Human Physiology

the diagram below shows a transverse section of the ileum State the name and function of the structures labeled 1 and 2 Distinguish between the muscles labelled 3 and 4 Pg. 3 of Absorption wkst.

(a) i. 1: villus - absorption of (soluble) food and increased surface area for digestion; 2: lacteal - transport of fat / lipid; ii. 3: circular; 4: longitudinal;

Type 1 vs Type 2 Diabetes

1- caused by an autoimmune reaction 2- Target cells fail to respond to insulin

Define nutrient

A nutrient is a chemical substance found in foods that is used in the human body

Explain the dietary advice that should be given to a patient who has developed type II diabetes

A person with type II diabetes needs to regulate their diet (calorie intake) and exercise in order to ensure a balanced energy budget Maintain a low fat diet in order to avoid weight gain Consume complex carbohydrates to ensure gradual release of glucose into blood Eat regular, small meals to ensure a steady supply of glucose into the bloodstream Consume foods with a low glycemic index to avoid abrupt changes in blood glucose levels

Compare the main dietary sources of energy in different ethnic groups

Dietary energy can come from a range of sources (carbohydrates, proteins or fats), but for the bulk of the population, the primary source is crops Most populations will supplement this with meat (primarily cattle in Western nations, chicken and fish in Eastern cultures) Independent island nations may rely on fish as their main dietary source of energy see chart

Absorption vs. Assimilation

Absorption: The movement of a fluid or dissolved substances across a membrane Assimilation: The conversion of nutrients into fluid or solid parts of an organism

State the source, substrate, products, and optimum pH conditions for one amylase, one protease, and one lipase. (see digestion ppt chart)

Amylase: Salivary amylase, salivary glands, amylose (starch), maltose and glucose, 7 (neutral) Protease: Pepsin, stomach cells, proteins, amino acids, 2 (very acidic) Lipase: Pancreatic lipase, pancreas, Lipids, glycerol and fatty acids, 8 (slightly basic)

Outline the consequences of anorexia nervosa

Anorexia nervosa is an eating disorder in which individuals severely limit the amount of food they intake It is most common in females with body image anxiety and is associated with the following health implications: Malnutrition - deficiency in essential nutrients due to inadequate eating patterns Hormonal imbalance - including changes in menstrual cycle and impairment of normal growth and development Bone and muscle problems - there is muscle and bone deterioration, resulting in reduced muscle mass and more fragile bones Mental health issues - development of mood swings, phobias and reduced mental focus Anaemia - can cause circulatory problems, including heart failure Skin problems - including discoloration and excess hair production Immune disorders - increased susceptibility to infections, diminished capacity for healing and repair Death - if left untreated for a prolonged period, death may finally result

Outline the function of the appetite control centre of the brain

Appetite is controlled by hormones (leptin, insulin, CCK) produced in the pancreas, small intestine and adipose tissue These send messages to the appetite control centre of the brain (hypothalamus), causing a person to feel that they have eaten enough (satiety) The release of hormones can be triggered in a number of ways: Stretch receptors in the stomach lining may become activated when the stomach is full Adipose tissue may release hormones (leptin) in response to fat storage

Explain why pepsin and trypsin are initially synthesised as inactive precursors and how they are subsequently activated

Both pepsin and trypsin are protease enzymes (specifically endopeptidases) which hydrolyse peptide bonds to digest proteins As proteins are essential components of cells, these enzymes could digest the cells that secrete them (auto digestion) Instead, they are synthesised as inactive forms and subsequently activated in the digestive tract PEPSIN: Pepsin is synthesized and secreted by chief cells into the stomach in an inactive form called pepsinogen. Pepsinogen is activated (into pepsin) in the stomach by HCL Pepsin does not auto digest stomach cells once it's activated as a layer of mucous protects the cells lining the stomach wall

Discuss the benefits of breastfeeding

Breastfeeding may have many benefits over bottle-feeding in helping a baby grow to be a big man, including: Bonding - may aid in mother-infant bonding and communication, reduces post-partum depression Immunity - colostrum and breast milk contain high levels of antibodies, protecting infant from infection Gut motility - breast milk is easier to digest than formula milk and stimulates digestive tract function and defecation Maternal health - improves weight loss, reduces risk of breast cancer and diabetes Affordability - breast milk is free and readily available (provided mother remains healthy) Nutritional value - more complete than formula milk, contains human proteins and more suitable fatty acids that are less likely to cause allergies

Which of the following structures help the absorption of food by the small intestine

Capillary networks Vili Microvilli Membrane proteins

Outline the causes and symptoms of type II diabetes

Causes: Type II diabetes occurs when the body becomes less responsive to insulin due to a down-regulation of insulin receptors in the liver Consequently, the body becomes inefficient at lowering blood glucose levels after feeding Type II diabetes may be caused by a genetic predisposition, dietary factors (high sugar intake) or a lack of exercise (obesity) Symptoms: Hyperglycemia (high glucose content in blood) Frequent urination (polyuria) and general thirst Tiredness and blurred vision Nerve damage and erectile dysfunction Kidney and back pain Incidence: Incidence of type II diabetes has been found to be higher in populations of Aboriginal Australians than those of non-native descent However it is currently unclear whether this is due to genetic factors or social factors (likely a combination of both)

State which cells secrete insulin and the organ in which they are located

Cells: Beta Cells Organ: Pancreas

State that digestive juices are secreted into the alimentary canal by glands, including salivary glands, gastric glands in the stomach wall, the pancreas and the wall of the small intestine

Chemical digestion in the alimentary canal involves the secretion of digestive juices capable of breaking down complex macromolecules These digestive juices are secreted from glands, which include: Salivary glands - secretes saliva which contains amylase Gastric glands - secretes gastric juices which include hydrochloric acid and pepsinogen Pancreas - secretes pancreatic juices containing lipase, trypsinogen and hydrogen Intestinal wall - The small intestine contains the crypts of Lieberkuhn, which secrete a variety of substances as part of the intestinal juice

Discuss the amount of vitamin C that an adult should consume per day, including the level needed to prevent scurvy, claims that higher intake gives protection against upper respiratory tract infections, and the danger of rebound malnutrition

Common sources of vitamin C (ascorbic acid) include citrus fruits, orange juice and vitamin C tablets The recommended daily allowance (RDA) of vitamin C will vary between individuals according to age and gender The recommended daily intake (RDI) of vitamin C has been set at 65 - 90 mg (this is based on the highest RDA and thus covers all individuals) This intake has been determined based on the levels required to ensure no person is at risk of a deficiency disease (i.e. scurvy) However, there is significant debate as to whether the daily intake should be higher (> 1000 mg), in order to achieve beneficial effects Vitamin C is a potent antioxidant that is also involved in detoxification and some claim that higher doses may boost the immune system, speed recovery from injury and protect against upper respiratory tract infections Others suggest that taking larger doses would promote rebound malnutrition, whereby the body adjusts to a larger intake and responds poorly whenever dosages drop back to normal levels Neither claims are currently well supported by large-scale, controlled trials and so the evidence for these claims must be considered weak

State that the liver has a role in detoxification

Detoxification is the removal of a toxic substance from a living organism The liver plays a role in the detoxification of a number of molecules, including alcohol, metabolic products, food preservatives, drugs and poisons

Outline the importance of fibre as a component of a balanced diet

Dietary fibre includes the components of foods which cannot be digested by the human body (predominantly cellulose) Dietary fibre is an important part of a balanced diet as it plays an important role in human health: Provides bulk in food, ensuring the continuous passage of materials through the digestive tract Stimulates peristaltic contractions to enable the digestive system to pass food Helps regulate blood sugar and reduces blood cholesterol Lowers risk of appendicitis and intestinal cancer Helps prevent constipation

Compare the composition of saliva, gastric juice and pancreatic juice

Digestion ppt. Table

State that non-essential amino acids can be synthesised in the body from other nutrients

Eleven out of the twenty amino acids are non-essential and can be synthesised in the body from other nutrients The body will only expend the energy required for their biosynthesis if they cannot be derived from the diet

Describe the process of erythrocyte and hemoglobin breakdown in the liver, including phagocytosis, digestion of globin and bile pigment formation

Erythrocytes rupture when they reach the end of their life span (~ 120 days) Kupffer cells are phagocytes found within the sinusoid lumen which engulf the contents and break down haemoglobin into globin and heme groups Globin is digested by peptidases to produce amino acids (which are either used in the synthesis of new proteins or metabolised by the liver) Heme groups are broken down into iron and bilirubin (bile pigment) The iron is transported to either the liver (for storage) or the bone marrow (to make new blood cells) The bilirubin is transported to the liver to be released as part of bile into the alimentary canal

List the type of nutrients that are essential in the human diet, including amino acids, fatty acids, minerals, vitamins and water

Essential nutrients are those that cannot be synthesised by the body and must be ingested in the diet Carbohydrates are not considered essential nutrients because in certain human diets energy is obtained from other sources without ill effect Essential nutrients include: Amino acids (e.g. lysine and methionine) Fatty acids (omega 3 and omega 6) Minerals (iron, sodium, potassium, calcium, phosphorus and iodine) Vitamins (vitamins A, C, D and folate) Water

Explain the possible health consequences of diets rich in carbohydrates, fats and proteins

Excess energy from carbohydrates, proteins or fats will all be converted and stored as fat, leading to obesity and an increased risk of heart failure A balanced diet is required in order to achieve sufficient intake of essential nutrients without the risk of unnecessary weight gain Carbohydrates Carbohydrates are broken down into monosaccharide subunits for transport in the blood (blood sugar levels) A sustained high intake of carbohydrates may lead to the development of diabetes, as the liver becomes less sensitive to insulin Individuals with diabetes may experience more frequent urination (polyuria), increased thirst and dizziness Proteins There are no major adverse health effects to a diet rich in protein, however excessive intake over a long period of time may cause kidney problems Deaminating proteins creates urea, and the kidneys will need to work overtime to flush out excess toxins, leading to damage over time Fats Excessive fat intake is strongly correlated to an increase in blood pressure, atherosclerosis and the incidence of coronary heart disease (CHD) Atheromas (fatty deposits) develop in the arteries and significantly reduce the diameter of the lumen of the artery wall needed for pulse flow This may lead to the formation of clots in the artery, and if this occurs in the coronary arteries it may lead to a heart attack

Explain the structural features of exocrine gland cells

Exocrine glands have ducts through which they secrete their product (these ducts may arise from the convergence of smaller ductules) The ducts / ductules arise from a cluster of cells called an acinus (plural = acini), surrounded by a basement membrane Acini are lined by a single layer of secretory cells which release the exocrine product into the lumen of the duct via secretory vesicles Secretory cells are held together by tight junctions, and possess a highly developed rough ER and golgi network for material secretion

Compare the energy content per 100 g of carbohydrate, fat and protein

Fats contain more than twice as much energy per 100 grams than carbohydrates and proteins Carbohydrates: 1,760 kJ per 100 g Proteins: 1,720 kJ per 100 g Fats: 4,000 kJ per 100 g

List two dietary sources of vitamin D.

Fish liver oil, Milk

Hormone that regulates the level of blood glucose

Glucagon

Discuss the roles of gastric acid and Helicobacter Pylori in the development of stomach ulcers and cancers

H. pylori is a bacterium which causes gastritis; stomach ulcers are open sores in the stomach wall; prolonged presence of ulcers may lead to the formation of tumours; cancer of the stomach is a malignant tumour in the stomach wall; H. pylori survives in the stomach mucosa; producing urease; which neutralizes gastric acid; colonization by H. pylori opens up/weakens the protective lining; for digestive attack by gastric acid/HCl causing ulcers; cause was previously thought to be stress/lifestyle/diet; H. pylori now thought to be primary cause

Label liver tissue

Hepatocytes Hepatic Vein Sinusoids

Explain the problem of lipid digestion in a hydrophilic medium and the role of bile in overcoming this

Lipids are hydrophobic and hence insoluble within the hydrophilic environment of the body They will group together (coalesce) to form large droplets of fat (fat globules) The enzyme responsible for lipid digestion (lipase) is water soluble and can only bind the lipids to its active site at the the surface of the fat globule As the interior of the fat globule is inaccessible to lipase in this form, this would make lipid digestion normally very slow Bile Bile is a watery fluid that contains bile salts and pigments (bilirubin) - it is produced by liver cells and stored in the gall bladder Bile salt molecules have both a hydrophobic and hydrophilic end The hydrophobic end attaches to the lipid while the hydrophilic end interacts with water - preventing lipids from attaching there This divides the fat globule into smaller droplets (emulsification), increasing the total surface area available for enzyme activity

Explain the role of the liver in regulating levels of nutrients in the blood

Many substances in the blood need to be kept within homeostatic limits to prevent damaging effects Sugar and salt levels need to be controlled in order to maintain the osmolarity of the blood and surrounding tissue Amino acids cannot be stored by the body and must be detoxified when in excess Many minerals and vitamins are essential for specific biological processes (e.g. vitamin A and vision), and so must be sequestered when not in use Absorbed nutrients pass through the liver (via the hepatic portal vein) prior to entering general circulation This enables the liver to regulate and maintain viable levels of nutrients in the blood in spite of variations in dietary intake and feeding frequency The liver stores excess glucose as glycogen granules within hepatocytes, and digests this glycogen when blood glucose levels are low The liver is responsible for the deamination of excess amino acids (made into ammonia before being converted into urea)

Explain the structural features of an epithelial cell of a villus as seen in electron micrographs, including microvilli, mitochondria, pinocytotic vesicles and tight junctions

Microvilli The microvilli border significantly increases surface area of plasma membrane (>100x), allowing for more absorption of digested food materials The membrane is embedded with digestive enzymes (e.g. peptidases, disaccharase) and channel proteins to assist in material uptake Mitochondria Large numbers of mitochondria provide energy (ATP) for active transport processes (uptake against concentration gradient) Pinocytotic vesicles Pinocytosis (cell "drinking") is the non-specific ingestion of fluid and dissolved solutes (a quick way to translocate digested food products in bulk) Pinocytotic vesicles (near the microvilli) contain fluid and dissolved food materials from the lumen of the ileum Tight junctions Tight junctions how each epithelial cell connects to the next. They form an impermeable barrier between adjacent epithelial cells, ensuring a one-way flow of food materials and ensuring that digestive fluids and body-tissue fluids remain separate at all times.

Explain how the structure of the villus is related to its role in absorption and transport of products of digestion

Microvilli: Greatly increase the surface area of the villus, allowing for a greater rate of absorption Rich capillary networks: Help to maintain a concentration gradient for absorption by rapidly transporting absorbed products away Single epithelial layer: Ensures minimal diffusion distance between the intestinal lumen and capillary network Lacteals: Absorb lipids from the intestine into the lymphatic system (which are later reabsorbed back into normal circulation) Intestinal crypts: Located between villi and release juices that act as a carrier fluid for nutrients Membrane proteins / mitochondria: High amounts to enable active transport into cells (contents then passively diffuse into bloodstream)

Explain why digestion of large food molecules is essential

Most food is solid and in the form of large complex molecules which are insoluble and not readily usable As food was synthesised by other organisms, it contains materials not suitable for human tissue - these need to be separated and removed Large molecules need to be broken down into smaller molecules that can be readily absorbed across membranes into cells and into the blood stream Small molecules can be reassembled into new products (e.g. amino acids can be reassembled to make new proteins)

Outline the control of digestive juice secretion by nerves and hormones, using the example of secretion of gastric juice

Pre-Ingestion The sight and smell of food triggers a reflex response in which gastric juice is secreted from gastric pits in the stomach wall This ensures that gastric juice is in the stomach by the time the food is consumed Post-Ingestion Food entering the stomach causes distension, which is detected by stretch receptors in the stomach lining Impulses are sent to the brain, which triggers the secretion of gastrin from the pits lining the stomach wall Gastrin causes the sustained release of gastric juice, particularly its acid component When the pH drops too low, gastrin secretion is inhibited by hormones (secretin from small intestine and somatostatin from the hypothalamus)

Outline the consequences of protein deficiency malnutrition

Protein deficiency malnutrition is caused by an inadequate supply of one or more essential amino acids As a result there are a lack of plasma proteins in the blood, leading to the retention of fluid in the tissues which causes abdominal bloating This is coupled with a wasting of muscles, flaky appearance of the skin and sparse hair with a lack of pigmentation In children especially, it results in a retardation of physical and mental development Individuals suffering from protein deficiency malnutrition will often present as lethargic, with little interest in their surrounding Protein deficiency malnutrition is a key factor in the development of kwashiorkor

Outline two methods that have been used to determine the recommended daily intake of vitamin C

Retrospective Research: An older method used was to identify sufferers of vitamin C diseases (e.g. scurvy) and determine their levels of vitamin C This was an inexact method for determining dietary requirements as it was based on preventing disease, not promoting cellular functions Clinical Trials: More recent attempts at determining the recommended daily intake of vitamin have involved undertaking experimental studies This has included testing cell cultures, guinea pigs and finally humans (during WWII, some objectors volunteered to participate in trials) The purpose of these tests are to identify cellular function and disease onset at different daily dosages of vitamin C

Evaluate the health consequences of diets rich in the different types of fatty acid

Saturated fats and (trans) polyunsaturated fatty acids raise levels of LDL cholesterol, leading to a higher risk of atherosclerosis and coronary heart disease (CHD) Monounsaturated and (cis) polyunsaturated fatty acids raise levels of HDL cholesterol and inhibit LDL cholesterol, lowering the risk of atherosclerosis and CHD Unsaturated fats are essential nutrients (cannot be synthesised by the body), saturated fats are not All types of fatty acid consumed as part of the dietary intake will cause weight gain and increase risks of heart disease if taken in excessive amounts

Label the indicated structures in the micrograph of exocrine gland cells below

Secretory cells Lumen

Draw and label a diagram showing a transverse section of the ileum as seen under a light microscope

See absorption ppt.

Where in the digestive system is the largest volume of water absorbed from

Small intestine

Outline the role of membrane-bound enzymes on the surface of epithelial cells in the small intestine in digestion

Some digestive enzymes are immobilized on the plasma membrane of the epithelial cells of the small intestine, serving two main benefits: 1. The enzyme is fixed in place and does not pass through the digestive system, meaning it can be reused 2. The enzyme can be linked to secondary functions (e.g. membrane transport) Example: Maltase is immobilised on the epithelial lining with its active site facing towards the intestinal lumen Maltase digests the disaccharide maltose into two glucose monomers, which are then absorbed by localised transporters

Outline the function of the stomach, small intestine and large intestine

Stomach The stomach acts as a temporary storage tank and is where protein digestion begins The stomach contains gastric glands which secrete digestive juices for chemical digestion Acids create a low pH environment (pH~1-2) that denatures proteins, while proteases like pepsin hydrolyse large proteins The stomach also releases a hormone (gastrin) that regulates stomach secretions The mechanical action of the stomach (churning) also promotes digestion by mixing the food The stomach turns food into a creamy paste called chyme Small Intestine The small intestine is where usuable food substances (e.g. nutrients) are absorbed into the bloodstream The pancreas and gall bladder (via the bile duct) both secrete substances into the small intestine to aid in digestion The small intestine is lined with smooth muscle to allow for the mixing and moving of digested food products (via segmentation and peristalsis) It also contains small pits (crypts of lieberkuhn) that secrete intestinal juices The small intestine contain infoldings called villi, to increase surface area and optimise the rate of absorption Large Intestine The large intestine absorbs water and dissolved minerals from the indigestible food residues, and by doing so converts what remains from a fluid state into a semi-solid faeces The faeces is stored in the rectum and eliminated out the anus

Which of the following parts of the digest system secrete proteases

Stomach: Yes Small Intestine: No Large Intestine: No

Outline the role of the liver in the storage of nutrients, including carbohydrate, iron, vitamin A and vitamin D

The hepatic portal vein passes ALL absorbed nutrients from the intestine to the liver BEFORE they enter the general circulation -The liver sequesters (stores) essential vitamins, minerals and molecules so they are available to the body at ALL times (to maintain homeostasis) regardless of the diet -An excess or a shortage of nutrients in the blood can cause damage to tissues/ organs -Carbohydrates (glucose) are stored as glycogen in hepatocytes (liver cells) - controlled by insulin/ glucagon (from the pancreas) -Iron is a component of hemoglobin, the inorganic prothetic group (from red blood cell breakdown) is stored as ferritin -Vitamin A (retinol) is stored for cone cells in the eye (rhodopsin) - deficiencies cause "night blindness" -Vitamin D (calciferol) is stored for skeletal development (helps with calcium uptake - deficiencies cause rickets

Outline the circulation of blood through liver tissue, including the hepatic artery, hepatic portal vein, sinusoids and hepatic vein

The liver is divided into segments called lobules which contain liver cells (hepatocytes) Each lobule is surrounded by branches of the hepatic artery and the hepatic portal vein The hepatic artery carries oxygenated blood from the heart to the liver The hepatic portal vein carries nutrient-laden blood from the intestines The hepatic artery and hepatic portal vein both connect to blood vessels called sinusoids Sinusoids are wide blood vessels (capillaries) surrounded by a single layer of hepatocytes (liver cells) that filter and detoxify the blood Kupfer cells line the sinusoids to break down old and damaged erythrocytes (red blood cells). The sinusoids drain into a central vein, which feeds into the hepatic vein The hepatic vein carries deoxygenated blood from the liver to the heart

State that the liver synthesises plasma proteins and cholesterol

The liver synthesis cholesterol, which is involved in bile production and is a component of animal cell membranes The liver is also involved in the synthesis of plasma proteins, which serve a variety of roles Albumin - helps regulate osmotic pressure of body fluids Fibrinogen - soluble precursor of the clotting protein fibrin

Discuss exposure to sunlight as a source of vitamin D.

UV light/sunlight on skin causes chemical production of vitamin D; UV too low in winter in high latitudes; vitamin D stored in liver so can make enough to last several months/through winter; UV light can damage skin and cause skin cancer so exposure needs to be limited; use of sun-block will inhibit vitamin D production; covering skin with clothing prevents UV reaching skin;

List the sources of vitamin D in human diets

Vitamin D can be produced by the skin in response to sunlight, but can also be sourced in a diet containing any of the following: Cereal (fortified) Oily fish (e.g. tuna) Milk (fortified) Egg (specifically yolk) Liver Yogurt

Define Absorption

absorption is taking up of a substance by the skin

Main function of the large intestine

absorption of water

Explain the liver damage caused by excessive alcohol consumption

can cause inflammation of the liver from alcohol abuse; usually from prolonged drinking; products of alcohol metabolism toxic to cells; replacement of healthy liver cells with scar tissue; blocks blood flow through liver; decreased ability to remove toxins (through bile); susceptible to infection;

Describe the causes, consequences and diagnosis of phenylketonuria (PKU).

cause: a genetic variation/mutation; change in gene coding for tyrosine hydroxylase; consequences: results in a failure to metabolize phenylalanine into tyrosine; results in mental retardation/brain damage; diagnosis: can be made by a simple blood test for the level of phenylalanine shortly after birth

List three of the materials that are egested

cellulose / lignin / bile pigments/ bacteria / intestinal cells

Outline the reasons for cellulose not being digested in the alimentary canal

cellulose; cellulase not present Glucose can exist in one of two isomeric forms: a-glucose or ß-glucose (cellulose that's a component of plant cell walls) While humans can digest polymers of a-glucose (e.g. starch, glycogen), they cannot digest the polymer of ß-glucose (cellulose) This is because they do not produce the necessary enzyme (cellulase) and lack bacteria in their gut capable of digesting cellulose

Outline the variation in the structure of fatty acids.

cis or trans; saturated or unsaturated; monounsaturated or polyunsaturated; location of the double bond; can be short chain or long chain; Saturated fatty acids have no double bonds between carbon atoms In cis isomers, hydrogen atoms attached to the double-bonded carbon atoms are on the same side In trans isomers, hydrogen atoms attached to the double-bonded carbon atoms are on different sides Monounsaturated fatty acids have a single double bond between two carbon atoms Polyunsaturated fatty acids have multiple double bonds between carbon atoms

Outline factors that can lead to an individual becoming obese.

diet rich in carbohydrate or fat; too much food intake and food cheap and readily available; lack of exercise; genetic disorder; malfunction of hunger centre;

Explain the need for enzymes in digestion

enzymes increase the rate of digestion; enzymes break large molecules down into small/soluble molecules; for absorption/diffusion into blood;

Describe the process of erthocyte and hemoglobin breakdown in the liver

erythrocytes rupture when they reach the end of their life span / after 120 days; absorbed by phagocytosis / Kupffer cells in liver from blood; hemoglobin split into globin and heme groups; iron removed from heme leaving bile pigment / bilirubin; bilirubin released into alimentary canal; digestion of globin to produce amino acids;

Draw and label a diagram of the digestive system

esophagus — attached to both mouth and stomach; stomach — j-shaped sac attached to esophagus and u-shaped portion of small intestine; large intestine — wider diameter than small intestine, attached to small intestine; pancreas — leaf-shaped, in u-shaped region of small intestine with small duct connected to small intestine; liver — large, triangular, to left of stomach; gall bladder — small sac drawn on top of liver with tube connected to small intestine at same region as duct from pancreas; anus —at end of large intestine but narrower in diameter;

Explain the benefits of artificial supplementation of iodine in the diet.

iodine deficiency can lead to mental retardation; iodine is necessary for thryoxine production; dietary supplementation usually through iodized salt; cost to supplement is minimal but cost of deficiency is high; few foods rich in iodine;

BMI =

mass in kg/(height in m)^2

Explain the mechanisms used by the ileum to absorb food Simple Diffusion Facilitated Diffusion Active Transport Endocytosis

microvilli increase the surface of the plasma membrane exposed to the digested food; increased surface area allows for increased absorption of foods (by diffusion); lipids are absorbed by simple diffusion; hydrophilic food substances are absorbed by facilitated diffusion; channel proteins help hydrophilic food substances to pass though the hydrophobic core of plasma membrane; mitochondria produce the ATP required for active transport; pump proteins in the plasma membrane actively transport glucose; pinocytic vesicles are formed by endocytosis; membranes from these vesicles originate from plasma membrane; these vesicles contain channels for facilitated diffusion and pumps for active transport; digested foods can be absorbed from these vesicles into the cytoplasm;

Distinguish between minerals and vitamins in terms of their chemical nature.

minerals are usually elements whereas vitamins are compounds; minerals are inorganic while vitamins are organic;

Distinguish between the composition of human milk and artificial milk used for bottle-feeding babies

see chart

Plants store carbohydrate in the form of starch. Explain the reasons for starch being digestive by the human digestive system.

starch is a large molecule; large molecules/starch cannot be absorbed by the intestine; glucose produced by digestion of starch can be absorbed; glucose is a useful source of energy; starch is not used in humans; starch is not soluble/could not be transported by blood

Outline two roles of the liver

storage of nutrients; detoxification of poisons; breakdown of hemoglobin; production of bile pigments; synthesis of cholesterol;

Using these diagrams, outline three ways in which the structure of the small intestine is related to its function of absorbing food.

villus intestinal wall has many folds to increase surface area; surface of villus close to blood vessels so materials can easily diffuse; greater surface area related to greater rate of diffusion; villus wall consists of single layer of cells;

Describe how pancreatic cells directly affect blood glucose levels

α cells (of pancreas) produce glucagon; glucagon promotes release of glucose; glucagon secreted when blood glucose levels are low; β cells (of pancreas) produce insulin; insulin promotes glucose uptake/storage of glycogen by liver; insulin secreted when blood glucose levels are high;