Unit 7: Human nutrition
Diet
carbohydrates are an energy source (e.g. rice, bread)
proteins allow for growth and repair of tissues (e.g. meat, beans)
fats allow for energy storage, insulation, protection (e.g. oils, butter)
vitamins are only needed in small amounts for various body functions (e.g. Vitamin C for immune function, Vitamin D for bones)
minerals are essential for bodily functions (e.g. Calcium for bones, Iron for blood)
water is necessary for hydration and transport in the body
fiber aids in digestion, excretion, and prevents constipation
a balanced diet is a diet that provides all essential nutrients in fair proportions to stay healthy
Parts of the System
the mouth allows for ingestion of food, mechanical (teeth breaking down food into smaller pieces) & chemical digestion (salivary amylase breaking down starch into smaller pieces)
the esophagus is a muscular tube that moves food to the stomach via peristalsis
the stomach secretes gastric juice (which contains hydrochloric acid and pepsin) which begins the digestion of proteins and kills bacteria
the duodenum is the first part of the small intestine which holds bile from the liver and the gallbladder emulsifies fats (the pancreatic juices contains enzymes). the ileum is the main site of digestion and absorbs nutrients, and is lined with villi for increased surface area. the insides of the intestines are slimy so food cannot get stuck.
the large intestine absorbs water and forms feces
Digestion
- mechanical digestion is the physical breakdown of food (stomach churning, chewing)
- chemical digestion is the chemical breakdown of food through reactions involving enzymes
amylase breaks down starch into maltose
protease breaks down proteins into amino acids.
lipase breaks down fats into fatty acids and glycerol.
maltase converts maltose into glucose
absorption is the movement of digested food molecules from the intestine into the bloodstream or lymph
the lining is covered with villi and microvilli which increases the surface area for absorption. the villi is one cell thick for a short diffusion path. a rich supply of blood capillaries carry absorbed nutrients to the liver through the hepatic portal vein. lacteals absorb fatty acids and glycerol into the lymphatic system
assimilation is the process where absorbed nutrients are used by the body to build new cells, tissues, and compounds
glucose is used for energy in respiration or stored as glycogen in the liver and muscles
amino acids are used to synthesize proteins for growth, repair, and enzymes
fatty acids and glycerol are stored as fat for insulation and energy reserves