Test

Write the general molecular formula for a monosaccharide (simple sugar)?

(CH2O)n

Describe the roles of the large intestine, rectum and anus?

A major role of the large intestine is to compact feces. The large intestine absorbs most of the water from digestive fluids and ingestion that was not absorbed in the small intestine, making the feces firmer. The large intestine is also home to a variety of prokaryotic cells that have important roles in supporting human health, including production of specific vitamins. The rectum stores feces. Two sphincters between the rectum and anus control elimination (defecation). Peristalsis of the large intestine pushes on the sphincters, causing the urge to defecate. One of the sphincters is under voluntary control and one is not. The anus is where the alimentary canal exits the body.

Distinguish between the alimentary canal and accessory organs?

Accessory organs: salivary glands, liver, gall bladder, pancreas. All of these organs deliver materials to the alimentary canal via ducts. Alimentary canal: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus

Explain what acid chyme is? How does acid chyme move from the stomach to the small intestine?

Acid chyme is a broth-like material made by mixing gastric juice with swallowed food, and allowing HCl and pepsin to act on food molecules. Acid chyme is released in spurts into the small intestine through a sphincter in the base of the stomach (fyi - the pyloric sphincter). Food usually spends about 2 to 6 hours in the stomach before being released slowly to the small intestine.

Explain why animal fats like butter are solid at room temperature while vegetable oils are liquid at room temperature?

Animal fats (triglycerides) are made from saturated fatty acids, and it is easier for the fats to solidify. Vegetable oils (also triglycerides) contain one or more unsaturated fatty acids. The kinks in the unsaturated chains make it harder for the oils to solidify.

Identify the roles of fats (triglycerides) in animals and plants? Why is storing extra energy as fat useful for organisms?

Animals - triglycerides store energy, cushion organs and provide insulation. Plants - triglycerides are found mostly in seeds where they store energy for growth of seedlings during germination.

Explain that osmosis is facilitated by channel proteins called aquaporins? (notes are probably enough, but you could look at page 76 and/or section 5.6)

Aquaporin is a cool channel protein that lets water molecules (and only water molecules!) flow across biological membranes at very high rates.

Explain the relationship between "free" water molecules and solute concentration? (Section 5.4)

As the concentration of solute increases, the concentration of "free" water will decrease because more water molecules will be interacting with the solute and not be free to just hang out with the other "free" water molecules.

Describe how a protein that is produced in the rough endoplasmic reticulum is secreted by the cell? Make sure to include the roles of transport vesicles and the Golgi apparatus. (Section 4.8, Rough ER subsection, and Section 4.9)

As the protein is synthesized, it is transferred from the ribosome into the lumen of the rough endoplasmic reticulum. For the protein to get out of the cell, it is first packaged into a vesicle that buds off of the RER. The vesicle travels to the Golgi apparatus, and fuses with the Golgi. The Golgi is able to interpret signals encoded in the amino acid sequence of the protein and it packages the protein in a vesicle that sends it to the plasma membrane. The vesicle fuses with the plasma membrane and releases (secretes) the protein to the outside of the cell.

Compare the composition of the blood arriving at the small intestine with the composition of the blood leaving the small intestine?

Blood that is arriving at the intestine from the heart is high in oxygen (recently having visited the lungs) and low in nutrients. Blood enters the capillaries of the villi, where oxygen diffuses down its concentration gradient from the blood to the tissue cells. Because the cells are constantly using oxygen, the concentration of oxygen in the tissues is lower that the concentration of oxygen in the blood. Remember that, because oxygen molecules are nonpolar, they pass through membranes easily without the need of a transport protein. As blood moves through the capillaries of the villi, nutrients are absorbed from the lumen of the intestine and into the blood with the support of specific transport proteins. Therefore, blood that leaves the intestines (heading for the liver) is low in oxygen and high in nutrients.

List the two chemical groups that are trademarks of a sugar?

Carbonyl (C double bonded to O) - one of the carbons Hydroxyl (-OH) - bonded to the rest of the carbons

Explain how a disaccharide is formed from two monosaccharides?

Dehydration reaction with the loss of water as a bond is formed between the two monosaccharides.

Explain that enzymes catalyze the hydrolysis of food molecules, breaking them down into their component parts? Note: make sure you know the component parts for each type of food molecule (proteins, carbohydrates, nucleic acids, lipids).

Enzymes hydrolyze food molecules, breaking molecules into their component parts by adding water to break covalent bonds. Proteins are hydrolyzed to amino acids by the digestion process, carbohydrates are hydrolyzed to monosaccharides, nucleic acids are hydrolyzed to nucleotides (and nucleotide components), triglycerides are hydrolyzed to glycerol and fatty acids.

Identify two digestive enzymes and one polypeptide hormone that are secreted from cells by exocytosis? (class notes)

Examples of digestive enzymes that are secreted by exocytosis: salivary amylase, pancreatic amylase, pepsin, lipase, trypsin, chymotrypsin. Examples of polypeptide hormones that are secreted by exocytosis: insulin and glucagon.

Distinguish between exocytosis and endocytosis? (Section 5.9. Do not worry about the different types of endocytosis.)

Exocytosis and endocytosis are processes that move larger materials across the plasma membrane. Exocytosis refers to the secretion of materials from the cell. Endocytosis refers to a process that brings materials into the cell. Both processes depend on the fluidity of the membrane. In exocytosis, a transport vesicle fuses with the plasma membrane, releasing its contents to the outside of the cell. In endocytosis, a vesicle pinches off of the inside surface of the plasma membrane to bring materials into the cell.

List three monosaccharides that provide a quick source of energy? (see class notes)

Glucose, fructose, galactose

Briefly describe the role of H. pylori in the formation of stomach ulcers? Explain how stomach ulcers are medically treated?

H. pylori can infect the lining of the stomach and grow between cells of the lining, causing inflammation that leads to the formation of an ulcer. Stomach ulcers are therefore treated with antibiotics that kill the H.pylori cells, thus resolving the infection, and allowing healing.

Explain what causes "heartburn?

Heartburn occurs when acid chyme or gastric juice leaks through the sphincter at the bottom of the esophagus. Would be more appropriately named esophagus burn.

Explain why humans cannot digest cellulose? Explain the role of cellulose in human digestion?

Humans do not make a digestive enzyme that can recognize and break the bond between beta glucose monomers in cellulose. However, cellulose has an important role in human digestion - it is dietary fiber, and it helps food move through the alimentary canal. Note: termites and cows can use cellulose as a nutrient because microorganisms that can digest cellulose live in their alimentary canals.

Draw and describe the structure of a triglyceride. Make sure you identify what molecules are joined together by dehydration synthesis reactions to build a triglyceride molecule. (See section 3.8.)

I will not ask you to draw the structure of a triglyceride. However, you should be able to recognize a diagram of the structure and describe its structure in words. So a triglyceride is formed from glycerol and three fatty acids by hydrolysis reactions. Triglycerides have three hydrocarbon tails and they are nonpolar molecules.

Given an example about a cell that is placed in a hypotonic, hypertonic OR isotonic solution, predict the net direction of water movement? (Section 5.5)

If a cell is placed in a solution that is hypotonic to the cytoplasm, net movement of water will be into the cell. An animal cell would burst when placed in a solution hypotonic to the cytoplasm. A plant cell will become turgid as water flows in and pushes against the plant cell wall. Plant cells love solutions that are hypotonic to the cytoplasm. If a cell is placed in a solution that is isotonic to the cytoplasm, there will be no net movement of water across the membrane. If a cell is placed in a solution that is hypertonic to the cytoplasm, the net flow of water will be out of the cell.

Identify the four stages of food processing?

Ingestion, digestion, absorption, elimination

Explain that glucose exists in equilibrium in solution between the linear form and two alternate ring forms? (see class notes)

Look at the figure in the class notes. The idea is to understand that all three forms of glucose are present at the same time in solution, and that the forms are constantly converting to each other (a dynamic equilibrium). In order for the alpha form to be converted to the beta form, it must first convert to the linear form which can then form the beta ring form. And vice versa. At any point in time, all three forms will be present.

Distinguish between mechanical and chemical digestion?

Mechanical digestion relates to mashing and mixing to increase surface area of food particles and mix food with digestive juices. It makes food more accessible to chemical digestion. Mechanical digestion occurs in the oral cavity through the action of chewing and in the stomach through contractions of the stomach that churn the contents of the stomach to mix food with gastric juice. Chemical digestion refers to the chemical hydrolysis of food molecules that breaks food molecules down into their component parts.

Identify the role of each component of gastric juice (mucus, HCl, pepsin) in the function of the stomach?

Mucus helps to protect cells in the lining of the stomach from the harsh effects of HCl. Hydrochloric acid disrupts the structures that hold tissues together, denatures molecules in food, and kills most bacteria that enter the stomach with food. Pepsin is an enzyme that begins the digestion of protein by breaking large polypeptides into smaller polypeptides. The low pH in the stomach (pH 2) denatures proteins, making peptide bonds accessible to pepsin.

Describe the role of the liver in adjusting blood composition?

One major function of the liver is to regulate blood glucose levels. If blood glucose is high, liver cells will absorb glucose from the blood (in response to the hormone insulin) and use the glucose to build glycogen. If you haven't eaten in a while and your blood glucose levels are low, liver cells will break down stored glycogen into glucose (in response to the hormone glucagon) and release glucose back into the blood to maintain homeostatic blood glucose levels.

Define osmosis? (Section 5.4)

Osmosis is the diffusion of water across a semipermeable membrane from an area of higher "free" water concentration to an area of lower "free" water concentration.

Identify three enzymes produced by the pancreas that act in the small intestine. Explain that many digestive enzymes are produced by the pancreas and that some digestive enzymes are produced in the small intestine?

Pancreatic juice contains several enzymes that hydrolyze food molecules. These include pancreatic amylase (breaks starch to maltose), the proteases trypsin and chymotrypsin which break polypeptides into smaller pieces and lipase which hydrolyzes fat molecules (triglycerides) to glycerol and fatty acids. Enzymes produced in the small intestine include maltase, lactase and sucrase.

Explain the process that moves food down the esophagus?

Peristalsis moves the food bolus down the esophagus. Rhythmic waves of contracting smooth muscles (in the wall of the esophagus) push the food in one direction toward the stomach.

Explain the process of peristalsis and its role in moving materials through the alimentary canal?

Rhythmic contractions of smooth muscles in the wall of the alimentary canal that propel food/chyme forward through the canal. Under involuntary control.

Explain the role of sphincters in the alimentary canal?

Sphincters control the passage of food/chyme between compartments of the alimentary canal. Allows different organs of the canal to have different chemical environments. Control entry and exit from the alimentary canal (esophagus and rectum/anus)

List three common disaccharides and their roles? (see class notes)

Sucrose is composed of glucose and fructose. It is the transport form of sugars in plants. Lactose is composed of glucose and galactose. It is found in milk and makes milk appetizing for infants. Maltose is composed of glucose and glucose. It is the product of amylase action on starch.

Describe the Heimlich maneuver and how it works?

The Heimlich maneuver is used when food enters the top of the trachea instead of going down the esophagus. The maneuver uses a sharp action on the abdomen to push the diaphragm up, creating pressure in the lungs and forcing lodged food out of the trachea.

Explain the role of the epiglottis in directing swallowed food into the esophagus?

The epiglottis is a flap of cartilage that flips down to block the trachea (windpipe) when you swallow, directing food down the esophagus and preventing food from entering the trachea.. Swallowing pushes the larynx up which makes the epiglottis flip down.

Identify the materials supplied to the small intestine by the liver, gallbladder and pancreas, and explain the role of each in promoting digestion?

The liver produces a solution of bile (bile salts) that is stored in the gallbladder. When chyme is present in the small intestine, a signal is sent to the gallbladder to shoot a bolus of bile solution into the small intestine via the bile duct. The job of bile is to emulsify fats. That means that the bile breaks large globs of fat into smaller globules, increasing the surface area of the fat and allowing more efficient breakdown of fat by the enzyme lipase. The pancreas produces pancreatic juice that travels to the small intestine via the pancreatic duct. The pancreatic juice contains important materials that are needed for digestion. These include sodium bicarbonate which neutralizes the acid chyme as it is released into the small intestine. The pH in the small intestine is adjusted to about pH 7 to 8 as sodium bicarbonate neutralizes the acid chyme. Pancreatic juice also contains several enzymes that hydrolyze food molecules. These include pancreatic amylase (breaks starch to maltose), the proteases trypsin and chymotrypsin which break polypeptides into smaller pieces, other enzymes that break polypeptides into amino acids, and lipase which hydrolyzes fat molecules (triglycerides) to glycerol and fatty acids.

Explain how the teeth, tongue and salivary glands work together to initiate the digestion of food?

The role of the teeth is to initiate mechanical digestion of food. The teeth are embedded in the bones of the jaw and move up and down through the action of jaw muscles (voluntary!). Salivary glands produce saliva which is released into the mouth through ducts. The components of saliva include buffers to neutralize acidic food and protect your teeth and mouth tissues, an antibacterial agent (lysozyme) that decreases the number of bacteria in the mouth/food (by killing bacteria), mucus which protects the lining of the oral cavity and makes the food slippery, and salivary amylase, an enzyme that initiates the digestion of starch. The tongue helps to manipulate food and position it between the teeth, and it forms the food into a bolus for swallowing, and pushes the bolus into the pharynx. And of course the tongue has lots of taste buds to help you distinguish between tasty and nasty food.

Identify the two functions of the small intestine? Which of these functions takes place primarily in the duodenum?

The small intestine functions in digestion and absorption of digested nutrients. Digestion takes place primarily in the duodenum which comprises about the first foot of the small intestine. Remember that the small intestine is 20-21 feet long.

Explain how the structure of the small intestine is adapted for absorption? Consider increased surface area (folds, villi and microvilli) as well as proximity to capillaries.

The small intestine has a large surface area for absorption. There are four structural features that increase the surface area. The small intestine is long. The inner wall of the intestine has circular folds. There are fingerlike projections of the inner wall called villi. The epithelial cells that line the inner wall have projections of their plasma membranes that face the lumen. Called microvilli. In addition, a capillary runs through the interior of each villus to facilitate efficient absorption of nutrients into the bloodstream. Substances that are absorbed through the intestinal epithelial cells do not have to travel far to get to the capillary.

Describe the composition of feces?

Undigested plant matter (including cellulose!) and prokaryotic cells.

State that specialized cells in gastric pits produce the components of gastric juice, including mucus, hydrochloric acid and pepsinogen

What you need to know here is that gastric juice is produced in gastric glands located in the wall of the stomach. There is not an accessory organ that produces fluids that move to the stomach through a duct. The stomach produces its own digestive juice in the gastric glands which is then released into the lumen of the stomach.

Identify the types of molecules that are considered carbohydrates?

he term carbohydrate refers to simple sugars (monosaccharides), disaccharides and polysaccharides. This is different from the language used to describe peptides, polypeptides and proteins. We do not refer to amino acids as peptides. The monomer unit is not included in a collective vocabulary term.