Section 2: Human nutrition Flashcards
balanced diet, energy from food, digestion, enzymes, the alimentary canal
What are the 7 nutrition groups
Carbohydrates, lipids, proteins, vitamins, mineral ions, water and dietary fibre
Balanced diet definition
A balanced diet should include all 7 nutrient groups in the correct proportions to meet the bodies needs
Describe the source, function and deficiency for carbohydrates
Source: bread, pasta
Function: provide energy, fuel for respiration
Deficiency: lack of energy
Describe the source, function and deficiency for proteins
Source: meat, fish, chickpeas
Function: growth and repair of tissues and to make enzymes
Deficiency: Kwashiorkor
Describe the source, function and deficiency for lipids
Source: butter, oil seeds
Functions: provide energy, act as an energy store, provide insulin, make cell membranes
Deficiency: Lack of energy, cell membranes are not formed
Describe the source, function and deficiency for Vitamin A
Source: liver, eggs, dairy
Function: Makes a chemical in the retina to protect the eye
Deficiency: Poor eyesight
Describe the source, function and deficiency for Vitamin C
Source: Citrus fruits, strawberries
Function: Make connective tissue
Deficiency: scurvy
Describe the source, function and deficiency for Vitamin D
Source: cheese, fish, eggs
Function: Absorption of calcium in the bones
Deficiency: Rickets (in children), Osteoporosis (adults)
Describe the source, function and deficiency for mineral calcium
Source: dairy products
Function: make bones and teeth strong and healthy
Deficiency: Rickets and osteoporosis
Describe the source, function and deficiency for mineral ion
Source: red meat
Function: needed to make haemoglobin for healthy blood
Deficiency: Anemia
Describe the source, function and deficiency for fibre
Source: wholegrain bread
Function: aids the movement of food through the gut
Deficiency: constipation, bowel cancer
Describe the source, function and deficiency for water
Source: liquids, wet foods e.g. watermelon
Function: provide medium for chemical reactions to occur
Deficiency: dehydration
What factors effects energy requirements
- Age
- Activity level
- Sex
- Pregnancy
- Breast feeding
How do energy requirements vary with age, activity and pregnancy
Age: children and teenagers require more energy as they are growing and more active
Activity level: the more active you are the more energy you need
Pregnancy: require more energy to support their larger mass and the foetus
Describe how mechanical digestion occurs in the mouth
Food is broken up into smaller pieces by mouth chewing
Describe how chemical digestion occurs in the mouth
The salivary glands secrete saliva which contains the enzyme amylase, this breaks down starch into maltose
How do we swallow
A bolus which is a ball of food shaped by the tongue, is moved to the back of the mouth and then pushed down the oesophagus by peristalsis
What is peristalsis
Two sets of muscles push the food down the oesophagus. The circular muscles contract behind the bolus pushing it along. When the longitudinal muscles contract they make the oesophagus wider.
What is the oesophagus
a long tube that connects the mouth to the stomach.
Describe how mechanical digestion occurs in the stomach
Food is churned by stomach muscles contracting
Describe how chemical digestion occurs in the stomach
Enzyme pepsin is release and breaks down proteins into peptides
Why is Hydrochloric acid released in the stomach
- Pepsins optimum pH is an acidic pH
- Kills bacteria that has been ingested with the food
What is the first section of small intestine call
duodenum
How do enzymes get to the duodenum and where are they made
The enzymes are made in the pancreas and releases into the duodenum via the pancreatic duct
What is the role of trypsin in the duodenum
To break down proteins into peptides.
What is the role of amylase in the duodenum?
To break down starch into maltose
What is the role of lipase in the duodenum
To break down lipids into fatty acids and glycerol
What is the role of the duodenum wall
Makes and secretes enzymes
What is the role of maltase in the duodenum
To break down maltose into glucose
What is the role of peptidase in the duodenum?
To break down peptides into amino acids
How does food move through the duodenum
peristalsis
Where is bile produced, stored and released
Produced by the liver and stored in the gall bladder,
before being released into the duodenum through the bile duct
What are the function of bile
- Neutralises the stomach acid. Enzymes in the duodenum work best at pH 7-8.
- Emulsifies lipids - breaks large droplets into smaller
droplets, increasing the surface area for lipase to digest the fats.
What is the second part of the small intestine called
Ileum
What is the purpose of the ileum
To absorb small molecules
How is the ileum adapted for absorption
- Large surface area - folding of ileum, villi and microvilli (folds on the surface of cells lining the villi) all increase surface area.
- Short diffusion distance - the villi walls are one cell thick
- High concentration gradient provided by capillary network
and lacteals removing absorbed molecules. - very long so there is time to absorb all everything
What is the role of the colon
The colon is the site for all reabsorption of water, leaving a semi- solid waste material
What is the role of the rectum and anus
The rectum is where the faeces is stored and then egested from the anus
Describe an investigation to find the energy in food
- Measure 25cm3 of water, pour it into the boiling tube
Record the starting temperature. - Light the foodstuff over a Bunsen, then hold the food under a boiling tube of water to heat it.
- If the food stops burning, it needs to be relit until it will no longer burn.
- Measure the finishing temperature of the
water and calculate the temperature change. - Use the following equation to determine energy:
Energy released (J) = mass of water (g) x rise in temperature (°C) x 4.2
