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.