2 - The Digestive System Flashcards
What is hydrolysis?
Breakdown of sucrose, starch, protein, fat etc., using water and specific digestive enzymes
What are the products of hydrolysis of disaccharides e.g., sucrose, lactose, maltose?
Monosaccharides (glucose + fructose/galactose/glucose)
What are the products of hydrolysis of polysaccharides e.g. starch, fiber?
Many monosaccharides
But fiber is not digestable in humans
What are the products of hydrolysis of proteins?
Amino acids + small peptides
What are the products of hydrolysis of fats e.g. triglycerides?
Mono-glyceride + 2 Fatty acid
or
Glycerol + 3 Fatty acid
How does digestion and absorption of macro-nutrients happen in the mouth?
Mechanical crushing
Starch (broken down by amylase)
(Some fats broken down by lipase)
No absorption
How does digestion and absorption of macro-nutrients happen in the stomach?
pH 2 gastric juice (activate pepsin, denature food proteins, destroy bacteria)
Protein (broken down by pepsin)
Glucose, amino acids, water and alcohol absorbed
How does digestion and absorption of macro-nutrients happen in the small intestine?
Carbohydrates (digested by pancreatic amylase and intestinal enzymes)
Fat (emulsification by bile, digestion by pancreatic and intestinal lipase)
Protein (break down by trypsin)
Carbohydrates, fat, protein, water, and alcohol absorbed
How does digestion and absorption of macro-nutrients happen in the large intestine?
Fiber (partly broken down by intestinal bacteria)
Water absorbed
Fat and undigested protein carried out as waste
Where are carbohydrates digested?
Mouth
Small intestine
Where are proteins digested?
Stomach
Small intestine
Where are fats digested?
Small intestine
Where are carbohydrates absorbed?
Stomach (glucose)
Small intestine
Where are proteins absorbed?
Stomach (amino acids)
Small intestine
Where are fats absorbed?
Small intestine
Where is water absorbed?
Stomach
Small intestine
Large intestine
Where is alcohol absorbed?
Stomach
Small intestine
Is optimal absorption of micro-nutrients dependent on the chemical found it is found in food?
Yes. Iron from meat is better absorbed than iron from vegetables.
What are some functions of water?
Maintain normal internal temperature
Medium for chemical reactions, transport of nutrients, enzyme action
Elimination of waste products (urine and stools)
Participates in energy formation
Why do we need to replenish water?
To replace water lost in urine, perspiration, stools and exhaled air (maintain homeostasis e.g., pH fluctuations)
Water needs are affected by: Activity Weather Illness Specific diets Specific foods
What is the adequate intake of water?
Women - 11 cups/day
Men - 15 cups/day
What can result from water deficiency?
Symptoms: Nausea Rapid heartbeat Increased body temperature Dizziness Difficulty moving
Unresolved dehydration can lead to kidney failure or death
Ingestion of fluids generally produces quick recovery
What can result from water toxicity?
Symptoms: Confusion Headache Vomiting Seizure Coma Death
Excess water intake can lead to low blood sodium
Drinking too much water too quickly e.g., marathon runners
How many calories are there in alcohol?
7 Calories/gram
Alcohol is an energy dense, empty calorie food
What are some of the ‘special privileges’ of alcohol in the body?
No digestion needed
Quick absorption in stomach and small intestine
In small intestine, alcohol absorption gets priority over other nutrients
Circulated to body tissues quickly and easily in the blood
HOW is alcohol absorbed?
Broken down in the liver (broken down by alcohol dehydrogenase into acetaldehyde, which is broken down by acetaldehyde dehydrogenase into acetic acid/acetate)
It is absorbed more slowly with food, decreasing effects of alcohol and blood alcohol concentrations.
What are the positives of consuming alcohol?
Moderate (men 2 drinks/day, women 1 drink/day) alcohol consumption has positive associations on health (heart disease, type 2 diabetes, hypertension, stroke, dementia).
Phytochemicals (especially red wine) act as antioxidants (heart protective, lowers inflammation)
What are the negatives of consuming alcohol?
Heavy drinking - 5 or more drinks/day
Increased risk of high blood pressure, stroke, dementia, some cancers, nervous system disorders
Likely to have nutrient deficiencies
Alcohol dependency
Alcohol poisoning (mental confusion, vomiting, seizures, slow or irregular breathing, low body temperature)
Liver damage (steatohepatitis, i.e., fatty liver, may progress to cirrhosis)
What are some other effects of alcohol? (not classified under positive or negative effects)
Intoxication (legal limit is 0.08%, body impaired at 0.13%, possible death at 0.35%)
Dehydration (increased urine output)
Hangover (dehydration and by-products of alcoholic fermentation)
