Human nutrition Flashcards
What is a balanced diet?
A balanced diet has the correct amount of each group of nutrients (carbohydrates, fats, proteins, vitamins, minerals, dietary fibre and water). We need a balanced diet to stay healthy.
What are the 7 main food groups?
Carbohydrates
Protein
Fats
Dietary fibre
Vitamins (C and D)
Minerals (Iron and calcium)
Water
Function and sources of carbohydrates
Function: Source of energy, nutrient for producing energy
Sources: Bread, cereals, pasta, rice, potatoes
Function and sources of protein
Function: Growth (getting bigger by growing new cells), repair (replacing damaged or worn out cells)
Sources: Meat, fish, eggs, beans, nuts
Function and sources of lipids
Function: Insulation and energy storage, making cell membranes of cells
Sources: Butter, oil, cheese, margarine
Function and sources of dietary fibre
Function: Ensures food moves through intestines at the correct rate
Sources: Vegetables, whole grains
Function and sources of vitamins
Function: Needed in small quantities to maintain health
Sources: Fruit and vegetables
Function and sources of vitamin C
Function: Used in creating connective tissue, blood vessels, bones and cartilage. It’s required for wound healing.
Sources: Citrus fruits (lemon, lime, orange), strawberries, kiwifruit
What is the deficiency of vitamin C?
Scurvy (wounds over the skin that isn’t healed)
Function and sources of vitamin D
Function: Helps the body to absorb calcium. Needed to maintain strong, healthy bones and teeth
Sources: Main source is sunlight but can also be gained from fatty fish, egg yolks and dairy products
What is the deficiency of vitamin D?
Rickets (bowed legs)
Function and sources of minerals
Function: Needed in small quantities to maintain health
Sources: Fruits and vegetables, meats, dairy products
Function and sources of calcium
Function: Needed for strong bones and teeth and maintaining blood clotting
Sources: Milk, cheese, eggs, fish with bones
Function and sources of iron
Function: Required for making haemoglobin in red blood cells which is used to bind oxygen
Sources: Red meat, whole grains, leafy green vegetables
Function and sources of water
Function: Acts as a solvent for cellular reactions, circulatory system and digestion system, helps to maintain body temperature
Sources: Water, juice, milk, fruits and vegetables
What are the main organs in the digestive system
mouth, salivary glands, oesophagus,
stomach, small intestine (duodenum and ileum), large intestine (colon, rectum,
anus), pancreas,
liver and gall bladder
What is the function of the mouth?
The mouth is where mechanical digestion takes place. The teeth grind the food into small pieces to increase its surface area to volume ratio. The salivary glands release saliva in the mouth. The saliva contains amylase enzymes which break down starch into maltose. Another enzyme maltase breaks down maltose to glucose. At the back of the mouth, the food is made into a ball called bolus by the tongue and lubricated in saliva so it can be swallowed easily.
What is the function of the oesophagus?
The tube that connects the mouth to the stomach. The bolus goes here after being swallowed and is pushed down the oesophagus by wave-like muscle contractions called peristalsis.
What is the function of the stomach?
The main organ where food is digested as it does both mechanical and chemical digestion. Food is mechanically digested by muscles that churn the food. Protease enzymes start to chemically digest proteins and hydrochloric acid is added to kill bacteria in food and provide the optimum pH for the enzymes to work.
What is the function of the small intestine?
Where nutrients are absorbed. The first section is the duodenum where food goes when it goes out of the stomach. This is where bile and digestive enzymes are added to further digest the food. At this point the pH of the small intestine is slightly alkaline at 8-9 because bile is basic. The second section is called the ileum and it’s where the absorption of digested food molecules takes place. The ileum is long and lined with villi to increase the surface area over which absorption takes place.
What is the function of the large intestine?
Mainly indigestible food and water enter the large intestine. Here water is absorbed back into the body to produce faeces. Faeces are stored in the rectum. The anus is the opening at the end of the digestive system and is where the faeces are removed.
What is the function of the salivary glands?
Release saliva in the mouth. The saliva contains amylase enzymes which break down starch into maltose.
What is the function of the pancreas?
Produces the enzymes involved in digestion: amylase, protease and lipase. It secretes these enzymes in an alkaline fluid into the duodenum to raise the pH of food coming out of the stomach. It also produces insulin and glycogen which are hormones that regulate blood sugar levels.
What is the function of the liver?
Produces bile which emulsifies fats (breaking large droplets into smaller droplets, mechanical digestion) helping to digest them. Bile contains lipase and neutralises the pH. Amino acids that aren’t used to make protein are broken down here which produces urea.
What is the function of the gall bladder?
Stores bile to release into the duodenum as required.
What is ingestion and where in the body does it happen?
the taking of substances, e.g. food and drink, into the body
Part of body: mouth (eating the food)
What is digestion and where in the body does it happen?
the breakdown of food
Part of body: mouth to the duodenum
What is absorption and where in the body does it happen?
the movement of nutrients from the intestines into the blood
Part of body: small intestine (ileum) and large intestine
What is assimilation and where in the body does it happen?
uptake and use of nutrients by cells
Part of body: small intestine
What is egestion and where in the body does it happen?
the removal of undigested food from the body as faeces
Part of body: anus
What is physical digestion?
the breakdown of food into smaller pieces without chemical change to the food molecules
What do the processes that happen in physical digestion help to do?
increase the surface areaof food for the action ofenzymesduring chemical digestion
Where does physical digestion happen?
chewingaction of theteeth, thechurningaction of thestomachand theemulsification of fatsbybilein the duodenum
How does the stomach do physical digestion?
The stomach lining containsmuscleswhich contract tophysically squeezeand mix the food with the strong digestive juices that are present (also known as “stomachchurning”)
How does bile do physical digestion?
Bile is used to emulsify (break down large fat molecules into smaller ones) fats and oils to increase the surface area for chemical digestion
What is the structure of the tooth?
- Teeth are embedded in bone and the gums
- Enamel is very resistant to tooth decay
- Dentine is less resistant to tooth decay
What do incisors do?
Work to bring the food into the mouth and cut it
What do canines do?
Cut and tear food up
What do premolars do?
Help incisors and canines grind and mix food while chewing
What do molars do?
Teeth that do the most chewing work while eating
What is chemical digestion?
the breakdown of large insoluble molecules into small soluble molecules
What is the role of chemical digestion?
to produce small soluble molecules that can be absorbed
What does amylase do in digestion?
- Breaks down starch to simple reducing sugars
- Amylasesare produced in themouthand thepancreas(secreted into theduodenum)
What does protease do in digestion?
- Break down protein to amino acids
- Proteases are in the stomach and small intestine (with the enzymes in the small intestine having been produced in the pancreas)
What does lipase do in digestion?
- Breaks down fats and oils to fatty acids and glycerol
- Lipaseenzymes are produced in thepancreasand secreted into theduodenum
What is the function of hydrochloric acid?
- The stomach produces several fluids which together are known asgastric juice. One of the fluids produced ishydrochloric acid
- The hydrochloric acid is used in killing harmful microorganisms in food and providing an acidic pH for optimum enzyme activity
- The low pH kills bacteria in food that we have ingested as itdenatures the enzymes in their cells, meaning they cannot carry out any cell reactions to maintain life
What happens in the digestion of starch?
- Amylaseis secreted into the alimentary canal in themouthand theduodenum(from the pancreas) and digestsstarch to maltose(a disaccharide)
- Maltoseis digested by the enzymemaltaseintoglucoseon the membranes of the epithelium lining of the small intestine
What is bile?
Bile is an alkaline mixture that neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action
What happens in the digestion of protein?
Protein digestion takes place in the stomach and duodenum with two main enzymes produced:
- Pepsinis produced in thestomach and breaks down protein in acidic conditions in the stomach (optimum pH of 3)
- Trypsinis produced in thepancreasand secreted into theduodenumwhere it breaks down protein inalkaline conditions (optimum pH of 8)
Where are nutrients and water absorbed?
The small intestine is the region where nutrients are absorbed. Most water is absorbed from the small intestine but some is also absorbed from the colon
How is the small intestine adapted for its function?
- The ileum is adapted for absorption as it isvery longand has ahighly folded surface with millions of villi(tiny, finger like projections). These adaptations massivelyincrease the surface areaof the ileum, allowing absorption to take place faster and more efficiently. Microvillion the surface of the villus further increase surface area for faster absorption of nutrients.
- Wall of the villus isone cell thickmeaning that there is only a short distance for absorption to happen by diffusion and active transport
- Villus contains anetwork of blood capillariesthat transport glucose and amino acids away from the small intestine in the blood. Blood flows through the capillaries which maintains the concentration gradient leading to fast diffusion
- Lactealruns through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph
