How Do You Build the Molecules of Life?

Better Known as Organic Molecules and Digestion…

Living Creatures Have Organization

• All organisms are made of the same collection of chemicals, which are organized into…• Molecules

• Made up of proteins, fats, carbohydrates, and nucleic acids

• Molecules are then organized into…• Organelles & Cells, specifically…

• Plant Cells & Animal Cells

Living Creatures Have Organization

• Going from a cell to baby…. • The original fertilized egg has to divide into

groups of cells• The groups of cells work together to perform

the same function and form tissue

Living Creatures Have Organization

• Tissue is then organized into…• Organs & Organ systems

• Respiratory, Circulatory, Digestive, etc.

Living Creatures Have Organization

Making the Body Systems Work

• Animals make energy using food and oxygen

• Animals build bodies using:• Food for raw

materials • Amino acids,

sugars, fats, nucleotides

• ATP energy for synthesis

But where do we get the raw material from? Food we eat!

O2

Food

ATP

Getting & Using Food• Ingest: Taking in food• Digest

• Mechanical digestion• Breaking up food into

smaller pieces• Chemical digestion

• Breaking down food into molecules small enough to be absorbed into cells

• Enzymes are proteins that help to speed up the breaking down process

• Absorb: Absorb across cell membrane• Diffusion• Active transport

• Eliminate: Undigested material passes out of digestive system

intracellulardigestion

extracellulardigestion

Digestive Systems – Many Forms

Ingestion Starts Digestion

• Mouth• Mechanical Digestion• Chemical Digestion

• Saliva -Enzyme digests starch• Slippery protein• Protects soft lining of digestive system• Lubricates food for easier swallowing

Oral Cavity

Upper lip

Lower lip

Uvula

Tongue

Palate

Salivary Glands

• Scattered throughout oral cavity• Functions:

• Hydrolysis• Dissolve things• Moisten food and mouth

• Composition of saliva• pH 6.35-6.85 (Slightly acidic)• Produce 1000-1500 ml a day• 99% of saliva is water

• Salivary amylase begins breakdown of starch

Esophagus• Moves both air and food• Epiglottis, a flap of tissue, prevents food from

entering the trachea• Food enters the esophagus instead• Muscular contractions and relaxations called

peristalsis moves food through the esophagus

Stomach• Can stretch to hold 2 L of food• “Growling” is contracting of stomach muscle• Three layers of muscle churn the food• Gastric pits in the stomach secrete acidic digestive fluid• Mucus protects the stomach lining – ulcers are a breakdown of this

protective lining• Mixed food particles and gastic fluid is called chyme

Fundus

Duodenum

Esophagus

BodyPylorus

Stomach

• Disinfect food• HCl = pH 2, will kill bacteria

• Chemical Digestion• Digestion of proteins by pepsin, a gastric

protease, into peptides. • Gastric lipase- pH 5-6, splits lipids

Liver • Produces bile to break up fats

• Bile is composed of bile acids and salts, phospholipids, cholesterol, pigments, water, and electrolyte chemicals

• Bile stored in gallbladder until needed• Large organ right of the stomach• Stores glucose, makes proteins, breaks down toxins – including

alcohol

Pancreas

• Lies behind the stomach• Produces sodium bicarbonate, to neutralize

stomach acid to protect the small intestine• Produces insulin in the Islets of Langerhans,

specialized cells in the pancreas• Pancreatic juices:

• Pancreatic amylase – breaks down all starches

• Trypsin, Chymotrypsin – separates amino acids (proteins)

• Pancreatic lipase - breaks down lipids• Nucleases - break down nucleic acids

Islet of Langerhans

Gallbladder

• A  pear shaped sac on underside of the right lobe of the liver. • About 7-10cm long. • Ducts

• Hepatic ducts• Cystic ducts• Common bile ducts

• Function• Store and concentrate bile by absorbing water• Contracts and releases bile to duodenum when

needed

Small Intestine• Nearly 7 m in length• Three sections:

• Duodenum (25 cm), Jejunum (2.5 m) and Ileum (4 m)

• Intestinal Juices• Maltase, sucrase, lactase – break down

carbohydrates• Aminopeptidase, Dipeptidase – break down amino

acids (proteins)• Deoxyribonuclease, ribonuclease- break apart

sugars and nucleic acids

Duodenum

• First section of small intestines• Receives acid food from stomach • Mixes with digestive juices from:

• Pancreas• Live• Gallbladder

Absorption by Small Intestines• Highly folded lining of the small intestine is called villi, which are

covered in microvilli• Give a surface area about 250 square meters (area of a tennis

court)• 90% of all nutrients are absorbed in the small intestine, 10% in

stomach and large intestine. • Carbohydrates: absorbed on surface of villi. • Proteins: amino acids are transported by active transport into

the capillaries • Water absorption: absorption accomplished by osmosis• Lipids: lipase breaks down glycerol

Circular creaseswith villi

Colon• Also known as large intestine• Four parts – ascending colon, transverse colon,

descending colon and sigmoid colon• Waste solidifies into feces and >90 % water is reabsorbed

• Diarrhea: not enough water absorbed • Constipation: too much water absorbed

Rectum

Sigmoid

Descendingcolon

Transversecolon

Ascendingcolon

Anus

You’ve Got Company!• Living in the large intestine is a community of

helpful bacteria• Escherichia coli (E. coli)

• produce vitamins • vitamin K; B vitamins

• generate gases• by-product of bacterial metabolism • methane, hydrogen sulfide

stomachkills germs break up fooddigest proteinsstore food

mouthbreak up fooddigest starchkill germsmoisten food

small intestinesbreakdown food

- proteins- starch- fats

absorb nutrients

pancreasproduces enzymes to digest proteins & carbs

liverproduces bile

- stored in gall bladderbreak up fats

large intestinesabsorb water

Appendix

• Vestigial organ located behind the ascending portion of colon

• Darwin suggested it might been used to digest cellulose

• Scientists are now studying how it might influence the immune system

Rectum • Last section of colon • Eliminate feces which are undigested materials

• extracellular waste• mainly cellulose from plants

• masses of bacteria

Length of Digestive System

• Herbivores & Omnivores• Long digestive

systems• Harder to

digest cellulose • Carnivores

• Short digestive systems

• Protein easier to digest

Teeth

• Carnivore• sharp ripping teeth• “canines”

• Herbivore• wide grinding teeth• molars

• Omnivore• both kinds of teeth

Vegetarian Diets

• Need to make sure you get enough protein• 20 amino acids to make protein

• 10 amino acids humans can produce • 8 “essential amino acids” come from food

• Grains (like corn) have 6 (missing 2)• Beans (like soybean & red beans) have 6 (missing

different 2)• Mix beans & grains for complete group of amino

acids• Rice & Beans• Tofu & Rice• Peanut Butter & Bread

Feedback: Maintaining Homeostasis • Balancing glucose levels in blood

pancreas

pancreas

insulin

liver takes upglucose

for storage

cellstake up

glucose from blood

liver releasesglucose to blood

depress appetite

stimulatehungerglucagon