For Class 8, 9 & 10
Master the basics - and everything after gets easier
Concept-first questions with clear model answers in Physics, Chemistry, Maths and Biology, all NCERT-aligned. Start early, build the habit, and walk into your boards, NEET and JEE already ahead.
Interactive lessons
learn by playingDrag, slide and build - watch each concept come alive, then reveal the answer.
200 interactive lessons
Ohm's law
Class 10 Physics
Slide V & R, watch the bulb glow
Open →pH scale
Class 10 Chemistry
Slide across acids and bases
Open →Atomic number and mass number
Class 9 Chemistry
Add protons & neutrons, build shells
Open →Laws of reflection
Class 8 Physics
Change the angle, watch it bounce
Open →Volume of a sphere
Class 9 Maths
Grow the radius, see the volume
Open →Area of a trapezium
Class 8 Maths
Drag the sides, read the area
Open →Power of a lens
Class 10 Physics
Move the object, trace the rays
Open →Food chain and energy flow
Class 10 Biology
Follow the energy as it flows
Open →Speed
Class 8 Physics
Slide distance & time, watch the speed
Open →Density
Class 9 Physics
Pack mass into volume, float or sink
Open →Work done
Class 9 Physics
Push harder or farther, watch work grow
Open →Kinetic energy
Class 9 Physics
Speed it up - energy grows with the square
Open →Power of a lens
Class 10 Physics
Shorten the focal length, boost the power
Open →Mole concept
Class 9 Chemistry
Weigh out grams, count the moles
Open →Avogadro's number
Class 9 Chemistry
Add moles, count the particles
Open →Microscope magnification
Class 8 Biology
Grow the image, read the magnification
Open →Population density
Class 10 Biology
Add individuals, shrink the land, see crowding
Open →Simple interest
Class 8 Maths
Slide money, rate & time, watch interest
Open →Pythagoras theorem
Class 9 Maths
Stretch the two sides, get the hypotenuse
Open →Probability of an event
Class 10 Maths
Change the outcomes, watch the odds
Open →Newton's second law
Class 9 Physics
Push a mass, pick an acceleration
Open →Momentum
Class 9 Physics
Slide mass & velocity, build momentum
Open →Pressure
Class 8 Physics
Shrink the area, feel the pressure rise
Open →Weight
Class 9 Physics
Change the planet's gravity, watch your weight
Open →Refractive index
Class 10 Physics
Slow light in the medium, raise the index
Open →Resistors in series
Class 10 Physics
Add two resistors in a line
Open →Mass percentage of a solution
Class 9 Chemistry
Dissolve solute, read the strength
Open →Concentration of a solution
Class 9 Chemistry
Pack solute into less liquid
Open →Population change
Class 10 Biology
Balance births against deaths
Open →Compound microscope
Class 8 Biology
Combine eyepiece & objective lenses
Open →Area of a circle
Class 8 Maths
Grow the radius, watch the area square
Open →Volume of a cuboid
Class 8 Maths
Stretch length, breadth & height
Open →Electronic configuration and valency
Class 9 Chemistry
Slide the atomic number, build the atom
Open →Homologous series (alkanes)
Class 10 Chemistry
Add carbons, name the compound
Open →Mass number
Class 9 Chemistry
Add protons & neutrons, get the mass number
Open →Power
Class 9 Physics
More work in less time = more power
Open →Potential energy
Class 9 Physics
Lift a mass higher, store energy
Open →Wave speed
Class 9 Physics
Tune frequency & wavelength, set the speed
Open →Electric current
Class 10 Physics
Push charge per second, get the current
Open →Percentage
Class 8 Maths
Compare part to whole as a %
Open →Electron dot structure
Class 9 Chemistry
Draw valence electrons as dots
Open →Acceleration
Class 9 Physics
Speed up over time, find acceleration
Open →Distance, speed and time
Class 8 Physics
Set speed & time, cover the distance
Open →Frequency and time period
Class 9 Physics
Shorten the period, raise the frequency
Open →Heating effect of current
Class 10 Physics
Raise the current, watch heating soar
Open →Area of a triangle
Class 8 Maths
Set base & height, halve the rectangle
Open →Area of a rectangle
Class 8 Maths
Set length & breadth, fill the area
Open →Mean (average)
Class 9 Maths
Share the total equally across items
Open →Discount
Class 8 Maths
Slide price & % off, see the saving
Open →Heart rate
Class 10 Biology
Set heart rate & time, count the beats
Open →Resistors in parallel
Class 10 Physics
Wire two resistors side by side
Open →Electric charge
Class 10 Physics
Flow current over time, collect charge
Open →Electrical energy and units
Class 10 Physics
Run appliances, add up the units
Open →Kelvin temperature scale
Class 9 Chemistry
Slide Celsius, read the Kelvin
Open →Moles from number of particles
Class 9 Chemistry
Divide particles by Avogadro's number
Open →Ten percent law
Class 10 Biology
See 10% of energy reach the next level
Open →Area of a square
Class 8 Maths
Grow the side, square the area
Open →Volume of a cube
Class 8 Maths
Grow the edge, cube the volume
Open →Circumference of a circle
Class 8 Maths
Grow the radius, roll out the rim
Open →Surface area of a cube
Class 9 Maths
Grow the edge, cover six faces
Open →Potential difference
Class 10 Physics
Share work across charge, get volts
Open →Resistance from Ohm's law
Class 10 Physics
Divide voltage by current, get resistance
Open →Echo and SONAR
Class 9 Physics
Time the echo, find the distance
Open →Mass from moles
Class 9 Chemistry
Multiply moles by molar mass
Open →Breathing rate
Class 10 Biology
Set breathing rate & time
Open →Volume of a cylinder
Class 10 Maths
Set radius & height, fill the can
Open →Compound interest
Class 8 Maths
Compound money over years
Open →Profit and loss percentage
Class 8 Maths
Set cost & selling price, see profit %
Open →Perimeter of a rectangle
Class 8 Maths
Set length & breadth, walk the border
Open →Surface area of a sphere
Class 10 Maths
Grow the radius, wrap the ball
Open →Time period
Class 9 Physics
Raise the frequency, shrink the period
Open →Relative velocity
Class 9 Physics
Two objects approach - add their speeds
Open →Average velocity
Class 9 Physics
Average the start and end speeds
Open →Equations of motion (v = u + at)
Class 9 Physics
Accelerate from u for a time t
Open →Kelvin to Celsius
Class 9 Chemistry
Slide Kelvin, read the Celsius
Open →Population growth rate
Class 10 Biology
Balance births vs deaths per population
Open →Perimeter of a square
Class 8 Maths
Grow the side, walk four edges
Open →Perimeter of a triangle
Class 8 Maths
Add the three sides
Open →Area of a parallelogram
Class 8 Maths
Set base & height, slide the shape
Open →Area of a rhombus
Class 8 Maths
Set the two diagonals
Open →Equations of motion (distance)
Class 9 Physics
Start, accelerate, cover ground
Open →Joule's law of heating
Class 10 Physics
Raise current, resistance or time
Open →Electric power (P = VI)
Class 10 Physics
Multiply voltage by current
Open →Average atomic mass of isotopes
Class 9 Chemistry
Mix two isotopes by abundance
Open →Seed germination percentage
Class 9 Biology
Count sprouted seeds out of the total
Open →Volume of a cone
Class 9 Maths
Set radius & height, fill the cone
Open →Surface area of a cylinder
Class 9 Maths
Wrap the side and both ends
Open →Surface area of a cuboid
Class 9 Maths
Cover all six rectangular faces
Open →nth term of an AP
Class 10 Maths
Step from the first term by d
Open →Sum of an AP
Class 10 Maths
Add up the first n terms
Open →Focal length of a mirror
Class 10 Physics
Halve the radius to find the focus
Open →Speed of light in a medium
Class 10 Physics
Raise the index, slow the light
Open →Percentage purity
Class 9 Chemistry
Weigh the pure part of a sample
Open →Slope of a line
Class 10 Maths
Rise over run gives the steepness
Open →Percentage change
Class 8 Maths
Compare a new value to the old
Open →Volume of a hemisphere
Class 9 Maths
Grow the radius of half a ball
Open →Area of a sector
Class 10 Maths
Cut a slice of angle from a circle
Open →Length of an arc
Class 10 Maths
Measure the curved edge of a slice
Open →Slant height of a cone
Class 9 Maths
Combine radius & height for the slant
Open →Unit conversion (km/h to m/s)
Class 9 Physics
Convert km/h into m/s
Open →Equations of motion (v^2 = u^2 + 2as)
Class 9 Physics
Accelerate over a distance, find v
Open →Impulse
Class 9 Physics
Hit harder or longer, change momentum
Open →Wavelength
Class 9 Physics
Speed over frequency gives wavelength
Open →Oscillations
Class 9 Physics
Vibrate at a frequency for a time
Open →Cost of electricity
Class 10 Physics
Units times rate gives the bill
Open →Number of neutrons
Class 9 Chemistry
Take protons away from the mass number
Open →Curved surface area of a cone
Class 9 Maths
Wrap the slanted side of a cone
Open →Total surface area of a cone
Class 9 Maths
Add the base circle to the cone's side
Open →Curved surface area of a hemisphere
Class 9 Maths
Cover the dome of a hemisphere
Open →Diagonal of a square
Class 9 Maths
Cross a square corner to corner
Open →Unit conversion (m/s to km/h)
Class 9 Physics
Convert m/s into km/h
Open →Distance from velocities
Class 9 Physics
From two speeds, find the distance
Open →Diagonal of a rectangle
Class 9 Maths
Cross a rectangle corner to corner
Open →Diagonal of a cuboid
Class 9 Maths
The longest rod that fits in a box
Open →Area by Heron's formula
Class 9 Maths
Area from just the three sides
Open →Interior angle sum of a polygon
Class 8 Maths
Add up a polygon's inside angles
Open →Exterior angle of a regular polygon
Class 8 Maths
Share 360 among a polygon's corners
Open →Number of diagonals of a polygon
Class 8 Maths
Count the diagonals of a polygon
Open →Discriminant
Class 10 Maths
Test how many roots a quadratic has
Open →Sum of roots
Class 10 Maths
Sum of a quadratic's roots
Open →Punnett square (monohybrid cross)
Class 10 Biology
Cross two parents, predict the offspring
Open →Balancing chemical equations
Class 10 Chemistry
Slide coefficients until atoms balance
Open →Writing chemical formulae (valency)
Class 9 Chemistry
Criss-cross valencies into a formula
Open →Current from power
Class 10 Physics
Divide power by voltage for current
Open →Power (P = V^2 / R)
Class 10 Physics
Voltage squared over resistance
Open →Sine ratio
Class 10 Maths
Opposite over hypotenuse
Open →Cosine ratio
Class 10 Maths
Adjacent over hypotenuse
Open →Tangent ratio
Class 10 Maths
Opposite over adjacent
Open →Area of an equilateral triangle
Class 9 Maths
Area of an equilateral triangle
Open →Curved surface area of a cylinder
Class 9 Maths
Wrap only the curved side
Open →Loss percentage
Class 8 Maths
Sell below cost, find the loss %
Open →Amount with simple interest
Class 8 Maths
Principal plus its simple interest
Open →Distance formula
Class 10 Maths
Straight distance between two points
Open →States of matter
Class 9 Chemistry
Heat particles solid → liquid → gas
Open →Parts of a plant cell
Class 8 Biology
Tap a cell part to see its job
Open →Diagonal of a cube
Class 9 Maths
Longest diagonal through a cube
Open →Total surface area of a hemisphere
Class 9 Maths
Dome plus its flat circle
Open →Sum of first n natural numbers
Class 10 Maths
Add 1 + 2 + ... + n instantly
Open →Range of data
Class 9 Maths
Spread from smallest to largest
Open →Class mark
Class 9 Maths
Midpoint of a class interval
Open →Selling price from profit percent
Class 8 Maths
Mark up cost by a profit %
Open →Perimeter of a sector
Class 10 Maths
Two radii plus the curved arc
Open →Circumference from diameter
Class 8 Maths
Circumference straight from diameter
Open →Power (P = F x v)
Class 9 Physics
Force times velocity gives power
Open →Percentage of a number
Class 8 Maths
Find a percentage of a number
Open →Series and parallel circuits
Class 10 Physics
Break a bulb in series vs parallel
Open →Symbols of elements
Class 9 Chemistry
Match each element to its symbol
Open →Free fall (velocity)
Class 9 Physics
Drop from a height, hit this speed
Open →Free fall (time)
Class 9 Physics
How long a drop takes
Open →Free fall (distance)
Class 9 Physics
Distance fallen in a given time
Open →Complement of an event
Class 10 Maths
Chance an event does NOT happen
Open →Product of roots
Class 10 Maths
Product of a quadratic's roots
Open →Exterior angle theorem
Class 9 Maths
Exterior angle = sum of remote interiors
Open →Complementary angles
Class 10 Maths
What adds to 90 degrees
Open →Supplementary angles
Class 9 Maths
What adds to 180 degrees
Open →Perimeter of a semicircle
Class 10 Maths
Curved half plus the diameter
Open →Area of a semicircle
Class 10 Maths
Half the area of a circle
Open →Turning effect (moments)
Class 9 Physics
Balance the see-saw with moments
Open →Reflex arc
Class 10 Biology
Step through a reflex, stimulus to action
Open →Buoyant force (upthrust)
Class 9 Physics
Displace liquid, feel the upthrust
Open →Relative density
Class 9 Physics
Compare a density to water's
Open →Power in lifting a load
Class 9 Physics
Lift a load, faster needs more power
Open →Cosecant ratio
Class 10 Maths
Hypotenuse over opposite
Open →Secant ratio
Class 10 Maths
Hypotenuse over adjacent
Open →Cotangent ratio
Class 10 Maths
Adjacent over opposite
Open →Height from angle of elevation
Class 10 Maths
Height from an angle of elevation
Open →Area of a quadrant
Class 10 Maths
A quarter of a circle's area
Open →Interior angle of a regular polygon
Class 8 Maths
One inside angle of a regular polygon
Open →Sum of first n odd numbers
Class 10 Maths
Add the first n odd numbers
Open →Sum of first n even numbers
Class 10 Maths
Add the first n even numbers
Open →Quadratic formula (a root)
Class 10 Maths
Larger root of a quadratic
Open →LCM from HCF
Class 10 Maths
LCM from the product and HCF
Open →Depreciation
Class 8 Maths
Value drops by a % each year
Open →Cost price from selling price
Class 8 Maths
Work back to the cost price
Open →Downstream speed
Class 8 Maths
Row with the current
Open →Upstream speed
Class 8 Maths
Row against the current
Open →Average speed for a round trip
Class 8 Maths
Average speed there and back
Open →Sales tax / GST
Class 8 Maths
Tax added on a price
Open →Area of a ring (annulus)
Class 10 Maths
Area of a ring between two circles
Open →Edge of a cube from volume
Class 9 Maths
Edge back from the volume
Open →Radius from area
Class 10 Maths
Radius back from a circle's area
Open →Side from area of a square
Class 8 Maths
Side back from a square's area
Open →Height of a triangle from area
Class 9 Maths
Height back from area and base
Open →Rate from simple interest
Class 8 Maths
Rate back from the interest
Open →Time from simple interest
Class 8 Maths
Time back from the interest
Open →Principal from simple interest
Class 8 Maths
Principal back from the interest
Open →Mean proportional
Class 10 Maths
Geometric mean of two numbers
Open →Fourth proportional
Class 8 Maths
Complete the proportion a : b = c : ?
Open →Marked price from selling price
Class 8 Maths
Marked price back from the sale price
Open →Chambers of the human heart
Class 10 Biology
Tap a heart chamber to see its job
Open →Equation of a line (y = mx + c)
Class 9 Maths
Read y off a straight line
Open →Average term of an AP
Class 10 Maths
Average of first and last term
Open →Number of terms in an AP
Class 10 Maths
How many terms in an AP
Open →Midpoint of two points
Class 10 Maths
x-coordinate of a midpoint
Open →Empirical mode
Class 10 Maths
Estimate the mode from mean & median
Open →Length of a shadow
Class 10 Maths
Shadow from height and sun angle
Open →Train crossing a pole
Class 8 Maths
Speed to cross a pole
Open →Time and work
Class 8 Maths
More workers, fewer days
Open →Dividing in a ratio
Class 8 Maths
Split a total in a ratio
Open →Unitary method
Class 8 Maths
Cost of a single item
Open →Your progress — Foundation - Class 8 to 10
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Showing 14 questions for Class 10. Tap a card to reveal the answer.
BiologyLife ProcesseseasyHow is oxygen transported from the lungs to the tissues in human beings?
Reveal answer ↓
What it is
Oxygen rides on haemoglobin in red blood cells from the lungs to every tissue.
Answer
Oxygen diffuses from the air sacs (alveoli) of the lungs into the blood, where it binds to the red pigment haemoglobin in red blood cells to form oxyhaemoglobin. The blood carries it to the tissues, where oxygen is released for respiration. Haemoglobin makes this transport efficient because it has a high affinity for oxygen.
- •O2 diffuses from alveoli into blood
- •Binds to haemoglobin in RBCs
- •Carried as oxyhaemoglobin
- •Released at tissues for respiration
Why learn this
It's why anaemia leaves you tired and why blood is red - the body's oxygen delivery system.
💡 Memory trick
Haemoglobin is the 'oxygen taxi': O2 boards at the lungs, gets off at the tissues.
BiologyLife ProcesseseasyGive two differences between arteries and veins.
Reveal answer ↓
What it is
Arteries carry blood away from the heart under high pressure; veins bring it back and have valves.
Answer
Arteries carry blood away from the heart, usually oxygenated (except the pulmonary artery), have thick elastic walls and no valves because blood flows under high pressure. Veins carry blood towards the heart, usually deoxygenated (except the pulmonary vein), have thinner walls and contain valves to prevent the backflow of low-pressure blood.
- •Arteries: away from heart, thick walls, no valves, high pressure
- •Veins: towards heart, thin walls, valves present, low pressure
Why learn this
It's basic to understanding blood pressure, heart attacks and how injections and IV drips work.
💡 Memory trick
Arteries = Away from the heart; Veins have Valves to stop backflow.
BiologyLife ProcessesmediumWhat is photosynthesis? Write its balanced equation and the conditions needed.
Reveal answer ↓
What it is
Photosynthesis is how green plants make their own food (glucose) from CO2 and water using sunlight.
Answer
Photosynthesis is the process by which green plants make their own food (glucose) from carbon dioxide and water using sunlight, releasing oxygen. The balanced equation is: 6CO2 + 6H2O -> C6H12O6 + 6O2. It requires chlorophyll (the green pigment), sunlight, carbon dioxide and water.
6CO2 + 6H2O -> C6H12O6 + 6O2
- •Green plants make glucose from CO2 and water using light
- •6CO2 + 6H2O -> C6H12O6 + 6O2
- •Needs chlorophyll, sunlight, CO2, water
- •Releases oxygen
Why learn this
It's the source of nearly all food and oxygen on Earth - the base of every food chain.
💡 Memory trick
6CO2 + 6H2O --(sunlight + chlorophyll)--> glucose + 6O2. Plants 'eat' light.
BiologyLife ProcesseseasyGive three differences between arteries and veins.
Reveal answer ↓
What it is
Arteries carry blood away from the heart; veins carry it back to the heart.
Answer
1) Arteries carry blood away from the heart, while veins carry blood back towards the heart. 2) Arteries carry oxygenated blood (except the pulmonary artery), while veins carry deoxygenated blood (except the pulmonary vein). 3) Arteries have thick, elastic, muscular walls to handle high pressure and have no valves, whereas veins have thinner walls, carry blood at low pressure, and contain valves that stop the blood flowing backwards.
- •Arteries: away from heart; veins: towards heart
- •Arteries carry oxygenated blood (except the pulmonary artery)
- •Arteries: thick walls, no valves
- •Veins: thin walls, have valves
Why learn this
Knowing how blood vessels differ helps explain blood pressure, bleeding and heart health.
💡 Memory trick
Artery = Away from heart. Veins have Valves to stop backflow.
BiologyLife ProcesseseasyAt 72 beats per minute, how many times does the heart beat in 10 minutes? Slide to explore.
Reveal answer ↓
What it is
The number of heartbeats is the heart rate multiplied by the time.
Answer
Heartbeats = heart rate x time = 72 x 10 = 720 beats. A resting heart beating about 72 times a minute beats roughly 100,000 times in a whole day, pumping blood non-stop.
heartbeats = heart rate x time
- •Beats = heart rate x time
- •Resting rate is about 72 bpm
- •About 100,000 beats a day
Why learn this
It shows how hard the heart works to keep blood circulating.
💡 Memory trick
Beats = heart rate (per minute) x minutes.
BiologyLife ProcesseseasyAt 16 breaths per minute, how many breaths are taken in 10 minutes? Slide to explore.
Reveal answer ↓
What it is
The number of breaths taken is the breathing rate multiplied by the time.
Answer
Breaths = breathing rate x time = 16 x 10 = 160 breaths. A resting adult breathes about 12 to 16 times a minute; the rate rises during exercise to bring in more oxygen.
breaths = breathing rate x time
- •Breaths = breathing rate x time
- •Resting rate about 12-16 per minute
- •Rate rises during exercise
Why learn this
It shows how the body keeps supplying oxygen for respiration.
💡 Memory trick
Breaths = breathing rate (per minute) x minutes.
BiologyLife ProcessesmediumWhat are the four chambers of the heart and what does each do? Tap a chamber to explore.
Reveal answer ↓
What it is
The human heart has four chambers that keep oxygenated and deoxygenated blood completely separate.
Left ventricle (oxygenated blood)
Pumps oxygenated blood to the whole body through the aorta; it has the thickest wall.
Answer
The right atrium receives deoxygenated blood from the body and passes it to the right ventricle, which pumps it to the lungs. The left atrium receives oxygenated blood from the lungs and passes it to the left ventricle, which pumps it to the whole body. The atria receive blood while the ventricles pump it out; the left ventricle has the thickest wall because it pushes blood the farthest. Keeping the two sides separate prevents oxygenated and deoxygenated blood from mixing.
- •Atria receive blood; ventricles pump it out
- •Right side carries deoxygenated blood, left side oxygenated
- •Left ventricle has the thickest wall
- •Separation prevents mixing (double circulation)
Why learn this
This double circulation delivers oxygen efficiently to power a warm-blooded body.
💡 Memory trick
Atria receive, ventricles pump. Right side = deoxygenated, left side = oxygenated.
BiologyLife ProcessesmediumWhat is photosynthesis? Write its balanced equation and the site where it occurs.
Reveal answer ↓
What it is
Autotrophs like green plants make their own food from carbon dioxide and water using sunlight in photosynthesis.
Answer
Photosynthesis is the process by which green plants (autotrophs) synthesise their own food in the form of glucose using carbon dioxide and water, in the presence of sunlight and the green pigment chlorophyll. The balanced equation is: 6CO2 + 6H2O, in the presence of sunlight and chlorophyll, gives C6H12O6 + 6O2. It occurs mainly in the chloroplasts of the mesophyll cells of the leaf. Oxygen is released as a by-product.
6CO2 + 6H2O -> C6H12O6 + 6O2
- •Autotrophs make their own food
- •Needs CO2, water, sunlight, chlorophyll
- •6CO2 + 6H2O -> C6H12O6 + 6O2
- •Occurs in chloroplasts; releases oxygen
Why learn this
It is the entry point of energy into almost every food chain on Earth.
💡 Memory trick
6CO2 + 6H2O -> glucose + 6O2, using sunlight and chlorophyll.
BiologyLife ProcessesmediumBriefly describe digestion of food in humans.
Reveal answer ↓
What it is
Human digestion breaks down food in the alimentary canal with the help of enzymes so that nutrients can be absorbed.
Answer
Digestion in humans begins in the mouth, where saliva contains the enzyme salivary amylase that breaks starch into sugar. In the stomach, gastric juice with hydrochloric acid and the enzyme pepsin digests proteins and kills germs. In the small intestine, bile from the liver emulsifies fats, and pancreatic and intestinal juices complete the digestion of carbohydrates, proteins and fats. The digested food is absorbed into the blood through finger-like projections called villi, and the undigested waste passes to the large intestine and is egested.
- •Mouth: salivary amylase digests starch
- •Stomach: HCl and pepsin digest proteins
- •Small intestine: complete digestion and absorption
- •Villi absorb nutrients into the blood
Why learn this
It is how the body gets usable nutrients and energy from food.
💡 Memory trick
Mouth (saliva) -> stomach (acid, pepsin) -> small intestine (most digestion and absorption).
BiologyLife ProcessesmediumDifferentiate between aerobic and anaerobic respiration with their end products.
Reveal answer ↓
What it is
Aerobic respiration uses oxygen and releases more energy; anaerobic respiration occurs without oxygen and releases less energy.
Answer
Aerobic respiration takes place in the presence of oxygen and completely breaks down glucose into carbon dioxide and water, releasing a large amount of energy; it occurs in the mitochondria. Anaerobic respiration takes place in the absence of oxygen and breaks glucose down incompletely, releasing much less energy; in our muscle cells it produces lactic acid (causing cramps during vigorous exercise), while in yeast it produces ethanol and carbon dioxide (used in baking and brewing).
Glucose -> CO2 + H2O + energy (aerobic)
- •Aerobic: with oxygen, CO2 + water, more energy
- •Occurs in the mitochondria
- •Anaerobic: no oxygen, less energy
- •Muscles -> lactic acid; yeast -> ethanol + CO2
Why learn this
It explains muscle cramps during heavy exercise and how yeast makes alcohol.
💡 Memory trick
Aerobic: oxygen, CO2 + water, lots of energy. Anaerobic: no oxygen, lactic acid or alcohol, less energy.
BiologyLife ProcessesmediumDescribe the path of air in the human respiratory system and where gas exchange occurs.
Reveal answer ↓
What it is
Air passes through the nose, trachea and bronchi to the alveoli of the lungs, where gases are exchanged.
Answer
During breathing, air enters through the nostrils, passes into the nasal cavity where it is filtered, warmed and moistened, then travels down the pharynx and larynx into the windpipe (trachea). The trachea divides into two bronchi, one entering each lung, which further branch into finer tubes called bronchioles. Each bronchiole ends in tiny balloon-like sacs called alveoli. It is in the alveoli, which have thin walls and a rich blood supply, that oxygen from the air diffuses into the blood and carbon dioxide diffuses out to be exhaled.
- •Nose -> trachea -> bronchi -> bronchioles -> alveoli
- •Alveoli are the sites of gas exchange
- •Oxygen diffuses into blood
- •Carbon dioxide diffuses out
Why learn this
It supplies oxygen to the blood and removes carbon dioxide.
💡 Memory trick
Nose -> trachea -> bronchi -> bronchioles -> alveoli (the gas-exchange balloons).
BiologyLife ProcesseshardWhat is double circulation? Why is it necessary in humans?
Reveal answer ↓
What it is
The human heart has four chambers, and blood passes through it twice in one complete cycle - double circulation.
Answer
The human heart has four chambers: two upper atria and two lower ventricles. Double circulation means that blood passes through the heart twice in each complete cycle. In pulmonary circulation, deoxygenated blood from the right side of the heart goes to the lungs and returns oxygenated. In systemic circulation, this oxygenated blood from the left side is pumped to the whole body and returns deoxygenated. Double circulation is necessary because it keeps oxygenated and deoxygenated blood completely separate, ensuring an efficient supply of oxygen to the body, which is needed by warm-blooded animals to maintain their body temperature.
- •Heart has 4 chambers (2 atria, 2 ventricles)
- •Blood passes through the heart twice per cycle
- •Pulmonary circulation: heart to lungs
- •Systemic circulation: heart to body; keeps blood separate
Why learn this
It keeps oxygen-rich and oxygen-poor blood separate for efficient supply.
💡 Memory trick
Right side = deoxygenated blood (to lungs); Left side = oxygenated blood (to body).
BiologyLife ProcessesmediumHow are water and food transported in plants?
Reveal answer ↓
What it is
Xylem transports water and minerals upward; phloem transports food in both directions by translocation.
Answer
In plants, water and dissolved minerals absorbed by the roots are transported upward through the xylem. This upward movement is mainly driven by transpiration pull, the suction created when water evaporates from the leaves. Food (mainly sucrose) prepared in the leaves during photosynthesis is transported to all parts of the plant, including growing and storage regions, through the phloem; this movement is called translocation and requires energy from ATP.
- •Xylem carries water and minerals upward
- •Driven by transpiration pull
- •Phloem carries food (translocation)
- •Translocation needs energy (ATP)
Why learn this
It supplies water to the leaves and food to the rest of the plant.
💡 Memory trick
Xylem = water up (transpiration pull). Phloem = food (translocation, needs energy).
BiologyLife ProcesseshardWhat is the functional unit of the kidney? Briefly describe how urine is formed.
Reveal answer ↓
What it is
The kidneys filter blood to form urine; the nephron is the functional unit that carries out filtration and reabsorption.
Answer
The functional unit of the kidney is the nephron. Urine is formed in three main steps. First, in glomerular filtration, blood is filtered under pressure in the glomerulus, and water, glucose, salts and urea pass into the nephron. Second, in selective reabsorption, useful substances such as glucose, most water and essential salts are reabsorbed back into the blood as the filtrate flows along the tubule. Third, the remaining liquid, containing urea, excess salts and water, forms urine, which passes to the urinary bladder through the ureters and is removed from the body.
- •Nephron is the functional unit of the kidney
- •Filtration occurs in the glomerulus
- •Useful substances reabsorbed (glucose, water)
- •Remaining fluid forms urine (contains urea)
Why learn this
It removes toxic wastes like urea and keeps the blood clean.
💡 Memory trick
Nephron: filter at the glomerulus, then reabsorb useful things, leaving urine.
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