Human Body: Nutrients, Metabolism and Digestion

• The body requires essential nutrients to build new cells and grow
• Proteins are needed to build cells
• Minerals like calcium contribute to bone growth and skeletal structure

Essential Nutrients

• These are substances required in the diet of animals/humans
• The human body cannot synthesize essential nutrients itself
• These nutrients must be obtained from food
• Examples include fatty acids, proteins, carbohydrates, vitamins, minerals, glucose, fiber, and water

Metabolism

• This is a series of chemical reactions in the body
• Converts nutrients from food into energy
• Repairs and builds tissues
• Excretes waste

Minerals

• These are inorganic nutrients
• Essential for human health
• Naturally occurring in food
• Examples include iron, calcium, and sodium

Digestion Steps

• Mouth: Food is chewed and saliva breaks it down into a paste-like substance
• Esophagus: The food travels down the esophagus (throat) to the stomach
• Stomach: The stomach lining releases acid to further break down the paste into a liquid (chyme)
• Small Intestine: Enzymes from the pancreas and liver continue to break down food and most nutrient absorption occurs here
• Large Intestine: Remaining liquid/undigested food is processed, water is absorbed, and waste becomes solid before being expelled

Stomach Function

• Breaks down food into a liquid substance for the small intestine
• Temporarily stores food

Intestine Function

• Small Intestine: Further processes food and absorbs nutrients like vitamins, minerals, and proteins; sends leftover material to the large intestine
• Large Intestine: Absorbs water and nutrients from leftover material, forming solid waste for expulsion

Intestine Lining

• Has a highly folded and curved structure with a shaggy/velvety texture
• This increases the surface area for efficient nutrient absorption

Food to Body

• Food enters the body and is broken down in the mouth by saliva into a mush-like paste
• The paste travels to the stomach, where acid further breaks it down into a nutrient-rich liquid
• Intestinal cells absorb the nutrients and store energy
• Leftover material goes to the large intestine, which absorbs water to create solid waste

Photosynthesis

• This is used by autotrophs (organisms that create their own food)
• Converts light energy into chemical energy (typically sugar/glucose)

Cellular Respiration

• This is used by heterotrophs (organisms that depend on others for food)
• Breaks down molecules like glucose
• Converts their chemical energy into a usable form of energy for the cell (ATP)

Photosynthesis Equation

• 6CO2 + 6H2O + sunlight = C6H12O6 (glucose) + 6O2 (oxygen)
• Carbon dioxide + water + light energy = glucose + oxygen

Cellular Respiration Equation

• 6O2 + C6H12O6 = 6CO2 + 6H2O + ATP
• Oxygen + glucose = carbon dioxide + water + chemical energy (ATP)

Definitions

• Autotrophs: Organisms that create their own food through photosynthesis
• Heterotrophs: Organisms that depend on photosynthesizers for food and energy

Trophic Levels

• The first trophic level (producers) has the most stored energy
• Light energy is converted into chemical energy stored in organic compounds in this level

Energy Storage in Consumers

• Energy decreases by approximately 10% with each increasing tier
• Primary consumers: 10,000 kcal (example)
• Secondary consumers: 100 kcal (example)
• Tertiary consumers: 10 kcal (example)

Energy Consumption

• Majority of energy consumed by an organism is lost to heat
• Only about 10% of energy is transferred to the next trophic level

Primary Succession

• Begins with a volcano erupting and lava creating rock layers
• Moss or algae break down rocks over hundreds of years, creating rocky soil
• Autotrophic bacteria contribute organic matter when they die
• Soil becomes suitable for larger plants (seeds brought by water or animals)
• Over time, an environment develops that can support animals and biodiversity

Primary vs. Secondary Succession

• Primary succession starts with bare rock and takes thousands of years
• Secondary succession starts with existing soil after an environment is destroyed, and takes tens of years

CO2 in Photosynthesis

• Comes from humans and animals, mainly through cellular respiration
• Carbon dioxide is released into the atmosphere as a waste product

Animal Carbon Intake

• Animals obtain carbon by eating plants that absorbed carbon dioxide through photosynthesis
• Carbon is passed through the food chain
• When animals die, they release carbon back into the atmosphere as carbon dioxide or through decomposition

Carbon After Death

• Decomposers break down organisms, releasing carbon into the atmosphere
• Producers reuse this carbon, which is then consumed by animals, continuing the cycle

Societal Food Issue

• There is not enough food or distribution systems to reach the entire world
• Many agricultural fields are used for ranching
• Food shortage issues can be fixed by replacing ranching fields with crops
• Opening more programs like the World Food Program can help distribute food worldwide