SciA

• Nutrition


  The process by which organisms obtain and use food
• Holozoic mode of nutrition


  Exhibited by humans
• Digestion


  1. Ingestion

  2. Digestion

  3. Absorption

  4. Assimilation

  5. Egestion
• Digestion


  A catabolic process which involves breaking down of complex food molecules into simple soluble molecules
• Types of Digestion


  • Mechanical Digestion
  • Chemical Digestion

  
• Mechanical Digestion


  • Involves the physical breakdown of large food molecules into small molecules
  • Occurs in mouth and stomach

  
• Chemical Digestion


  • Involves breakdown of complex food molecules into smaller molecules through hydrolytic reaction catalyzed by digestive enzymes
• Enzymes


  Proteins that speed up chemical reactions that turn nutrients into substances that our digestive tract absorb
• Mouth


  • Intake of food starts from here where solid food is broken down by the chewing action of the teeth
  • Contains salivary glands that secrete saliva which contains mucin to soften and moisten the food
• Salivary amylase (ptyalin)


  Enzyme that digests carbohydrates such as starch into simple sugar
• Mouth


  Tongue rolls the food into small, slippery masses of boli (bolus)
• Pharynx


  • Common passage for food and air which pushes the food into the esophagus
  • Epiglottis is a lid-like structure that covers the trachea at the time of swallowing of food
• Esophagus


  • Also known as food pipe that carries the bolus to the stomach
  • The process of movement of food from the esophagus to stomach is known as peristalsis

  
• Stomach


  • J-shaped organ found at the end of the esophagus
  • Cardiac sphincter is a valve that closes and opens to allow the flow of food
  • Mechanical digestion happens here where twisting, squeezing, churning and mixing of food takes place

  
• Stomach


  • Chemical digestion also takes place here where stomach lining also bears gastric glands that release gastric juice which is the solution of hydrochloric acid, water, mucus and enzymes
• Hydrochloric acid


  Helps breakdown food and destroys most of the bacteria
• Enzymes produced in the stomach

  Mostly proteases which break down proteins such as pepsin and rennin
• Partially digested bolus


  Becomes liquefied forming chyme
• Small Intestine


  • The first part of the small intestine through a muscular valve called pyloric sphincter
  • Composed of 3 parts: Duodenum, Jejunum, Ileum
  • Carbohydrates, proteins, and fats are digested
  • Final digestion and absorption of food take place here

  
• Enzymes produced by the cells of intestinal epithelium


  • Peptidases
  • Maltase
  • Sucrase
  • Lactase
  • Lipase
• Pancreas


  • Secretes hormones to regulate blood sugar level in the body such as insulin and glucagon
  • Secretes pancreatic juice that neutralizes the acidic stomach content (chyme)
  • Produces digestive enzymes such as pancreatic lipase, pancreatic amylase and trypsin
• Liver


  • Aids digestion by producing an alkaline, greenish-yellow liquid, containing bile salts and bile pigments called bile
  • As the food moves into small intestine, the bile will be released through the bile duct into the small intestine
• Bile


  Not an enzyme, acts as an emulsifier by breaking down fat molecules into smaller ones which in turn will be easily digested by the enzymes in the small intestine
• Absorption of Food in the Small Intestine


  1. After 3-5 hours, most of the food is digested in the small intestine

  2. Nutrients are absorbed in the bloodstream through the walls of small intestine particularly by the villi

  
• Large Intestine


  • Absorb water and mineral salts from undigested food material
  • Feces is made up of dead bacteria, undigested food roughage, dried out digestive juices, mucus and discarded intestinal cells
• Rectum


  • The concluding part of the large intestine that terminates in the anus
  • Serves as the temporary storage for the feces
• Anus


  • Made of the muscles that line your pelvis (pelvic floor muscles) and two other muscles called anal sphincters (internal and external)
  • When the rectum contracts, the feces will be expelled through this opening
• Assimilation


  • The process of transport and use of the absorbed nutrients
  • Simple Sugars- converted into glycogen/glucose
  • Amino Acids- converted into new protoplasm
  • Fats- used to protoplasm in cell membranes and some are stored in adipose tissues which serve as insulating tissues
• Plant tissues

  Groups of similar cells with a common function that make up plant organs
• Two main types of plant tissue

  • Meristematic tissue
  • Permanent tissue

  
• Meristematic tissue

  • Found at the tip of the stems
  • Located in the leaves and internodes at the intercalary position
  • Located in the stems and roots on the lateral side

  
• Apical meristem

  • Present at the tips of the roots and shoots
  • Facilitates growth of the cells in the roots and shoots
  • Contains promeristem zone and meristematic zone
• Intercalary meristem

  • Located in the leaves and internodes
  • Helps to increase the length of the internode
  • Found in grass, monocots and pines
• Lateral meristem

  • Located in the stems and roots
  • Increases the thickness of the plant
  • Includes vascular cambium and cork cambium
• Permanent tissue

  • Dermal tissue
  • Ground tissue
  • Vascular tissue

  
• Dermal tissue

  • Covers and protects the surface of plant organs
• Ground tissue

  • Also known as fundamental tissues, form the main bulk of plants
  • Includes parenchyma, collenchyma and sclerenchyma cells

  
• Vascular tissue

  • Complex conducting tissues extending from the roots to the leaves
  • Includes xylem and phloem

  
• Plants are multicellular organisms composed of several organs known as vegetative organs
• Plant organs are made up of plant tissues