Bio Nutrition in Man

Nutrition in Man Definitions: Starvation: when the cells do not receive enough energy and begin to die Other nutrients: Calcium: bones degenerate without them Why does food need to be broken down? Because it needs to be small enough to pass through the partially permeable membrane of the small intestine and enter the bloodstream. Large Intestine: Role of Large Intestine: To absorb water, mineral salts and electrolytes from indigestible food matter. Shades of stool: brown (healthy) green (green food colouring, or food is not digested enough), yellow (excess fat or malabsorption disorder like celiac disease), black (internal bleeding or vitamins), white (bile duct obstruction) Blood-stained/red (cancer). Stool can be a reflection of the digestive system’s health. Anus: It carries out egestion, which is defined as the removal of undigested matter from the body. Colon: a. located in the large intestine b. absorbs remaining water and dissolved mineral salts to e absorbed at the large intestine Small intestine: Chyme = partially digested food Duodenum (the start, mostly digestion) and Ileum (near the end, mostly absorption) Enzymes present: 1. pancreatic amylase a. digests starch into maltose b. It is found in pancreatic juice. The other kind of amylase is salivary amylase (the usual) 2. maltase a. digests maltose into glucose

3. lipase a. digests fats into fatty acids and glycerol 4. protease a. digests protein into polypeptides b. digests polypeptides to amino acids c. More than 1 protease are present in the small intestine d. Found in pancreatic juice T.B pg 83 All food should be fully digested by this point and absorbed. Ileum i. Less digestion takes place and more absorption takes place ii. The inner wall of the small intestine is highly-folded

iii. There are many tiny protrusions allied Villi (singular: villus) in the inner wall. ii and iii both increase surface area to volume ratio, which increases the efficiency of absorption iv. Villi are structurally adapted via 1. Surrounded by a 1 cell thick wall called the epithelium, made up of epithelial cells. The epithelial cells have more protrusions on them called microvilli. 2. Adaptation of Epithelial Cells: contains many mitochondria to provide energy for active transport of the nutrients into the villi 3. fatty acids and glycerol are reformed as fats after passing through. 4. Inside the villi, amino acids and glucose enter the capillary. They get transported away almost immediately through the hepatic portal vein , and into the liver. 5. While the lacteal is used to transport the reformed fats into a separate system

This allows for a steep concentration gradient between the outside of the villi compared to the inside of the villi, allowing diffusion to take place alongside active transport. Small intestine carries out most of the digestive processes in the body Amino Acids and glucose are transported to the blood vessels, then through the hepatic portal vein to the liver. Fats are transported to the lacteal into a separate system. Other organs that are involved in digestion but are not actively digesting: 2. pancreas a. Connected to the small intestine via the pancreatic duct, which releases the pancreatic juice that contains the mentioned amylase into the small intestine. 3. gall bladder a. connected to the small intestine by the bile duct which is also connected to the liver

b. Role: temporarily store bile produced by the liver. When it contracts, it releases the bile into the duodenum. It also helps in physical digestion. c. Without it, you digest more slowly d. Bile is a thick greenish yellow liquid that has a bitter taste to it. It is needed to digest and absorb fats and breaks down dietary fats into smaller droplets via emulsification. If the bile duct is blocked, the rate of digestion simply slows down. A person can survive without the gall bladder e. Emulsification: definition: it is a physical break up of any fat. Is also on the page. This increases surface area to volume ratio, which increases the rate of digestion. 4. liver Bolded text is a MUST KNOW a. produces bile i. bile is produced by liver but stored in gall bladder ii. bile is secreted into duodenum of small intestine via the bile duct

iii. biles’s purpose is to emulsify fats b. detoxifies alcohol i. converts harmful substances to harmless substances such as alcohol and food preservatives by breaking down the harmful substance. ii. E.g: Alcohol -> Acetaldehyde. The enzyme involved in catalysing this reaction is alcohol dehydrogenase. c. deamination of excess amino acids i. Definition of deamination: the process by which amino groups are removed from amino acids and converted to urea. ii. NH 2 (amino group) —> CH —> COOH (converted to urea). (converted to glucose, . stored as glycogen) d. Regulation of blood glucose concentration i. Constant between 70 to 90 mg/100cm 3 1. After a meal, you would have higher blood glucose levels 2. Islets of Langerhans in pancreas secrete insulin (a protein based hormone) that regulates glucose. 3. The liver converts glucose into glycogen. 4. Blood glucose levels return to normal. ii. Between meals/fasting 1. Blood glucose levels are lower than usual 2. Islets of Langerhans in pancreas secrete Glucagon. 3. The liver converts Glycogen to Glucose 4. Blood glucose levels return to normal e. Manufacture of Plasma Proteins i. Plasma is the fluid component of blood ii. Amino Acids caused to synthesise proteins f. Heat Production i. Heat is produced due to numerous activities in the liver ii. Distributed to body to maintain overall temperature g. Storage of iron i. When red blood cells die or are worn out, they are destroyed in the spleen. ii. Haemoglobin from RBC is sent to the liver to be broken down into iron to create new RBCs.

Effects of alcohol: Digestive: - Liver failure as the liver is overloaded, and the cells are continuously broken down, creating an excess of scar tissue. This is called liver cirrhosis which may lead to internal bleeding of the liver. Nervous system: - Slows down brain functions. This slows reaction time and compromises self-control. Social: - Addiction Peristalsis: (check textbook definition) A series of wave-like, involuntary muscle contractions that move food and waster throughout the digestive system. It doesn’t only occur in the oesophagus btw, the stomach, small intestine and large intestine all have peristalsis too.