Food and Your Digestive SystemThe 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 InfoProteins

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: energy input = energy output

Any 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

Digestion – the Players Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine

Function: Convert foods into simpler molecules for absorption and use by cells.

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Mouth & Esophagus Teeth – cutting, tearing, crushing food Saliva – secreted by salivary glands;

Moisten food Start chemical digestion of starches with enzyme

called amylase.

Create chewed clump of food (“bolus”)

Bolus travels down esophagus to stomach by peristalsis

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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

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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

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Small Intestine & Accessory Structures Other two parts of SI: jejunum and ileum

About 6 meters long!

Small intestine lined with villi (finger-like projections) Increase surface area for absorption of nutrient

molecules

Pancreas – regulate blood sugar levels

Liver – produces bile to break down fatty molecules

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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

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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

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Large Intestine (Colon) Removes water from undigested material

Bacteria in the large intestine produce vitamin K

Concentrated waste material exits through the rectum (poop)

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•Chewing•amylaseMouth

•chemical•mechanicalStomach

•Chemical•Absorption

Small Intestine

•Water•Bacteria

Large Intestine

Chemical: acid and enzymes

Mechanical: muscle contractions

Chemical: enzymes

Food leaves nutrient-free

Pancreas & Liver play role here

Amylase: breaks down starches

Poop

Vitamin K

RECAP!

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bolus chyme

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)

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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)

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