Study guide: Life Processes

📋 Course Outline

1. Life and Maintenance Processes
2. Nutrition and Photosynthesis
3. Heterotrophic and Human Nutrition
4. Cellular Respiration and ATP
5. Respiratory Gas Exchange
6. Human Circulation
7. Transport in Plants
8. Excretion in Organisms

📖 1. Life and Maintenance Processes

🔑 Key Concepts & Definitions

• Life processes: The maintenance functions that keep an organism’s structures from being damaged and breaking down.

★ Must-know

• Visible movement alone does not establish whether something is alive, because living organisms may have no visible movement while molecular movement continues.

• Life maintenance requires:

  • nutrition
  • respiration
  • transport of materials
  • excretion

Further detail

• Organisms obtain food and other raw materials from outside the body, and chemical reactions convert these materials into usable energy and molecules for growth.

💡 Memory Hook

Environmental breakdown → continuous molecular repair and maintenance

📖 2. Nutrition and Photosynthesis

🔑 Key Concepts & Definitions

• Autotrophs: Organisms that use simple materials such as carbon dioxide and water to make food; green plants and some bacteria are examples.
• Heterotrophs: Organisms that obtain complex food directly or indirectly from autotrophs and break it down for use; animals and fungi are examples.
• Photosynthesis: The process in which autotrophs use sunlight and chlorophyll to convert carbon dioxide and water into carbohydrates, storing energy in chemical form.

★ Must-know

• Photosynthesis involves absorption of light by chlorophyll, conversion of light energy to chemical energy with splitting of water, and reduction of carbon dioxide to carbohydrates.

Further detail

• Carbohydrates not used immediately by plants are stored as starch, while some energy from food is stored in humans as glycogen.

• Plants obtain these materials from soil:

  • water through roots
  • nitrogen
  • phosphorus
  • iron
  • magnesium

💡 Memory Hook

Autotrophs build food from simple substances; heterotrophs obtain complex food from other organisms

📖 3. Heterotrophic and Human Nutrition

★ Must-know

• Amoeba takes in food with temporary finger-like extensions that surround it in a food vacuole, where complex substances are broken down and simpler substances diffuse into the cytoplasm.

• 🔄 Food passes through:

  1. mouth
  2. oesophagus
  3. stomach
  4. small intestine
  5. large intestine
  6. anus

• Salivary amylase in saliva breaks starch into simple sugars, while chewing and the tongue mix and move food in the mouth.

• Gastric glands release:

  • hydrochloric acid
  • pepsin
  • mucus

Further detail

• Fungi such as bread mould, yeast, and mushrooms digest food outside the body and then absorb it.

• Paramoecium takes in food at a specific spot, and cilia move food across its surface to that spot.

💡 Memory Hook

Mouth → oesophagus → stomach → small intestine → large intestine

📖 4. Cellular Respiration and ATP

🔑 Key Concepts & Definitions

• ATP: The energy currency used by cells to drive activities such as muscle contraction, protein synthesis, and conduction of nervous impulses.

★ Must-know

• Glucose first breaks down into pyruvate in the cytoplasm; pyruvate is then converted into ethanol and carbon dioxide in yeast without oxygen, into carbon dioxide and water in mitochondria with oxygen, or into lactic acid in oxygen-deficient muscle cells.

📌 Aerobic respiration releases much more energy than anaerobic respiration.

Further detail

• Lactic acid can build up in muscle cells during sudden activity when oxygen is insufficient, causing cramps.

• Breaking ATP’s terminal phosphate linkage with water releases energy equivalent to 30.5 kJ/mol.

💡 Memory Hook

Oxygen leads to greater energy release; without oxygen, pyruvate follows other pathways

📖 5. Respiratory Gas Exchange

🔑 Key Concepts & Definitions

• Alveoli: Balloon-like structures at the ends of lung air passages where gases are exchanged across walls surrounded by blood vessels.

★ Must-know

• Aquatic organisms breathe faster than terrestrial organisms because water contains less dissolved oxygen than air.

• 🔄 During inhalation: the ribs lift, the diaphragm flattens, the chest cavity becomes larger, air enters the lungs and fills the expanded alveoli

• Haemoglobin in red blood cells carries oxygen from the lungs to oxygen-deficient tissues, while most carbon dioxide is transported dissolved in blood because it is more soluble in water than oxygen.

Further detail

• Fish take water in through the mouth and pass it over the gills, where dissolved oxygen enters the blood.

💡 Memory Hook

Alveoli form tiny air-filled balloons wrapped in blood vessels

📖 6. Human Circulation

★ Must-know

• Blood consists of plasma, which transports dissolved food, carbon dioxide, nitrogenous wastes, and salts, and red blood cells, which carry oxygen.

• 🔄 Double circulation follows this route: deoxygenated blood returns from the body to the right side of the heart, the right side pumps blood to the lungs, oxygenated blood returns to the left side of the heart, the left side pumps blood to the body

📌 Arteries carry blood away from the heart under pressure and have thick elastic walls, whereas veins return blood to the heart and have valves that keep blood flowing in one direction.

Further detail

📌 Birds and mammals have four-chambered hearts that keep oxygenated and deoxygenated blood separate; amphibians and many reptiles have three-chambered hearts with some mixing, while fish have two-chambered hearts and single circulation.

• Capillaries have walls one cell thick and enable exchange between blood and surrounding cells; platelets help clot blood at vessel injuries, and lymph returns excess tissue fluid to the blood and carries absorbed fat from the intestine.

💡 Memory Hook

Body → right heart → lungs → left heart → body

📖 7. Transport in Plants

🔑 Key Concepts & Definitions

• Transpiration: The loss of water as vapour from a plant’s aerial parts, creating a suction that pulls water upward through xylem and helping regulate temperature.
• Translocation: The movement of soluble photosynthetic products and other substances through phloem from leaves to other plant parts.

★ Must-know

📌 Xylem transports water and minerals from roots, whereas phloem transports products of photosynthesis from leaves to other parts of the plant.

Further detail

• 🔄 Root uptake contributes to water movement: root cells take up ions from soil, water enters the roots to reduce the concentration difference, root pressure pushes a water column upward through xylem

• Phloem transports materials in both upward and downward directions using energy from ATP; sucrose loading increases osmotic pressure, drawing in water and driving movement toward tissues at lower pressure.

💡 Memory Hook

Xylem carries water and minerals; phloem carries food

📖 8. Excretion in Organisms

🔑 Key Concepts & Definitions

• Excretion: The biological process of removing harmful metabolic wastes from the body.

★ Must-know

• The human excretory system consists of:

  • two kidneys
  • two ureters
  • a urinary bladder
  • a urethra

• In each nephron, blood is filtered into Bowman’s capsule; useful substances such as glucose, amino acids, salts, and much of the water are selectively reabsorbed as filtrate passes along the tubule, and the remaining urine travels through the ureter to the bladder.

• Plants deal with wastes by: removing excess water by transpiration, storing wastes in vacuoles, shedding waste-containing leaves, storing wastes as resins and gums in old xylem, releasing wastes into the surrounding soil

Further detail

• A healthy adult initially filters about 180 L of filtrate per day, but reabsorption reduces urine output to about one or two litres per day.

💡 Memory Hook

Kidneys filter blood and reabsorb useful substances; plants store, shed, or release wastes

📊 Synthesis Tables

Transport pathways

Feature	Xylem	Phloem
Main materials	Water and minerals	Photosynthetic products and other substances
Direction described	Upward movement	Upward and downward movement
Energy basis	Largely physical forces	Movement uses ATP