Transcript Digestive System

Nutrition &
Digestive System
Homeostasis
Process by which organisms maintain a
relatively stable internal environment.
Food and Nutrition
 Why do we eat food?
 Cells convert chemical energy stored in the sugar
glucose and other molecules into ATP.
 Energy in food is measured by the amount of heat
given off by the food. We measure this in calories.
One calorie is the amount of heat needed to raise
the temperature of one gram of water by 1 degree
Celsius.
 Calorie (capital C) is the energy stored in food.
One Calorie is equal to 1000 calorie or 1
kilocalorie kcal.
Nutrients
 Nutrients- Substances in food that supply the
energy and raw materials your body uses for
growth, repair and maintenance.
 The nutrients that the body needs are:
 Water, Carbohydrates, fats, proteins, vitamins, and
minerals
 Water is the most important of all!
 Every cell in the human body needs water because
of many of the body’s processes.
Nutrients continued
 Carbohydrates- Main source of energy for the body.
Sugar found in fruit, honey and sugar can are
simple carbohydrates.
 Monosaccharides and disaccharides
 Complex carbohydrates those found in pasta,
potatoes and other starches
 Polysaccharides
 Fats or lipids. Fats are formed from fatty acids and
glycerol. Your body cannot make all the fatty acids
it needs. These can be found in vegetable oils.
 Fats are used to produce cell membranes
Dehydration Synthesis
of a Disaccharide
Hydrolysis of a Disaccharide
Fatty Acid Structure
Fatty Acid
•Carboxyl group (COOH) forms the acid.
•“R” group is a hydrocarbon chain
Synthesis of a Fat
Glycerol
Nutrients continued
 Proteins- supply raw materials for growth and
repair of structures such as skin and muscle.
Proteins have regulatory and transport functions.
 Insulin controls sugar levels
 Hemoglobin transports oxygen
 Another example of maintaining homeostasis!
 Examples of proteins? (Contains Nitrogen)
 Vitamins- Organic molecules that help regulate
body processes, often working with enzymes.
 Minerals- Inorganic nutrients that the body needs,
usually in small amounts.
 Organic vs Inorganic?
 Organic contains Carbon and Hydrogen
Proteins
 What are the building blocks of proteins???
 Amino Acids!
Formation of a Dipeptide
Dehydration synthesis
Amino group
Carboxyl group
Alanine
Serine
Organic not organic?
 CO2 ____________
 H2O _____________
 C6H12O6 ________________
 HCl ______________
Process of Digestion
 Purpose of digestion- break food down into small
molecules that can be passed to the cells that
need them
 The digestive system includes the mouth,
pharynx, esophagus, stomach, small intestine,
and large intestine.
 Accessory structures are salivary glands,
pancreas, and the liver. They add secretions to
the digestive system.
Mouth
 Digestion starts in the mouth with mechanical
digestion with chewing.
 Also chemical digestion happens here with
digestive enzymes.
 Teeth – mechanical digestion cutting tearing and
crushing food.
 Saliva- Created by salivary glands, moisten food
make it easier to chew. Contains enzyme amylase.
 Amylase- breaks chemical bonds between the sugar
monomers in starches.
How do human
teeth reflect an
omnivorous diet?
Esophagus
 Esophagus- Food tube into the stomach.
 The reason food can travel through the esophagus
into the stomach is because of peristalsis. Food is
moved along by contractions of smooth muscle
surrounding the esophagus.
 Peristalsis- Rhythmic muscular contractions that
squeeze food through the esophagus into the
stomach.
http://www.nlm.nih.gov/medlineplus/ency/a
natomyvideos/000097.htm
Stomach
 Stomach is a large muscular sac. The size enables
you to eat a few large meals a day.
 Mechanical digestion in the stomach
 Contractions of its smooth muscles churn and mix the
food you swallow.
 After churning and mixing stomach fluids and food it
becomes chyme.
 Chemical digestion in the stomach
 The lining of the stomach contains millions of
microscopic gastric glands that release substances.
 Some produce mucus others hydrochloric acid.
 Very acidic which activates pepsin. Pepsin is an enzyme
that breaks down proteins.
More about the stomach
 Powerful acids released into the stomach can
sometimes damage the lining producing a hole.
This would be a peptic ulcer. Usually peptic
ulcers caused from bacteria not stomach acid.
Pancreas and Liver
 As chyme is pushed from the
stomach to the small intestine it
first enters the duodenum. The
first of three parts of the small
intestine.
 Small intestine is the location
where most of the chemical
digestion happens. As chyme
enters the duodenum is mixes
with enzymes and digestive fluids
from the pancreas and liver.
Pancreas and Liver
 Pancreas- Has 3 important functions (2 for digestion)
 1. Produce hormones that regulate blood sugar.
 2. Produces enzymes to break down carbs, proteins,
lipids, and nucleic acids.
 3. Produces sodium bicarbonate, a base which
neutralizes stomach acid. Allows enzymes to work.
Acid can change the shape. (lock and key)
 Liver- Produces bile, a fluid loaded with lipids and
salts. Dissolves the droplets of fat found in fatty
foods. Bile is stored in the gallbladder.
Small Intestine
 The small intestine absorbs NUTRIENTS. The
folded surfaces of the small intestine are covered
with projections called villi.
 The surfaces of the cells of the villi are covered
with thousands of fingerlike projections known as
microvilli.
 LOTS OF SURFACE AREA!!
 More surface area allows absorption of nutrients.
Large Intestine aka colon
 Is shorter, but wider, than the small intestine.
 The main job of the large intestine is to remove
water from the undigested material that is left.
 Colonies of bacteria grow on the undigested
material left in the colon that help with the
digestive process.
The Excretory
System
Excretion
 Every cell in the body produces metabolic wastes
to maintain homeostasis the body must rid of the
waste products.
 Excretion is the process by which metabolic
wastes are eliminated.
 Organs: Skin, lungs, and kidneys are the main
components of the excretory system.
The Kidneys
 Main organs involved with excretion are
the 2 kidneys.
 A tube called the ureter leaves each
kidney carrying urine to the urinary
bladder where it is stored.
 The kidneys remove urea, excess water,
and other waste produces from the blood
and is collected as urine.
 Cleans the blood! Filtration.
Control of kidney function
 The kidneys play an important role in
maintaining homeostasis.
 They regulate the water content of the blood,
volume, pH level and remove waste products
from blood.