Bio f4 chap 9 Flashcards
Importance of the digestion process for humans
- food consumed is in the form of large and complex molecules
- food needs to be broken down to a smaller and simpler form that can diffuse into the blood vessels and transported to body cells
Name the main cells in gastric glands and explain the functions of these cells
- chief cells - pepsinogen
- parietal cells - hydrochloric acid
- goblet cells - mucus
Explain the adaptations of the small intestine to increase the surface area for absorption of nutrients.
- long
- inner layer of the small intestine is highly folded and covered with villi
- increase surface area for nutrient absorption
- many microvilli found on the epithelial surface of the villi
Explain the functions of the liver in the assimilation of digested food.
i) carbohydrate metabolism
- glucose is oxidised to yield energy
- glucose are converted to glycogen and stored in the liver
ii) protein metabolism
- amino acids synthesise plasma proteins and enzymes
iii) storage of nutrients
- storing glycogen
- provides a place to store vitamins and mineral salts
iv) detoxification
- serves as a filter and detoxifies dangerous particles such as drugs, alcohol and other foreign substances
Explain the importance of water absorption and vitamins in the large intestine.
- absorption of water helps to form semi-solid faeces
- enables the body to retain water
absorption of vitamins maintains health
Why fibre is important in the defaecation process?
- facilitates the movement of faeces and prevents health conditions such as constipation, colon cancer, rectal cancer and haemorrhoids (痔疮)
- stimulate peristalsis, absorb and dispose off toxins, regulate glucose absorption especially in diabetic patients and increase the bacterial population in the large intestine
Predict the effect of modifying digestive organs such as gastric bypass on human health.
- gastric bypass involves the reduction of the stomach’s size using diverse operative methods
- short term effects: acid reflux, nausea and vomiting, dilated oesophagus, prohibition of certain types of foods, risk of infection and body weight gain or loss
- long term side effects: nausea and dizziness, low blood sugar, malnutrition, stomach ulcer and complications in bowel movement
Some people cannot drink milk because it causes diarrhoea and a bloated stomach. Explain why.
- the intestinal juice of the individual may possibly not contain or lacks lactase to digest milk sugar (lactose) in the small intestine
- the bacteria in the large intestine will digest the lactose to yield fatty acids and methane which causes diarrhoea and bloating
- the individual is advised to drink lactose-free milk
Amin had some meat dishes for lunch. Explain how the protein is digested in Amin’s stomach.
- the gastric glands in the stomach secrete gastric juice
- gastric juice contains hydrochloric acid and pepsin
- the medium in the stomach is acidic and optimum for enzyme action
- protein is hydrolysed into polypeptides by pepsin
Explain the processes that the fat molecules undergo starting from the duodenum until it is finally used by body cells.
- Lipid digestion begins in the duodenum.
- Bile salts produced by the liver emulsify fats into lipid droplets.
- Pancreas secretes pancreatic juice which contains lipase into the duodenum.
- Lipase hydrolyses lipid droplets to fatty acids and glycerol.
- Lipid + water Glycerol + fatty acids
- Absorption of fatty acids and glycerol occurs in the small intestine.
- In the epithelial cells of villi, the condensation of fatty acid and glycerol forms lipid.
- Lipid droplets are absorbed into the lacteals of villi.
- Lipid is transported from the lacteal by the lymphatic system into the thoracic duct and finally enters the blood flow through the left subclavian vein.
- Assimilation occurs in the cells.
- Cells use lipids to form the complex compounds of the plasma membrane.
Why diet rich in fats is not good for health?
- cause high blood pressure and lead to cardiovascular disease
- excess fat will be deposited in the arterial walls (Atherosclerosis) causing blocked arteries
- lumen of the artery becomes narrow
- difficult for blood to flow
- increase blood pressure (hypertension)
- if coronary artery narrows (heart), this may cause heart attack due to lack of oxygen supply to the cardiac muscles
Suggest suitable types of food for someone who wants to reduce weight and reduce the risk of contracting cardiovascular disease. Explain your answer.
- food with less carbohydrates and fats
- less carbohydrates will be converted to fats
- food with less fats and cholesterol
- less cholesterol will be deposited on the arterial walls blocking the arteries
- blood flow in the heart will also not be blocked
Explain the processes of starch digestion, absorption and assimilation in the human body.
- The hydrolysis of starch by salivary amylase produces maltose.
- Next, the hydrolysis of maltose by maltase produces glucose.
- The final product of starch is glucose.
- Glucose is absorbed through the ileum epithelial cells and then absorbed into the blood circulatory system through blood capillaries.
- Glucose is then transported by the hepatic portal vein to the liver.
- Assimilation occurs in the liver. Depending on the body’s needs, glucose in the liver is oxidised, excess glucose is converted into glycogen to be stored in the liver or changed to fats to be transported to other body parts for storage.
- From the liver, some of the glucose is carried in the blood circulatory system to the heart and then pumped to the whole body.
- In body cells, glucose is oxidised to yield energy, water and carbon dioxide.
- Energy is used for chemical processes in the cell, for example, muscle contraction and protein synthesis.
- Excess glucose is stored in the muscles.
Medicines in the form of capsules are not broken down in the stomach but absorbed easily by the small intestine. When the blood sample of the patient is taken and analysed, it is found that the molecular structure of this medicine is medicine is different from its original molecular structure. Explain why.
- the medicine may have been modified by the liver
- the medicine that is absorbed though the small intestine is transported by blood to the liver
- in the liver, any toxic components in the medicine is metabolised and converted into a less toxic form which is easily excreted though the kidney
- the original molecular structure of the medicine swallowed is different from the one found in the blood
How are drinks with added artificial sweeteners produced and marketed?
- artificial sweeteners such as saccharine, aspartame and sucralose provide sweet taste to the drinks, but contribute only a small caloric value
- sucralose is made from modified sucrose whereby the three hydroxyl groups of the sucrose are substituted by chlorine atoms
- sucralose stimulates taste buds (sweet) such as sucrose but it is not digested by enzymes
- sucralose does not give any caloric value to food
- sucralose is more stable compared to other artificial sweeteners
Nowadays, many individuals prefer ready-to-eat or frozen food products due to their busy lifestyles. Predict the health risks that may arise if these foods are taken continuously for a long period of time and in large quantities.
The ingredients in fast or frozen foods usually contain a lot of fats, salt, sugar and processed chemicals.
* Most of the fats found in fast or frozen foods are trans fats. Trans fats are fats that naturally exist in liquid form but have been modified to become solids. Trans fats make fast food last longer. However, trans fats can also increase the bad cholesterol (LDL) level and decrease the good cholesterol (HDL) level. This increases the risks of heart diseases and causes clogged arteries. Some fast foods contain red meat and cheese which naturally consists of saturated fats but can increase bad cholesterol.
* Salt is usually used as flavour enhancer and as a preservative. A serving of fast food contains more salt than what our body needs on a daily basis. This may increase cholesterol level, and blood pressure. The high salt content in the food is also associated with kidney diseases.
* Starch or complex sugar is used in fast food to enhance flavour and texture. The body will break down starch into sugars in the form of glucose during digestion. The excessive intake of sugar may cause serious health issues and is associated with increased risk of getting diabetes, heart diseases and obesity. Excessive sugar is also associated with depression.
* Chemicals are added to fast and frozen foods to make it last longer and tastier. On the other hand, the high chemical content can be toxic to the body. For example, monosodium glutamate (MSG) is associated with headaches, nausea, chest pain, lethargy and breathing difficulties.
* Sodium nitrates and artificial colourings that make fast foods appear fresh and attractive have been associated with various cancers. Some of the preservatives are actually carcinogenic (cause of cancer).
* Besides, substances that are used as volume enhancers such as cellulose and potassium bromate may disturb the nutrient-absorbing system in the body. This contributes to various problems of the digestive system.
