7. Human Nutrition Flashcards
What is a balanced diet?
A balanced diet consists of all of the food groups in the correct proportions
What are the necessary food groups?
Carbohydrates Proteins Lipids Vitamins Minerals Dietary Fibre Water
What is the function of carbohydrates?
Source of energy
What is the function of proteins?
growth and repair
What is the function of lipids?
insulation and energy storage
What is the function of dietary fibre?
provides bulk (roughage) for the intestine to push food through it
What is the function of vitamins and minerals?
needed in small quantities to maintain health
What is the function of water?
needed for chemical reactions to take place in cells
What are sources of carbohydrates?
bread, cereals, pasta, rice, potatoes
What are sources of proteins?
meat, fish, eggs, pulses, nuts
What are sources of lipids?
butter, oil, nuts
What are sources of dietary fibre?
vegetables, whole grains
What are sources of vitamins?
fruits and vegetables
What are sources of minerals?
fruits and vegetables, meats, dairy products
What are sources of water?
water, juice, milk, fruits and vegetables
What 4 specific vitamins and minerals do we need?
vitamin c
vitamin d
calcium
iron
What is the function of vitamin c?
- forms and essential part of collagen protein which makes up skin, hair, gums and bones
- deficiency causes scurvy
What is the function of vitamin d?
- helps the body to absorb calcium and so required for strong bones and teeth
What is the function of calcium?
- needed for strong teeth and bone and involved in the clotting of blood
- deficiency can lead to rickets or osteoporosis later in life
What is the function of iron?
- needed to make haemoglobin, the pigment in red blood cells that transports oxygen
- deficiency leads to anaemia
What are sources of vitamin c?
citrus fruit (oranges, lemons)
strawberries
green vegetables
What are sources of vitamin d?
oily fish, eggs, liver, dairy products, also made naturally by the body in sunlight
What are sources of calcium?
milk, cheese, eggs
What are sources of iron?
red meat, liver, leafy green vegetables like spinach
What could be the cause of a vitamin d deficiency?
-lack of sunlight, fish, eggs, butter in diet
What could be the cause of an iron deficiency?
lack of leafy green vegetables, red meat, liver
What does a vitamin d deficiency lead to?
causes RICKETS
- where bones become soft and deformed (this is because vitamin D is needed for absorption of calcium into the body which is a key component of bones and teeth)
What does an iron deficiency lead to?
causes ANAEMIA
- where there are not enough red blood cells so tissues do not get enough oxygen delivered to them (this is because iron is a key component of haemoglobin)
What is malnutrition caused by?
Malnutrition is caused by not eating a balanced diet
What does the type of malnutrition depend on?
There are different types of malnutrition depending on the cause of the imbalance
What 4 types of malnutrition are there?
Starvation
Coronary heart disease
Constipation
Obesity
What is the cause of starvation?
taking in less energy than is used (over a long period)
What is the cause of coronary heart disease?
diet too high in saturated fat and cholesterol
What is the cause of constipation?
lack of fibre in the diet
What is the cause of obesity?
taking in more energy than is used
What is the effect of starvation?
body starts to break down energy stores
- first fat and then muscle tissue leading to severe weight loss and eventually damage to heart and immune system, increasing the risk of many diseases
What is the effect of coronary heart disease?
fat deposits build up in arteries supplying the heart, reducing flow of blood to the heart muscle cells which do not work properly due to the lack of oxygen. Can lead to heart attacks and death
What is the effect of constipation?
Food lacks bulk for muscles to push it through the alimentary canal and so risk of diseases such as bowel cancer are increased
What is the effect of obesity?
extra energy stored as fat, weight increases and contributes to development of many diseases such as heart disease and diabetes
What can lead to mass malnutrition in certain countries?
In many countries in the world, droughts, natural disasters, wars and a poor economy can lead to mass malnutrition in large areas of the country
What are the two type of most common malnutrition termed in (mainly) LEDC’s?
Protein energy malnutrition (PEM)
What are two types of PEM?
Kwashiorkor and Marasmus
What is kwashiorkor caused by?
caused by a lack of protein in the diet
In whom is kwashiorkor most common?
most common in children under 2
Why is kwashiorkor common is places of poverty?
Often caused by poverty as high protein foods tend to be more expensive and scarcer
What are signs that a child has kwashiorkor?
Children suffering from kwashiorkor are always underweight for their age but they often have a swollen abdomen as their diet may contain a lot of carbohydrate
What causes marasmus?
a lack of both protein and energy in the diet
What are signs that a person has marasmus?
People suffering from this have a much lower body weight than normal and look emaciated
What 4 factors affect dietary needs?
age
activity levels
pregnancy
breastfeeding
How does age affect dietary needs?
The amount of energy that young people need increases towards adulthood as this energy is needed for growth.
Children need a higher proportion of protein in their diet than adults as this is required for growth.
Energy needs of adults decrease as they age
How do activity levels affect dietary needs?
The more active, the more energy required for movement as muscles are contracting more and respiring faster
How does pregnancy affect dietary needs?
- During pregnancy, energy requirements increase as energy is needed to support the growth of the developing foetus, as well as the larger mass that the mother needs to carry around
- extra calcium and iron are also needed in the diet to help build the bones, teeth and blood of the foetus
How does breastfeeding affect dietary needs?
energy requirements increase and extra calcium still needed to make high quality breast milk
What 6 stages does the food go through in the alimentary canal?
Ingestion Mechanical digestion Chemical digestion Absorption Assimilation Egestion
Ingestion definition
the taking of substances, e.g. food and drink, into the body through the mouth
Mechanical digestion definition
the breakdown of food into smaller pieces without chemical change to the food molecules
Chemical digestion definition
the breakdown of large, insoluble molecules into small, soluble molecules
Absorption definition
Absorption is the movement of digested food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol)
Assimilation definition
the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
Egestion definition
the passing out of food that has not been digested or absorbed, as faeces, through the anus
Function of mouth
the mouth is where mechanical digestion takes place - teeth chew food to break it into smaller pieces and increase it’s surface area to volume ratio
Function of salivary glands
amylase enzymes in saliva start digesting starch into maltose the food is shaped into a bolus (ball) by the tongue and lubricated in saliva so it can be swallowed easily
Function of the oesophagus
tube that connects the mouth to the stomach where the food bolus goes after being swallowed wave - like contractions (peristalsis) will take place to push the food bolus down without relying on gravity
Function of stomach
food is mechanically digested by churning actions while protease enzymes start to chemically digest proteins
What is present in the stomach and what does it help?
hydrochloric acid is present to kill bacteria in food and provide the optimum ph for protease enzymes to work
What is the first section of the small intestine called and what is its function?
first section is called the duodenum and is where the food coming out of the stomach finishes being digested by enzymes produced here and also secreted from the pancreas
What is the pH of the small intestine
ph of the small intestine is slightly alkaline - around ph 8 - 9
What is the second section of the small intestine called and what is its function?
second section is called the ileum and is where absorption of digested food molecules takes place
What are some of the adaptations of the ileum?
the ileum and is where absorption of digested food molecules takes place surface area over which absorption can take place
What is the function of the large intestine?
water is absorbed from remaining material in the colon to produce faeces faeces is stored in the rectum and removed through the anus
What is the function of the pancreas?
produces all three types of digestive enzyme: amylase, protease and lipase secretes enzymes in an alkaline fluid into the duodenum for digestion to raise ph of fluid coming out of the stomach
What is the function of the liver?
produces bile to emulsify fats (break large droplets into smaller droplets) - an example of mechanical digestion amino acids not used to make proteins broken down here (deamination) which produces urea
What is the function of the gall bladder?
stores bile to release into duodenum as required
What is diarrhoea?
Diarrhoea is the loss of watery faeces from the anus
What can severe diarrhoea lead to?
If it is severe and continues for a long time, it can lead to death
Severe diarrhoea can cause the loss of significant amounts of water and ions from the body, causing the tissues and organs to stop working properly
How can diarrhoea be effectively treated?
It can be effectively treated by oral rehydration therapy
This is a drink with a small amount of salt and sugar dissolved in it
What is one cause of diarrhoea?
There are many causes of diarrhoea, one of which is infection with Vibrio cholera bacteria, which causes the disease cholera
How does cholera lead to diarrhoea?
Ingested via infected water or food, if it enters the small intestine it can cause illness
What does C bacteria attach to?
What do they release?
Bacteria attach to the wall of the small intestine
They produce a toxin
What does the toxin produced by C do?
The toxin stimulates the cells lining the intestine to release chloride ions from inside the cells into the lumen of the intestine
Why is the accumulation of chloride ions harmful?
- The chloride ions accumulate in the lumen of the small intestine and lower the water potential there
- Once the water potential is lower than that of the cells lining the intestine, water starts to move out of the cells into the intestine (by osmosis)
How are large quantities of water lost during diarrhoea?
Large quantities of water are lost from the body in watery faeces
How does C affect the blood?
The blood contains too little chloride ions and water
What are the main examples of mechanical digestion? (3)
It is mainly carried out by the chewing action of the teeth, the churning action of the stomach and the emulsification of fats by bile in the duodenum
Where are teeth held?
Teeth are held firmly in the bone of the jaw
What are teeth used for?
used for chewing to increase the surface area of the food so that it can be exposed to saliva and other digestive juices and broken down more quickly
What do the different sizes of teeth allow them to do?
The differing shapes and sizes of teeth enable them to perform slightly different functions
What are the 4 main types of teeth?
- incisors
- canines
- premolars
- molars
Function of incisors
chisel-shaped for biting and cutting
Function of canines
pointed for tearing, holding and biting
Function of premolars and molars
larger, flat surfaces with ridges at the edges for chewing and grinding up food
What kind of problems can bacteria cause to teeth?
Tooth decay and gum disease are both caused by bacteria
When do bacteria in the mouth become a problem?
Many bacteria live in the mouth and most are harmless, however some form a sticky film with saliva, called plaque, which coats teeth and the areas where they attach to gums
When does plaque become a problem?
To begin with, plaque is soft and easy to remove, however if it hardens and forms tartar, it cannot be removed by brushing
What can the accumulation of tartar cause?
Tartar around the edges of teeth and gums can allow bacteria to work their way into roots, causing gum disease and loss of teeth
What can feed the bacteria in the mouth?
If sugar is left in the mouth after eating, bacteria in plaque will feed on it
What do bacteria in the mouth use sugar for?
They use it in respiration and turn it into acids
Why is the acid produced by bacteria in the mouth harmful?
The acids gradually dissolve the enamel coating of the teeth, working its way into the dentine
Why is it a problem when the acid (produced by bacteria in the mouth) reaches dentine?
Dentine is softer than enamel and so dissolves more easily and quickly
What is called when the acid reaches dentine and what does this lead to?
This is tooth decay and if not dealt with, can cause painful infections and loss of teeth
What can prevent tooth decay?
Reducing the amount of sugar eaten can prevent tooth decay
How is brushing teeth regularly helpful?
Brushing teeth regularly removes the buildup of plaque that can cause gum disease and removes the sugars in the mouth so bacteria cannot turn them into acids and cause tooth decay
What specific type of toothpaste should be used and how is it beneficial?
Teeth should be brushed with a fluoride toothpaste as this helps to strengthen enamel and reduce damage from acids
What is also useful in maintaining healthy teeth and preventing the development of tooth decay etc?
Regular visits to a dentist ensures that any signs of gum disease or tooth decay can be dealt with promptly
What is the purpose of digestion?
The purpose of digestion is to break down large, insoluble molecules (carbohydrates, proteins and lipids) into small, soluble molecules that can be absorbed into the bloodstream
Why is food partially digested mechanically?
Food is partially digested mechanically (by chewing, churning and emulsification) in order to break large pieces of food into smaller pieces of food which increases the surface area for enzymes to work on
In what way does digestion take place mainly? How does this work?
Digestion mainly takes place chemically, where bonds holding the large molecules together are broken to make smaller and smaller molecules
What is chemical digestion controlled by?
Chemical digestion is controlled by enzymes which are produced in different areas of the digestive system
What are the main types of digestive enzymes?
carbohydrases, proteases and lipases
Where is amylase produced?
Amylases are produced in the mouth (salivary gland) and the pancreas
Where are amylases secreted into
The mouth and the duodenum
What does amylase digest?
digests starch to maltose (a disaccharide)
What is maltose digested by? What is it converted to?
Maltose is digested by the enzyme maltase into glucose
Where is maltose digested?
on the membranes of the epithelium lining the small intestine
What are proteases?
Proteases are a group of enzymes that break down proteins into amino acids in the stomach and small intestine
Where does protein digestion take place?
Protein digestion takes place in the stomach and duodenum
What are the two types of proteases?
Pepsin and trypsin
Where is pepsin produced?
in the stomach
Where is trypsin produced and where is it secreted into?
Trypsin is produced in the pancreas and secreted into the duodenum
Where are lipase enzymes produced and where are they secreted into?
Lipase enzymes are produced in the pancreas and secreted into the duodenum
What do lipases digest?
They digest lipids into fatty acids and glycerol
What is the gastric juice?
The stomach produces several fluids which together are known as gastric juice
How does HCl in the stomach kill bacteria?
The low pH kills bacteria in food that we have ingested as it denatures the enzymes in their cells, meaning they cannot carry out any cell reactions to maintain life
What is pepsin’s optimum ph?
around pH 2
What does the HCl ensure in relation to pepsin?
The hydrochloric acid produced in the stomach ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate
What are the 2 main roles of bile?
- It is alkaline to neutralise the hydrochloric acid which comes from the stomach
- It breaks down large drops of fat into smaller ones. This is known as emulsification.
What is the difference between the enzymes in the stomach and in the small intestine?
The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach
How is emulsification beneficial?
The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster
Is emulsification a chemical or physical process?
This is an example of MECHANICAL DIGESTION, not chemical digestion – breaking something into smaller pieces does not break bonds or change the chemical structure of the molecules which make it up, which is the definition of chemical digestion.
Where is water absorbed?
Water is absorbed in both the small intestine and the colon, but most absorption of water also happens in the small intestine
Where does absorption take place?
Absorption takes place in the second section of the small intestine, the ileum
What adaptations does the ileum have?
The ileum is adapted for absorption as it is very long and has a highly folded surface with millions of villi (tiny, finger like projections)
How do the ileum’s adaptations help with absorption?
These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently
What are (briefly) the 4 adaptations that a villus has?
- have microvilli
- thin wall of villus
- connected to a network of blood capillaries
- has a lacteal
How do microvilli help the villus with its function?
Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
How does the wall being thin help the villus with its function?
Wall of villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport
How does the villus being connected to a network of blood vessels help the villus with its function?
Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
(creates a conc. gradient)
How does a lacteal help the villus with its function?
Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph
