Homework 7 Flashcards
- Give two examples of organisms in which digestion is intracellular. What does this mean? In which cases is digestion extracellular? Explain.
In intracellular digestion the food has to cross over a cell membrane. Therefore, in extracellular digestion food is digested without crossing the cell membrane. However, enzymes aid in both forms of digestion in order to break down the macromolecules.
Elk and Cows are examples of animals which undergo extracellular digestion, the digestion process in these animals takes place in the lumen.
Humans and most mammals use intracellular digestion, which means the food is taken into the body in some form before it is broken down into anything useful.
Why is it advantageous for the largest animal on the planet, the blue whale, to eat one of the smallest ones in its habitat?
It is advantageous for the blue whale to feed on the small animals in its habitat, such as krill, because they are available in abundance and the food energy available per unit of time is greater, only about 10% of the energy in an animal makes it through each step of food chain, meaning small animals provide the greatest amount of energy to the blue whale with regards to bodyweight.
With reference to figure 47.9 in your text that illustrates both chief cells and parietal cells in gastric glands, discuss the integral relationship between structure and function. With respect to this figure, explain how the digestive tract is uniquely designed anatomically to coordinate digestion of food but not one’s own body.
Chief and parietal cells together secrete about 1500 ml of gastric juice each day.
Chief cells secrete pepsinogen which is converted by the acid in the gastric lumen to pepsin.
Parietal cells secrete the hydrochloric acid of the gastric juice.
Parietal and chief cells respond to the presence of gastrin by accelerating their rates of secretion. The effect on the parietal cells is the most noticeable, and the pH of the gastric juice declines as a result.
We don’t digest our own stomach because our stomach is lined with a protective mucous barrier that keeps us from digesting ourselves. In effect, the acid never really touches the “meat” of the stomach.
What are zymogens (inactive enzymes or proenzymes)? Give several examples. With reference to one example explain their role in physiology of digestion. Relate your answer to a course theme.
Zymogens are inactive enzyme precursors that require a biochemical change, such as hydrolysis, to become an active enzyme.
Examples include Trypsinogen, Angiotensinogen, Prolipase, Pepsinogen, and many others.
Enzymes like pepsin are created in the form of pepsinogen, an inactive zymogen. Pepsinogen is activated when Chief cells release it into HCl which partially activates it. Another partially activated pepsinogen completes the activation by removing the peptide turning the pepsinogen into pepsin. This process takes place in the pancreas to prevent the enzymes from digesting proteins in the cells in which they are synthesized.
oral cavity
Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.
esophagus
The esophagus is a muscular tube extending from the pharynx to the stomach. Through peristalsis, a series of contractions, the esophagus delivers food to the stomach.
*Just before the connection to the stomach there is a “zone of high pressure,” called the lower esophageal sphincter; this is a “valve” meant to keep food from passing backwards into the esophagus.
stomach
The stomach is a sac-like organ with strong muscular walls. In addition to holding the food, it’s also a mixer and grinder. The stomach secretes acid and powerful enzymes that continue the process of breaking down the food. When it leaves the stomach, food is the consistency of a liquid or paste. From there the food moves to the small intestine.
small intestine
The the small intestine is a long tube loosely coiled in the abdomen. The small intestine continues the process of breaking down food by using enzymes released by the pancreas and bile from the liver. Bile is the compound that aids in the digestion of fat and eliminates waste products from the blood. Peristalsis also moves food through the small intestine and mixes it up with digestive secretions.
There are the parts to the small intestine, the duodenum is largely responsible for continuing the process of breaking down food, and the jejunum and ileum are mainly responsible for the absorption of nutrients into the bloodstream.
pancreas
The pancreas secretes enzymes into the small intestine. These enzymes break down protein, fat, and carbohydrates from the food we eat.
liver
The liver has many functions, but two of its main functions within the digestive system are to make and secrete bile, and to cleanse and purify the blood coming from the small intestine containing the nutrients just absorbed.
gall bladder
The gallbladder sits just under the liver and stores bile. Bile is made in the liver then travels to the gallbladder through the cystic duct. During a meal the gallbladder contracts and sends bile to the small intestine.
Once the nutrients have been absorbed and the leftover liquid has passed through the small intestine, what is left of the food you ate is handed over to the large intestine, or colon.
colon
The colon is a 6-foot long muscular tube that is part of the large intestine and connects the small intestine to the rectum. Stool, or waste left over from the digestive process, is passed through the colon by means of peristalsis, first in a liquid state and ultimately in a solid form. As stool passes through the colon, water is removed. Stool is mostly food debris and bacteria. These bacteria perform several useful functions, such as synthesizing various vitamins, processing waste products and food particles, and protecting against harmful bacteria. When the descending colon becomes full of stool, or feces, it empties its contents into the rectum to begin the process of elimination.
circulatory system (specifically the hepatic portal system)
The digestive system and the circulatory system work closely together in order to deliver nutrients to the cells of the body. The digestive system takes the food that you ingest and breaks it down into parts that the body can use. These parts, such as amino acids, sugars and vitamins, are then absorbed into the cells, which then pass it into the nearby blood vessels. These blood vessels then take these important nutrients and deliver them to the other cells of the body which will use them to make the many different chemicals and proteins, etc. that they need to perform their functions.
The hepatic portal system basically consists of the hepatic portal artery, it responsible for taking the products of digestion from the small intestine to the liver and breaking them down further, cleaning them of any microbes, and sending them to all the body cells via the hepatic portal vein.
Explain with either reference to specific syndromes of deficiencies in humans or with animal behavior how vitamin and mineral needs are so integral to the success of an organism.
Iron is essential for making hemoglobin, the red substance in blood that carries oxygen to body cells. Most iron is stored in bone marrow that makes blood cells. If there is not enough iron in the body, it goes to the bone marrow reserves. If this iron stored in the bone marrow is low, red blood cells don’t form properly, they are smaller than usual and there are fewer.
Symptoms from a deficiency in iron: Skin pallor; weakness; fatigue; headaches; shortness of breath, difficulty concentrating, brittle nails, cracked lips
Symptoms from overdosing on iron: Constipation, Type II diabetes, and toxic buildup in liver and in rare instances the heart
Osteichthyes
Water enters the gill chamber through a fish’s mouth and exits through gill openings under the operculum. Blood flowing through the gill filaments absorbs oxygen from the water. Some species of bony fishes can absorb considerable amounts of oxygen through their skin.
Arthropoda
crab’s breathing adaptations equip it for life both in and out of water. Crabs are well adapted for life out of water; they can absorb air through special parts of its legs which are thinner. It also absorbs water from the sand through silky hairs on the abdomen.
Chordata (bird)
Birds have one-way flow of air in their lungs. As a result, the lungs receive fresh air during inhalation and again during exhalation. The advantages of this one-way flow include: no residual volume and that all old (stale) air leaves with each breath.
Cnidaria
The hydra has no respiratory organ, it respires by diffusion alone.
Chordata (dog)
The respiratory system of the dog includes the mouth and nose, trachea, lungs, and smaller airways. The respiratory system is responsible for taking in oxygen and eliminating waste gases like carbon dioxide. Because dogs do not sweat through the skin, the respiratory system also plays an important role in regulation of temperature.
Arthropoda (fly)
insects have a system of fine branching tubes called a tracheal system that delivers the oxygen directly to each cell in the body, this relies solely on diffusion. This is largely why insects cannot get very big. One disadvantage of their respiratory system is that if the tracheal system fills with water, it takes much longer for air to diffuse through the system, causing them to drown fairly easily.
Chordata (frog)
the frog has three respiratory surfaces on its body that it uses to exchange gas with the surroundings: the skin, in the lungs and on the lining of the mouth. While completely submerged all of the frog’s repiration takes place through the skin. The skin is composed of thin membranous tissue that is quite permeable to water and contains a large network of blood vessels. The thin membranous skin is allows the respiratory gases to readily diffuse directly down their gradients between the blood vessels and the surroundings. When the frog is out of the water, mucus glands in the skin keep the frog moist, which helps absorb dissolved oxygen from the air. Frogs also have a respiratory surface on the lining of their mouth on which gas exchange takes place readily. While at rest, this process is their predominate form of breathing, only fills the lungs occasionally. This is because the lungs, which only adults have, are poorly developed.
State and explain Fick’s Law. Why is Fick’s Law the first section in a discussion of adaptations for gas exchange? (What do animals adapt their gas exchange structures to?)
“The rate of transfer of a gas through a sheet of tissue is proportional to the tissue area and the difference in gas partial pressure between the 2 sides and inversely proportional to the tissue thickness.”
The rate of diffusion between two regions (gas exchange) is governed by Fick’s Law, it is therefore very important to the discussion of gas exchange, and is therefore the first thing in discussion.
Animals adapt in different ways, amphibians breathe through their skin, fish through their gills, etc. Adaptations such as fish breathing through their gills increases surface area to allow for greater gas exchange.
Volume of gas (per unit time)=Area/Thickness x Diffusion constant x (Partial Pressure 1 - Partial Pressure 2)
What are globin proteins (e.g. blood pigments such as hemoglobin and myoglobin), and what “problem” do they solve?
Globins are a new discovered family of globular proteins. Globular proteins are spherical proteins that are somewhat water-soluble and have a multitude of functions.
Myoglobin is the primary oxygen-carrying pigment of muscle tissues. Myoglobin is released from damaged muscle tissue, which has very high concentrations of myoglobin, and filtered, by the kidneys.
Hemoglobin in the blood carries oxygen from the respiratory organs (lungs or gills) to the rest of the body where it releases the oxygen to burn nutrients to provide energy to power the functions of the organism in metabolism.
Draw a hemoglobin/oxygen dissociation curve and label the axes properly. Indicate the PO2 of metabolically active tissues and the PO2 in the lungs.
The dissociation curve shifts to the right when carbon dioxide concentration, temperature, or hydrogen ion concentration is increased. This facilitates increased oxygen dumping. This makes sense because increased CO2 concentration and lactic acid build-up occur when the muscles need more oxygen. Changing hemoglobin’s oxygen affinity is the body’s way of adapting quickly to this problem.
What is the Bohr shift. What is its significance?
The Bohr shift states that in the presence of carbon dioxide, the oxygen affinity for dissociation of respiratory pigments, such as hemoglobin decreases; because of the Bohr shift, an increase in blood carbon dioxide level, a decrease in pH, an increase of a glycolysis by-product, 2,3-biphosphoglycerate, or increased temperature causes hemoglobin to bind to oxygen with less affinity.
This facilitates oxygen transport as hemoglobin binds to oxygen in the lungs, but then releases it in the tissues, particularly those tissues in most need of oxygen. When a tissue’s metabolic rate increases, its carbon dioxide production increases. The carbon dioxide is quickly converted into bicarbonate molecules and acidic protons by the enzyme carbonic anhydrase: CO2+ H2O H+ + HCO3−
This causes the pH of the tissue to decrease, and so increases the dissociation of oxygen from hemoglobin, allowing the tissue to obtain enough oxygen to meet its demands.
