Transcript digestion and excretion notes

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 energy
2. 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
1
2
Enzyme-substrate
complex
Products
4
3
Enzyme breaks the
bond holding the
substrate together
 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 food

The 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 pseudopods

Process 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
Pharynx
Salivary
glands
Liver
Gall bladder
Esophagus
Stomach
Small
intestine
Large
intestine
Pancreas
Appendix
Anus
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
 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







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 bacteria


Helicobacter pylori
The hydrochloric acid breaks down the stomach wall
 Pancreatitis
happens when the duct that
connects the pancreas to the small intestine is
blocked

Enzymes build up in the pancreas and start to digest it
 Colon
cancer occurs in the large intestine
May be genetic
 May be caused by low-fiber diets where the feces
remain in the intestine for too long
 Fiber = 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
Nephron
Kidney
Kidney
Renal artery
Renal vein
Ureter
Urinary
bladder
Urethra
Ureter
Bowman’s capsule
Glomerulus
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
calcium


May pass on their own (painful!) or require surgery
GOUT: 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.