bio

• process of changing foodstuffs into simple absorbable forms is called digestion
• This process is accomplished with the aid of hydrolases
• hydrolysis of proteins to amino acids
• lipids to fatty acid and glycerol
• nucleic acids to nucleotides
• 2 parts of nutrition: ingestion and digestion
• Ingestion is the process of taking food into the digestive system so that it may be   hydrolyzed or digested
• Digestion is the breakdown of food (either chemically or mechanically) in order to utilize nutrients
• Micronutrients - vitamins, minerals, & water
• Macronutrients - proteins, lipids, carbohydrates
• GI (gastrointestinal) tract = alimentary canal
• mechanical digestion: teeth
• chemical digestion: saliva
• amylase/ptyalin - enzymes digests starch
• mucin is a slippery protein
• buffers neutralizes acid to prevent tooth decay
• antibacterial chemicals - kill bacteria that enter mouth with food
• mouth - chemical and mechanical digestion
• food is chewed (masticated) mechanically
• A bolus (lump) is formed with saliva and the tongue
• epiglottis is a flap of cartilage
• closes trachea (windpipe) when swallowing
• food travels down esophagus
• peristalsis is the involuntary muscle contractions
• chewing a saltine - mechanical
• Saliva breaking the saltine down into molecules of glucose - chemical
• Your tongue breaking pieces of a hamburger apart - mechanical
• Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids - chemical
• pharynx - the back of the throat
• larynx - passage for air, closes when swallowing
• approximately 15cm long
• digestive glands - groups of specialized secretory cells
• stomach - where food is temporarily stored
• gastric juices are secreted
• has layers of muscle that line the inside
• stomach can stretch to fit 2L food
• stomach disinfect food HCl=pH 2
• pepsin - enzyme breaks down proteins
• gastric mucosa - mucus secreted by stomach cells protects stomach lining
• gastric juices - secreted by the stomach