Nutrition Flashcards
2. Structure and Function in Living Organims
Photosynthesis
CO2 + Water -> Glucose + Oxygen
Photosynthesis theory
This is an endothermic reaction in which energy from sunlight is transferred to the chloroplasts. These plants use glucose from CO2 and water.
Products of photosynthesis
Plants use glucose as a source of energy for respiration.
They also use it to
- Produce starch for storage
- To form cellulose to make cells walls
- Produce amino acids which are building blocks for protein
Temperature in photosynthesis
The lower the temperature the less kinetic energy particles have resulting in fewer successful collisions occurring over a period of time
However if the temperature is too high, enzymes that control the process of photosynthesis denature (active site changes shape and no longer complementary to its substrate) - this reduces overall rate of photosynthesis.
Light intensity in photosynthesis
More light a plant receives the faster the rate of photosynthesis
CO2 concentration in photosynthesis
The more carbon dioxide that is present, the faster the reaction can occur
Leaf structure
Use diagram online:
Waxy cuticle
Upper epidermis
Palisade mesophyll
Spongey mesophyll
Lower epidermis
Guard cell
Stomata
Vascular bundle
Xylem
Phloem
Mineral ions in plants
Magnesium: Needed to make chlorophyll however causes yellowing between the veins of leaves
Nitrate: A source of nitrogen needed to make amino acids however causes stunted growth and yellowing of leaves
Carbohydrates
source of energy
Protein
growth and repair
Lipid
Insulation and energy storage
Dietary fibre
provides bulk for the intestine
Vitamins and minerals
maintains health
Water
Needed for chemical reactions to take place in the body
Mouth/salivary glands
Mechanical digestion: Breaks down food into smaller pieces and increases its surface area to volume ratio
Chemical digestion: amylase enzymes in saliva starts digesting starch into maltose
Oesphagus
The tube that connects the mouth to the stomach. Wave-like contractions occur to push down the food
Stomach
Food is mechanically digested by churning actions while protease enzymes chemically digest proteins
Small intestine
First section is called the duodenum; where digestion of the food exiting the stomach is completed by enzymes and secreted by the pancreas
Second section is called the ileum and is where the absorption of water and digested food molecules takes place
Large intestine
Water is absorbed from the remaining material and produces faeces
Faeces are stored in the rectum and exit the body
Pancreas
Produces all three types of digestive enzymes: amylase, protease and lipase
Secretes enzymes in an alkaline fluid into duodenum for digestion
Liver
Amino acids that aren’t used to make proteins are broken down here to produce urea
Produces bile to emulsify fats
Gall bladder
Stores bile to release into the duodenum
Stages of food breakdown
Ingestion - taking in of substances
Mechanical digestion - breakdown of food into smaller pieces without chemical change in food molecules
Chemical digestion - the breakdown of large, insoluble molecules into small soluble molecules
Absorption - movement of molecules through the wall of the intestine into the blood
Assimilation - the movement of digested food molecules into cells of the body
Egestion - the passing out of food that has not been digested or absorbed through the anus
Peristalsis
It is a mechanism that helps move food along the alimentary canal.
Step 1: Contraction of circular muscles
Step 2: Contraction of longitudinal muscles ahead of food mass
Step 3: Contraction of circular muscle layer forces food mass forward
Carbohydrases (digestive enzyme)
It breaks down carbohydrates into simple sugars like glucose. Amylase is a carbohydrase and it breaks down starch into maltose
Starch is first broken down by amylase (turns into maltose) and then maltase turns it into glucose
Protease (digestive enzyme)
Breaks down protein into amino acids
Pepsin is an enzyme made in the stomach which breaks down proteins into smaller polypeptide chains
Protease enzymes then break the polypeptide chains into amino acids
Lipase (digestive enzyme)
Breaks down lipids to glycerol and fatty acids
Lipase enzymes are produced in the pancreas and secreted into the small intestine
Role of Bile
2 roles:
- Neutralises hydrochloric acid
- Emulsifies fats
Adaptations of Small Intestine
The small intestine is adapted for absorption as it is very long and has a highly folded surface with millions of villi
Villi of the small intestine
- Large surface area
- A short diffusion distance
- A steep concentration gradient
