Transport and Nutrition
Nutrition in the Flowering Plant
Plants are autotrophic, they produce their own food.
Transpiration: Loss of water vapour from the aerial parts of the plant
Transpiration Stream: Movement of water through a plant
Water and Mineral Uptake in Plants
Water Uptake
1) Water enters the root hair by osmosis, from a low concentration to a high concentration
2) Minerals dissolve into water and either enter the root hair through diffusion or active transport
3) Water moves across the ground tissue (root cortex) and into the xylem tissue
4) Water is then transported up the plant
Cohesion Tension model of Water Transport in Xylem tissue
- Scientists = Henry Dixon and John Joly
1) Water moving into xylem tissue causes a pressure build up which helps to move the water upwards, Root Pressure force exerted by water on the walls of the xylem vessels
2) Water molecules have hydrogen bonds between them - this is the cohesion of water molecules
3) Water tends to easily stick to the walls of the xylem vessels - adhesion of water molecules
4) Transpiration occurs in the leaf which creates a upwards pull on the column of water molecules, which creates a tension between the molecules.
Control of Transpiration
- Waxy cuticle prevents too much water loss from the plant
- Rate of transpiration directly controlled by the opening and closing of stomata
Stomatal Opening and Closing
- In general open during the day and close at night
- High water levels can stimulate the stomata to open. Low water levels can stimulate the stomata to close
- Windy conditions cause an increase of transpiration, to avoid too much water loss stomata will close. They remain open during calm conditions
- Guard cells control the opening and closing of the stomata which is controlled by their turgidity. Walls of guard cells are thicker of the inside than on the outside. When turgid (full of water), the cells bend so that the stomata is open. When there is a loss of water (cell becomes flaccid) cell doesn't bend and the stomata closes.
- Low levels of CO2 (during the day as it is used in photosynthesis) causes the stomata to open
- High levels of CO2 (during the night as only respiration is occuring) causes the stomata to close
Transport of Products of Photosynthesis
- Oxygen is either used for respiration or is released into the atmosphere
- Glucose is used immediately in respiration, or is converted into sucrose for transport and starch for transport.
- Transported up and down the phloem via sieve tube cells.
Modified Plant Food Storage
Tap root: Root swells with starch, e.g. carrot and parsnip
Tuber (modified stem):Swells with starch, e.g. potato
Bulb (modified leaf): Swells with starch e.g. onion
Nutrition in the Human
Heterotophic Organisms: Obtain their food and nutrients from other living organisms\
Digestion: Breaking down of Food
- Mechanical: Break down food into smaller pieces for more effective chemical digestion
- Chemical: Enzymes & Acids, for further breakdown
Ingestion: Taking in of food
Absorbtion: Passage of single biomolecules from the gut into the cells
Egestion: Getting rid of undigested materials
Human Alimentary Canal
- Oral Cavity
- Saliva; produced in the salivary glands = water, mucous, amylase- Amylase breaks down starch to maltose
- Food is mixed with saliva (chemical) and is chewed by the teeth (meachanical), this creates a bolus.
- Swallowed using tongue. Epiglottis closes over glottis to stop food going down the wind pipe.
- Teeth
- Break down food into smaller pieces making it easier to swallow and increase surface area for enzymes to work on.
- Dental formula; 2(I 2/2, C1/1, PM2/2, M3/3)
- Poor dental hygiene and modern diet leads to a build up of bacteria in the mouth. Bacteria produce lactic acid which creates holes in the teeth.
- Pharynx
- Swallowing
- Ensures food travels down the oesophagus
- Oesophagus
- Muscular tube = smooth muscle
- Peristalisis: Rhythmical muscle contractions which push food along the alimentary canal in one direction only.
- Stomach
- Muscular bag
- Folded internal walls to increase surface area for reactions, food is chemically digested by gastric juices. Food is mechanically digested by stomach churning.
Gastric juices
1) Water; solvent for food to dissolve and enzymes to act
2) HCL; Kills pathogens and denatures proteins. Maintains the optimum pH for pepsin (pH 2)
3) Mucous; alkaline which protects the walls of the stomach
4) Pepsin; Protein digesting enzyme
- Liver
- Produces bile
- Produces cholesterol
- Detoxifies alcohol
- Breaks down red blood cells
- Breaks down excess amino acids into urea
* Receives blood from the hepatic artery (branch from aorta) and from hepatic portal vein (from intestine, blood = rich in nutrients and white blood cells)
* Leaves liver through hepatic vein
- Bile and Gall Bladder
- Bile is produced by the liver
- Bile is composed of water, mucous, salts, cholesterol, bilirubin and bilerubin (from the breakdown of red blood cells)
- Gall bladder stores bile
Emulsification of Fats
- Large fat globules to smaller ones
- Increases surface area to increase rate of reaction
Bile - Neutralises stomach acid
- Pancreas
- Pancreatic juices are deposited with bile into the duodenum
1) Sodium Hydrogen Carbonated - Helps neutralise chyme from stomach
2) Lipase - Digests fats into fatty acids and glycerol
3) Amylase - Digests starch to maltose
- Small Intestine
= Duodenum, Jejudum, Ileum
- Food moved by peristalisis
- Duodenum; Chemical digestion occurs here from bile and pancreatic juices
- Ileum: Absorbtion of nutrients
Villi
- Microvilli to increase surface area for absorbtion
- 1 cell thick for quick absorbtion
- High blood supply to transport nutrients
- Lacteal to absorb fatty acids and glycerol
- Large Intestine
Colon: Absorbs water, hosts symbiotic bacteria which produce Vit K and B. Some bacteria digest cellulose into fatty acids which can then be absorbed. Prevent the growth of pathogens.
Role of Fibre: Stops constipation by stimulating peristalisis, decreases blood cholesterol levels, controls glucose absorbtion,
- Rectum
- Storage organ for faeces
Balanced Diet
- Contains all the 7 nutrients in the correct proportions
e.g. Carbohydrates, Lipids, Protein, Fibre, Vitimins, Minerals, Water
- Imbalance results in malnutrition or obesity
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