Transcript Food and Your Metabolism

Food and Your
Digestive System
The basics
We need food for 2 things:
Nutrients
 Serve
as building
blocks
 Used to maintain
and build tissues
Energy
 Release
energy
when metabolized
in cells

Break down large
organic molecules
to make ATP
The chemical composition
of your body is roughly
equal to the proportions of
the same elements and
molecules in the food you
eat.
(You are what you eat!)
Nutrient
 Any
component of the food that we eat
that our body needs to function properly.
 Macro: essential elements we need in
large amounts
 Micro: essential elements we need in very
small amounts
Getting to the Matter and Energy
 Most
foods have essential and
nonessential nutrients the we use
 If our diet isn’t balanced:


Get too much or too little of a particular
nutrient
Get too much or too little energy
Key Info
Carbs
 Used
for energy,
DNA/RNA,
digestion
 Excess converted
to glycogen and
fats
Lipids



Give food flavor and
tenderness
Carry vitamins A, D, E
&K
Used for alternate
fuel, insulation, cell
membranes,
emulsifiers,
hormones, bile salts
Key Info
Proteins

2 kinds: animal &
plant

Enzymes, fiber
(collagen), active
transport, salt/water
balance, energy
alternative,
hormones,
antibodies,
hemoglobin


Vitamins & Minerals
Vitamins: cell formation,
antioxidant, calcium
absorption, blood
clotting, vision, growth,
bone remodeling,
immune system
Minerals: bones and
teeth, nerve transport,
muscle contractions,
heart rhythm, ATP,
nerve impulses
Some Thoughts
 We
take in energy continuously
 We
use energy periodically
 Optimal:
 Any
energy input = energy output
calories above daily need are
converted and stored as fat
Food and Energy
 Energy
available in food is measured by
“burning” food.

Energy in food is converted to heat and
measured as a calorie
 Energy
stored in food called dietary
Calories (capital “C”).

One Calorie = 1000 calories
Chapter 38
Digestion – the Players







Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Function: Convert foods into simpler
molecules for absorption and use by cells.
Chapter 38
Mouth & Esophagus
 Teeth
– cutting, tearing, crushing food
 Saliva – secreted by salivary glands;


Moisten food
Start chemical digestion of starches with enzyme
called amylase.
 Create
 Bolus
chewed clump of food (“bolus”)
travels down esophagus to stomach by
peristalsis
Chapter 38
Stomach
 Large,
muscular sac
 Chemical



digestion: Needs glands!
Mucus – protects stomach lining
Hydrochloric acid – makes contents acidic
Pepsin – enzyme to digest proteins
 Mechanical

digestion: Needs muscle!
Muscles contract to churn and mix stomach fluids
and food. Result: chyme
Chapter 38
Small Intestine
 Pyloric
valve opens and chyme flows from
stomach to small intestine.
 Most
chemical digestion and absorption happens
in small intestine.
 First


of three parts of SI: duodenum
Where almost all digestive enzymes enter
Enzymes from pancreas, liver and lining of duodenum
Chapter 38
Small Intestine & Accessory Structures
 Other

About 6 meters long!
 Small

two parts of SI: jejunum and ileum
intestine lined with villi (finger-like projections)
Increase surface area for absorption of nutrient
molecules
 Pancreas
 Liver
– regulate blood sugar levels
– produces bile to break down fatty
molecules
Chapter 38
Accessory Structures
Pancreas

Gland

Produces enzymes for
carbs, proteins, lipids,
and nucleic acids

Produces sodium
bicarbonate – neutralizes
stomach acids so
enzymes can work
Liver

Organ

Bile – acts like a
detergent

Allows enzymes to
reach smaller fat
molecules
Chapter 38
Absorption in Small Intestine
 When
chyme enters jejunum and ileum, it has
become mix of small and medium nutrient
molecules
 These
molecules rapidly absorbed into the cells
lining the SI


Capillaries in the villi – carbs and protein
Lymph vessels – undigested fat and fatty acids
 What’s
left: water, cellulose, other undigestible
substances
Chapter 38
Large Intestine (Colon)
 Removes
 Bacteria
water from undigested material
in the large intestine produce vitamin K
 Concentrated
rectum (poop)
waste material exits through the
Chapter 38
RECAP!
chyme
bolus
Mouth
•Chewing
•amylase
Amylase:
breaks down
starches
Stomach
•chemical
•mechanical
Small
Intestine
•Chemical
•Absorption
Chemical: acid
and enzymes
Chemical:
enzymes
Mechanical:
muscle
contractions
Food leaves
nutrient-free
Pancreas & Liver
play role here
Large
Intestine
•Water
•Bacteria
Poop
Vitamin K
Chapter 38
Disorders
 Peptic
ulcers – hole in stomach wall
 Vitamin
K deficiency – loss of bacteria in LI
 Diarrhea
& Constipation – disruption in the removal
of water by large intestine
 Recall:

enzymes are proteins
No sodium bicarbonate = enzymes can change
shape and become ineffective (active site doesn’t
match substrate)
Chapter 38 - 3
Organs of Excretion
 Skin
– excretes excess water, salts, and small
amount of urea
 Lungs
– excrete carbon dioxide
 Liver
– converts amino acids, producing nitrogen
waste. Then converts nitrogen waste into urea.
 Kidneys



– principle organs of excretion
Remove waste products from blood
Maintain blood pH
Regulate water content of blood (blood volume)