Biology 20 - Unit D1: Human Systems (Digestive System) (Terms)

Chapter 8 terms + short concepts

What are the building blocks of organic molecules?

Monomers, which are built into complex polymers

What are the four classes of organic molecules?

Amino acids, monosaccharides, fatty acids + glycogen, nucleotides

What is the macromolecule of an amino acid?

Polypeptide/protein

What is the macromolecule of a monosaccharide?

Carbohydrate

What is the macromolecule of a fatty acid + glycerol?

Lipid

What is the macromolecule of a nucleotide?

Nucleic acid

What are the functions of amino acids/polypeptides/proteins?

Structural component of cells

Perform chemical reactions (are enzymes)

What are the functions of monosaccharides/carbohydrates?

Primary energy source and short term energy storage for cells

What are the functions of fatty acids + glycogen/lipids?

Structural component of cell membranes

Long term energy storage for cells

What are the functions of nucleotides/nucleic acids?

Genetic material (DNA)

What are carbohydrates made of?

Carbon, hydrogen, oxygen

What is the function of carbohydrates in animals?

Serve as an important source of energy

What is the function of carbohydrates in plants?

Serve as an important source of energy, provide structure

What biochemical functions do carbohydrates serve? (Metabolism)

Monosaccharides are the fuel for cellular metabolism

What biochemical functions do carbohydrates serve? (Polysaccharides)

Monosaccharides may be converted into space-saving polysaccharides, providing short term energy for plants and animals

What biochemical functions do carbohydrates serve? (Structure)

They are used to form structural elements in plants and animals

What is the relationship between the monosaccharides?

They are all isomers of C6H12O6

What two monosaccharides make up sucrose?

Glucose and fructose

What two monosaccharides make up maltose?

Two glucose molecules

What two monosaccharides make up lactose?

Glucose and galactose

Starch, glycogen, and cellulose are made up of what subunit?

Glucose

What is the main function of lipids?

Used as long term storage molecules in animals and plants

Why are fats solid at room temperature?

Because all of its carbon bond spots are saturated, the fatty acids are straight and stack nicely

Why are oils liquid at room temperature?

Because of the double bond that makes it unsaturated, there is a kink/bend in the chain of fatty acids. As a result, the acids don’t stack nicely, creating space in between them

What is the main function of proteins?

Play a role in performing chemical reactions (biological catalysts/enzymes)

Why do amino acids have so many forms?

Every amino acid contains a set amino group and a carboxylic acid group, but they have interchangeable R groups

How do secondary protein structures form?

The sequence of amino acids in a primary protein structure are linked together by hydrogen bonds, forming a pleated sheet or an alpha helix

How do tertiary protein structures form?

Interactions between hydrophobic and hydrophilic R structures in the amino acids of alpha helixes and pleated sheets causes them to fold

Why does the primary structure of a protein remain intact after denaturation?

Denaturation is not strong enough to break peptide bonds

What is the relationship between denaturation and coagulation?

Denaturation is a prerequisite to coagulation, but denaturation doesn’t always lead to coagulation

What is the relationship between dehydration/condensation synthesis and hydrolysis reactions?

Hydrolysis reactions are the reverse of dehydration/condensation synthesis reactions

Can a reaction take place without an enzyme?

Yes, enzymes just speed up reactions and are not necessary to the reaction

What is the effect of enzymes on activation energy?

Enzymes lower activation energy

What are the factors that affect the rate of enzyme activity?

Temperature, pH, concentrations of substrate and enzymes

Why does temperature affect the rate of enzyme activity?

At low temperatures, enzymes are stiff and change shape (perform reactions) with difficulty; at high temperatures, enzymes become denatured, and because the function of the enzyme depends on its shape, enzyme function is greatly reduced

Why does pH affect the rate of enzyme activity?

The amino acids that make up an enzyme molecule contain many positive and negative regions, some of which are around the active site, and H+/OH- ions bond with these regions and prevent the substrate from reacting

Why do concentration of substrate and enzymes affect the rate of enzyme activity? (Set Enzyme Concentration)

If there is a set concentration of enzyme present in a reaction mixture, and the concentration of substrate increases, the rate of production of the products will increase because there is a greater chance of collisions between substrate and enzyme molecules

Why do concentration of substrate and enzymes affect the rate of enzyme activity? (Maximum Enzyme Rate)

If the concentration of a substrate increases to much, it will exceed the maximum rate at which an enzyme can work because at any one moment all the active sites are occupied by substrate molecules, and so adding more substrate has no further effect

How does non-competitive feedback inhibition happen?

The end product of a metabolic pathway binds to the allosteric site of an enzyme in that pathway, changing the shape of the enzyme and thus reducing its function

How does competitive feedback inhibition happen?

The inhibitor competes with a substrate for binding in the active site, and if an inhibitor occupies the active site then the substrate enzyme complex is unable to undergo an enzymatic reaction

Why are enzymes essential to digestion?

Enzymes are essential to speed up the rate of digestion so that it is fast enough to process nutrients to supply our needs

Why is the process of digestion essential?

It breaks food molecules into small molecules, and only small molecules can enter cells and be used in the body

What happens in the mouth during digestion?

Food is broken into small pieces by the jaws and teeth and is mixed with saliva containing salivary amylase, which begins the chemical digestion of any starch the food contains into maltose

What is the pH of the mouth?

7

What happens in the esophagus during digestion?

The food, now a bolus, is passed down the esophagus to the stomach by peristalsis

What happens in the stomach during digestion?

The digestion of proteins begins, as glands on the wall of the stomach secrete pepsinogen that is activated by HCl into pepsin (a protein digesting enzyme)

What is the pH of the stomach and what is it maintained by?

1\.5-2.0, HCl

Why does the HCl in the stomach not cause harm to it?

Cells in the stomach lining secrete mucus to protect the interior of the stomach from the acid and enzymes

What are the three distinct regions of the small intestine?

Duodenum, jejunum, ilium

What is the pH of the small intestine?

Around 8

What is the role of the pancreas in digestion? (Bicarbonate)

It produces bicarbonate ions to neutralize chyme from the stomach that enters the duodenum to protect the small intestine from developing ulcers and allow pancreatic enzymes to work at their optimum pH

What is the role of the pancreas in digestion? (Enzymes)

Releases a number of enzymes, which completes the digestion of polymers into monomers that can be absorbed into the bloodstream

What is the role of the liver in digestion?

Bile is produced in the liver from the breakdown of red blood cells, which helps to digest lipids

What is the role of the gallbladder in digestion?

Stores bile and releases it into chyme to help digest lipids

Why do lipids present a problem for digestion in the intestine?

In the intestine, where the medium is aqueous and lipase is water soluble, while lipids are insoluble

How are lipids digested?

Lipase can only hydrolyze the outer lipid molecules, so the internal areas of the droplet remain undigested. Bile salts emulsify large fat droplets, producing many small fat droplets, making them water soluble

How are proteins digested?

Small polypeptides from the stomach are further broken down in the duodenum by pancreatic enzymes called proteases, and digestion of proteins is completed by peptidases from the pancreas to produce amino acids that can be absorbed into the bloodstream

How are carbohydrates digested?

Simple sugars and other complex carbohydrates enter the duodenum, where they are further broken down by a number of enzymes. Carbohydrases released by the membrane of the duodenum converts disaccharides to monosaccharides, which can be absorbed

How are nutrients absorbed in the small intestine?

The epithelial cells of the villi transport amino acids and carbohydrates from the lumen of the intestine into capillaries of the bloodstream and lipids into lacteals of the lymphatic system, taking place mostly in the jejunum and occasionally in the duodenum and ilium

How are glucose and amino acids absorbed?

Come into contact with jejunum wall and are absorbed by active transport into the epithelial cells of the villi, then diffused into the blood following their concentration gradient

How are lipids (glycerol and fatty acids) absorbed?

Come into contact with jejunum wall and are absorbed by diffusion into the epithelial cells of the villi, reassembled into triglycerides and gain a protein coat to increase solubility, are actively transported to the lymphatic system via vesicles

How is the small intestine folded to increase efficiency?

What increases absorption in the small intestine?

Villi/micro villi that increase surface area, thin epithelium to increase diffusion, long length

What is the main role of the large intestine?

Reabsorbing water and mineral ions such as sodium (Na+) and chloride (Cl−)

Where does additional water in our gut contents come from?

Hydrolysis occurs during digestion, which is where the additional water added to the intestine in digestive juices comes from

Why can’t humans/mammals digest cellulose?

Cellulose is a complex carbohydrate requiring the enzyme cellulase to catalyze its digestion, which humans and other mammals are unable to produce

What is the role of gastrin in regulating the digestive system?

Stimulates the release of HCl when food enters the stomach and touches the stomach lining

What is the role of enterogastrone in regulating the digestive system?

Decreases the production of digestive juices in the small intestine when fatty meals are detected to slow down digestion and give time for fat emulsification and digestion

What is the role of CCK in regulating the digestive system?

Stimulates the release of bile salts when fatty chyme is released into the duodenum

What is the role of secretin in regulating the digestive system?

Stimulates the release of pancreatic enzymes and bicarbonate as acidic chyme enters the duodenum

Why is negative feedback important in regulating processes and substances in the body?

It results in homeostasis

How is gastrin/acid secretion regulated in the body?

Food in the stomach causes cell walls to start release gastrin, which stimulates stomach glands to release HCl. Once the stomach reaches a pH of 1.5, the cells on the stomach wall stop releasing gastrin

Which reagent reacts with simple/reducing sugars? What does a positive test look like?

Benedict, blue → orange/red

Which reagent reacts with protein? What does a positive test look like?

Biuret, blue → purple

Which reagent reacts with starch? What does a positive test look like?

Iodine, orange → black

Which reagent reacts with lipids? What does a positive test look like?

Paper, non-translucent → translucent