Comprehensive lecture notes for lecture 2
ProfessorAngela B Lange
BIO204 Lecture 2 t Animal Nutrition: Benefits and Problems of Complex Molecules
- A nutrient is a substance that an organism requires to remain alive. Nutrients may be sources of
energy or raw materials required to synthesize compounds for growth and maintenance of cell
functions. Water is an essential nutrient to nearly every organism.
- Animals may be classified based on the method by which they acquire carbon compounds and
energy. Carbon compounds that have high potential energy are oxidized to ATP to form a more
readily available store of energy.
- Carbohydrates, fats, and proteins supply organisms with energy. Fat is more saturated than
carbohydrates and proteins and thus contains a far greater amount of energy per unit mass
(aprox. 2X the amount of E per gram)
- The average human adult male is composed primarily of water (aprox. 60%). Protein is the
second-most abundant molecule category in the body (18%), while fats account for 14% and
carbohydrates for about 2%.
- Water is a crucial nutrient as it is necessary for nearly all biological functions. Water is a solvent
for biological reactions, facilitates heat exchange, lubricates tissues and facilitates passage of food
through the digestive tract.
- Carbohydrates are the primary energy source for most organisms. Although they provide less
energy than fats, nervous tissues can only be supplied with energy by carbohydrates. Sugars are
also very important in cell-cell signaling and adhesion.
- Lipids are the ultimate energy source for most organisms; they provide twice the amount of
energy per gram as sugars. In addition, fats have high satiation values, making organisms feel full
more quickly, thus preventing overconsumption. Additionally, fats are major components of cell
PM, are solvents for steroids and vitamins, and are excellent insulators of heat.
- Proteins are found in all tissues, but occur in large amounts in muscle tissues. Proteins catalyze
biological reactions, are necessary for growth and metabolism, and may even be used as energy
sources when all other sources have been depleted.
- Inorganic salts are crucial for the smooth operation of metabolic and biological processes. Salts
are used in virtually all body functions, since they allow regulation of osmolarity and hydrostatic
forces in the body[µ}µvÀ]}vuvX^}]µuv}]µuv(}]}v
potentials, calcium is needed for muscle contraction, phosphorous is used in the production of
bone (hydroxyapatite), iron is used in hemoglobin, and iodine is necessary to maintain proper
thyroid gland function.
- Vitamins (both fat and water soluble) are essential for survival, although only small quantities are
required. Vitamin C is essential for collagen synthesis, Vit. D is necessary for proper bone
formation and nutrient absorption, and other vitamins are needed for various biological reactions.
- Caloric intake describes the amount of energy that is taken in by an organism; undernourishment
refers to when the body must catabolize its own energy reserves in order to compensate for
deficits in caloric intake
- Malnutrition results when an organism lacks essential nutrients; this state may result in diseases
such as Rickets, Scurvy, and Goiter.
- Animals can be divided into two categories:
- Autotrophs: can produce organic compounds
- Heterotrophs: must absorb organic compounds
- Heterotrophs can be further divided into:
- Herbivores: eat only plants
- Carnivores: eat only animals
- Omnivores: eat plants and animals
- Saprophytes: eat dead organisms
- Parasites: feed on living organisms
- Steps in nutrition:
- Ingestion: consumption of food
- Digestion: breakdown of food chemically and physically in preparation for absorption
- Absorption: uptake of nutrients into the circulatory system
- Metabolism: Conversion of nutrients to other source of energy and uptake of nutrients
and energy sources into cells
energy needs that must be met by absorption
taking place during a resting state (Males: 1600-1800 kcal/day; Females: 1300-1500 kcal/day)
- Measurement of the metabolic rate is done via calorimetry (direct or indirect) and is calculated in
units of the calorie (1 cal = amount of E required to raise the temperature of 1g of water by 1
- Physiological functions are never 100% efficient, so heat is always generated due to
metabolism; heat can be measured to give metabolic rate by direct calorimetry
- Metabolic rate is inversely proportional to body mass; although large organisms will have a higher
overall metabolic rate, their metabolic rate per unit mass will be less than that of smaller
- Intermittent feeders: organisms that eat only periodically and that must store energy and
nutrients for periods of no consumption
- Carbohydrates are stored in the liver and in the muscle as glycogen
- Fat is stored in adipose tissues
- Glucose metabolism in humans is governed by peptide hormones secreted by the Islets of
Langerhans in the pancreas
- Insulin ~(}ut-cells) results in increased permeability of PMs to glucose and in
the conversion of glucose to glycogen; net effect is to lower plasma glucose
- 'oµP}v~(}ur-cells) results in the breakdown of glycogen to glucose; net
- Diabetes mellitus is a result of decreased insulin activity either by a decrease in insulin
production or by a decrease in the activity of insulin receptors
- Gestational diabetes is a condition in which pregnant women have high blood glucose
levels t may result in Type2 DM