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What are you made of????

Approximate composition of a bacterial Cell Adapted from Alberts et.al Molecular Biology of the Cell, 3rd edition

Molecule class % total

weight

# diff. types

Water 70 1

Inorganic ions 1 20

Sugars & precursors 1 ~250

Amino acids & precursors 0.4 ~100

Nucleotides & precursors 0.4 ~100

Fatty Acids & precursors 1 ~50

Other small molecules 0.2 ~300

Macromolecules* 26 >3000

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What are these molecules doing?

• Digesting the food you eat

– they are the food you eat!

• Storing your genetic information

• Keeping your cells together

• Making chemistry happen in your body

• All of the things living organisms do!

Approximate composition of a bacterial Cell Adapted from Alberts et.al Molecular Biology of the Cell, 3rd edition

Molecule class % total

weight

# diff. types

Water 70 1

Inorganic ions 1 20

Sugars & precursors 1 ~250

Amino acids & precursors 0.4 ~100

Nucleotides & precursors 0.4 ~100

Fatty Acids & precursors 1 ~50

Other small molecules 0.2 ~300

Macromolecules* 26 >3000

Wow! – how can we keep track of all of these!

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How can we keep track of these?

Categories!

• Four basic categories:

1. Proteins

2. Nucleic acids (DNA, RNA)

3. Carbohydrates

4. Lipids

Macromolecules are usually chains built of smaller “Links”

• Smaller molecules called “monomers”

• Long chains are called “polymers”

• All show similar

patter of construction

Entire chain = polymer

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Thousands of different Proteins

Monomer subunits called…

• Amino Acids

– 20 different types

– All organisms use the same 20 a.a.

• Basic structure of all is the same

– same functional group

• Amino acids are bonded together to make proteins

Amino Acid Structure

Variable region “R”

Every amino acid (there are 20) has a different set of atoms attached here

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Thousands of different Proteins

How do they differ?

• Primary structure – Which amino acids are used

– Their order

Secondary structure forms as chains interact

• The folded structure may resemble coils, helices, or sheets

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A ribbon model of lysozyme (a)

Groove

• Tertiary structure – the final 3-D shape of the protein

• The final twists and folds that lead to this shape are the result of polarity differences in regions of the polypeptide

Figure 4.7

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(b) A space-filling model of lysozyme

Groove

Carbohydrates

• This is a monosaccharide

• A disaccharide is formed when a reaction joins two monosaccharides

Glucose

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Fig. 5-5

(b) Dehydration reaction in the synthesis of sucrose

Glucose Fructose Sucrose

Maltose Glucose Glucose

(a) Dehydration reaction in the synthesis of maltose

1–4 glycosidic

linkage

1–2 glycosidic

linkage

• Two glucose monomers hooked together make a sugar we call Maltose

• Linking different monomers makes different types of disaccharides

Polysaccharides

• Polysaccharides, the polymers of sugars, have storage and structural roles

– Starch

– Glycogen

– Cellulose

• The structure and function of a polysaccharide are determined by its sugar monomers and the organization of linkages

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Polysaccharides

Starch

• Plant energy storage

• Digestible to animals

Cellulose

• Plant structure

• Indigestible to animals

Glycogen

• Animal energy storage

(b) Glycogen: an animal polysaccharide

Starch

Glycogen Amylose

Chloroplast

(a) Starch: a plant polysaccharide

Amylopectin

Mitochondria Glycogen granules

0.5 µm

1 µm

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Glucose monomer

Cellulose molecules

Microfibril

Cellulose microfibrils in a plant cell wall

0.5 µm

10 µm

Cell walls

Lipids: Fats

Fats are constructed from two types of smaller molecules: • Glycerol • fatty acids A fatty acid has long carbon chain

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Fats

• Fats are constructed from two types of smaller molecules: glycerol and fatty acids

• A fatty acid has long carbon chain

• May be:

– Saturated

– Unsaturated

• Depends on if they are completely covered by hydrogen atoms

(a)

Saturated fat

Structural formula of a saturated fat molecule

A saturated fatty acid has no double bonds

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(b)

Unsaturated fat

Structural formula of an unsaturated fat molecule

cis double bond causes bending

An unsaturated fatty acid has double bonds that make chain “kink”

(b)

Space-filling model (a)

Structural formula

Fatty acids

Choline

Phosphate

Glycerol

Hyd

rop

ho

bic

tai

ls

Hyd

rop

hili

c h

ead

Phospholipids

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Lipids • Biological membranes involve lipids

– phospholipids make up the two layers of the membrane

– cholesterol is embedded within the membrane

Cell membrane

Phospholipid

Inside of cell

Membrane proteins

Outside of cell

Carbohydrate chains

Learning Objectives

• Know the difference between intracellular and extracellular digestion

• Be able to the digestive processes of sponges, jelly fish, birds, ruminant, and humans

• Identify and describe the various organs in a vertebrate digestive system

• Know the variety of adaptations vertebrates have to accommodate various eating strategies

• Outline the steps in human digestion: The path food takes, the purpose of each organ/gland in the process and where vitamins and nutrients are absorbed.

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Tasks of the Digestive System

• Ingestion

• Mechanical Digestion

• Chemical Digestion

• Absorption

• Elimination

Each task is performed by a different component in complex systems

Intracellular Digestion

Simplest system, only found in sponges

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Gastrovascular Digestion

• Simple system involving a sac-like chamber

• Chamber contains in opening where ingestion and excretion occur

• Cniderians: Jelly fish, hydra, coral, sea anemones

Discuss with a partner:

• Why do you think saclike digestive systems are unsuitable for animals that eat frequently?

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Tubular Digestive Systems

• Most animals have tubular system which specialized structures including a mouth and an anus

Teeth tell a lot about diet

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Triceratops

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But what if you don’t have teeth?

Ruminants ferment their food with the help of microorganisms

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Cellulose Cows can’t digest

cellulose – how do they survive?

Bacteria living in the rumen can break down the cellulose!

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Glucose monomer

Cellulose molecules

Microfibril

Cellulose microfibrils in a plant cell wall

0.5 µm

10 µm

Cell walls

Human Digestion: Activity

Activity:

1. Working alone, put the following words in order according to how food moves through

the body of a mammal.

2. Check your answers/fill in any blanks with a partner.

~2 minutes

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Digestive System

Food Mouth _____ etc. Anus

Jejuno-ileum Esophagus

Pyloric sphincter Large intestine

Stomach Rectum

Cardiac sphincter Ileum

Duodendum Mouth

Mesentary/Blood vessels Liver

The Digestive System

Mouth Esophagus Cardiac

Sphincter Stomach

Pyloric

Sphincter

Duodendum Jejuno-ileum

Large

Intestines Rectum

Small Intestines

Mesentery

Blood

Vessels Liver

Blood to

Rest of Body

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The Human Digestive Tract

Fig. 34-12

Oral cavity, tongue,

teeth: mechanical digestion

Stomach: Breaks down

food and begins protein

digestion

Small intestine:

Food is digested

and absorbed

Rectum: Stores feces

Salivary glands: Secrete

lubricating fluid and

starch-digesting enzymes

Pharynx: Shared digestive

and respiratory passage

Epiglottis: Directs food

down the esophagus

Esophagus: Transports

food to the stomach

Liver: Secretes bile (also

has many non-digestive

functions)

Gallbladder: Stores

bile from the liver

Pancreas: Secretes pH

buffers and several

digestive enzymes

Large intestine: Absorbs

vitamins, minerals, and

water; houses bacteria;

produces feces

Stomach • Stores slow release

• Churns

• Protein breakdown begins

• Secretes gastrin

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Liver: Produces bile, which is

stored in the gallbladder

Gallbladder: Stores

and releases bile into

the small intestine via

the bile duct

Stomach: Releases

acidic chyme into

the small intestine

Pancreas: Produces sodium

bicarbonate and digestive

enzymes, and releases them

into the small intestine via

the pancreatic duct

Cells in small intestine

lining: Produce enzymes

that complete carbohydrate

and protein digestion

bile duct

duodenum

pancreatic

duct

Small intestine is where the magic happens!

Fig. 34-15

The Structure of the Small Intestine

Fig. 34-16

villi

capillaries

arteriole

lymph

vessel venule

lacteal

microvilli

intestinal

gland

fold of the

intestinal

lining

(a) Small intestine (b) A fold of the

intestinal lining

(c) A villus (d) Cells of a villus

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The Human Digestive Tract

Fig. 34-12

Oral cavity, tongue,

teeth: mechanical digestion

Stomach: Breaks down

food and begins protein

digestion

Small intestine:

Food is digested

and absorbed

Rectum: Stores feces

Salivary glands: Secrete

lubricating fluid and

starch-digesting enzymes

Pharynx: Shared digestive

and respiratory passage

Epiglottis: Directs food

down the esophagus

Esophagus: Transports

food to the stomach

Liver: Secretes bile (also

has many non-digestive

functions)

Gallbladder: Stores

bile from the liver

Pancreas: Secretes pH

buffers and several

digestive enzymes

Large intestine: Absorbs

vitamins, minerals, and

water; houses bacteria;

produces feces