| What is food? (2) | substance that is consumed for nutrition to grow and reproduce
solid and are large complex molecules |
| Steps of food processing? (idaae) | ingestion
digestion
absorption
assimilation
elimination |
| Why is digestion of food molecules necessary? (2) | small molecules are more soluble (easier to absorb)
small molecules can form new products (reassembled) |
| What is the alimentary canal? (5) | all the organs which food passes through
oesophagus, stomach, small + large intestine |
| What are accessory organs? (5) | help with digestion but food doesn't pass through these organs
salivary glands, pancreas, liver and gall bladder |
| What is the oesophagus? (2) | tube connecting the mouth to stomach
food is mixed w saliva to form bolus + moved down by peristalsis |
| what is the stomach? (3) | temporary storage
releases digestive juices + highly acidic environment
secretes proteases |
| What is the small intestine? (2) | absorbs nutrients
has 3 sections: duodenum, jejunum + ileum |
| What is the large intestine? (2) | absorbs water and dissolved minerals
changes undigested material into semi solid feces for excretion |
| what is the salivary glands for? (3) | releases saliva to moisten food = bolus
includes parotid, submandibular and sublingual gland
secretes amylase |
| What is the pancreas for? (2) | produces digestive enzymes and hormones
enzyes are released into the small intestine via the duodenum |
| What is the liver for? (3) | converts absorbed materials into chemicals
used for detoxification, metabolism, storage and bile production
stores and metabolizes nutrients to regulate chemical composition |
| What is the gall bladder for? (2) | stores and releases bile
bile salts are released via the bile duct to emulsify fats |
| How is digested food moved through the body? (2) | peristalsis: longitudinal muscles = squeezes the food through happens in the stomach and intestines (contract and relax to move the food in one direction)
segmentation: circular muscles = food moves back and forth (mixes with enzymes) bidirectional |
| What is mechanical digestion? (2) | food is physically broken down into smaller pieces
chewing (mouth), churning (stomach), segmentation (intestines) |
| What is chemical digestion? (2) | food is broken down with chemicals
saliva, stomach acids, bile and pancreatic juices |
| What is a digestive enzyme? (4) | a protein that acts as a biological catalyst by speeding up the rate of a chemical reaction by lowering the activation energy
they aren't changed or used up in the reaction
allows digestion to happen at body temp at sufficient speeds
specific molecules which bind to specific substrates |
| What are the different types of digestive enzymes? (4) | amylase: carbohydrates = monosaccharides
lipase + bile: lipid = fatty acids + monoglycerides
peptidases: protein = amino acids
nucleases: nucleic acid = nucleotides |
| Where are enzymes secreted from? | mainly produced by the pancreas = secreted into small intestine
salivary glands secrete amylase
stomach secretes proteases |
| How are carbohydrates digested? (7) | starch is the main polysaccharide and has 2 types:
amylose: glucose monomers in linear chains
amylopectin: monomers in branched chains
STARCH is digested by AMYLASE = MALTOSE (Disaccharide)
MALTOSE is digested by MALTASE = GLUCOSE (Monosaccharide)
Glucose monomers is used for cell respiration / processed and stored in the liver as GLYCOGEN (polysaccharide)
occurs in small intestine and products are transported to the liver |
| What are inactive precursors? (zymogen) | needs a biochemical change (eg: hydrolysis reaction revealing the active site) = active enzyme. |
| How are proteins digested? (5) | proteases are secreted as inactive precursors (zymogens) so that they don't digest the cells that made them
Proteases can be activated with specific enzymes or chemical agents(low pH = acidic conditions)
Starts in stomach and continues in small intestine
pepsin: made and used in stomach (pepsinogen), activated by hydrochloric acid
trypsin: made in pancreas (trypsinogen), activated by enterokinase in the intestine |
| How are lipids digested? (4) | lipids are insoluble in water so they are combined with proteins to be transported in blood
lipids are emulsifies with bile salts before being chemically digested by lipase
components are combined w protein = chylomicrons = transported to liver
liver converts chylomicrons = soluble lipoproteins |
| What is absorption? (3) | movement of a fluid across a membrane
nutrients absorbed into bloodstream within the small intestine = transported to cells by the liver
Water and dissolved mineral ions are absorbed in the large intestine |
| What is assimilation? | conversion of nutrients into a fluid or solid part of an organism |
| What are the layers of the small intestine? (5) | Serosa: protective outer layering
Muscle layer: for digestive movement
Outer = lOngitudinal (peristalsis)
Inner = cIrcular (segmentation)
Submucosa: connective tissue layer
Mucosa: Inner layer for absorption |
| What are villi? (4) | finger-like projections on the epithelial lining of the intestine
absorb monomers formed by digestion + mineral ions & vitamins
increase the surface area = optimize absorption rate
Epithelial cells are connected by tight junctions = impermeable barrier bw body tissues and digestive juices |
| What are the key features of villi? MR SLIM | Microvilli = increases SA :Vol ratio
Rich capillary network = transports digested products
Single later epithelium = minimise diffusion distance
Lacteals = absorb lipids into lymphatic system
Intestinal glands = exocrine pits release enzymes
Membrane proteins = help transport products |
| What are the different transport mechanisms for different nutrients? (4) SFSO | Simple diffusion = hydrophobic (fats) cross the hydrophobic part of the membrane. Then passes through the lacteals
Facilitated diffusion = monosaccharides, vitamins and minerals are transported by channel proteins helps hydrophilic food pass through the hydrophobic part of the membrane
Secondary Active Transport = glucose + amino acids are co-transported with sodium ions (Active translocation) with a transport protein
Osmosis: water diffuses across membrane passively as ions and solutes move across in the small and large intestine |
| How does bulk transport work? (pinocytosis) | endocytosis
vesicles form around fluid containing dissolved materials
takes less time than using membrane proteins |
| How can we model absorption? | size specific permeability of the intestinal membrane can be modeled with dialysis tubing
the tubing is impermeable to polysaccharides (starch) but is permeable to maltose = semi permeable
rate of digestion can be measures by osmosis |
| Draw the digestive system | Stomach: J-shaped bag + connected to oesophagus and small intestine
Liver: right-angled triangle left of stomach
Bile duct (connected to gall bladder) and pancreatic duct
Small intestine should be thinner than the large intestine |
| How does chewing break down food? (2) | grinding action of teeth and the tongue pushes the food to the back of the throat
travels down the throat as a bolus |
| How does churning break down food in the stomach? | stomach lining muscles squeezes and mixes the food with digestive juices |
| How does stomach acids break down food? | gastric glands release digestive acids = low pH (2)
acidity denatures proteins and other macromolecules = digestion
mucous membrane on epithelium prevents the acids damaging the gastric lining
pancreas releases bicarbonate ions (alkaline) to neutralise the acids before entering the intestine |
| How does bile break down food? (3) | made in the liver and stored in the gall bladder before released into small intestine
bile salts mix with fat globules = smaller droplets (emulsification)
= increases total SA for lipase activity |
| What are key features of the villi epithelium? (4)
(Just Mix Monkey Poop) | Tight Junctions: impermeable barrier = keeps digestive juices separate from tissues + maintains conc gradient + 1 way movement
Microvilli: increase SA = more absorption + immobilized enzymes and channel proteins on the microvilli to increase uptake
Mitochondria: ATP for active transport and pinocytosis
Pinocytotic vesicles: bulk transport of fluid and dissolved solutes |
| label intestine diagram | labelled |
| What do the hormones produced in the pancreas do? (4) | produces insulin and glucagon which is released from the endocrine glands
regulates the conc of glucose in blood
insulin lowers blood glucose levels = increases glycogen synthesis and storage in liver
glucagon increases blood glucose levels = limits synthesis and storage |
| Describe the method for measuring meniscus levels (5) | dialysis tubing attached to gunnel and filled with starch solution (control)
another tubing is attached to a thistle funnel with starch and amylase solution (Experiment)
placed in beakers of water
over time water moves into tubing by osmosis (towards solute) = water line rises (meniscus)
amylase tube will have less solute bec starch is being digested = lower meniscus |
| Describe the method for measuring maltose diffusion | dialysis tubing filled with starch and kept in a beaker of water (control)
second tubing filled with starch and amylase and kept in a beaker of water (Experiment)
amylase in 2nd tube will digest the starch into maltose = small enough to diffuse out into beaker
presence of amltose can be tested with Benedicts test |
