Option D

• What is nutrition?


  Nutrition is defined as the supply of nutrients
• What are essential nutrients?

  Essential nutreients are substances that the body needs but it cannot synthesize, and thus they must be in the diet
• What are the four chemical groups of essential nutreints?


  Minerals - specific elements such as calcium or iron

  Vitamins - chemically diverse carbon compounds needed in small amounts, such as ascorbic acid and calciferol

  Amino acids - some of the 20 are not able to be synthesized by humans but obviously necessary for protein creation

  Fatty acids - essential for the same reason, example: omega-3 fatty acids
• What is malnutrition?


  Malnutrition is a deficiency, imbalance, or excess of specific nutrients in the diet.
• Where is appetite controlled?


  Appetite is controlled by a center in the hypothalamus. The small intestine, pancreas and adipose tissue secrete different hormones when nutrient levels are too high. If the hypothalamus receives these chemicals it reduces the desire to eat.
• What is obesity?


  Obesity is the excessive storage of fat in adipose tissue, due to the prolonged intake of more energy in the diet than is used in cell respiration.
• What health issues does obesity make more likely?


  Obese persons are more likely to experience hypertension (high blood pressure) and type II diabetes
• What is starvation and what can it lead to?


  Starvation is a prolonged shortage of food. Once glycogen and fat reserves are used up, starvation can lead to the breakdown of body tissue to be used in cellular respiration
• What is vitamin C deficiency and why does it happen?


  Vitamin C, also known as ascorbic acid, is needed to synthesize collagen fibres in body tissues such as skin and blood vessel walls. Humans cannot synthesize ascorbic acid so it must be ingested. Without it humans get scurvy. Scurvy only happens in us and few other mammals because most mammals have the enzyme needed for abscorbic acid synthesis.
• What is Phenylketonuria ?


  Phenylketonuria (PKU) is when the level of phenylalanine (an essential amino acid) becomes too high in the bloodstream. It is caused by an insufficiency or lack of phenylalanine hydroxylase, which turns phenylalanine into tyrosine. The insufficiency or lack of this enzyme is due to a mutation of the gene that codes for it.
• How is phenylketonuria treated?


  Phenylketonuria symptoms are not present in fetuses because the mother's body regulates phenylalanine concentrations. Phenylketonuria is now tested for at birth so that a diet can be implemented to prevent most/all harmful consequences
• Explain vitamin D deficiency in humans


  Without sufficient vitamin D the body cannot absorb enough calcium from food in the gut. The consequence is osteomalacia. Osteomalacia is inadequate bone mineralization due to calcium salts not being deposited or being reabsorbed, so bones soften. In children, osteomalacia is called rickets.
• What is anorexia and what are its consequences?


  Anorexia is a condition in which an individual does not eat enough food to sustain the body, even though the food is available. As with starvation body tissues can be broken down, and with severe anorexia even the heart muscle is broken down.
• Explain the relation between cholesterol and heart disease.


  There has been research showing a correlation between high levels of cholesterol in blood plasma and an increased risk of coronary heart disease(CHD).

  -Only low-density lipoprotein is implicated in CHD

  -Reducing cholesterol consumption has very little effect on blood cholesterol levels

  -The liver can synthesize cholesterol, so dietary cholesterol is not the only source

  -Genetic factors are more important than dietary intake

  -Positive correlation between intake of saturated fats and of cholesterol, so maybe its the sat fats, not the cholesterol, that caues risk of CHD
• How do you measure the energy content of food?


  You burn the food then use this formula:

  Energy content of food ( J g⁻¹) =

  
  

  temp rise (C) x water volume (ml) x 4.2J

  -------------------------------

  mass of food (g)
• What does RDA stand for when relating to the nutritional content of foods?


  Recommended Daily Amount

  Can be in either percentage or mass units
• What controls the secretion of digestive juices?

  Secretion of digestive juices is controlled using nerves and hormones.
• What are the two types of glands?


  Exocrine and endocrine glands.

  Exocrine glands secret through a duct onto the surface of the body or into the lumen of the gut. Digestive-juice-excreting glands are exocrine.

  Endocrine glands are ductless and secrete hormones directly into blood.
• Explain the specific control of volume and content of gastric secretions.


  -The sight/smell of food stimulates brain to send nerve impulses to parietal cells

  -Parietal cells respond by secreting acid, known as a reflex action

  -Sodium and chloride ions also secreted, causing water to osmos into the stomach to form gastric juice

  -Food enters the stomach and chemoreceptors detect amino acids

  -Brain sends impulses via vagus nerve to endocrine cells to make them secret gastrin

  -Hormone gastrin stimulates further sectrion of acid and pepsinogen

  -Secretin and somatostatin inhibit gastrin sectrion if pH gets too low
• Explain the role of acid conditions in the process of digestion.


  Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food. The acid secreted by the parietal cells disrupts the extracellular matrix that holds cells together and denatures proteins exposing their polypeptide chains.
• Describe the adaptations of the villus epithelium cells.


  The structure of cells in the epithelium of the villi is adapted to the absorption of food.

  -Epithelial cells on covering the villus adhere to each other ensuring that most materials pass through epithelial cells on the way to the blood stream

  -Surface membrane of lumen has many microvilli, created a brush border, increasing surface area for absorption

  -Many mitochondria in epithelial cells to power active transport

  -Many pinocytic vesicles due to absorption of some food by endocytosis

  -In epithelial cells, the side facing the lumen (apical surface) has different types of proteins to help with transport from the side facing the blood vessels (basal surface)
• Explain the role of dietary fibre in digestion


  The rate of transit of materials through the large intestine is positively correlated with the fibre content.

  Fibre is non-readily digestible material, and increases the mass of material passing through the intestines. This helps prevent constipation because it draws water into the intestine, which speeds movement of fecal matter.

  Fibre may also reduce bowel cancer, haemorrhoids and appendicitis, and reduce appetite to prevent obesity, absorption of sugars can be slowed preventing type II diabetes.
• What happens to ingested materials that are not absorbed?


  Materials that have been ingested but then not absorbed are egested (pooped out). An example of a material like this is dietary fibre.
• Explain how protein pumps can be inhibited by drugs.


  Many diseases are worsened by the release of stomach acid. Acidity in the stomach is produced by a proton pump called the "H⁺, K⁺-ATPase". The pump uses 1 ATP to exchange 2 protons from the cytoplasm for two potassium ions in the lumen. Treating stomach acid diseases is done by proton pump inhibitors (PPIs). Each PPI permanently bonds to one pump, reducing its activity. They're not permanently effective because proton pumps are eventually replaced.
• Explain dehydration due to cholera.


  Cholera is a disease caused by infection from the bacterium Vibrio cholera. The bacterium releases a toxin that binds to receptors on intestinal cells. Once brought into the cell by endocytosis the toxin triggers a cascade response that leads to the discharge of Cl⁻ and HCO₃⁻ ions from the cell into the intestine. Water follows these ions through osmosis, leading to diarhea, and water is drawn in to replace the lost water from the blood stream, leading to dehydration.
• Explain how bacterial infections cause ulcers.


  Stomach ulcers are caused by the bacterium Heliobacter pylori. It causes part of the stomach lining to be digested by pepsin and HCl leading to open sores.
• How does the liver act as a detoxifier?


  The liver removes toxins from the blood and detoxifies them. It does this using a range of chemical conversions.

  Examples:

  alcohol converted into less toxic substance by ethanol dehydrogenase

  Ammonia into urea

  One general method the liver uses is to convert hydrophobic comounds into hydrophillic compounds for easier excretion
• State the liver's role as red blood cell recycler


  Red blood cells in adults last about 120 days. Old and damaged red blood cells undergo changes making them susceptible to recognition by macrophages. At the end of life they are removed from circulation and broken down in the spleen and liver.
• Explain the role of Kupffer cells in the breakdown of red blood cells.


  The breakdown of erythrocytes (red blood cells) starts with phagocytosis by Kupffer cells.

  When cells get old they are engulfed by Kupffer cells, macrophages lining the liver.
• Explain the transport of iron to bone marrow.


  Iron is carried to the bone marrow to produce hemoglobin in new red blood cells.

  Red blood cells are created in bone marrow, and hemoglobin is synthesized in red blood cells. Iron is added to the heme group here.
• Explain the conversion of cholesterol to bile salts.


  Surplus cholesterol is converted into bile salts.

  Cholesterol is both absorbed through food and synthesized by liver cells. The liver also regulates cholesterol levels, synthesizing or breaking down cholesterol as necessary.
• Explain how the liver processes nutrients.


  The liver intercepts blood from the gut to regulate nutrient levels.

  The liver regulates glucose levels by storing glucose as glycogen or breaking glycogen into glucose.

  The body can't store proteins or amino acids so excess is broken down in the liver and the nitrogenous waste is processed by the liver.
• Explain storage of nutrients in the liver.


  When glucose levels are high insulin is released triggering the liver to store glucose as glycogen. When glucose levels are low glucagon is released and glycogen, glycerol, amino acids and fatty acids are broken down in the liver releasing glucose.

  Iron, vitamin A, vitamin D are stored in the liver when in excess and released into blood when there is a deficit.
• What are the causes of jaundice?


  When the liver breaks down red blood cells, a pigment is produced called bilirubin. Buildup of bilirubin causes jaundice. In adults, liver problems that contribute to jaundice can be caused by alcoholism, liver diseases and blood diseases.
• What are the consequences of jaundice?


  People with jaundice experience discoloration in the skin and eyes due to the deposition of excess bilirubin (pigment) in the skin tissues. Jaundice is actually a symptom, not really a disease.
• Explain the dual supply of blood to the liver.


  Blood is brought to the liver by both the hepatic portal vein and the hepatic artery.

  The hepatic portal vein carries the most blood and brings blood from the stomach and intestines. The blood can be rich in nutrients if eating has just occurred but oxygen levels are low.

  The vein subdivides into sinusoids in the liver, like capillaries but wider and walls are not continuously lined with cells. This allows blood flowing through to come in contact with liver cells.

  The hepatic artery brings oxygen-rich blood from the aorta.
• Diagram of heart

  
• Explain the structure of cardiac muscle cells. What does their structure allow them to do?


  Cardiac muscle cells are striated, like skeletal muscles. However cardiac muscle cells are shorter and wider than skeletal muscles, and normally only have one nucleus per cell. The cells are Y-shaped and all interconnected into a complex network. Where one cell connects to another there is a junction called an "intercalated disc". This junction consists of a double membrane with gap junctions allowing cells to connect cytoplasms. This overall structure allows them to be physically connected (Y-shapes) and have quick electrical/ion transport (connected cytoplasms) meaning that stimuli in one cell causes the entire network to contract as if it were one large cell.See an expert-written answer!We have an expert-written solution to this problem!

  
• What is the definition of systole?

  Systole is the contraction of the heart's chambers.
• What is the definition of diastole?


  Diastole is the relaxation of the heart's chambers