TEST - Nutrition, Digestion, Absorption & Homeostasis

Question 1

Distinguish between essential and non-essential nutrients.

Answer 1

Essential - CANNOT be synthesized by the body(must be consumed through the diet).
Non-Essential - CAN be synthesized by the body.

Question 2

Outline the causes and treatments of PKU.

Answer 2

Cause - genetic, lack of enzyme that breaks phenylalanine into tyrosine, causes buildup of phenylalanine
Treatment for PKU - low protein diet, limit intake of protein sources that contain phenylalanine; supplemented with formula containing essential aa’s/ tyrosine

Question 3

Outline WHY food needs to be digested.

Answer 3

Food macromolecules need to be hydrolyzed into smaller molecules in order to be absorbed.

Question 4

Pepsin / endopeptidase

Answer 4

• Hydrolyzes protein into amino acids
• Pepsin secreted by the gastric glands in the stomach (acidic pH)
• Endopeptidase secreted by pancreas into the lumen of the small intestine (neutral pH)

Question 5

Amylase

Answer 5

• Hydrolyzes carbs (starch) into maltose
• Salivary produced in salivary glands and acts in mouth (neutral pH)
• Pancreatic produced in pancreas and acts in lumen of small intestine (neutral pH)

Question 6

Lipase

Answer 6

• Hydrolyzes lipids into di- / mono-glycerides / fatty acids / glycerol
• Produced by pancreas and acts in the lumen of the small intestine (neutral pH)

Question 7

Nuclease

Answer 7

• Hydrolyzes nucleotides (nucleic acids) into nucleosides
• Produced by pancreas and acts in the lumen of the small intestine (neutral pH)

Question 8

If IB simply states “digestion” in a question without stating which type they mean, what do they mean?

Answer 8

“Chemical Digestion”

Question 9

Outline the roles of hydrochloric acid in the stomach.

Answer 9

• Lowers the pH, which initially denatures proteins
• Activates pepsinogen into pepsin
• Kill pathogenic bacteria and fungi in ingested foods

Question 10

Outline the roles of proton pumps in the stomach.

Answer 10

• Maintain acidic conditions (low pH) by actively pumping protons into the stomach
• Cl combines to form HCL

Question 11

Outline the roles of PPI’s in the reduction of stomach acid/ ulcers.

Answer 11

• Proton pumps maintain acidity
• PPI’s bind irreversibly to proton pumps
• Lowers the amount of acid produced

Question 12

Outline the hormonal and nervous mechanisms that control the secretion, content, and volume of gastric juice.

Answer 12

• Sight/smell of food triggers medulla to send signal to stomach to secrete gastric juice via vagus nerve
• Impulses from stretch receptors send signals to medulla via vagus nerve which sends signals to stomach to trigger production of gastrin
• Gastrin causes sustained release of gastric juices (HCL)

Question 13

Which cells in the gastric pits secrete which components of gastric juice?

Answer 13

• HCl secreted by parietal cells
• Pepsinogen secreted by chief cells

Question 14

Where does chemical digestion and most absorption happen?

Answer 14

Small intestine

Question 15

Where does protein digestion begin?

Answer 15

Stomach

Question 16

What enzymes does the pancreas secrete?

Answer 16

Amylase, Lipase, Endopeptidase(Protease), Nuclease

Question 17

Function of the villi.

Answer 17

Maximum absorption of nutrients by increasing surface area.

Question 18

Explain how the structure of a villus is adapted to its function.

Answer 18

Epithelial cells - surround each villus (decreases diffusion distance of nutrients into bloodstream)
Rich Capillary Network - large concentration gradient (between blood and fluid in small intestine) allows for rapid absorption of nutrients
Lacteals - Absorb lipids (into lymphatic system – transports fats, drains tissues of excess fluids)
Intestinal crypts - release juices that act as ‘carrier fluids’ for nutrients

Question 19

List and explain the different forms of transport used by the small intestine to absorb different nutrients.

Answer 19

Diffusion - fatty acids absorbed through conc. gradient
Facilitated Diffusion - fructose pumped through protein channels in the epithelial cell membrane
Active transport (uses ATP) - glucose/amino acids pumped through protein channels against conc. gradient
Endocytosis - cholesterol in lipoprotein particles transported by means of vesicles.

Question 20

Outline the role of the large intestine.

Answer 20

• Absorbs water / minerals / vitamins / ions
• Peristalsis (contraction of muscles) to move food undigested food
• Secretes mucous (lubrication)

Question 21

Explain why cellulose and lignin are not digested in humans.

Answer 21

Humans do not possess the enzymes needed to break them down.

Question 22

Outline the roles of fiber in the diet.

Answer 22

• More fiber = faster rate of material movement through the intestine
• Decreases hunger (prevents obesity)
• Absorbs water to keep faces soft to pass (reduces constipation)
• “Works out” microflora

Question 23

State the other substances that are egested (excreted) by the body.

Answer 23

BELCH
- Bile pigments
- Epithelial Cells
- Lignin
- Cellulose
- Human Microflora / bacteria

Question 24

Outline how the cholera toxin can cause dehydration.

Answer 24

• Vibrio cholerae produces toxin
• Toxin causes ions to be pumped into small intestine
• Water follows gradient by osmosis, diluting faces (diarrhea) causing dehydration because water is being constantly removed from body

Question 25

Outline the cause, consequences, and treatments for stomach ulcers.

Answer 25

Cause - Helicobacter pylori infection, increases pH to neutralize stomach acid that kills it (urease), degrades mucous lining (mucinase) Consequences - Inflammation, digestion of stomach lining by pepsin & HCL, pain Treatments - Proton pump inhibitors reduce stomach acid production (bind irreversibly to proton pumps), lower acidity (high pH) helps ulcers to heal, antibiotics

Question 26

Outline the dual supply of blood to the liver and reasons why it is necessary.

Answer 26

- Dual blood supply is blood entering liver form Haptic Artery and Hepatic Portal Vein. - Hepatic Portal Vein delivers nutrient-rich blood from the gut to liver - Hepatic Artery delivers oxygen-rich blood from the heart to liver

Question 27

Outline the circulation of blood through the sinusoids of the liver.

Answer 27

- Blood enters thru the hepatic artery and hepatic portal vein and flows into sinusoids - Sinusoids surrounded by single layer of hepatocytes - Sinusoids remove excess nutrients to be stored in the liver, toxins, and add stored nutrients to the blood when needed (filter, detoxify, balance) - Prevents osmotic imbalance in blood - Clean & balanced blood exits liver thru HPV back into the heart

Question 28

Outline the structure and function of liver sinusoids.

Answer 28

- Sinusoids remove excess nutrients to be stored in the liver, toxins, and add nutrients (stored in the liver) to the blood when needed. - Each sinusoid is lined with a single layer of hepatocytes, which detoxify, & store vitamins, minerals and molecules so they are available at ALL times. (carb and protein metabolism) - Contains Kupffer cells which engulf bacteria and break down old / damaged red blood cells (erythrocytes)

Question 29

Outline the role of the liver in the regulation of nutrient levels in the blood.

Answer 29

- Liver stores glucose as glycogen (under influence of insulin/ glucagon (depending on blood glucose lvls): carbohydrate metabolism) - Kupffer cells in liver break down hemoglobin into heme and globin - Iron (from heme) is carried to bone marrow to produce new hemoglobin for new red blood cells - Some excess nutrients (Vitamins A/D, Iron) stored in liver - Liver detoxifies blood - Excess cholesterol covered into bile salts for bile which is secreted by liver (lipid metabolism)

Question 30

Explain how erythrocytes (red blood cells) are broken down and the recycling of their components by the liver.

Answer 30

- Erythrocytes rupture after 120 days - Kupffer cells ingest erythrocytes in sinusoids of liver - Hemoglobin split into heme and globin groups - Heme broken down into iron group - Globin provides amino acids - Iron stored and transferred to bone marrow - Bilirubin becomes part of bile

Question 31

Outline the roles/ functions of hepatocytes in the sinusoids of the liver.

Answer 31

- Excess glucose is stored as glycogen in hepatocytes - Hepatocytes break down globin into amino acids - Hepatocytes stores essential vitamins, minerals and molecules so they are available to the body at ALL times (to maintain homeostasis) - Hepatocytes synthesize and regulate cholesterol (for bile salt production)

Question 32

Outline the production of bile by the liver.

Answer 32

- Bile is made of bile salts and bilirubin(bile pigment) - Hepatocytes convert heme into bilirubin - Bilirubin transferred to bile and normally excreted

Question 33

Outline the causes and consequences of jaundice.

Answer 33

Cause - blockage of bile ducts / disease in liver Consequence - Bilirubin accumulates in blood, yellowing skin,

Question 34

Explain how the pancreas is able to act as an endocrine gland to regulate blood glucose levels.

Answer 34

- Pancreas produces hormones that control levels of glucose - Beta cells produce insulin when blood-glucose is high - Alpha cells produce glucagon when blood-glucose is low - Insulin causes calls to take up glucose (increases muscle mass) - Glucagon causes liver to break down glycogen into glucose (increases glucose lvls in blood / decrease muscle mass) - Negative feedback control -

Question 35

Explain the causes, symptoms, and treatments of type I diabetes.

Answer 35

- Early onset Cause: Beta cells damaged/ destroyed by body’s own immune system: autoimmune disease (not enough insulin produced) Symptoms: High blood glucose levels, glucose in urine, increased thirst, fatigue. Treatments: Insulin injections which regulate blood-glucose levels

Question 36

Explain the causes, symptoms, and treatments of type II diabetes.

Answer 36

Adult onset Cause: Insulin receptors on cells less sensitive to insulin, poor diet, obesity, genetics Symptoms: High blood glucose levels, glucose in urine, thirst, fatigue Treatments: High fiber foods satisfy appetite but aren't broken down / small meals to avoid rapid rise in glucose / complex carbs w low glycemic index digested & absorbed slower

Question 37

Outline the role of leptin in the body.

Answer 37

- Leptin secreted by adipose tissue - Acts on cells in the hypothalamus (appetite control center) to inhibit appetite - More adipose tissue = more leptin (means reduced appetite/eating) - Obese people can develop resistance to leptin