Study guide: Plant Water and Human Health

📋 Course Outline

1. Water Absorption by Root Hairs
2. Water Transport Through Xylem
3. Investigating Water Transport
4. Transpiration Through Leaves
5. Why Plants Need Water
6. Excretion and Waste Materials
7. Kidneys and Urine Formation
8. Fetal Needs and Maternal Diet
9. Smoking and Drugs During Pregnancy

📖 1. Water Absorption by Root Hairs

🔑 Key Concepts & Definitions

• Root hair cells: Specialized cells on the root surface that provide a large surface area for absorbing water and mineral ions from the soil.

★ Must-know

• Water and dissolved mineral ions move from the spaces between soil particles through the root hair cell wall and membrane into its cytoplasm.

Further detail

• Magnesium and nitrate are examples of mineral ions absorbed by root hair cells from the soil water.

📖 2. Water Transport Through Xylem

🔑 Key Concepts & Definitions

• Xylem vessels: Long, hollow tubes formed from dead cells whose contents and end walls have disappeared, leaving cell walls around an empty space.

★ Must-know

• 🔄 Water follows this route through the plant:
  1. Moves from the outside of the root toward its centre
  2. Enters the xylem vessels
  3. Travels upward through the plant

Further detail

• The wood in a tree trunk is made up of xylem vessels, which carry water from the roots toward the top of the tree.

• The diameter of a xylem vessel is about 0.05 mm.

💡 Memory Hook

Picture xylem as long, hollow pipes running from roots to the plant’s highest parts.

📖 3. Investigating Water Transport

★ Must-know

• In the coloured-water stalk investigation, blue spots in a cross-section indicate xylem cells.

Further detail

• 🔄 The investigation proceeds as follows:

  1. Place the clean cut end of the stalk in coloured water
  2. Observe the dye moving upward
  3. Cut across the stalk to locate the stained xylem

• A fair test of temperature’s effect on water movement changes temperature, measures the movement rate, keeps other relevant variables constant, and assesses risks.

📖 4. Transpiration Through Leaves

🔑 Key Concepts & Definitions

• Transpiration: The loss of water vapour from leaves.

★ Must-know

• 🔄 Water vapour leaves the plant in this sequence:
  1. Water moves from the xylem into leaf cells
  2. Water evaporates from cell walls into air spaces
  3. Water vapour diffuses through stomata into the air

Further detail

• Most transpiration occurs through the underside of a leaf rather than the top.

• To compare water loss from leaf surfaces, coat different groups of similar leaves with petroleum jelly on the upper surface, lower surface, both surfaces, or neither, then compare their mass changes.

💡 Memory Hook

Xylem → leaf cells → air spaces → stomata → outside air.

📖 5. Why Plants Need Water

🔑 Key Concepts & Definitions

• Wilting: When its cells lack enough water, become soft and floppy, and the plant collapses.

★ Must-know

• Water in plant cell vacuoles makes cells firm, and the pressure of firm cells against one another supports the plant.

• Water transports dissolved mineral salts through the xylem from roots to other parts of the plant.

• Water is a reactant in photosynthesis, in which plants change water and carbon dioxide into glucose and oxygen.

Further detail

• Evaporation of water from leaf cell walls removes heat and cools the cells.

📖 6. Excretion and Waste Materials

🔑 Key Concepts & Definitions

• Excretion: The removal of waste substances made in cells or substances present in excess that have been inside the body.

★ Must-know

📌 Faeces are not excretory waste because food travelling through the digestive system has not been part of the body.

• Human excretory wastes include:
  • Carbon dioxide made during respiration
  • Urea made in liver cells
  • Excess water

Further detail

• When protein intake exceeds the body’s needs, the liver changes small molecules from digested proteins into urea, which is carried away in the blood.

💡 Memory Hook

Faeces pass through the digestive tube; excretory wastes have been inside the body.

📖 7. Kidneys and Urine Formation

🔑 Key Concepts & Definitions

• Urine: The solution formed when urea dissolves in excess water removed from the blood by the kidneys.

★ Must-know

• The kidneys filter the blood, remove urea and excess water, and form urine.

• Urine flows from each kidney through a ureter to the bladder, where it can be stored, and leaves the body through the urethra.

Further detail

• The excretory system is also called the renal system.

💡 Memory Hook

Kidneys → ureters → bladder → urethra.

📖 8. Fetal Needs and Maternal Diet

🔑 Key Concepts & Definitions

• Fetus: A baby developing inside its mother before birth.

★ Must-know

• The fetus depends on its mother to supply needed substances and remove substances it excretes.

• The mother’s and fetus’s blood do not mix; substances diffuse between the two blood systems, and fetal excretory substances diffuse in the opposite direction.

• During pregnancy, a woman needs a balanced diet and slightly more food than usual because some nutrients are passed to the fetus.

• Important dietary nutrients have these roles:

  • Protein supports fetal cell production and growth
  • Carbohydrate supplies energy
  • Iron is needed to make haemoglobin
  • Calcium supports fetal bone growth and the mother’s bones and teeth

Further detail

• A pregnant woman needs vitamins in her diet.

📖 9. Smoking and Drugs During Pregnancy

★ Must-know

• Carbon monoxide and nicotine from a pregnant woman’s blood diffuse into the fetus’s blood.

• Carbon monoxide reduces the amount of oxygen haemoglobin can transport, so fetal cells receive less oxygen, respire less, release less energy, and may develop differently.

• Most drugs taken by a pregnant woman enter the fetus’s blood, and drugs that are not needed can harm the fetus.

📌 Pregnant women should stop smoking, avoid alcohol and illegal drugs, check before taking non-prescription drugs, and avoid drinking a lot of coffee or cola because caffeine may harm a developing fetus.

Further detail

• Babies born to mothers who smoked during pregnancy tend to be smaller than babies born to non-smoking mothers.

📌 A pregnant woman who regularly takes a prescribed drug should check with a doctor or pharmacist before continuing or stopping it.

💡 Memory Hook

Carbon monoxide reduces oxygen transport → fetal cells receive less oxygen for respiration.