Y3 Biology Leftover Topics (PDF)

Nutrition in humans describe functions of various parts of digestive system (mouth, salivary glands, gullet, stomach, duodenum, pancreas, gallbladder, liver, ileum, colon, rectum, anus) describe functions of digestive system in relation to ingestion, digestion, absorption,...

Nutrition in humans describe functions of various parts of digestive system (mouth, salivary glands, gullet, stomach, duodenum, pancreas, gallbladder, liver, ileum, colon, rectum, anus) describe functions of digestive system in relation to ingestion, digestion, absorption, assimilation and egestion describe peristalsis as rhythmic wave of contractions of the muscles to mix and propel the contents of alimentary canal describe the functions of enzymes in digestion and list the substrates and end products explain how the structure of a villus, including capillaries and lacteal, is suitable for absorption function of hepatic portal vein role of liver in conversion of glucose to glycogen (vice versa), fat digestion, metabolism of amino acids, formation of urea, breakdown of alcohol and hormones effects of alcohol consumption on brain, long-term effects of excessive consumption and social implications Processes of Nutrition Ingestion - the process of taking in food into the body through the mouth Digestion - the process of physically breaking up food into smaller pieces and chemically breaking down large insoluble food molecules into smaller simpler soluble food molecules by enzymes Absorption - nutrients move from the small intestine into the bloodstream Assimilation - nutrients are used by cells to provide energy or for growth Egestion - process of passing our undigested food like faeces through the anus Organs of alimentary canal (food passes through) Mouth Gullet Stomach Small intestine (duodenum, ileum) Large intestine (colon, rectum, anus) Associated organs (food does not pass through but helps with digestion) Salivary glands Pancreas Gall bladder Liver Peristalsis Peristalsis refers to rhythmic wave-like contractions of the muscles of the alimentary canal Process  ○Behind the bolus of the food, the inner circular muscle contracts while the outer longitudinal muscle relaxes, making the lumen become smaller ○ At the bolus, the inner circular muscle relaxes while the outer longitudinal muscle contracts, making the lumen become wider Function ○ Propel contents further down the alimentary canal ○ To mix food with digestive juices Peristalsis occurs in all parts of the alimentary canal excluding the mouth Peristalsis is an involuntary action and an example of physical digestion Digestion physical digestion chemical digestion definition physical break up of food into chemical break down of large smaller pieces complex food molecules into smaller simpler food molecules reaction no chemical reaction occurs or chemical reaction occurs, new new substances forms substance forms enzymes no yes purpose increase surface area to ensure that nutrients are small enough volume ratio of food for higher and soluble to be absorbed by the rate of chemical digestion by small intestine enzymes Mouth 1. Ingestion Ingestion occurs in the mouth 2. Physical digestion Chewing action by teeth physically breaks up large pieces of food into smaller pieces —> increases surface area to volume ratio of the food Tongue mixes food with saliva and rolls food into a bolus  3. Chemical digestion Salivary glands secrete saliva ○ Saliva contains amylase which can break down starch into maltose ○ Saliva is pH 7 which is the optimum ph for salivary amylase Gullet 1. Physical digestion Peristalsis in the walls of the gullet pushes food into the stomach Stomach 1. Physical digestion Peristalsis in the walls of the stomach mixes the food with gastric juices Churning action physically breaks up large pieces of food into smaller pieces 2. Chemical digestion Gastric glands secrete gastric juice ○ Gastric juice contains the protease pepsin which chemically breaks down proteins into polypeptides ○ pH of gastric juice is 2, the optimal pH of pepsin ○ layers of mucus that protect the stomach walls from the highly acidic gastric juices 3. Others Food is temporarily stored in the stomach before being passed to the small intestine Hydrochloric acid in the gastric juice kills harmful microorganisms like bacteria Small intestine duodenum (start), ileum (end) 1. Physical digestion Peristalsis in the wall of small intestine ○ Pushes food through small intestine ○ Mixed the food with bile, pancreatic juice and intestinal juice ○ Bile is produced by the liver and excess bile is stored in the gallbladder. Bile is secreted into the duodenum when food with fat is consumed Bile physically breaks up large fat globules into smaller fat droplets (process: emulsification) —> increases the surface area to volume ratio of fat for higher rate of chemical digestion of fat by lipase 2. Chemical digestion Pancreas secretes pancreatic juice into the duodenum Pancreatic juice contains ○ amylase which chemically breaks down starch into maltose ○ Protease trypsin chemically breaks down proteins into polypeptides ○ lipase which chemically breaks down fats into glycerol and fatty acids  Small intestine wall secretes intestinal enzymes ○ maltase breaks down maltose to glucose ○ peptidases breaks down polypeptides to amino acids ○ lipase which chemically breaks down fats into glycerol and fatty acids ○ intestinal juice is pH 8 (alkaline) which helps neutralise acid from stomach Large intestine colon, rectum and anus opening of rectum is anus 1. Egestion Rectum stores faeces temporarily Faeces is egested from the anus Absorption Adaptation of small intestine for absorption of digested nutrients one-cell thick surface layer, villus (singular) or villi (plural) specialised feature / adaptation relation to function small intestine is very long (organ) ensures sufficient time for absorption of digested nutrients small intestine walls has many folds (organ) increases the surface area to volume ratio for higher rates of absorption of digested nutrients by diffusion from the lumen small intestine walls has many small finger increases the surface area to volume ratio for like projections called villi (organ) higher rates of absorption of digested nutrients by diffusion from the lumen each villus has a network of blood capillaries transports glucose and amino acids away (organ) from small intestine to maintain concentration  gradient for higher rates of diffusion each villus has a lacteal (organ) transports fats away from small intestine to maintain concentration gradient for higher rates of diffusion walls of villi / epithelium walls are one decreases diffusion distance, allowing for cell-thick (tissue) higher rates of absorption of digested nutrients by diffusion from the lumen epithelial cells of small intestine have many further increases the surface area to volume small finger like projection called microvilli ratio for higher rates of absorption of digested (cell) nutrients by diffusion NO LUMEN epithelial cells of small intestine have high to release more energy required for active numbers of mitochondria (cell) transport of glucose and amino acids 📈 absorption of glucose and amino acids when the conc of glucose & amino acids is in the intestine lumen than in the small intestine epithelium, glucose and amino acids are absorbed from the intestine lumen to 📉 the epithelium by diffusion when the conc of glucose and amino acids is in the intestine lumen than in the small intestine epithelium, glucose and amino acids are absorbed from the intestine lumen to the small intestine epithelium by active transport the glucose and amino acids diffuse from the small intestine epithelial cells to the blood in the capillaries by diffusion absorption of glycerol and fatty acids glycerol and fatty acids are absorbed from the intestine lumen into the epithelium of the small intestine by diffusion in the epithelial cells, glycerol and fatty acids are chemically combined to form fat molecules which are physically combined into small fat droplets fat droplets are transported into the lacteal and away from the small intestine absorption of digested nutrients is completed in the small intestine’s ileum absorbed nutrients in the blood are transported away from the small intestine absorption of water and mineral salts most of water and mineral salts are absorbed from the undigested food into the small intestine through osmosis (for water) and diffusion and active transport (for mineral salts) some are absorbed in parts of the alimentary canal before the small intestine and absorption of water and mineral salts is completed in the colon of the large intestine assimilation state function of hepatic portal vein as the transport of blood rich in absorbed nutrients from small intestine to liver  describe role of liver - metabolisms of glucose, amino acids, breakdown of rbc and alcohol and production of bile hepatic portal vein ○ transports blood rich in absorbed nutrients from small intestine to liver functions of liver 1. Glucose metabolism - regulation of blood glucose by converting glucose to glycogen (storage molecule) and vice versa 2. Amino acid metabolism - deamination of excess amino acids and conversion to urea 3. Alcohol metabolism - chemical breakdown of alcohol and and detoxification 4. Breakdown of old red blood cells 5. Bile production - stored in gall bladder 6. Chemical breakdown of hormones glucose metabolisation (assimilation) regulation of blood glucose by converting glucose to glycogen for storage or vice versa ○ after a carb heavy meal and blood glucose concentration is above normal level, liver converts excess glucose to glycogen for storage, blood glucose concentration decreases ○ while fasting, decrease in blood glucose levels below normal levels, liver converts glycogen to glucose for use, increase in blood glucose concentration amino acid metabolisation excess amino acids are deaminated, where they are chemically broken down to remove the amino group the amino group converts into ammonia, which is toxic to cells and is further converted to urea, to be excreted in urine carbon skeleton left behind from deamination is converted into glucose alcohol metabolism liver detoxifies, converts toxic substances (ammonia, alcohol) into non-toxic substances liver plays a key role in alcohol metabolism where alcohol is chemically broken down into non-toxic substances breakdown of old RBCs and bile production liver chemically breaks down haemoglobin from old RBCs to form bile (physical fats digestion), amino acids and iron liver produced bile, gall bladder stores the excess