Download Test September 13, 2013 Option H: Digestion and Topic 6.1.1

Test September 13, 2013 Option H: Digestion and Topic 6.1.1-6.1.7
6.1.1 ingestion, digestion, absorption, transport
Protein>>>>protein>>>>amino acids
Lipids>>>>triglycerides>>>>>glycerol and fatty acids
Carbohydrates>>>>polysaccharides, disaccharides, monosaccharides>>>>monosaccharides
Nucleic Acids>>>>>DNA, RNA>>>>>nucleotides
6.1.2 enzymes specific for specific food type…..act as catalysts for reactions….lower activation energy of
the reactions they catalyse….input of energy is usually in form of heat and this allows reactions to
proceed at higher reaction rates at a lower temp than the same reaction without an enzyme. Helps
reactions to more likely occur at physiologically normal temperature. Digestive enzymes all help to
catalayze hydrolysis reactions.
6.1.3
6.1.4 Draw and label a diagram of the digestive system including, mouth, esophagus, stomach, small
intestine, large intestine, anus, liver, pancreas and gall bladder. Diagram should clearly show the
interconnections between these structures.
6.1.5 Stomach—storage for mixing food with gastric juice made up of pepsin (protease enzyme most
active in acidic pH; hydrochloric acid---helps degrade and break down foods and creates the high acidic
pH necessary for pepsin to be active; mucus-lines inside of stomach wall to prevent stomach damage
from the hydrochloric acid. Churning and peristalsis helps mix all of these together.
Small intestine—
Secretions into the duodenum include bile from liver and gall bladder, trypsin (a protease) lipase,
amylase and bicarbonate from pancreas. Villi have a capillary bed and a lacteal (a small vessel of
lymphatic system much like a capillary) villi increase surface area for absorption of molecules. Lacteal
more efficiently absorbs fatty acids. Assimilation occurs within body cells when nutrients are used to
build larger molecules such as saliva, a protein. Large Intestine---Water absorption, Escherichia coli—
mutualistic organisms that help synthesize vitamin K and a healthy large intestine.
6.1.6 Absorption and Assimilation
6.1.7 Structure of the Villus
Option H
H.2.1 Salivary glands>>>saliva which includes salivary amylase; gastric glands in stomach secrete
mucus, hydrochloric acid and pepsinogen, precursor of pepsin which is activated by high acidity of
stomach. Pancreas>> Pancreatic juice through a duct to duodenum. Juice contains protease enzymes,
amylase and lipase. Also contain hydrogen carbonate . liver>> bile into small intestine (bile may be
stored in gall bladder). Bile emulsifies lipids and increases surface area of lipids for action of lipase.
Intestinal glandular cells>> additional enzymes some attach to villi cells and these membrane-bound
enzymes catalayze digestive reactions as the undigested substrate molecules flow past in the lumen of
small intestine
H.2.2 Exocrine gland cells…produce and secrete products which are carried to specific locations in the
body by way of a duct. Secretion is usually a protein. Due to process of protein synthesis you could
expect to find exocrine glands cells containing extensive numbers of endoplasmic reticulum and well as
many ribosome, Golgi bodies, vesicles and mitochondria. Cells of exocrine glands are usually arranged in
an acinus (a cluster of exocrine cells surrounding a duct which usually leads to a larger duct)
H.2.3 Saliva’s solvent is water, contains amylase and mucus; Gastric juice’s solvent is water, contains
mucus, hydrochloric acid and pepsin (secreted as pepsinogen); Pancreatic juice’s solvent is water,
contains amylase, bicarbonate, trypsin (secreted as trypsinogen) and lipase
H.2.4 Control of digestive juice secretion of gastric juice>>> Sight and smell of food influences the
secretion of saliva as well as gastric juice from stomach. Once food is in stomach receptors within
stomach wall ate stimulated and send sensory signals to the brain which responds by causing stomach
to secrete even more gastric juice. As stomach distends and this results in production of hormone,
gastrin. This hormone leads to the sustained release of gastric juice and especially hydrochloric acid.
H.2.5 Membrane-bound digestive enzymes…Most enzymes have limited molecular life span and either
digest themselves orare eliminated however some remain in membranes of cells lining small intestine.
Maltase, hydrolyses disaccharide maltose into two glucose molecules. Maltase embeds in epithelial cell
membranes of villi and microvilli of small intestine. Maltose moves to active site and enzyme then
catalyses the hydrolysis reaction. Maltase remains in lumen of small intestine longer than free-floating
enzymes.
H.2.6 Cellulose is a polysaccharide carbohydrate composed of thousands of glucose monosaccharides
however we do not have mutualistic microorganisms which produce cellulase, enzyme necessary to
hydrolyse cellulose into glucose. Most plant material we eat makes its way through the alimentary canal
and exits the body in feces.
H.2.7 Pepsin and trypsin are digestive protease enzymes (enzymes that collectively hydrolyse peptide
bonds within proteins), An active protease can’t tell the difference between ingested protein and the
protein of the human body and to keep us from digesting ourselves they are initially synthesized in a
molecular form that is not chemically active. Inactive forms are known as zymogens. Pepsinogen (44
additional amino acids than pepsin) produced in inner lining of stomach walls and does not turn into
pepsin until exposed to hydrochloric acid of stomach secretions and the additional 44 amino acids are
removed. Pepsinogen converts into pepsin and becomes active. Trypsinogen made in pancreas and
enters duodenum. Partially digested food from stomach enters duodenum with an enzyme known as
enterokinase which converts trypsinogen into trypsin and thus activates this protease enzyme.
H.2.8 Helicobacter pylori Dr. Marshall and Dr. Warren isolated living bacterial cells from the stomach
lining of patients suffering from stomach ulcers and gastritis proving that bacteria could live within a pH
of 2. These doctors were awarded a Nobel Prize in medicine and physiology. Old thoughts may be
incorrect with new evidence being found.
H.2.9 Lipids are insoluble in water and fluids in alimentary canal are aqueous..Lipids are hydrophobic in
hydrophilic medium!! Lipids stick together so the surface area must be increased. Lipase an enzyme
hydrolyses triglyceride lipids. It is added in the duodenum and comes from the pancreas. Lipase
catalyzes the hydrolysis of lipid molecules on the outside of the globules however bile (hydrophilic and
hydrophobic end) from the liver help to emulsify or breakdown fats into smaller portions.
H.3.1 Draw and label a diagram of a cross-section (transverse) of the ileum…include mucosa and the
layers of longitudinal and circular muscle. Mucosa is innermost cellular lining of the intestine and is
responsible for absorption. Mucosa includes invaginations known as villi, which increase surface area for
absorption. Villi contain both a capillary bed and a lacteal.
H.3.2 Microvilli of villi are found on surface of each villus that face into lumen of small intestine. These
are microscopic projections and also help to increase surface area for absorption . Mitochondria and
pinocytotic vesicles…ATP is necessary for active transport to occur and pinocytosis is another active
transport mechanism used to absorb molecules from the lumen of the intestine therefore you see many
in this location. Tight junctions -union between epithelial cells that will not allow intercellular fluid to
move between adjoining cells. This forces the digested molecules to only pass through the selectively
permeable membrane of the villus,. Membranes of cells with a tight junction share some membrane
proteins therefore holding the two cells tightly together.
H.3.3 Transport Mechanisms used to absorb foods: Facilitated diffusion..protein channels in microvilli
because channels have a relatively non-polar makeup facing the lumen which allows polar molecules to
easily diffuse from the lumen of the intestine into the cytoplasm of the villi cells Active Transport
..membrane pumps using ATP to transport molecules across membrane Pinocytosis Microvilli plasma
membranes also perfom endocytosis or more specifically pinocytosis (cell drinking)
H.3.4 Never absorbed and become part of feces. Cellulose, lignin, bile pigments, bacteria, intestinal
cells.
H.4.1 Circulation of blood through liver >>> liver receives blood through two major blood vessels the
hepatic artery and the hepatic portal vein. Carry blood into the capillaries of the liver called sinusoids.
All sinusoids are then drained by the hepatic vein which is the sole blood vessel taking blood away from
the liver. The hepatic portal vein receives blood from the capillaries within all the villi of the small
intestine…blood is deoxygenated and carries varying quantities of nutrients. The liver stabilizes
nutrients within the hepatic vein by storing nutrients and this is one of the major functions of the liver.
Liver removes and adds things to the blood. Hepatocytes (liver cells) perform this function. Sinusoids
contain cells called Kupffer cells that help break down older red blood cells for recycling cell
components. Sinusoids are wider than capillaries.
H.4.2 Sinusoids of liver will convert excess glucose into glycogen with the presence of insulin. Insulin
stimulates hepatocytes to take in and convert glucose into glycogen. Glucagon from pancreas stimulates
hepatocytes to convert glycogen back into glucose. Negative feedback!!
H.4.3 glycogen> polysaccharide carbohydrate; iron>iron is removed and stored following breakdown of
erythrocytes and hemoglobin molecules; vitamin A> associated with good vision; vitamin D> helps with
bone formation
H.4.4 Liver synthesizes plasma proteins and cholesterol. Plasma proteins…albumin helps regulate
osmotic pressure of fluids in the body; fibrinogen is a soluble form of blood clotting protein which is
converted to fibrin when clot is needed; globulins are widely diverse groups of blood proteins.
Cholesterol- some are ingested and absorbed in foods and some are made in the liver, cholesterol is
used to make bile and some is carried in bloodstream to be used for cell membranes
H.4.5 Liver has a role in detoxification >>.ethanol found in alcoholic drinks; food preservatives;
pesticides; herbicides
H.4.6 Erythrocytes live about 4 months. Cell membrane of blood cells weaken and ruptures and usually
occurs in spleen or bone marrow but can happen anywhere in bloodstream. Hemoglobin in sinusoids of
liver are ingested by Kupffer cells through phagocytosis because hemoglobin molecules are large.
Globin molecules are hydrolysed into amino acids. Iron atom removed from heme group and stored
within liver and eventually sent to bone marrow to make more red blood cells. Bilirubin…left over iron
from hemoglobin is absorbed by hepatocytes and become a key component of bile.
H.4.7 Females more susceptible to liver damage from excessive drinking. Partially reversible and some
damaged areas of liver can regenerated
Damage occurs due to scar tissue…cirrhosis: fat accumulation due to damaged areas being filled with
fat; inflammation…swelling of damaged liver tissue due to alcohol exposure