Module 2 - Nutrition

• Nutrient - required for the growth and maintenance of an organism
• Autotrophs - organisms that obtain energy from sunlight and chemicals to produce their own food.
• Heterotrophs - organisms hat cannot make their own food and they obtain energy from eating other organisms
• The nutritional requirements of plants:

  • water and carbon dioxide - process need for photosynthesis to convert energy from sunlight to chemical energy (glucose)
• Essential nutrients or elements

  • Macronutrients - are normally required in amounts above 0.5% like Carbon and Hydrogen
  • Micronutrients - are required in minute or trace amounts like Chlorine and Iron
• Apoplast pathway

  • non-living pathway that consists of cell walls and the intercellular spaces between cells.
  • Water and solutes can move freely through this by diffusion or bulk flow
  • Primitively faster for water transport as it has no membranes to cross
• Symplast pathway

  • living pathway that consists of the cytoplasm of all the cells in a plant connected by plasmodesmata, which are tiny channels that pass through the cell walls.
  • Water and solutes can move through the symplast by osmosis.
  • This pathway is slower than the apoplast because water and solutes must pass through cell membranes.
• Root Hairs – slender extensions of specialized epidermal cells that greatly increase the surface area available for absorption.
• Root nodules - localized swellings in roots of certain plants where bacterial cells exist symbiotically with the plant. The bacteria help the plant fix nitrogen and in turn, the bacteria are able to utilize some organic compounds provided by the plant.
• mycorrhizae (singular, mycorrhiza) – a symbiotic interaction between a young root and a fungus. The fungus obtains sugars and nitrogen containing compounds from root cells while the plant is able to get some scarce minerals that the fungus is better able to absorb from the soil.
• Calorie - unit of energy that indicates the amount of energy contained in food. It specifically refers to the amount of heat energy required to raise the temperature of 1 kg (2.2 lb.) of water by 1oC (1.8oF). The greater the number of Calories in a quantity of food, the greater energy it contains (Johnson and Raven, 1996).
• Nutritional Requirements of Animals

  • Carbohydrates - major energy source for the cells in the body.
  • Proteins - building materials for cell structures and as enzymes, hormones, parts of muscles, and bones
  • Fats - build cell membranes, steroid hormones, and other cellular structures, also used to insulate nervous tissue.
• Main Stages of Food Processing

  1. Ingestion

  2. Digestion

  3. Absorption

  4. Elimination
• Ingestion


  Act of eating or feeding; this is coupled with the mechanical breakdown of food into smaller pieces allowing for a greater surface area for chemical digestion
• Digestion


  Breakdown of food into particles, then into nutrient molecules small enough to be absorbed; Chemical digestion by enzymes involves breaking of chemical bonds through the addition of water, i.e., enzymatic hydrolysis
• Absorption


  Passage of digested nutrients and fluid across the tube wall and into the body fluids; the cells take up (absorb) small molecules such as amino acids and simple sugars
• Elimination


  Expulsion of the undigested and unabsorbed materials from the end of the gut
• Organs Involved in Food Processing

  • Oral Cavity
  • Pharynx
  • Epiglottis
  • Esophagus
  • Stomach
  • Small Intestine
  • Liver
  • Gallbladder
  • Pancreas
  • Large Intestine
  • Rectum
  • Anus
• Oral Cavity


  Shredded by teeth and mixed with saliva. Salivary glands are located at upper and lower jaw
• Pharynx


  Serves as entrance to the esophagus
• Epiglottis


  Prevent food and drink from going down the wrong way and into your lungs
• Esophagus


  Contractions within its muscular wall propel the food past a sphincter, into the stomach
• Stomach


  Mixes and stores food, secretes gastric juice, to degrade the protein, regulates the passage of food
• Small Intestine


  Three regions: duodenum, jejunum, and ileum. Most enzymatic hydrolysis of the macromolecules occur
• Liver


  Secretes bile for emulsifying fats
• Gallbladder


  Stores bile from liver
• Pancreas


  Secretes enzymes to break down all major food molecules, secretes buffers against HCI, and secretes insulin to control of glucose metabolism
• Large Intestine


  Stores undigested matter by absorbing ion and water
• Rectum


  Short extension of large intestine, final segment of digestive tract. Where all compacted undigested food from the colon are pushed via peristaltic contractions
• Anus


  Terminal opening of the digestive system
• Mechanisms of Digestion and Absorption

  
  

  Carbohydrate digestion begins in the mouth but could not continue in the stomach due to the acidic pH that destroys the amylase. It resumes in the small intestine where the resulting monosaccharides are absorbed.

  
  

  Proteins are digested in the stomach and small intestine. Resulting amino acids are absorbed in the small intestine where they leave the intestinal cell and enter the blood through a facilitated diffusion carrier in the plasma membranes on the opposite side.
• Mechanisms of digestion and Absorption

  
  

  Fat digestion occurs entirely in the small intestine. Although fatty acids and monoglycerides enter epithelial cells from the intestinal lumen, it is triglycerides that are released on the other side of the cell and carried by blood capillaries to be transported throughout the body.

  
  

  Most water-soluble vitamins are absorbed by diffusion or active transport. Fat-soluble vitamins follow the pathway for fat absorption.
• How nutrients are delivered into cells:

  
  

  Substances pass through the brush border cells that line the free surface of each villus by active transport, osmosis, and diffusion across the lipid bilayer of plasma membranes.

  
  

  The nutrients then proceed into the internal environment and pass to the blood which is collected into the hepatic portal vein leading to the liver.

  
  

  After flowing through the liver, the blood carrying the nutrients passes into the hepatic vein which carries the blood back to the heart to be distributed to the different body tissues