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State Board · Class 10 · Science and Technology Part 2

Lesson 2: Life Processes in Living Organisms Part-1

5 concepts · 40 practice questions with answers · Free to read

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Life processes and energy

From daily life

A mobile phone stops working when its battery is empty. Our body also needs energy all the time, even when we sleep, and that energy comes from food.

Simple definition

Life processes (जीवनप्रक्रिया) are the basic activities that keep an organism alive, such as nutrition, respiration, transport and excretion.

Rule 1: Energy from food — Life processes need energy from food. Energy per gram: carbohydrate 4 kcal, protein 4 kcal, lipid (fat) 9 kcal. The energy is stored in the cell as ATP (adenosine triphosphate, the energy currency), and mitochondria (सूत्रकणिका) are the powerhouse of the cell where most ATP is made.

Carbohydrate and protein give 4 kcal per gram and fat gives 9Energy from 1 gram of food (kcal)4Carbohydrate4Protein9Lipid (fat)

In the figure : In the figure the energy value of food.

  • Easy : Easy: 20 g of carbohydrate gives 20 × 4 = 80 kcal.
  • Medium : Medium: 10 g of fat gives 10 × 9 = 90 kcal, more than twice the energy of 10 g of protein (40 kcal).
  • Exam-type : Exam: a snack has 50 g carbohydrate, 20 g protein, 10 g fat. Energy = 50 × 4 + 20 × 4 + 10 × 9 = 200 + 80 + 90 = 370 kcal.
Remember

Carbohydrate 4, protein 4, fat 9 kcal per gram. ATP = energy currency. Mitochondria = powerhouse.

Common mistake

Thinking that protein gives the most energy. Fat gives the most (9 kcal/g).

Shortcut

Memory clue: "4-4-9" — carbohydrate, protein, fat.

Spot the difference

NutrientEnergy per gram
Carbohydrate4 kcal
Protein4 kcal
Fat (lipid)9 kcal

Practice questions

Easy
  1. 1What are life processes?
  2. 2What is ATP called?
  3. 3Which cell organelle is the powerhouse?
Medium
  1. 4How much energy does 1 g of fat give?
  2. 5How much energy does 1 g of protein give?
  3. 6Find the energy in 30 g of carbohydrate.
Challenging
  1. 7A meal has 40 g carbohydrate, 15 g protein and 20 g fat. Find the energy.
  2. 8Why is fat a good store of energy?
Show answers (try them yourself first)
  1. 1Basic activities such as nutrition and respiration that keep an organism alive.
  2. 2The energy currency of the cell.
  3. 3Mitochondria.
  4. 49 kcal.
  5. 54 kcal.
  6. 630 × 4 = 120 kcal.
  7. 7160 + 60 + 180 = 400 kcal.
  8. 8It gives the most energy per gram, 9 kcal.

Aerobic cellular respiration

From daily life

When you run up the stairs you breathe hard. Your cells are burning glucose with oxygen at a faster rate to make more energy.

Simple definition

Aerobic respiration (ऑक्सिश्वसन) is the breakdown of glucose with oxygen in the cell to release energy.

Rule 1: Three steps of aerobic respiration — Glycolysis (ग्लायकोलिसिस) occurs in the cytoplasm: one glucose gives 2 pyruvic acid, 2 ATP and 2 NADH2. The Krebs cycle (क्रेब्ज चक्र) occurs in the mitochondria (named after Hans Krebs, Nobel Prize 1953). The electron transfer chain makes the most ATP. The products are CO₂, water and energy.

Glucose passes through glycolysis, the Krebs cycle and the electron transfer chain to make ATP, CO2 and waterAerobic respiration🍬Glucose🧫Glycolysis(cytoplasm)2 ATP🔋Krebs cycle(mitochondria)⚡Electron chainmost ATP

In the figure : In the figure the steps of aerobic respiration.

  • Easy : Easy: the overall equation is glucose + oxygen → carbon dioxide + water + energy, so breathing out gives out CO₂.
  • Medium : Medium: glycolysis in one glucose gives 2 pyruvic acid, so 5 glucose molecules give 10 pyruvic acid and 10 ATP (net from glycolysis).
  • Exam-type : Exam: the three steps in order and their places: glycolysis (cytoplasm), Krebs cycle (mitochondria), electron transfer chain (mitochondria).
Live figure

Aerobic cellular respiration

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Remember

Glycolysis: cytoplasm. Krebs cycle and electron chain: mitochondria. Most ATP: electron transfer chain.

Common mistake

Thinking that breathing and cellular respiration are the same. Breathing brings oxygen in; respiration is the chemical process in cells.

Shortcut

Memory clue: "Glyco — Krebs — Chain": cytoplasm, then mitochondria twice.

Spot the difference

StepPlaceResult
GlycolysisCytoplasm2 pyruvic acid, 2 ATP
Krebs cycleMitochondriaCO₂ released
Electron transfer chainMitochondriaMost ATP, water

Practice questions

Easy
  1. 1What is aerobic respiration?
  2. 2Where does glycolysis take place?
  3. 3What are the products of glycolysis of one glucose?
Medium
  1. 4After whom is the Krebs cycle named?
  2. 5Which step gives the most ATP?
  3. 6Name the three products of aerobic respiration.
Challenging
  1. 78 glucose molecules undergo glycolysis. How many pyruvic acid and ATP (net) are formed?
  2. 8Why is breathing different from cellular respiration?
Show answers (try them yourself first)
  1. 1Breakdown of glucose with oxygen to release energy.
  2. 2In the cytoplasm.
  3. 32 pyruvic acid, 2 ATP, 2 NADH2.
  4. 4Hans Krebs.
  5. 5Electron transfer chain.
  6. 6Carbon dioxide, water and energy.
  7. 716 pyruvic acid and 16 ATP.
  8. 8Breathing is taking air in and out; respiration is the chemical release of energy in cells.

Anaerobic respiration

From daily life

After a sprint your legs ache. Muscles ran short of oxygen and made lactic acid. In bread dough, yeast also makes energy without oxygen but gives alcohol instead.

Simple definition

Anaerobic respiration (विनॉक्सिश्वसन) is the release of energy from glucose without oxygen.

Rule 1: Respiration without oxygen — In yeast, glucose gives alcohol and CO₂. In muscles, glucose gives lactic acid (लॅक्टिक आम्ल). Much less energy is released than in aerobic respiration. Extra glucose is stored as glycogen (ग्लायकोजेन) in the liver and muscles.

Yeast makes alcohol and CO2; muscles make lactic acidAnaerobic respiration (no oxygen)In yeast🍄Glucose →🍷Alcohol + CO₂In muscles💪Glucose →😣Lactic acid

In the figure : In the figure respiration without oxygen gives less energy.

  • Easy : Easy: a sprinter's muscles make lactic acid when oxygen is short, which causes cramps.
  • Medium : Medium: yeast in dough makes CO₂ (the dough rises) and alcohol (which evaporates during baking).
  • Exam-type : Exam: compare aerobic and anaerobic respiration. Aerobic needs oxygen and gives CO₂, water and a lot of energy; anaerobic needs none and gives alcohol or lactic acid and little energy.
Remember

Yeast: alcohol + CO₂. Muscles: lactic acid. Anaerobic gives less energy. Glycogen stored in liver and muscles.

Common mistake

Thinking that anaerobic respiration gives more energy. It gives much less.

Shortcut

Memory clue: "Yeast — alcohol; muscle — lactic".

Spot the difference

FeatureAerobicAnaerobic
OxygenNeededNot needed
ProductsCO₂ + waterAlcohol or lactic acid
EnergyMuchLittle

Practice questions

Easy
  1. 1What is anaerobic respiration?
  2. 2What does yeast produce in anaerobic respiration?
  3. 3What do muscles produce without oxygen?
Medium
  1. 4Where is glycogen stored?
  2. 5Which respiration gives less energy?
  3. 6Why do muscles get cramps after hard exercise?
Challenging
  1. 7Why does bread dough rise?
  2. 8Write any two differences between aerobic and anaerobic respiration.
Show answers (try them yourself first)
  1. 1Release of energy from glucose without oxygen.
  2. 2Alcohol and carbon dioxide.
  3. 3Lactic acid.
  4. 4In the liver and muscles.
  5. 5Anaerobic respiration.
  6. 6Lactic acid collects when oxygen is short.
  7. 7Yeast releases CO₂ gas in anaerobic respiration.
  8. 8Aerobic needs oxygen and releases much energy; anaerobic does not need oxygen and releases little energy.

Nutrients

From daily life

Dal gives protein for growth, oil gives fat, rice gives carbohydrate, fruits give vitamins. A plate with all of them is a balanced diet.

Simple definition

Nutrients (पोषक घटक) are the substances in food that the body needs for energy, growth and protection.

Rule 1: Kinds of nutrients — Proteins are made of amino acids and build the body. Fats and carbohydrates give energy. Vitamins protect the body; A, D, E and K are fat-soluble. Minerals are needed in small amounts. Water makes up 65–70% of the body.

Six kinds of nutrients and their workNutrients🍚Carbohydratesenergy🥚Proteinsgrowth🧈Fatsstored energy🍊Vitamins A,D,E,K,Cprotection🧂Mineralsstrong bones💧Water65–70% of body

In the figure : In the figure nutrients and what they do.

  • Easy : Easy: a person of 60 kg has about 60 × 65/100 = 39 kg of water at the lower figure of 65%.
  • Medium : Medium: butter and oil contain fat-soluble vitamins like A and D, while vitamin C dissolves in water.
  • Exam-type : Exam: why do growing children need more protein? Proteins (amino acids) build new cells and tissues.
Remember

Proteins: body-building. Fats and carbohydrates: energy. Vitamins A, D, E, K: fat-soluble. Water: 65–70%.

Common mistake

Thinking all vitamins dissolve in water. A, D, E, K dissolve in fat.

Shortcut

Memory clue: "ADEK in fat".

Spot the difference

NutrientMain job
ProteinGrowth and repair
Carbohydrate, fatEnergy
Vitamins, mineralsProtection, small needs
Water65–70% of the body

Practice questions

Easy
  1. 1Of what are proteins made?
  2. 2Name the fat-soluble vitamins.
  3. 3What percentage of the body is water?
Medium
  1. 4Which nutrients give energy?
  2. 5What is the main job of proteins?
  3. 6Which vitamin dissolves in water?
Challenging
  1. 7A person weighs 50 kg and has 70% water. How much water is that?
  2. 8Why is a balanced diet needed?
Show answers (try them yourself first)
  1. 1Amino acids.
  2. 2A, D, E and K.
  3. 365–70%.
  4. 4Carbohydrates and fats (and proteins).
  5. 5Building and repairing the body.
  6. 6Vitamin C.
  7. 750 × 70/100 = 35 kg.
  8. 8To supply all nutrients in the right amounts.

Cell division

From daily life

A tiny wound heals when the cells around it divide to fill the gap, and a child grows taller because cells keep dividing. But the cells that make eggs and sperm divide in a special way.

Simple definition

Mitosis (सूत्री विभाजन) gives two identical cells; meiosis (अर्धसूत्री विभाजन) gives four cells with half the chromosomes.

Rule 1: Mitosis — Mitosis occurs in somatic (body) cells. Its stages are prophase, metaphase, anaphase and telophase; in anaphase the sister chromatids separate. It is needed for growth and repair.

Four stages of mitosis: prophase, metaphase, anaphase and telophaseMitosis (growth): one cell → two identical cellsProphasechromosomes appearMetaphaseline up in middleAnaphasechromatids separateTelophasetwo cells form

In the figure : In the figure the stages of mitosis.

  • Easy : Easy: one cell dividing by mitosis gives 2 cells; after 3 divisions there are 2 × 2 × 2 = 8 cells.
  • Medium : Medium: a human body cell has 46 chromosomes, and each daughter cell from mitosis also has 46.
  • Exam-type : Exam: arrange the stages: prophase, metaphase, anaphase, telophase; separation of sister chromatids happens in anaphase.

Rule 2: Meiosis — Meiosis occurs in germ cells. One diploid cell gives four haploid cells (gametes).

A diploid cell divides twice to give four haploid cellsMeiosis (gametes): one cell → four haploid cells2nnnnnnndiploidhaploidfour gametes

In the figure : In the figure meiosis makes gametes.

  • Easy : Easy: a human germ cell has 46 chromosomes, and each gamete after meiosis has 23.
  • Medium : Medium: when sperm (23) fuses with egg (23), the zygote gets 23 + 23 = 46 chromosomes again.
  • Exam-type : Exam: difference – mitosis gives 2 identical diploid cells for growth; meiosis gives 4 haploid cells for gametes.
Remember

Mitosis: somatic cells, 2 cells, growth. Meiosis: germ cells, 4 haploid cells, gametes.

Common mistake

Thinking that meiosis gives two cells. It gives four.

Shortcut

Memory clue: "Mitosis = Making more; Meiosis = Making gametes, half".

Spot the difference

FeatureMitosisMeiosis
CellsSomaticGerm
Daughter cells24
ChromosomesSameHalf

Practice questions

Easy
  1. 1Where does mitosis occur?
  2. 2Name the four stages of mitosis.
  3. 3In which stage do sister chromatids separate?
Medium
  1. 4Where does meiosis occur?
  2. 5How many cells are formed by meiosis?
  3. 6How many cells are there after 4 mitotic divisions from one cell?
Challenging
  1. 7A pea plant body cell has 14 chromosomes. How many does its gamete have?
  2. 8Why is meiosis necessary for sexual reproduction?
Show answers (try them yourself first)
  1. 1In somatic (body) cells.
  2. 2Prophase, metaphase, anaphase, telophase.
  3. 3Anaphase.
  4. 4In germ cells.
  5. 5Four haploid cells.
  6. 62⁴ = 16.
  7. 77.
  8. 8It halves the chromosomes in gametes, so that fertilization restores the normal number.

Quick revision

  • Glycolysis, Krebs cycle, electron transfer chain make ATP.
  • Mitosis for growth; meiosis for gametes.