Biology: Metabolism and Plant Functions

Study Notes

Catabolism breaks down large molecules into smaller pieces, releasing energy into the environment (exergonic).
Anabolism builds large molecules from smaller ones, requiring energy input (endergonic).
ATP releases energy by breaking its high-energy bonds, powering other reactions within a cell.
Enzymes are proteins that speed up chemical reactions by bringing substrates to their active sites, facilitating bond breaking or formation.
Enzyme activity is affected by:
- Temperature: influencing the movement of substrates and enzymes.
- pH: affecting an enzyme's shape and reactivity.

Angiosperms are flowering plants, with distinct structures:
- Flowers: responsible for sexual reproduction, producing fruits.
- Roots: absorb water and nutrients from the soil, anchor the plant, and store carbohydrates.
  - Adventitious roots: grow from the shoot system, providing extra support or anchoring.
  - Pneumatophore roots: specialized roots for gas exchange.
  - Storage roots: store carbohydrates.
- Shoots: harvest light and carbon dioxide for photosynthesis and transport water upwards.
  - Stems: vertical aboveground structures with nodes (leaf attachments) and internodes.
    - Herbaceous stems: exhibit vertical growth, without bark.
    - Woody stems: exhibit vertical and outward growth, forming bark.
  - Leaves: large surface area for photosynthesis.
Plants with a large surface area to volume ratio are more efficient at absorbing sunlight, water, and nutrients.
Essential Elements are necessary for plant growth and reproduction.
- Macronutrients: needed in large amounts (C, H, O, N, S, P, K, Ca, Mg).
- Micronutrients: needed in small amounts (Cl, Fe, Mn, B, Zn, Cu, Ni, Mo).
Soil can be modified to support plant growth by adjusting its composition and nutrient content.

Photosynthesis is the process of converting light energy into chemical energy in the form of sugars.
It happens in the chloroplasts of plant cells.
The light-dependent reactions capture light energy and convert it to chemical energy stored in ATP and NADPH.
The light-independent reactions (Calvin cycle) use ATP and NADPH to fix carbon dioxide into sugars.

Cellular respiration is the process of breaking down sugars to release energy in the form of ATP.
It occurs in the mitochondria of cells.
Glycolysis breaks down glucose into pyruvate, generating a small amount of ATP.
The Krebs cycle further oxidizes pyruvate, releasing CO2 and generating electron carriers.
Electron transport chain uses electron carriers to pump protons across a membrane, creating a proton gradient that drives ATP synthesis.

C4 plants have adapted to hot, dry environments by concentrating CO2, reducing photorespiration and increasing photosynthetic efficiency.
CAM plants also adapt to arid environments by opening their stomata at night to collect carbon dioxide and store it for use during the day.

Plant-based foods provide essential nutrients including carbohydrates, proteins, fats, vitamins, and minerals.
Legumes are important sources of protein, fiber, and iron.
Grains are good sources of carbohydrates and fiber.
Fruits and vegetables provide vitamins, minerals, and antioxidants.