Plant and Animal Nutrition

Autotrophic organisms

Organisms that produce their own organic food from simpler inorganic substances; green plants commonly do this through photosynthesis.

Heterotrophic organisms

Organisms that obtain food or organic nutrients from other organisms or organic materials rather than producing all of their own food.

photosynthesis

The process by which plants and other photosynthetic organisms use light energy to convert carbon dioxide and water into glucose, releasing oxygen as a by-product.

Glucose

A monosaccharide that serves as a major cellular fuel and is the principal sugar produced during photosynthesis.

Oxygen

A gas released as a by-product of photosynthesis and used by many cells in aerobic cellular respiration.

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration.

Cation Exchange

A soil-root process in which hydrogen ions released by roots displace positively charged mineral ions from soil particles, making those minerals more available for uptake.

Active transport

Energy-requiring movement of substances across a membrane against their concentration gradient.

Nitrogen

A plant macronutrient needed for amino acids, proteins, chlorophyll formation, and healthy vegetative growth.

Phosphorus

A plant macronutrient important in ATP, nucleic acids, energy transfer, and the development of roots, flowers, and fruits.

Potassium

A plant macronutrient that activates many enzymes, supports root growth, regulates water balance, and helps move sugars within the plant.

Germination

The stage in which a seed resumes growth and begins developing into a seedling, including early root establishment.

Vegetative Phase

The period of plant growth mainly devoted to producing roots, stems, and leaves before reproduction.

Reproductive Phase

The stage of a plant life cycle associated with flowering and the production of reproductive structures, fruits, or seeds.

Senescence

The natural aging phase of a plant or plant organ in which physiological activity gradually declines toward maturity or death.

Boron

A plant micronutrient involved in cell-wall formation, cell division, reproductive development, and several metabolic processes.

Silicon

A beneficial plant element that can strengthen tissues and support stress resistance and mineral transport in many species.

Calcium

A plant nutrient important for cell-wall stability, membrane function, and intracellular signaling.

Magnesium

A plant nutrient that is a central component of chlorophyll and is important in photosynthesis and enzyme activity.

Carbon

An element obtained mainly from carbon dioxide and incorporated into glucose and other organic molecules during photosynthesis.

Holozoic Nutrition

A mode of heterotrophic nutrition in which an organism ingests food, digests it internally, and absorbs the resulting nutrients.

Herbivores

Animals that obtain most or all of their food by eating plants or plant materials.

Carnivores

Animals that obtain most or all of their food by eating other animals.

Omnivores

Animals that eat both plant and animal materials.

Saprophytic Nutrition

A mode of nutrition in which an organism obtains nutrients from dead or decaying organic matter, typically after external digestion.

Parasitic Nutrition

A mode of nutrition in which an organism obtains nutrients from a living host, usually harming the host in the process.

Carbohydrates

Biomolecules made mainly of carbon, hydrogen, and oxygen that include sugars and starches and serve as a major source of metabolic energy.

Monosaccharides

The simplest carbohydrates, consisting of a single sugar unit that cannot be hydrolyzed into a smaller carbohydrate.

Fructose

A monosaccharide commonly found in fruits, honey, and many sweetened foods; it can be metabolized by the body and ultimately contribute to energy production.

Galactose

A monosaccharide found mainly as part of lactose in milk; it is commonly converted to glucose during metabolism.

Disaccharides

Carbohydrates formed when two monosaccharides are chemically linked together.

Maltose

A disaccharide composed of two glucose units and produced during the digestion of starch.

Lactose

The main sugar in milk, a disaccharide composed of glucose and galactose.

Sucrose

Common table sugar, a disaccharide composed of glucose and fructose and naturally present in many plants.

Starches

Plant storage polysaccharides made of many glucose units and commonly found in grains, legumes, and root vegetables.

Glycogen

A highly branched polysaccharide used by animals to store glucose, especially in the liver and skeletal muscles.

Fibers

Plant-derived carbohydrates and related structural substances that human digestive enzymes cannot fully digest; some are fermented by microorganisms in the large intestine.

Proteins

Biomolecules made of amino-acid chains that perform structural, enzymatic, transport, signaling, movement, storage, and defense functions.

Lipids

A diverse group of mostly water-insoluble biomolecules, including fats and oils, involved in energy storage, membranes, insulation, and signaling.

Triglycerides

Lipids composed of glycerol bonded to three fatty acids; they are the major form of stored fat in the body and the main form of lipid in the diet.

Saturated fatty acids

Fatty acids with no carbon-carbon double bonds; they are common in many animal fats and some tropical plant oils.

Unsaturated fatty acids

Fatty acids containing one or more carbon-carbon double bonds; common sources include fish, nuts, seeds, and many plant oils.

Phospholipids

Lipids with a phosphate-containing head and fatty-acid tails that are major structural components of cell membranes and can act as emulsifiers.

Steroids

Lipids characterized by a four-ring carbon structure; examples include cholesterol and several hormones.

Mechanical digestion

The physical breakdown of food into smaller pieces without changing the chemical identity of its molecules.

Chemical digestion

The enzymatic breakdown of large food molecules by breaking chemical bonds to produce smaller absorbable molecules.

Small Intestine

The digestive organ where most chemical digestion is completed and most nutrients are absorbed into the blood or lymph.

Villi

Finger-like projections lining the small intestine that greatly increase surface area for nutrient absorption.

Microvilli

Microscopic projections on the surface of intestinal epithelial cells that further increase surface area for nutrient absorption.

Salivary amylase

A digestive enzyme secreted by the salivary glands that begins starch digestion in the mouth by breaking starch into smaller carbohydrates such as maltose.

Pepsin

A protein-digesting enzyme active in the stomach that breaks proteins into shorter peptide chains.

Lipase

A digestive enzyme, produced mainly by the pancreas for intestinal digestion, that breaks triglycerides into fatty acids and other smaller lipid products.

Pancreatic amylase

A digestive enzyme released by the pancreas into the small intestine that continues the breakdown of starch into smaller sugars.

Trypsin

A pancreatic protease released into the small intestine that continues protein digestion by breaking peptide bonds.

Maltase

An enzyme of the small-intestinal lining that hydrolyzes maltose into two glucose molecules.

Peptidase

An enzyme that breaks peptides into smaller peptides or amino acids, helping complete protein digestion in the small intestine.