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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 # diff. types weight
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 # diff. types weight
Water 70 1 Inorganic ions 1 20
Sugars & precursors 1 ~250 Wow! – howAmino acidscan & precursorswe keep 0.4 ~100 track of allNucleotides of these! & precursors 0.4 ~100 Fatty Acids & precursors 1 ~50
Other small molecules 0.2 ~300 Macromolecules* 26 >3000
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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”
Entire chain = polymer
• All show similar patter of construction
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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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Groove
(a) A ribbon model of lysozyme
Figure 4.7
• 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
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Groove
(b) A space-filling model of lysozyme
Carbohydrates
• This is a Glucose monosaccharide • A disaccharide is formed when a reaction joins two monosaccharides
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Fig. 5-5
1–4 glycosidic linkage
Glucose Glucose Maltose (a) Dehydration reaction in the synthesis of maltose
1–2 • Two glucose monomers hooked togetherglycosidic make a linkage sugar we call Maltose • Linking different monomers makes different
Glucosetypes of disaccharidesFructose Sucrose (b) Dehydration reaction in the synthesis of sucrose
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 Cellulose Glycogen
• Plant energy • Plant • Animal storage structure energy • Digestible to • Indigestible storage animals to animals
Chloroplast Starch Mitochondria Glycogen granules
0.5 µm
1 µm
Amylose Glycogen
Amylopectin
(a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide
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Cell walls Cellulose microfibrils in a plant cell wall Microfibril
10 µm
0.5 µm
Cellulose molecules
Glucose monomer
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
Structural formula of a saturated fat molecule
A saturated fatty acid has no double bonds
(a) Saturated fat
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Structural formula of an unsaturated fat molecule
An unsaturated fatty acid has double bonds that make chain “kink”
cis double bond causes (b) Unsaturated fat bending
Phospholipids
Choline
Phosphate
Glycerol
Hydrophilic head Hydrophilic
Fatty acids Hydrophobic tails Hydrophobic
(a) Structural formula (b) Space-filling model
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Lipids • Biological membranes involve lipids – phospholipids make up the two layers of the membrane – cholesterol is embedded within the membrane
Outside of cell Carbohydrate chains Cell membrane
Membrane proteins Phospholipid
Inside of cell
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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Cell walls Cellulose microfibrils in a plant cell wall Microfibril
10 µm
0.5 µm
Cellulose molecules
Glucose monomer
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
Cardiac Stomach Mouth Esophagus Sphincter Small Intestines
Pyloric Duodendum Jejuno-ileum Sphincter
Large Mesentery Rectum Intestines
Blood to Blood Liver Rest of Body Vessels
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The Human Digestive Tract Salivary glands: Secrete lubricating fluid and starch-digesting enzymes
Pharynx: Shared digestive Oral cavity, tongue, and respiratory passage teeth: mechanical digestion Epiglottis: Directs food down the esophagus Breaks down Esophagus: Transports Stomach: food to the stomach food and begins protein digestion Liver: Secretes bile (also has many non-digestive functions)
Gallbladder: Stores bile from the liver Small intestine: Pancreas: Secretes pH Food is digested buffers and several and absorbed digestive enzymes Rectum: Stores feces Large intestine: Absorbs vitamins, minerals, and water; houses bacteria; produces feces Fig. 34-12
Stomach • Stores slow release • Churns • Protein breakdown begins • Secretes gastrin
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Small intestine is where the magic happens! Liver: Produces bile, which is stored in the gallbladder
bile duct pancreatic duct
Gallbladder: Stores and releases bile into Stomach: Releases the small intestine via acidic chyme into the bile duct the small intestine
duodenum Pancreas: Produces sodium Cells in small intestine bicarbonate and digestive lining: Produce enzymes enzymes, and releases them that complete carbohydrate into the small intestine via Fig. 34-15 and protein digestion the pancreatic duct
The Structure of the Small Intestine
fold of the capillaries intestinal lining microvilli villi
lacteal
arteriole intestinal lymph gland vessel venule
(a) Small intestine (b) A fold of the (c) A villus (d) Cells of a villus intestinal lining
Fig. 34-16
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The Human Digestive Tract Salivary glands: Secrete lubricating fluid and starch-digesting enzymes
Pharynx: Shared digestive Oral cavity, tongue, and respiratory passage teeth: mechanical digestion Epiglottis: Directs food down the esophagus Breaks down Esophagus: Transports Stomach: food to the stomach food and begins protein digestion Liver: Secretes bile (also has many non-digestive functions)
Gallbladder: Stores bile from the liver Small intestine: Pancreas: Secretes pH Food is digested buffers and several and absorbed digestive enzymes Rectum: Stores feces Large intestine: Absorbs vitamins, minerals, and water; houses bacteria; produces feces Fig. 34-12
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