Animals use the organs of their digestive systems to extract important nutrients from food they consume, which can later be absorbed.
Carbohydrates, which break down to glucose, are a major source of energy for humans, but are not an essential nutrient.
Fats store energy, facilitate absorption of fat-soluble vitamins, aid brain growth and development, and protect against many diseases.
Proteins are composed of 20 different amino acids, about half of which are essential, meaning they must be obtained from the diet.
The citric acid cycle is a series of reactions that produces two carbon dioxide molecules, one GTP/ATP, and reduced forms of NADH and FADH2.
Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism.
Catabolic pathways are controlled by enzymes, proteins, electron carriers, and pumps that ensure that the remaining reactions can proceed.
Cellular respiration is the process of transforming chemical energy into forms usable by the cell or organism.
Sugars, such as galactose, fructose, and glycogen, are catabolized into new products in order to enter the glycolytic pathway.
Excess amino acids are converted into molecules that can enter the pathways of glucose catabolism.
Catabolic reactions that break complex molecules provide the energy needed by anabolic reactions to produce complex molecules.
When the gastrointestinal tract is full, anabolism exceeds catabolism; this is the absorptive state.
The post-absorptive state occurs around three to five hours after a meal has been completely digested and absorbed.
One quarter of body cholesterol is produced by the liver, and 50% of this is reabsorbed back into the circulation via the small intestine.
Cholesterol is transported through the blood by lipoproteins which direct cholesterol to where it is needed.
Animals use different modes of thermoregulation processes to maintain homeostatic internal body temperatures.
The endocrine system controls the release of hormones responsible for starting, stopping, slowing, and quickening digestive processes.
All three phases of digestive responses to food (the cephalic, gastric, and intestinal stages) are managed through enzymatic neural control.
Animals use energy for metabolism, obtaining that energy from the breakdown of food through the process of cellular respiration.
The gut or gastrointestinal tract is an endoderm-derived structure.
Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder due to a mutation in the phenylalanine hydroxylasegene gene.
Galactosemia and GSD are two diseases that are caused by improper carbohydrate metabolism.
Diabetes mellitus type 1 results from autoimmune destruction of insulin-producing beta cells of the pancreas and is potentially fatal.
Animals can be carnivores, herbivores, or omnivores in their eating strategies.
Invertebrate digestive systems include a gastrovascular cavity with one opening or an alimentary canal with a true mouth and anus.
Vertebrates may have a single stomach, several stomach chambers, or accessory organs that help to break down ingested food.
Animal digestion begins in the mouth, then moves through the pharynx, into the esophagus, and then into the stomach and small intestine.
Nutrients are absorbed in the small intestine and waste is prepared for elimination in the large intestine.
The first step to obtaining nutrition is ingestion, a process where food is taken in through the mouth and broken down by teeth and saliva.
In order for nutrients (carbohydrates, lipids, vitamins) to be absorbed for energy, food must undergo chemical and mechanical digestion.
Undigested food enters the colon where water is reabsorbed into the body and excess waste is eliminated from the anus.
The transfer of electrons between molecules via oxidation and reduction allows the cell to transfer and use energy for cellular functions.
ATP, produced by glucose catabolized during cellular respiration, serves as the universal energy currency for all living organisms.
In the first half of glycolysis, energy in the form of two ATP molecules is required to transform glucose into two three-carbon molecules.
In the second half of glycolysis, energy is released in the form of 4 ATP molecules and 2 NADH molecules.
One glucose molecule produces four ATP, two NADH, and two pyruvate molecules during glycolysis.
After glycolysis, pyruvate is converted into acetyl CoA in order to enter the citric acid cycle.
The acetyl carbons of acetyl CoA are released as carbon dioxide in the citric acid cycle.
The electron transport chain uses the electrons from electron carriers to create a chemical gradient that can be used to power oxidative phosphorylation.
Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient.
The amount of energy (as ATP) gained from glucose catabolism varies across species and depends on other related cellular processes.
Some prokaryotes and eukaryotes use anaerobic respiration in which they can create energy for use in the absence of oxygen.
Lipids can be both made and broken down through parts of the glucose catabolism pathways.
Cellular respiration can be controlled at each stage of glucose metabolism through various regulatory mechanisms.
Every animal has a distinct body plan, adapted in response to environmental pressures, that limits its size and shape.
Animal body plans can have varying degrees of symmetry and can be described as asymmetrical, bilateral, or radial.
Animal shape and body size are influenced by environmental factors as well as the presence of an exoskeleton or an endoskeleton.
Less efficient diffusion in larger cells led to multicellular organisms with specialized tissues that supply nutrients and remove waste.
An animal's body size, activity level, and environment impacts the ways it uses and obtains energy.
Vertebrates can be divided along different planes in order to reference the locations of defined cavities.
Epithelial tissues cover the outer surfaces of the body and the lumen of internal organs; they are classified by shape and number of layers.
Connective tissue is found throughout the body, providing support and shock absorption for tissues and bones.
Bone, adipose (fat) tissue, and blood are different types of connective tissue that are composed of cells surrounded by a matrix.
The function of muscle tissue (smooth, skeletal, and cardiac) is to contract, while nervous tissue is responsible for communication.
Homeostatic processes ensure a constant internal environment by various mechanisms working in combination to maintain set points.
Homeostasis is typically achieved via negative feedback loops, but can be affected by positive feedback loops, set point alterations, and acclimatization.
Animals have processes that allow for heat conservation and dissipation in order to maintain a homeostatic internal body temperature.