Chapter 8 - Nutrients and Enzymes & Disgestive System Flashcards
Define carbohydrate
A molecule composed of sugar subunits that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio
Define polymer
A molecule composed of three or more subunits
Define monosaccharide
A single sugar unit
Define isomer.
One of a group of chemicals that have the same chemical formula but different arrangements of atoms
Define disaccharide.
A sugar formed by the joining of two monosaccharide subunits.
Define dehydration synthesis.
The process by which larger molecules are formed by the removal of water from two smaller molecules. (Water is formed from the two smaller molecules)
Define hydrolysis.
The process by which larger molecules are split into smaller molecules by the addition of water. (Water molecule is used to break the bond of the disaccharide)
What are the 5 chemicals of life?
Vitamins and Minerals, Lipids (fats), Carbohydrates, Proteins, and Nucleic Acids.
What are the roles of carbohydrates?
Carbohydrates are the primary source of energy for cells, and are the structural material of plant cells.
Why should you not eat excess amounts of carbohydrates?
It will be stored as fat.
What is the source of carbohydrates for humans? Why are they a source?
The main source of carbohydrates come from plants. Humans rely on plants because humans cannot make carbohydrates.
How can you identify a sugar?
You can identify sugars by the -ose suffix.
Define polysaccharide.
A carbohydrate composed of many single sugar subunits.
What is starch? What is it composed of?
Starch is a plant polysaccharide/carbohydrate used to store energy in the starch molecule. It is composed of many subunits of glucose.
What are the 2 forms of starch? What do they have in common? Describe them both.
Amylose and amylopectin. Both molecules tend to bend in the shape of a helix or coil.
1) Amylose: Contains up to 1000 or more glucose units. The first carbon of a glucose molecule is linked to the fourth carbon of the next molecule.
2) Amylopectin: Contains between 1000 and 6000 glucose subunits and have short branching chains of between 24 and 36 glucose units extending from the main branch.
Define glycogen. What form of starch does it resemble?
Glycogen is the form of carbohydrate storage in animals. It resembles a amylopectin starch molecule, except that it’s branching structures only contain 16 to 24 glucose units.
Define cellulose. What is it made of? How is it formed?
Cellulose is a plant polysaccharide that makes up plant cell walls. Over 50% of all organic carbon in the biosphere is cellulose. Cellulose is made of glucose subunits. Cellulose does NOT form coiled structures. The layers of cellulose are attracted to one another by hydrogen bonds between the -OH groups.
Are lipids polar or non-polar? What are most lipids composed of?
Non polar. Most lipids are composed of 2 structural units: glycerol and fatty acids.
What is a triglyceride? How are they formed?
What are monoglycerides and diglycerides?
A triglyceride is a lipid composed of glycerol and three fatty acids. They are formed by dehydration synthesis.
Monoglycerides and diglycerides are the joining of glycerol with one or two fatty acids.
What are the functions of lipids?
Lipids are energy storage compounds, structural components of cell membranes and insulation.
What are fats?
Fats are lipids composed of glycerol and saturated fatty acids. (Fats are triglycerides that are solid at room temperature.)
What are oils?
Oils are lipids composed of glycerol and unsaturated fatty acids. (Oils are triglycerides that are liquid at room temperature.)
What are saturated fats? What type of fats are mostly saturated?
Saturated fats are fats where only single bonds exist between the carbon atoms. Most of the fatty acids in animal fats are saturated. Because single covalent bonds tend to be stable, animal fats are hard to break down.
What are unsaturated fats? What fats are mostly unsaturated?
Unsaturated fats contain double bonds between the carbon atoms. The fatty acids of most plants are unsaturated. The unsaturated double bonds are somewhat reactive so plant oils are more easily broken down.
What is it called when the fatty acid contains only one double bond? What is it called when the fatty acid contains two or more double bonds?
If it contains one double bond, it is monounsaturated. If it contains two or more double bonds, it is polyunsaturated.
Define phospholipids.
A lipid with a phosphate molecule attached to the glycerol backbone, making the molecule polar. Phospholipids are the major component of cell membranes. O= (diagram) O is the polar phosphate molecule, = is the non polar glycerol backbone.
What are waxes?
Waxes are a long-chain fatty acids that is insoluble in water. The long-chain lipids are joined to long-chain alcohols or to carbon rings.
What is a protein? When are proteins manufactured?
A chain of amino acids that form the structural parts of cells or act as antibodies or enzymes. Whenever cells are damaged and require repair, proteins are manufactured.
What is an amino acid?
A chemical that contains nitrogen, can be linked together to form proteins.
What is a peptide bond?
A bond that joins amino acids.
What is a polypeptide?
A chain of three or more amino acids.
What are essential amino acids? How many essential amino acids are there? What happens when there is a lack of an amino acid?
An amino acid that must be obtained from the diet, as your body cannot synthesize them. There are 8 essential amino acids. The lack of any of them call lead to specific diseases and deficiencies.
___________ are polypeptides. What shapes are they?
Proteins are polypeptides that are folded into specific 3D shapes. Some proteins contain more than one polypeptide.
What determines a structure of a protein?
It’s sequence of amino acids.
What determines a protein’s function?
A protein’s shape, or structure determines it’s function.
What are the levels of protein structure?
Primary, secondary, tertiary, and quaternary.
Describe the four levels of proteins.
- Primary structure: is the sequence of amino acids in the polypeptide strand.
- Secondary structure: hydrogen bonds form with nearby amino acids, and coil and fold the polypeptide into a helices and B-pleated sheets.
- Tertiary structure: the polypeptide folds further. The tertiary structure forms because of interactions between the R groups of different amino acids.
- Quaternary structure: the clustering of two or more polypeptides in the tertiary structure makes up the quaternary structure.
Define denaturation. What are factors that can denature a protein?
Denaturation is the process that occurs when the bonds of a protein molecule are disrupted, causing a temporary change in shape. Factors include excess heat, radiation, or a change in pH.
Define coagulation.
Coagulation is the process that occurs when the bonds of a protein molecule are disrupted, causing a permanent change in shape.
Define catalyst.
A chemical that increases the rate of chemical reactions without altering the products or being altered itself.
Define enzyme.
A protein catalyst that permits chemical reactions to proceed at low temperatures by reducing the reaction’s activation energy.
Define substrate.
A molecule on which an enzyme works.
Define active site.
The area of an enzyme that combines with the substrate.
Explain the “lock-and-key model”. Who was it proposed by?
It is said that each enzyme has a specially shaped active site that provides a “dock” for specific substrate molecules. The temporary joining of the enzyme with the substrate forms the enzyme-substrate complex. It was proposed by Emil Fischer in 1890.
Define cofactor. Give examples of one.
An inorganic ion that helps an enzyme combines with a substrate molecule. Ex: iron, zinc, potassium and copper-containing compounds.
Define coenzyme. What is the source of coenzymes?
An organic molecule synthesized from a vitamin that helps an enzyme to combine with a substrate molecule. Coenzymes are synthesized from vitamins.
What are the factors that affect enzyme reactions?
pH, substrate molecule concentration, temperature, and competitive inhibition.
Define competitive inhibitor.
A molecule with a shape complementary to a specific enzyme that competes with the substrate for access to the active site of the enzyme and blocks chemical reactions.
Define feedback inhibition. What is it’s purpose?
The inhibition of an enzyme in a metabolic pathway by the final product of that pathway. It slows the reaction rate and prevents the accumulation of final products.
Define precursor activity. What is it’s purpose?
The activation of the last enzyme in a metabolic pathway by the initial substrate. It speeds up the formation of final products.
Define allosteric activity. What are the 2 examples of allosteric activity?
A change in an enzyme caused by the binding of a molecule. Ex: feedback inhibition and precursor activity.
What are the 4 components of the digestive process? Explain them.
Ingestion, digestion, absorption and egestion.
1) Ingestion: the taking in of nutrients
2) Digestion: the breakdown of complex organic molecules into smaller components by enzymes
3) Absorption: the transport of digested nutrients to the cells of the body
4) Egestion: the removal of waste from the body.
Define amylase.
An enzyme that breaks down complex carbohydrates (starches).
What are the roles of saliva in digestion?
Saliva contains amylase which break down starches (complex carbohydrates) to simpler carbohydrates. Saliva also dissolves food particles and makes it possible to taste what is being eaten. Saliva also lubricates the food so that it can be swallowed.
What is the role of teeth in digestion? What kinds of teeth are there?
Teeth help physically digest foods. There are incisors, canines, premolars, and molars.
Define peristalsis.
Rhythmic, wavelike contractions of muscle that move food along the gastrointestinal tract.
What occurs in the esophagus? What is the function of the esophagus?
Peristalsis occurs in the esophagus. The function of the esophagus is to move food from the mouth to the stomach.
What is voluntary and involuntary along the digestive tract?
Swallowing and egestion are voluntary. Peristalsis contractions are involuntary.
Define sphincter.
A constrictor muscle that regulates the opening and closing of a tubelike structure.
What are the roles of the stomach?
The stomach stores food and begins the initial protein digestion.
What are the parts of the stomach and their functions?
There is 3 muscle layers, the lower esophageal sphincter (LES) and the pyloric sphincter.
- 3 muscle layers: Run in different directions so that the muscle contractions can churn the food.
- LES: Regulates opening/closing of the stomach. It prevents food and acid from being regurgitated up into the esophagus.
- Pyloric sphincter: Regulates the movement of food and stomach acids into the small intestine.
How are gastric juices/fluids produced? What is gastric juice made of?
Millions of cells that line the inner wall of the stomach produces gastric juices. Gastric juices are made of mucus, hydrochloric acid (HCl), pepsinogens, and other substances.
Define mucus. What is it a component of?
A protective lubricating substance composed mostly of protein. It is a component of gastric juices.
Define pepsin. What is it’s function?
A protein-digesting enzyme produced in the stomach. Pepsin breaks the long amino acid chains in proteins into shorter chains, called polypeptides.
What is the role of hydrochloric acid in the stomach?
HCl is found in gastric juices. It kills many harmful substances that are ingested with food. It also converts pepsinogen into its active form pepsin.
What is the regular pH of the stomach?
A pH of a stomach ranges from 2.0 and 3.0.
How does the stomach avoid being broken down by HCl and pepsin?
A layer of alkaline mucus protects the stomach lining from being digested.
Define ulcer.
A lesion on the surface of an organ.
Define duodenum.
The first segment of the small intestine. The majority of digestion occurs here.
Define villi. What is found in them?
Small, fingerlike projections that extend into the small intestine to increase surface area for absorption. Capillary networks and lacteals are found in villi.
Define microvilli.
Microscopic, fingerlike projections of the cell membrane.
Define capillary. Where are they found?
A blood vessel that connects arteries and veins; the site of fluid and gas exchange. Capillaries are found in the villi.
Define lacteal. Where are they found?
A small vessel that transports the products of fat digestion to the circulatory system. Lacteals are found in villi.
What is the function of the small intestine? What is in the small intestine?
It completes the breakdown of proteins and absorbs nutrients, water, vitamins and more that the stomach did not absorb. Villi and microvilli are in the small intestine.
Define secretin. What is it’s role in the pancreas?
A hormone released from the duodenum that stimulates pancreatic and bile secretions. It stimulates the release of a solution containing bicarbonate ions (HCO3).
Define enterokinase.
An enzyme of the small intestine that converts trypsinogen to trypsin.
What is the role of pancreatic secretions?
It contains enzymes that promote the breakdown of three major components of food: proteins, carbohydrates, and lipids.
Define trypsin.
A protein-digesting enzyme that breaks down polypeptides into peptide bonds.
Define erepsin.
An enzyme that completes protein digestion by converting short-chain peptides to amino acids and they complete protein digestion.
Define lipase. What are the 2 types of lipases and their roles?
A lipid-digesting enzyme. Pancreatic lipase which breaks down fats into fatty acids and glycerol, and phospholipase which acts on phospholipids.
What enzymes are produced by the small intestine?
Erepsin and maltase.
What enzymes are produced by the pancreas?
Lipase, trypsin, erepsin, and pancreatic amylases.
What is the function of the liver?
Emulsifies fat, releases bile salts, stores glycogen and vitamins, breaks down hemoglobin, and detoxify many substances.
Define bile salt. Where is it stored when the stomach is empty? What form of digestion does it cause?
A component of bile that breaks down large fat globules which aid fat digestion. It is then stored in the gallbladder if the stomach is empty. Bile salts is a form of physical digestion, not chemical.
Define cholecystokinin. How is the release of it stimulated?
A hormone secreted by the small intestine that stimulates the release of bile salts. It is released when fat enters the duodenum.
Define colon.
The largest segment of the large intestine, where water reabsorption occurs.
What is complete by the time food reaches the large intestine?
Cehmical digestion is complete by the time food reaches the large intestion.
What is the role of the large intestine?
It helps the movement of food waste and houses Escherichia coli (E. coli) which synthesizes vitamins B and K.
What is the purpose of cellulose?
It provides bulk as it is not digested by humans.
What controls digestion?
The nervous and hormonal systems.
Define gastrin. When is it produced?
A hormone secreted by the stomach that stimulates the release of HCl. It is produced when the walls of the stomach are distended by the presence of food.
Define enterogastrone. What is it’s function?
A hormone secreted by the small intestine that decreases gastric secretions and motility. It slows peristaltic movements, allowing time for fat digestion and absorption.
What are enzymes?
Enzymes are proteins.
Define protease.
Enzyme that breaks down proteins and peptides.
What happens to an enzyme after a chemical reaction occurs?
The enzyme is present in the same amount as the beginning of the reaction.
What are the functions of lipids?
Lipids stores energy, they are important parts of cell membranes, and cushions delicate organs.
What does Benedict’s reagent indicate when heated? What change occurs?
It indicates sugars and the colour changes from blue when there are sugars.
What does Biuret solution indicate? What change occurs?
It indicates proteins and the colour changes to pink/purple.
What does the Iodine solution indicate? What change occurs?
It indicates starch and the colour changes to black.
What does the Sudan IV indicate? What change occurs?
It indicates fats and the Sudan IV dissolves.
What happens to fats when bile emulsifies them?
The fats physically break down which let enzymes to work on a larger surface area.
Chewing foods aids digestion by:
Increasing the surface area of food exposed to enzymes.
What does the absorption of fats require?
It requires the presence of hydrochloric acid.
What are the three secretions that mix with food in the small intestine?
Pancreatic juice, bile, and intestinal juice.
What is the liver responsible for?
The storage of glycogen.
What is the small intestine’s pH?
About 10.
Define gallstone. What does it do?
Crystals of bile salts that form in the gallbladder which blocks the bile duct, impairing fat digestion and causing considerable pain.
Define jaundice. What is it caused by?
The yellowish discoloration of the skin and other tissues brought about by the collection of bile pigments in the blood. It is caused by the accelerated destruction of red blood cells or obstruction of the bile duct.
Define cirrhosis. What is it caused by?
Chronic inflammation of the liver tissue characterized by the growth of nonfunctioning fibrous tissue. It is caused from nutritional deprivation or infection.
