Human Nutrition Ch 28 Flashcards
Autotroph
Makes their own food
Heterotroph
Takes in food from the environment
Parasite
Heterotroph that feeds on live sources
Saprophyte
A heterotroph that feeds on dead matter
Herbivore
Animals that feed mainly on plants
Herbivore
Animals that feed mainly on plants
Carnivore
Animals that feed mainly on animals
Omnivore
Animals that feed on both plants and animals
Digestive system
Aka alimentary canal / gut
Needed so that digestive enzymes are not needed in every cell in the body eg like sponges or tapeworms
Four processes
Ingestion - taking food in
Digestion - breakdown of food
Absorption - food passes into the blood
Egestion - removal of waste
Name the types of teeth and give function
Incisors - cutting and slicing
Canines - for gripping and tearing
Premolars - for crushing and grinding
Molars - for crushing and grinding
How many teeth do humans have
Max 32
Dental formula:
2(I2/2 C1/1 P2/2 M3/3)
What are the two types of digestion in the mouth
Mechanical and chemical
Mechanical digestion in the mouth
Chewing and grinding action of teeth breaks down food
Chemical digestion in the mouth
The action of the enzyme amylase breaks down food
What does saliva contain
Water, salts, mucus, lysozyme (destroys microorganisms *), amylase
What ph does amylase work best at
Ph7
How much saliva do humans produce per day
1 litre
Amylase
Converts starch to maltose
Peristalsis
A wave of muscular action in the walls of the alimentary Canal that moves the food along
What does fibre do
Stimulates peristalsis by causing waste to absorb water and expand
What type of digestion is peristalsis
Mechanical
Oesophagus function
Carries food from the mouth to the stomach using peristalsis
Epiglottus
A flap that closes over the trachea when eating to ensure food passes into the oesophagus
Types of digestion in the stomach
Mechanical - churning action
Chemical - gastric juice
Chyme
Formed when food is churned with gastric juice
Stomach
Muscular bag that holds and digests food
- holds 1 l of food for approx 4 hrs
What prevents self digestion in the stomach
Mucus coating
Oh of hydracholric acid
Oh 1-2
Function hydrochloride acid
Kills bacteria, loosens food no activates pepsinogen
Pepsinogen
Inactive so that it does not digest the stomach lining
- pepsinogen is converted to the active enzyme pepsinogen when it chemically reacts with HCl
Pepsin
Active enzyme
A type of protease
Converts proteins to smaller peptides
Lipase
Breaks lipids into fatty acids & glycerol
The pancreas
- secretes insulin
- secretes pancreatic juice (sodium bicarbonate, amylase, lipase)
How does pancreatic juice enter the duodenum
Through the pancreatic duct
What is the function of sodium bicarbonate
Neutralises the chyme
What ph does lipase work best as
Ph 7 to 9 in the duodenum
The liver
A gland
- breaks down red blood cells
- converts glucose to glycogen for storage
- breaks down poisons (alcohol, drugs)
- breaks down excess amino acids to form urea - deamination
- converts excess carbohydrate to fat
-makes BILE !
Ingestion
Taking of food into digestive system, happens when food is placed in the mouth
Digestion
Breakdown of food
-physical digestion
The mechanical breakdown. Eg when we chew food or churn in the stomach
-increases the surface area so that chemical digestion can take place more efficiently
-chemical digestion
The breakdown of food using enzymes
Absorption
Occurs when the digested food passes from the digestive system and enters the blood system
Egestion
The removal of unabsorbed waste from the digestive system
Bile
Made from
Made in
Stored
-yellow-green viscous liquid
Water, bile salts, bile pigments
Liver
Gall bladder - entered the duodenum through the bile duct
Functions of bile
-to emulsify liquids - break down fats and oils into tiny droplets
- neutralises chyme - contains sodium hydrogen carbonate ( alkaline)
- to excrete pigments (biliverdin and bilirubin) made from damaged red blood cells.
Small intestine
Two main parts- duodenum (25cm), ileum (5.5m)
Food is in small intestine for 1- 6 hrs
Duodenum
Function : to digest food
Adaptations:
Cells of duodenum produce enzymes
Products of pancreas and liver (are excreted) enter duodenum
Ileum
Food entering the ileum is almost completely digested :
Function: to absorb nutrients
Adaptions :
1. Long to allow time for absorption
2. Has unfolding called villi -> increases surface area for absorption
Amylase
Made in
Active in
Substrate
Product
Preferred pH
Salivary glands, pancreas
Mouth, duodenum,
Starch
Maltose
7-9
Pepsin
Made in
Active in
Substrate
Product
Preferred pH
Stomach lining
Stomach
Proteins
Peptides
2
Villi adaptations for absorptions / small intestine
-large numbers of villi (increase s.a)
- each villus covered in large numbers of microvilli (increase s.a)
- wall is only 1 cell thick ( to allow for diffusion of food)
- They have rich blood supply
Lacteal:
-inside each villus is a lacteal -> absorbs fats
-each lacteal contains lymph
-fatty acids and glycerol are absorbed into the lacteal and transported to the blood.
Capillaries
-all digested food (not fatty a and glycerol) are absorbed into capillaries
-capillaries carry the food to the hepatic portal vein and to the liver]
Deamination
Amino acids cannot be stored in the liver, so they are broken down to form urea in a process called deamination
Large intestine
-about 1.5 m long
-called large intestine a diameter of 6cm compared to 3 cm for small intestine.
-food stays her from 10 hrs to a few days
Caecum and appendix
Functions not fully known .
- in many herbivores , the c and a contain bacteria to digest cellulose
- we no longer need to digest cellulose as we get energy from more easily digestible starch.
-vestigal organs - lost their former use
Why are faeces egested
Faeces are egested not excreted, as faeces are not a waste product of metabolism
Colon
Function -reabsorb water
- in colon/ large intestine, liquid waste is converted to faeces (water is reabsorbed)
- faeces are stored in the revtum before being egested through the anus
2 benefits of symbiotic bacteria
- bacteria in the colon produce some B vitamins and vitamin K.
- beneficial bacteria prevent the growth of disease causing bacteria and fungi
Balanced diet
Contains all the necessary food types and their correct proportions.
7 components of food
Carbs, proteins, lipids, minerals, vitamins, fibre, wate
4 main food groups (contain similar nutrient)
- cereals, bread, pasta
- fruit, veg
- milk, cheese, yoghurt,
-meat, fish, poultry
Amy of food required depends on
-age
-activity levels
- gender
- health
Role fibre
Fibre stimulated peristalsis
-fibre absorbs and stores water. This causes the unabsorbed wastes to expand, stimulates the walls of the intestine to work.
Fibre sources
Whole meal bread
Cereals
Veg
Fruits
What is dietary fibre made from
Aka roughage
Made from cellulose (can’t digest) from -pant cell walls
What is dietary fibre made from
Aka roughage
Made from cellulose (can’t digest) from -pant cell walls
