Download 6.1 - Digestion

6.1 - Digestion
I. Purpose of digestion
A. Food is made of cells, and therefore
macromolecules (carbs, lipids, proteins,
nucleic acids) that your body needs to
function
B. Macromolecules are too big to cross cell
membranes
C. Your digestive system breaks polymers
down into monomers so that they can get
into your cells
D. Your cells use the monomers to build
macromolecules
II. 4 steps
A. Ingestion – eat
B. Digestion – break
down into smaller
molecules
C. Absorption –
molecules move
from digestive
tract into blood
and lymph
D. Transport –
circulatory system
delivers molecules
to cells
III. Digestion is an enzyme-driven process
A. Digestive enzymes catalyze hydrolysis reactions –
hold macromolecules in place and stress bonds until
body heat causes them to break
Salivary
Amylase
Pepsin
Trypsin
Pancreatic
Lipase
Pancreatic
Amylase
Source
Salivary
Glands
Stomach
cells
Pancreas
Pancreas
Pancreas
Location of
action
Mouth
stomach
Small
intestine
Small
Intestine
Small
Intestine
Substrate
Amylose
(starch)
proteins
proteins
lipids
Amylose
(starch)
Product
maltose,
glycerol and
amino acids amino acids
glucose
fatty acids
pH
7
pH 3
8
8
maltose,
glucose
8
IV. Absorption
A. Villi – finger-like projections that line the small
intestine – increase surface area!
1. Contain a capillary network for nutrients to
pass into the blood (carbs and proteins) and a
lacteal for the lymph system (lipids)
B. Passive Transport
1. Simple diffusion - fatty acids
2. Facilitated diffusion – glucose, amino acids
C. Active Transport
1. Pumps – glucose, amino acids
2. Endocytosis – not fully digested macromolecules
V. Importance of smooth muscle
A. Longitudinal – moves food through
B. Circular – mechanical digestion