperoni, and cheese into a big wet ball. Chemicals in your saliva start chemical reactions. Seemingly like magic, starch in your pizza crust begins to turn to sugar! A couple of more chews and, then, your tongue pushes the ball of chewed food to the back of your throat. A trap door opens, and there it goes, down your gullet!

Next, your muscles squeeze the wet mass of food down, down, down a tube, or oesophagus, the way you would squeeze a tube of toothpaste. It’s not something you tell your muscles to do — they just do it — in a muscle action called peristalsis. Then, the valve to the stomach opens and pizza mush lands in your stomach!

Inside your stomach
Imagine being inside a big pink muscular bag — sloshing back and forth in a sea of half-digested mush and being mixed with digestive chemicals. Acid rains down from the pink walls which drip with mucus to keep them from being eroded.

Sound a little like an amusement ride gone crazy? Every time you think you’ve got your equilibrium back, the walls of muscle contract and fold in on themselves again. Over and over again, you get crushed under another wave of slop. Every wave mixes and churns the food and chemicals together more–breaking the food into even smaller and smaller bits. Then another valve opens. Is the end in sight you ask, as the slop gets pushed into the small intestine.

Inside the small intestine, chemicals and liquids from places like your kidneys and pancreas break down and mix up the leftovers. The small intestine looks like a strange underwater world filled with things that resemble small finger-like cactus. But they’re not cactus, they’re villi. Like sponges, they’re able to absorb tremendous amounts of nutrients from the food you eat. From the villi, the nutrients will flow into your bloodstream.

But hold on! The story’s still not over yet — the leftovers that your body can’t use still have more traveling to do! Next, they’re pushed into the large intestine. It’s much wider and much drier. You find that the leftovers getting smaller, harder and drier as they’re pushed through the tube. After all, this is the place where water is extracted and recycled back into your body. In fact, the leftovers that leave your body are about 1/3 the size of what first arrived in your intestines!

Where Food Turns Into Poop
Finally, the end of the large intestine is in sight! Now the drier leftovers are various handsome shades of brown. They sit, at the end of their journey, waiting for you to expel them — out your anus. Of course, you know the rest! A glorious,if slightly stinky, journey, don’t you think?

• An adult’s intestines are at least 25 feet. Be glad you’re not a full-grown horse … their coiled-up intestines are 89 feet long!
• Chewing food takes from 5-30 seconds
• Swallowing takes about 10 seconds
• Food sloshing in the stomach can last 3-4 hours
• It takes 3 hours for food to move through the intestine
• Food drying up and hanging out in the large intestine can last 18 hours to 2 days!

• In your lifetime, your digestive system may handle about 50 tons!!

Digestive System – Accessory Organs

Salivary Glands
There are three pairs of salivary glands that secret saliva into the oral cavity:
1. Parotid salivary glands – located anterior to the outer ear. These glands produce secretions that empty by way of the parotid duct into the vestibule near the second upper molar.
2. Sublingual salivary glands – are under the floor of the mouth and are drained by numerous sublingual ducts.
3. Submandibular salivary glands – located on the medial side of the mandible under the mylohyoid line. Submandibular ducts drain secretions through an opening on either side of the lingual frenulum.

The saliva contains salivary amylase which begins digestion of complex carbohydrates and mucins which are glycoproteins that enhance the lubricating qualities of saliva. Saliva also helps to control oral bacterial populations.

Mastication, or chewing, is performed by the teeth.
Tooth Anatomy
The bulk of the tooth is formed by a bony substance called dentin. Cytoplasmic processes extend into the dentin from cells in the pulp cavity. Highly vascular connective tissue within the pulp cavity receives blood and sensation through blood vessels and nerves that enter the root at the apical foramen and travel through the root canal.
The tooth is anchored to the bony socket of the alveolar process by collagen fibers of the periodontal ligament. A bony substance called cementum covers the dentin of the root and the fibers of the periodontal ligament are anchored in cementum.
The crown is the visible portion of the tooth above the gingivae. The dentin of the crown is covered by enamel, the hardest material in the body. The neck is the boundary between the crown and the root.

The liver is the largest visceral organ and has more than 200 different functions that fall in one of three categories:
1. Metabolic regulation – for example, regulation of circulating levels of carbohydrates, lipids and amino acids.
2. Hematological regulation – liver cells synthesize plasma proteins and phagocytic cells remove old or damaged red blood cells.
3. Synthesis and secretion of bile – bile helps neutralize acidic chyme from the stomach and enables digestion of lipids in the small intestines.

Blood supply to the liver
The liver has two sources of blood: hepatic artery proper which delivers oxygenated blood and hepatic portal vein which delivers blood containing nutrients from the intestines. The stomach, spleen, pancreas and large intestines also drain blood into the hepatic portal vein. The hepatic veins drain blood from the liver and delivers it to the inferior vena cava.

Bile secretion
The right and left ducts collect the bile secreted by their respective liver lobes. These ducts combine to form the common hepatic duct. The common hepatic duct fuses with the cystic duct to form the common bile duct.

Gall Bladder

The gall bladder is a hollow pear-shaped, muscular organ that stores and concentrates bile. Between meals, bile secreted by the liver enters the gall bladder through the cystic duct. Under the stimulation that occurs during a meal, bile is ejected from the gall bladder into the cystic duct which fuses with the common hepatic duct to form the common bile duct which opens into the duodenum at the duodenal papilla.

The pancreas is primarily an exocrine organ producing digestive enzymes and buffers and is secondarily an endocrine organ. The pancreatic exocrine secretions are delivered to the duodenum by a large pancreatic duct which joins the common bile duct at the duodenal ampulla. A small accessory pancreatic duct may branch from it and empty its secretion separately at the lesser duodenal papilla.

Mitosis and Meiosis


Cell is the basic structural and functional unit of life / all living organsims.
When its time for development and maturity it undergoes Cell cycle.

Cell Cycle:
Each dividing cells passes through a cycle. The sequence of events a cell undergoes from the end of one cell division to the end of next cell division is called Cell Cycle.
It may also be defined as those changes which occur during cell growth and cell division.
The cell cycle involves two distinct phases as Interphase and Mitotis [M-Phase]

The Need for New Cells

To divide, each new cell has to undergo a phase of GROWTH and DEVELOPMENT.
It is after this phase that the cell attains enough maturity and can complete all metabolic processes that are necessary before entering the phase of cell division.
This preparatory phase of cells is termed as Inter-phase followed by cell division MITOSIS.

Body Cells are also known as Somatic Cells and the type of cell division seen in them is Mitosis / Homotypic cell division in which the number of chromosomes remains as their parent cell. i.e. for humans the body cells possess 46 chromosomes and during Mitosis the number of chromosomses in the newly formed daughter cells are also 46

Reproductive Cells are also known as Germ Cells. The type of cell division seen in them is Meiosis ( it undergoes 2 cell division i.e.First Heterotypic Cell division and Second Homotypic cell division).
In Heterotypic Cell division the number of chromosomes becomes half i.e. it reduces.
While in Homotypic Cell division the number of chromosomes it remains same.
At the end of Meiosis the total number of daughter cells formed are 4 having haploid number of chromosomes.
E.g. in humans the reproductive cells undergoes Meiosis. 46 number of chromosomes in the Germinal Epithelial cells undergoes first Heterotypic Cell division forming 2 cells having 23 number of chromosomes i.e. half than its parent cell.
Then it undergoes Homotypic cell division with same number of chromosomes forming 4 daughter cells.


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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.

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.

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 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.

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