Life Processes

Why This Chapter Matters

Most important Biology chapter — 10-12 marks in board exams. Nutrition (digestion, photosynthesis), respiration (aerobic/anaerobic), transportation (blood, xylem/phloem), excretion (nephron) all tested with diagrams.

Prerequisites

•Cell structure and organelles

•Basic chemistry: CO2, O2, glucose

•Previous biology from Class 7-8

Core Concepts

1. Nutrition

Autotrophic (Plants) — Photosynthesis:

6CO2 + 6H2O --(chlorophyll, sunlight)--> C6H12O6 + 6O2

Location: Chloroplasts (grana = light reaction, stroma = dark reaction/Calvin cycle)

Steps: Light splits water (O2 released, ATP/NADPH made) -> CO2 fixed to glucose.

Heterotrophic (Animals) — Human Digestion:

Mouth (saliva, amylase: starch->maltose) ->

Stomach (gastric juice, pepsin in HCl: proteins->peptides) ->

Small intestine (pancreatic juice: amylase+lipase+trypsin; bile: emulsifies fats) ->

Intestinal juice: final digestion ->

Absorption by villi (large surface area) ->

Large intestine: water absorption ->

Rectum -> Anus

2. Respiration

Aerobic: C6H12O6 + 6O2 -> 6CO2 + 6H2O + 38 ATP

Steps: Glycolysis (cytoplasm, 2 ATP) -> Krebs cycle (mitochondria) -> ETC (34 ATP)

Anaerobic (yeast/fermentation): Glucose -> 2 Ethanol + 2CO2 + 2 ATP

Anaerobic (muscle): Glucose -> 2 Lactic acid + 2 ATP (causes cramps)

Human respiratory system:

Nostrils -> Nasal cavity -> Pharynx -> Larynx -> Trachea -> Bronchi -> Bronchioles -> Alveoli

Alveoli: thin walls, rich blood supply, gas exchange by diffusion.

3. Transportation

In Plants:

Xylem: water+minerals, UPWARD, by transpiration pull + root pressure.

Phloem: food/sucrose, BOTH directions, pressure-flow mechanism.

In Humans:

Heart: 4 chambers (RA, RV, LA, LV). Double circulation.

Pulmonary: Heart -> Lungs -> Heart (deoxygenated -> oxygenated)

Systemic: Heart -> Body -> Heart (oxygenated -> deoxygenated)

Blood components: RBC (haemoglobin, O2 transport), WBC (immunity), Platelets (clotting), Plasma (liquid phase).

4. Excretion

In Plants: CO2 via stomata/lenticels | O2 via photosynthesis | H2O via transpiration | Some wastes stored in vacuoles, bark.

In Humans:

Nephron (functional unit of kidney) — 1 million per kidney.

Urine formation 3 steps:

1.Filtration: Blood filtered in glomerulus/Bowman's capsule

2.Reabsorption: Glucose, amino acids, water reabsorbed in renal tubule

3.Secretion: Additional H+, K+, creatinine added to tubule

Final: urine (water + urea + salts) -> ureter -> bladder -> urethra

Dialysis (artificial kidney): semi-permeable membrane removes urea from blood when kidneys fail.

PYQs

2023: Draw excretory system. Label kidney, ureter, urinary bladder, urethra.

(Draw diagram with labels)

2022: Explain urine formation in kidneys.

Three steps: Filtration (glomerulus) -> Reabsorption (tubule: glucose/amino acids/water back to blood) -> Secretion (waste into tubule) -> Urine formed.

2021: How does water transport differ from food transport in plants?

Water: xylem, upward only, transpiration pull + root pressure.

Food: phloem, both directions, pressure-flow (source to sink).

2020: List steps of Amoeba nutrition (holozoic).

Ingestion -> Digestion (food vacuole) -> Absorption -> Assimilation -> Egestion

MCQ Practice

Q1. Salivary amylase acts on:

(A) Proteins (B) Fats (C) Starch (D) Glucose

Answer: C

Q2. Which heart chamber pumps oxygenated blood to body?

(A) Right auricle (B) Left auricle (C) Right ventricle (D) Left ventricle

Answer: D

Q3 (Hard). During fermentation by yeast:

(A) O2 required (B) CO2 absorbed (C) Ethanol produced (D) Lactic acid produced

Answer: C

Revision Notes

PHOTOSYNTHESIS: 6CO2 + 6H2O -> C6H12O6 + 6O2 (chlorophyll + light)
AEROBIC RESP: Glucose + O2 -> CO2 + H2O + 38 ATP
ANAEROBIC (yeast): Glucose -> Ethanol + CO2 + 2 ATP
ANAEROBIC (muscle): Glucose -> Lactic acid + 2 ATP (cramps)

TRANSPORT IN PLANTS:
Xylem: water + minerals, upward, transpiration pull
Phloem: food, both directions, pressure flow

BLOOD CIRCULATION - DOUBLE:
Pulmonary: heart -> lungs -> heart
Systemic: heart -> body -> heart

NEPHRON - 3 steps:
1. Filtration (glomerulus/Bowman's capsule)
2. Reabsorption (glucose, amino acids, water)
3. Secretion (additional wastes)
Urine = water + urea + salts (NO glucose - fully reabsorbed)

Common mistakes: Xylem transports food (WRONG - phloem does). Urine contains glucose (WRONG in healthy person).