Chapter 2 - human diet and digestion Flashcards
- What is an example of carbohydrates
- What is a carbohydrate’s function
- Example - potatoes, pasta, rice
- Function - to release energy in respiration
- What is an example of a fat source
- What is its function
- What can high levels of saturated fat cause
- Sources - Plant oils, fatty meat
- Function - energy storage; making cell membranes
- High levels of saturated fat increase risk of coronary heart disease
- What is a souce of protein
- What is protein’s function
- Source - meat, fish, pulses, dairy
- Function - building cells, making enzymes, making haemoglobin
- What is a source of vitamin C
- What is its function
- What does a lack of vitamin C cause
- Source - citrus fruits
- Function - making collagen (an elastic protein found in skin and bones)
- A lack of vitamin C causes scurvy
- What is a source of vitamin D
- What is the function of vitamin D
- What can a lack of vitamin D cause
- Source - dairy products; formed in skin when sunlight falls
- Function - helps calcium to be absorbed, important for strong bones
What is a source of calcium
What is the function of calcium
- Source - dairy products
- Function - strong bones and teeth
- What is a source of iron
- What is the function of iron
- What does a lack of iron cause
- Source - red meat, dark green vegetables
- Function - making haemoglobin
- Lack of iron causes anaemia
What is a source of fibre
What is fibre’s function
What does a lack of fibre cause
- Source - fruit, vegetables, brown rice
- Function - helps muscles in the alimentry canal to work
- lack of fibre causes constipation
- What is a source of water
- What is the function of water
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- Source - drinks, most foods
- Function - acts as a solvent
What are the dietary needs of a person affected by
- Age - younger people need more protein for growth; older people need less energy as they’re inactive
- Gender - men need more energy intake than women
- Pregnancy and breast feeding - a woman needs plenty of protein, vitamins and minerals to upply her fetus or young baby
- Activity - a more active lifestyle requires more energy intake
- What does low protein intake result in
- What does the conditions entail
- A low protein intake results in kwashikor
- The person will have a very low body weight but may have a swollen abdomen
- What can a low energy intake result in
- What does this condition entail
- A low energy intake results in marasmus
- The person has a very low body weight and looks emaciated
What happens in the mouth in the alimentry canal
- Mechanical digestion by teeth takes place - chews up food in smaller bits for larger surface area
- Salivary glands contain the enzyme maltose to digest starch into glucose
- Ball of food is lubricated by the saliva
What occurs in the oesophagus during digestion
- The tube that connects the mouth to the stomach
- Contractions take place to push the food down relying on gravity
What happens in the stomach during the alimentry canal
- Food is mechanically ingested due to the churning actions
- Protease enzymes start to digest proteins
- Hydrochloric acid is produced to kill bacteria in the stomach and to provide the optimum Ph for protease enzymes to work
What occurs in the two sections of the small intestine
Section 1 - duodenum
- Food coming out of the stomach is finsihed being digested here; site of amylase, protease, lipase,
Section 2 - ileum
- Absorbtion of food molecules takes place here
What occurs at the large intenstine during the alimentry canal
- Water is absorbed in the colon to produce faeces
- Faeces is stored in the rectum
- Faeces is egested from the anus
What is the function of the pancreas
Produces enzymes: Amylase, protease and lipase
- Secretes enzymes into the duodenum in an alkaline solution
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What is the function of the liver
- Produces bile to emulsify fats - mechanical digestion
- Amino acids here are used to produce urea
What is the function of the gall bladder
- To secrete bile into the duodenum
What are the four types of human teeth
- Incisors
- Canines
- Premolars and molars
What are incisors
- Teeth at the front of the mouth
- Chisel-shaped and bite off food
What are canines
- Just behind the incisors
- They are more pointed and are used to bite and hold food
What are premolars and molars
- At the sides and back of the mouth
- They have broad, ridged surfaces that grind food into smaller pieces
What is dental decay
- Where acid dissolves the enamel and dentine
- Caused by leaving sugary layers on or between teeth
- Bacteria on the teeth break down by respiration to form acid
How can dental decay be avoided
By eating too many sugary foods
Brushing teeth regularily to remove food remains
What is the definition of ingestion
Taking substances into the body through the mouth
What is the definition of mechanical digestion
Breakdown of food into smaller pieces without chemical changes to the food molecules
What is the definition of chemical digestion
Breakdown of large, insoluble molecules into small, soluble molecules
What is the definition of absorbtion
Movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
What is the definition of assimilation
Movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
What is the definition of egestion
Passing out of food has not been digested or absorbed, as faeces, through the anus
What does amylase do
Breaks down starch to simple sugars
What does protease do
Breaks down proteins into amino acids
What does lipase do
It breaks down fats into fatty acids and glycerol
In carbohydrate digestion, what do amylase and maltase break down starch and maltose into
- Starch—amylase—> disaccharide maltose
- Maltose—maltase—> monosaccharide glucose
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What are the two cases where amylase is secreted
- From the salivary glands -
- From the pancreas in pancreatic juice
Where is maltase secreted from
Epithelial cells covering the villi in the small intestine
What are the two protease molecules secreted in protein digestion
- Pepsin - secreted in the stomach, has a low optimum Ph provided by the secretion of HCL
- Trypsin - secreted by the pancreas into the pancreatic juice; works in the small intestine
What does bile contain, what do these things do?
- Sodium hydrogencarbonate - a base which neutralises acidic mixture of food and gastric juice entering the duodenum from the stomach
- Bile salts - break large globules of water-insoluble fats into smaller droplets; these mix with watery fluids in the small intestine to produce an emulsion. This increases the surface area of fat droplets. which aloows lipase to work quicker
Why does the small intestine have villi
To increase the rate at which absorbtion can take place
What is a villi in the small intestine made up of
- Epithelium - a layer of cells that covers the villus, secretes enzymes, including maltase, which completes the chemical digestion of nutrient molecules
- Blood capillary - absorbs amino acids, glucose, vitamins and minerals ; transports these along the liver by the heptic portal vein
- Lacteal - absorbs digested fats
What is cholera
- A disease caused by bacterium which causes the loss of watery faeces
- It produces a toxin that causes the cells covering the villi to secrete chloride ions into the small intestine
In cholera, what do the chloride ions secreted into the small intestine do
- It decreases the water potential inside the small intestine; so water moves out of the cells by osmosis, down a water potential gradient
- This causes the patient to suffer from diarrhoea
Why is cholera dangerous
- The patient loses salts from the blood
- The patient loses a lot of water and becomes severely dehydrated
