Chapter 3 7digestion metabolism

The Mitochondria power houses house all the enzymes involved in the conversion of pyruvate to acetyl CoA, fatty acid oxidation, the TCA cycle, and the electron assemble AA into prot

Digestion & Absorption & Transport and Metabolism

of Nutrients

• The process of physically &

chemically changing the

composition of food in the

gastrointestinal tract

• The process by which food is broken

down into absorbable units

• The process of assimilating the

products of DIGESTION into the body.

Absorption

Anatomy of Absorption

Anatomy of Absorption

• Folds in the small intestinal wall

• Villus - fingerlike projections on the

folds

• Microvilli - hair like projections on

each cell of the small intestine

• Increases the surface area

Vessels in the Villi

• Capillaries in the villi

– carry water soluble nutrients to

liver

– amino acids

– monosaccharides

Vessels in the Villi

• Capillaries in the villi

– water soluble vitamins

– minerals

– water

– glycerol

Vessels in the Villi

• Lymph vessels in the villi

– carry fat soluble nutrients

– triglycerides

– fat soluble vitamins

– cholesterol

Small intestine - villi

• Are complex protein molecules

• Enable a chemical reaction to take

place but do not change during the reaction

Digestive or gastrointestinal system

Esophagus

The Muscular Action of

Digestion

• Peristalsis

• Segmentation

• Gastrointestinal(GI) tract muscular

• Movement of food/chyme through

the GI tract

• Food moves ahead of the

constriction

Stomach Muscles

The Muscular Action of

Digestion

pH

of

Common Substances

pH Changes in GI Tract

• Neutral pH in mouth & esophagus

• Stomach pH is very acid

– Inactivates some salivary enzymes – Activates some enzymes

– Bacterioside

• Shift back to neutral in the small

intestine

• Occurs within individual cells

• It includes the use of basic nutrients

for the work of the cell & chemical

changes are involved

• Building new compounds

• Breaking down compounds

Inside the cell membrane lies the

cytoplasm

Nucleus.

Inside the nucleus are

the chromosomes,

that contain the

genetic material DNA.

The Mitochondria (power houses)

house all the enzymes involved in

the conversion of pyruvate to

acetyl CoA, fatty acid oxidation,

the TCA cycle, and the electron

assemble AA into proteins.

The cell membrane encloses each cell’s contents and regulates the passage of molecules

in and out of the cell.

THE CELL

• Work of the cell includes:

– Anabolism: building new compounds

– Catabolism: breaking down compounds for energy

Anabolism

Anabolism

Catabolism

Catabolism

What’s Involved?

• Enzymes - proteins that cause or enable a

chemical reaction to take place without entering into the reaction and without being changed in the process.

• Remember they are “picky” molecules!

• Require particular compounds as substrates (substances to act upon)

• Require a narrow pH range (relative acidity)

• Require a narrow temperature range

Carbohydrates

Digestion

Carbohydrates Digestion

• Stomach

– What happens to the salivary

amylase in the stomach?

– acid continues to hydrolyze starch – fiber delays gastric emptying

– feeling of fullness (satiety).

Carbohydrates Digestion

• Small intestine (cell surface)

• Disaccharides:

– Maltose Glucose + Glucose

– Sucrose Glucose + Fructose – Lactose Glucose + Galactose

Maltase

Sucrase

Lactase

Carbohydrates Digestion

Carbohydrates Digestion

• End products

– All Monosaccharides

• Glucose Fructose

• Galactose

Carbohydrates Digestion

• Large Intestine:

– fibers remain intact and attract

water, soften stools and ferment.

CHO Absorption

CHO Absorption

Glucose & Galactose Fructose

Digestion of Carbohydrates

– lactase deficiency due to a natural

decrease that occurs with aging or damaged intestinal villi.

Lactose Intolerance

• Dietary Changes

  consumption of milk products

gradually.

– Mix dairy with other foods.

– Spread dairy intake throughout the day – Consume yogurt.

END PRODUCTS Carbohydrate Digestion

• Glucose

• Fructose

• Galactose

CHO Digestion and

Absorption

• Where does CHO digestion start?

• Which is the main site for CHO digestion?

• Which are the END Products of CHO

Digestion?

• How are the END products absorbed?

Metabolism of CHO

• Liver

• Monosaccharides converted to glucose

• Glucose: - released to blood

- burned for energy

- converted to glycogen (stored)

- converted to FA and stored in adipose tissues

Metabolism of CHO

• In other tissues

– Burned for energy

– Stored as glycogen (muscles)

– Converted to FA and stored in adipose tissue

If not energy is needed

Fatty Acids CO2

End Products of CHO

Metabolism

• Energy

• Water

• CO2

Lipid Digestion

Lipids Digestion

• Digestive enzymes are hydrophilic, or

water loving

• Bile from the liver emulsifies lipids

• Enzymes are then able to break down

lipids to monoglycerides and fatty acids.

Lipids Digestion

• Mouth:

– The salivary glands release:

• Lingual Lipase.

Lipids Digestion

• Stomach:

– Muscle contractions - fat into

smaller droplets

– Fat is exposed to Gastric Lipase

– Some end products:

• Short chain fatty acids, Glycerol &

free fatty acids, Mono & diglycerides

Lipids Digestion

• Small Intestine:

• Cholecystokinin (CCK) signals

the gallbladder to release bile.

• Pancreatic and intestinal

enzymes hydrolyze lipids to monoglycerides and fatty acids.

Lipids Digestion

• Small Intestine:

– Phospholipids are hydrolyzed – Sterols are absorbed as is.

END Products of Lipids

• Glycerol

• Monoglycerides

• Fatty Acids

• Cholesterol

Digestion

Bile Acid Amino Acid

How is fat absorbed?

Absorption of Lipids

• Glycerol and short- and

medium-chain fatty acids:

– diffuse and are absorbed directly

into the bloodstream.

Absorption of Lipids

• Monoglycerides and long-chain fatty

acids form micelles, are absorbed, and are reformed into new

triglycerides

• With protein they are transported by

Chylomicrons.

Fig 5-17a, p 152

Small intestine

Short-chain fatty acids Medium-chain fatty acids

Via blood to liver

Glycerol and small lipids such as short- and medium-chain fatty

acids can move directly into the bloodstream.

Via lymph to blood

Large lipids such as monoglycerides and long-chain fatty acids combine

with bile, forming micelles that are sufficiently water soluble to penetrate

the watery solution that bathes the absorptive cells There the lipid contents

of the micelles diffuse into the cells.

Fat Emulsification

Triglyceride Digestion

Bile’s Routes

Bile: release in the Small Intestine

and emulsifies fat

Then:

• Can be reabsorbed or

• Soluble fibers trap some bile and

excreting it from the body

through the large intestine.

Enterohepatic Circulation

Transport of Lipids

• Is made possible by a group of

vehicles known as Lipoproteins.

Transport of Lipids

• Chylomicrons:

– Largest of the lipoproteins

– Least dense

– Get smaller as triglyceride portion

is removed by the cells

Transport of Lipids

• VLDL (Very-Low-Density Lipoproteins)

• Composed primarily of

triglycerides

• Made by the liver

• Transport lipids to the tissues

• Get smaller and more dense as

triglyceride portion is removed

Transport of Lipids

• LDL (Low-Density Lipoproteins)

– Composed primarily of cholesterol – Transport lipids to the tissues

Transport of Lipids

• HDL (High-Density Lipoproteins)

• Composed primarily of protein

• Transport cholesterol from the

cells to the liver for recycling or disposal

Chylomicron VLDL LDL HDL

Chylomicrons: little protein and much triglyceride, the lowest density Very-low-density lipoproteins (VLDL) are half TG, very  density.

Low-density lipoproteins (LDL) are half cholesterol, accounting for

their implication in heart disease

High-density lipoproteins (HDL) are half protein,  density.

Transport of Lipids

• Health Implications

• Factors that lower LDL and raise HDL

– Weight control – Replace sat fat with monounsat fat and polyunsat fat in the diet

– Soluble fibers – Moderate alcohol consumption – Physical activity

• Genes influence lipoprotein activity.

Digestion, Absorption &

Transport of Lipids

• Where does Fat digestion start?

• Which is the main site for Fat digestion?

• Which are the END Products of Fat

Digestion?

• Why do we need Bile?

• Which are the transporters of Fat?

• Where are the Chylomicrons made?

• Where are the other Lipoproteins made?

Fat Metabolism

• Fatty Acids

– Lengthen or shorten the FA chain – Saturate or desaturate the FA chain – Burned for energy

– Stored in adipose tissues

Fat Metabolism

• Glycerol

– Can be converted to fatty acids (5% of total

TG carbons)

Fatty Acids Oxidation

(2 Carbon each cycle)

FA

Glucose cannot be made from Fatty Acids

Metabolism of Lipids

End Products Energy

CO 2

H 2 0 Ketones

Protein Digestion

Protein Digestion

• Mouth

– No chemical breakdown

Pepsin

Protein Digestion

• Small Intestine

– Proteases hydrolyze protein into

smaller peptides (oligopeptides, 4-9 AA) and amino acids so it can be absorbed.

– Peptidases split proteins into amino

acids.

Protein Digestion

• Small intestine

– Polypeptides to amino acids &

dipeptides by pancreatic protease

– Dipeptides to amino acids by

intestinal protease

• End products of Protein digestion?

Amino Acids

Protein Absorption

• Used by intestinal cells for energy or

synthesis of necessary compounds

• Transported to the liver

Digestion of Protein

Protein Digestion and

Absorption

• Where does Protein digestion start?

• Which is the main site for Protein

digestion?

• Which are the END Products of Protein

Digestion?

Metabolism of Protein

Metabolism of Protein

• If we consume more protein than we need or if we need them for energy:

– Some AA Pyruvate

– Some AA Acetyl CoA

– Some AA TCA (Krebs Cycle)

Metabolism of Amino

Acids

• Must remove the acid group COOH: decarboxylate

• Must remove the amino group: NH 3 deaminate

– Ammonia + Keto-acid

Amino Acid Structure

C

Side Group

O

H

Remove COOH

Remove

Amino

Group

Metabolism of Amino

AcidsThe remaining carbon skeleton is used:

• to make glucose - if there is a glucose shortage

• to make fatty acids - when amino acids are

consumed above the body’s needs for glucose or protein synthesis

Metabolism of Amino

AcidsThe remaining carbon skeleton is used:

• as a carbon skeleton for Transamination: make other Non Essential AA (liver)

B 6 (Co-enzyme)

What happens with the

Ammonia (NH3)?

Urea Formation

UREA PRODUCTION

UREA PRODUCTION

&

EXCRETION

What happens if we consume too much

protein?

• Urea is excreted by the Kidney with water.

  Protein Intake  Urea production

  water loss

• We don’t store Proteins

End Products of Protein

Metabolism

Energy

CO2

H20 Urea

Summary

End Products of

Digestion

• Small intestine

– Intest Amylase – Intest Protease – Intest Lipase

Bile Acid

• NOT an enzyme

• Emulsifies fat in the small intestine

Digestion-Absorption-Metabolism

Integrated with End Products

Mono-saccharides

Glycerol, FA, Cholesterol

Energy,

CO 2 ,

H 2 O, Urea

Integration of CHO, P,

Lipid

How do we use food for

energy?

After Eating!

CHO Glucose Glycogen Fat Fatty Ac Fat stores Protein AA Body Proteins

Urea

Cells

• Where do metabolism occurs?

• Anabolism

• Catabolism

If not energy is needed

Fatty Acids

END PRODUCTS

Metabolism of Lipids

Glucose Pyruvate

Acetyl CoA

TCA CO2 Glycerol

FA

Fatty Acids Oxidation

(2 Carbon each cycle)

FA

Glucose cannot be

made from Fatty Acids

End Products of Lipid

Metabolism

Energy

CO2

H20 Ketones

Metabolism of Protein

• If we consume more protein than we need or if we need them for energy:

– Some AA Pyruvate

– Some AA Acetyl CoA

– Some AA TCA (Krebs Cycle)

End Products of Protein

Metabolism

Energy

CO2

H20 Urea

Questions ?