digestion and excretion. the need for digestion digestion: the process of breaking down food...
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Digestion and Excretion
The Need for Digestion Digestion: the process of breaking down food
particles into molecules small enough to be absorbed by cells
Polymers are too large to pass through the cell membrane in humans
The mitochondria will use the digested nutrients to make energy
There are four macromolecules: carbohydrates, proteins, lipids, and nucleic acids
Carbohydrates Sugars Polymers = large molecules Carbohydrate polymers are polysaccharides Monomers = small subunits Carbohydrate monomers are simple sugars or
monosaccharide's Ex: glucose, sucrose, lactose, maltose The functions of carbohydrates are:
1. to store energy2. to provide building materials for the body
Lipids Fats and oils Polymers are sometimes called triglycerides Monomers are 1 glycerol and 3 fatty acids The energy stored in lipids is for long-term use
and is not used up quickly It takes a lot of exercise to burn fat
Vegetable oils contain unsaturated fats; meats and dairy contain saturated fats
Unsaturated fats are less likely to cause heart disease than saturated fats
Nucleic Acids Carry hereditary information Polymers are DNA and RNA Monomers are nucleotides
Proteins Proteins are large polymers made of amino acid
monomers There are 20 different amino acids The order of the amino acids determines the
protein’s properties
Enzymes Enzymes: proteins that speed up reactions in
organisms Also called organic catalysts Work on substances called substrates Substrates are turned into products Condensation synthesis = enzymes help make a
big molecule from smaller ones Hydrolysis = enzymes help break a larger
molecules down into smaller pieces
Enzymes have an area called the active site that matches the shape of the substrate
Enzymes are specific for their substrates The active site and substrate are said to fit
together just as a key fits in a lock (lock and key model)
Enzymes are not changed or used up in reactions
Enzymes speed up reactions by lowering the activation energy
Activation energy = the energy needed to get a reaction started
Enzyme-substrate complex
Products
Enzyme breaks the bond holding the substrate together
3
2
1
4
Enzymes lose their specific shape (they denature) if they are exposed to unfavorable conditions
Most enzymes work best at 37°C and a neutral pH
Pepsin, an enzyme in the stomach, works best at an acidic pH
Types of Digestion Extracellular digestion: food is broken down by
enzymes outside the body Fungi have special structures called rhizoids that
secrete enzymes onto foodThe food is then absorbed by the fungus
Rhizoids
Intracellular digestion: food is broken down by enzymes inside the cells
The amoeba engulfs its food using extensions of its cytoplasm called pseudopodsProcess is called phagocytosis
The paramecium uses hair-like extensions called cilia to push food into its oral groove
Human Digestion Human digestion is intracellular Unlike the amoeba and paramecium, humans
have digestive organs
Mouth
Salivary glands
Pharynx
Esophagus
LiverStomach
Pancreas
Gall bladder
Appendix
Anus
Small intestine
Large intestine
Rectum
Pathway of Digestion 1. Mouth: site of mechanical and chemical
digestion Ingestion the process of taking food into the organism)
Carb digestion begins in the mouth. Teeth: grind up food (mechanical) Salivary glands: secrete saliva into the mouth
Saliva contains the enzyme salivary amylase that breaks down carbohydrates (chemical)
Epiglottis closes off the trachea when you swallow 2. Peristalsis: rhythmic waves of muscle
contractions that push food down the esophagus
3. Stomach: both mechanical and chemical digestion occurs. Protein digestion begins here.
The walls grind and churn food Gastric juice contains pepsin and hydrochloric acid Pepsin: enzyme that breaks down proteins CHYME: liquid material found in stomach (digested
food) 4. Small intestine: where most chemical
digestion occurs Has many finger-like projections called villi that
absorb nutrients into the blood Other organs secrete substances into the small
intestine
Pancreas: secretes enzymes for breaking down lipids, proteins, and carbohydrates into the small intestines.
Liver: makes bile, which breaks fat globules into smaller pieces Called emulsification Allows enzymes to digest the fats
Gall bladder: stores bile until it is needed secretes into the small intestines.
Absorption of nutrients. 5. Large intestine: absorbs water from undigested
material No digestion occurs Indigestible matter becomes feces, which pass through the
rectum and anus
Diseases Peptic ulcers form when the protective mucus
lining of the stomach is destroyed by bacteriaHelicobacter pyloriThe hydrochloric acid breaks down the stomach wall
Pancreatitis happens when the duct that connects the pancreas to the small intestine is blockedEnzymes build up in the pancreas and start to digest it
Colon cancer occurs in the large intestineMay be geneticMay be caused by low-fiber diets where the feces
remain in the intestine for too longFiber = roughage
Gallstones: bile/cholesterol hardens in the form of stones and blocks the passage of bile into the small intestines. Pain and discomfort are the symptoms.
Anorexia: eating disorder, person under eats, psychological issue.
Bulimia: Binge and Purge. Eat large quantities and then vomit. Psychological issue at start then resulting in bodily damage.
Excretory System Excretion: the removal of metabolic wastes from
the body Includes the liver, skin, lungs and kidneys The liver breaks down old red blood cells,
recycles useful materials, and breaks down extra amino acids(deamination)
The skin gets rid of water and salts through sweat
Kidneys filter the blood
Urinary bladder
Urethra
Kidney
Kidney
Nephron
Renal artery
Renal vein
Ureter
Ureter
Glomerulus
Bowman’s capsule
Tubule
Capillaries
Kidneys Filter wastes out of the blood Urea is a waste made by cells during metabolism The filtering is done by microscopic structures
called nephrons in the kidneys Blood is brought to the kidneys by the renal
artery and enters the glomerulus of the nephron Wastes leave the blood and enter Bowman’s
capsule Urine is made as the wastes travel through the
tubule
Urine leaves the kidneys through the ureters Urine is stored in the urinary bladder The urethra carries urine out of the body
Diseases Nephritis: inflammation of the kidney caused by a
bacterial infection Bladder infection. If not treated with antibiotics, it can lead to kidney
failure Kidney stones are caused by a build up of
calciumMay pass on their own (painful!) or require surgeryGOUT: Uric acid crystals in the joints. Painful and
swollen joints.
Kidney Failure: kidneys are not working for a variety of reasons.
DIALYSIS: a machine that filters the blood in place of the kidney.
Transplant: a donor kidney is implanted into another persons body. (Match it) Immunosuppressant drugs are taken.