Plant & Human Nutrition: Units 6, 7, & 8

• Study notes for Units 6, 7, and 8 cover plant nutrition, human nutrition, and transport in plants.

6.1 Photosynthesis

• Photosynthesis is how plants create food using sunlight, carbon dioxide, and water to produce glucose and oxygen.
• Photosynthesis word equation: Carbon dioxide + Water yields Glucose + Oxygen (using Light + Chlorophyll).
• Balanced chemical equation: 6CO₂ + 6H₂O yields C₆H₁₂O₆ + 6O₂ (using Light + Chlorophyll).
• Key requirements include light energy absorbed by chlorophyll in chloroplasts, carbon dioxide from the air via stomata, and water absorbed by roots from the soil.
• Photosynthesis is affected by light intensity, carbon dioxide concentration, and temperature.
• Testing for starch involves boiling a leaf in water to kill cells and stop reactions.
• Next, boil the leaf in ethanol to remove chlorophyll, then rinse in warm water to soften the leaf.
• Adding iodine solution will turn the leaf blue-black if starch is present, confirming photosynthesis.

6.2 Leaf Structure and Adaptations

• A leaf's cuticle is a waxy layer that prevents water loss.
• The upper epidermis is transparent to allow light to pass through.
• Palisade mesophyll contains many chloroplasts for photosynthesis.
• Spongy mesophyll contains air spaces that facilitate gas exchange.
• Stomata are openings that allow CO₂ in and O₂ out, and are controlled by guard cells.
• Leaves have broad, flat structures to maximize light absorption.
• Thin leaves provide short diffusion distances for gases.
• Veins contain xylem and phloem to transport water, minerals, and food.

7.1 Nutrients and Their Functions

• Carbohydrates function as an energy source and are found in bread, rice, and pasta.
• Proteins are essential for growth and repair, found in meat, eggs, and beans.
• Fats are used for energy storage and insulation and are present in butter, oils, and nuts.
• Vitamins are vital for bodily functions; food sources include fruits and vegetables.
• Minerals support bone health and oxygen transport, with sources like milk (calcium) and red meat (iron).
• Fiber aids digestion and is found in vegetables and whole grains.
• Water is necessary for hydration and chemical reactions; sources include water and fruits.

7.2 The Human Digestive System

• The mouth starts mechanical digestion through chewing; saliva contains amylase to break down starch.
• The esophagus moves food to the stomach through peristalsis.
• The stomach uses acid and pepsin to digest proteins.
• The small intestine absorbs nutrients into the blood via villi.
• The large intestine absorbs water and forms feces.
• The rectum and anus store and expel waste.

7.3 Enzymes in Digestion

• Enzymes breakdown large molecules into smaller, absorbable molecules.
• Amylase is produced in the salivary glands and pancreas, and breaks down starch into maltose.
• Protease (Pepsin) is produced in the stomach and breaks down proteins into amino acids.
• Lipase is produced in the pancreas and breaks down fats into fatty acids and glycerol.

7.4 & 7.5 Balanced Diet and Deficiency Diseases

• Vitamin C deficiency causes Scurvy, leading to bleeding gums and a weakened immune system.
• Vitamin D or Calcium deficiency leads to Rickets, resulting in weak bones.
• Iron deficiency causes Anemia, leading to tiredness and low oxygen transport.
• Recommendations for a balanced diet include eating a variety of food groups, drinking enough water, and limiting fats and sugars.

8.1 Xylem and Phloem

• Xylem transports water and minerals upwards from the roots.
• Phloem transports sugars (food) in both directions.
• Xylem transports water & minerals upwards only, containing thick walls and dead cells.
• Phloem transports sugars & nutrients both upwards and downwards and contains living cells.

8.2 Water Uptake and Movement

• Roots absorb water from the soil through osmosis.
• Water travels through the root cortex into the xylem.
• Transpiration pull draws water upwards.

8.3 Transpiration

• Transpiration is defined as the loss of water vapor from leaves through stomata.
• More light increases transpiration.
• Higher temperatures speed up transpiration.
• Higher humidity slows down transpiration.
• More wind speeds up transpiration.

8.4 Translocation

• Translocation is the movement of sugars and nutrients via the phloem.
• Substances move from source (leaves) to sink (roots, fruits, storage organs).
• Active transport is used to move substances.