Nutrition and Food Processing in Animals and Plants

Chapter 6: Nutrition and Food Processing in Animals and Plants

Objectives

• Describe digestion in lower forms of animals.

• Describe digestion in humans.

• Understand the functions of enzymes in chemical digestion.

• Identify the accessory glands of the digestive system.

• Describe how plants obtain the nutrients they need to grow and develop.

• Identify the macronutrients and micronutrients needed by plants for growth and development.

• Describe the process of photosynthesis.

Lesson 1: Nutrition and Food Processing in Animals

Introduction

• All living organisms need nutrients to survive.

• Most animals obtain nutrients by consuming other organisms.

• Biological molecules necessary for animal cell function:

  • Amino acids

  • Lipid molecules

  • Nucleotides

  • Simple sugars

• Animal food contains:

  • Proteins

  • Fats

  • Complex carbohydrates

• Animals must convert macromolecules into simple molecules for cell functioning.

• Digestion is the breakdown of food particles.

• Absorption is the uptake of digestion components into the bloodstream or lymph.

• Animals must balance food intake, storage, and energy expenditure.

Digestive Systems

• Animals obtain nutrients from eating plants (herbivores), meat (carnivores), or both (omnivores).

• Nutrients and molecules in food must be processed before they are accessible to cells.

• Animal digestive systems have evolved to accommodate various dietary needs.

Herbivores, Omnivores, and Carnivores

• Herbivores:

  • Primary food source is plant-based.

  • Evolved digestive systems to handle large amounts of plant material.

  • Categories:

    • Frugivores: fruit-eaters (birds)

    • Granivores: seed-eaters (hamsters)

    • Nectivores: nectar-feeders (butterflies)

    • Folivores: leaf-feeders (caterpillars)

• Carnivores:

  • Primary food source is animals.

  • Obligate carnivores: rely entirely on animal flesh (lions)

  • Facultative carnivores: also eat non-animal food (dogs)

• Omnivores:

  • Eat both plant- and animal-derived food (humans)

Essential Factors of a Diet

1. Vitamins: Organic compounds that function as co-enzymes and co-factors of enzymes.

   • Two Types of Vitamins:

     • Water-soluble vitamins: Vit. C and B; transported as free compounds in the blood and serve as co-enzymes in metabolic reactions.

     • Fat-soluble vitamins: Vit. A, D, E, and K; transported in the blood as complexes that are linked to lipids.

   • Water-Soluble Vitamins:

     1. Dissolve in water and are not stored in the body to a significant extent.

     2. Easily excreted in urine, so they need to be consumed regularly through the diet.

     3. Examples include Vitamin C and the B-complex vitamins (such as B1, B2, B3, B5, B6, B7, B9, and B12).

     4. Commonly found in fruits, vegetables, and whole grains.

     5. Play crucial roles in energy metabolism, immune function, and nervous system function.

   • Fat-Soluble Vitamins:

     1. Dissolve in fats and oils and are absorbed along with dietary fats in the small intestine.

     2. Can be stored in the body's fatty tissue and liver, unlike water-soluble vitamins.

     3. Excessive intake can lead to toxicity.

     4. Examples include Vitamins A, D, E, and K.

     5. Commonly found in fatty foods such as dairy products, eggs, meat, and oily fish.

     6. Essential for various functions in the body, including vision (Vitamin A), bone health (Vitamin D), antioxidant function (Vitamin E), and blood clotting (Vitamin K).

2. Minerals: Inorganic molecules that provide ions essential for the functioning of many enzymes or proteins.

   • Two Classifications of Minerals

     • Principal elements (macro nutrients): Occur in living tissues in comparatively large amounts; daily requirement exceeds 100mg.

     • Trace elements (micro nutrients): Occur in living tissues in small amounts; required in amounts less than 100mg.

   • Macrominerals:

     1. Needed by the body in relatively large amounts.

     2. Include minerals such as calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur.

     3. Play crucial roles in various bodily functions such as bone health, nerve function, muscle contraction, fluid balance, and maintaining pH balance.

     4. Typically found in a wide range of foods, including dairy products, fruits, vegetables, nuts, seeds, and whole grains.

   • Microminerals (Trace Minerals):

     1. Required by the body in much smaller amounts compared to macrominerals.

     2. Equally essential for maintaining good health.

     3. Include iron, zinc, copper, manganese, iodine, selenium, fluoride, chromium, and molybdenum.

     4. Play roles in various physiological processes such as enzyme function, immune function, oxygen transport, hormone synthesis, and antioxidant defense.

     5. Found in a variety of foods, including seafood, meat, poultry, nuts, seeds, whole grains, and certain fruits and vegetables.

Major Minerals

• Calcium (Ca2+)

  • Food Sources: Milk, cheese, sardines, salmon, some dark green leafy vegetables

  • Functions:

    • Development of bones and teeth

    • Transmission of nerve impulses

    • Blood clotting

    • Normal heart action

    • Normal muscle activity

  • Deficiency/Toxicity:

    • Osteoporosis

    • Osteomalacia

    • Rickets

    • Tetany

    • Retarded growth

    • Poor tooth and bone formation

• Phosphorus (P)

  • Food Sources: Milk, cheese, lean meat, poultry, fish, whole-grain cereals, legumes, nuts

  • Functions:

    • Development of bones and teeth

    • Maintains normal pH of the blood

    • Constituent of all body cells

    • CHO, CHON and fat metabolism

  • Deficiency/Toxicity:

    • Poor tooth and bone formation

    • Weakness

    • Anorexia

    • General malaise

• Potassium (K+)

  • Food Sources: Oranges, bananas, dried fruits, vegetables, legumes, milk, cereals, meat

  • Functions:

    • Contraction of muscles

    • Maintenance of fluid balance

    • Transmission of nerve impulses

    • Regular heart rhythm

    • Cell metabolism

  • Deficiency/Toxicity:

    • Deficiency: hypokalemia, muscle weakness, confusion, abnormal heartbeat

    • Toxicity: hyperkalemia, potentially life-threatening irregular heartbeats

• Sodium (Na+)

  • Food Sources: Table salt, beef, eggs, poultry, milk, cheese, soy sauce, moderate amounts in breads and vegetables, large amounts in processed foods

  • Functions:

    • Maintenance of fluid balance

    • Transmission of nerve impulses

    • Acid-base balance

    • Muscle contraction

  • Deficiency/Toxicity:

    • Deficiency: nausea, exhaustion, muscle cramps

    • Toxicity: hypertension, edema

• Chloride (Cl+)

  • Food Sources: Table salt, eggs, seafood, milk

  • Functions:

    • Gastric acidity

    • Regulates acid-base balance in the body

    • Maintains fluid and electrolyte balance

    • Formation of hydrochloric acid

  • Deficiency/Toxicity:

    • Imbalance in gastric acidity

    • Imbalance in blood pH

    • Nausea

    • Exhaustion

• Magnesium (Mg2+)

  • Food Sources: Green, leafy vegetables, whole grains, avocados, nuts, milk, legumes, bananas, seafood, chocolate, cocoa

  • Functions:

    • Nerve transmission

    • Synthesis of ATP

    • Activation of metabolic enzymes

    • Muscle activity

    • Constituent of bones, muscles, and RBCs

  • Deficiency/Toxicity:

    • Normally unknown

    • Mental, emotional and muscle disorders

Trace Minerals

• Iron (Fe+)

  • Food Sources: Muscle meat, Poultry Shellfish, Liver, Legumes, Dried fruits, Whole grain or enriches breads and cereals Dark green and leafy vegetables, Molasses

  • Functions: Transports oxygen and $CO_2$, Hemoglobin formation, Component of cellular enzymes essential for energy production

  • Deficiency/Toxicity: Deficiency: iron deficiency anemia

• Iodine (I)

  • Food Sources: lodized salt seafood

  • Functions: Regulation of basal metabolic rate

  • Deficiency/Toxicity: Goiter, Cretinism, Myxedema

• Zinc (Zn)

  • Food Sources: Liver, Eggs, Seafood, esp. oysters, Milk, Wheat bran, legumes

  • Functions: Formation of collagen, Wound healing, Taste acuity, Essential for growth, Immune reactions

  • Deficiency/Toxicity: Dwarfism, Anemia, Loss of appetite, Skin changes, Impaired wound healing, Decreased taste acuity

• Fluoride (F-)

  • Food Sources: Fluoridated water, Seafood

  • Functions: Increases resistance to tooth decay, Component of bones and teeth

  • Deficiency/Toxicity:

    • Deficiency: Tooth decay, Possibly osteoporosis

    • Toxicity: Fluorosis - discoloration of teeth or mottling

Invertebrate Digestive Systems

• Simplest digestive system: gastrovascular cavity.

  • Only one opening for digestion.

  • Blind tube or cavity; "mouth" and "anus" are the same opening.

  • Cells secrete digestive enzymes.

  • Food particles are engulfed by cells lining the cavity.

  • Examples: jellyfish and sea anemones.

• Alimentary canal: More advanced, with separate mouth and anus.

  • Single tube.

  • Food passes through the mouth and is stored in the crop.

  • Food then passes to the gizzard where it is churned and digested.

  • Food particles then pass through the intestine where absorption occurs.

  • Feces (castings) are eliminated through the anus.

  • Examples: tapeworms and earthworms.

Incomplete vs Complete Digestive Tracts

• The castings produced by worms (or earthworm poop) is actually a very desirable natural fertilizer for plants. Some gardeners even purchase earthworm castings to mix with their soil.

Parts of the Digestive System

• Humans: Complete digestive tract (alimentary canal).

• Part of a tube-within-a-tube body plan.

• Begins with a mouth and ends in an anus.

• Digestion is entirely extracellular.

• Digestive enzymes are secreted by:

  • The wall of the digestive tract, or

  • By nearby glands.

Human Digestive Tract

• Mouth: Salivary enzymes begin carbohydrate digestion and break up food particles.

• Salivary glands: Moistens and lubricates food. The enzyme amylase digests carbohydrates.

• Pharynx: Directs food into the stomach to prevent choking.

• Esophagus: Carries food down from the mouth to the stomach

• Stomach: Secretes gastric juice and hydrochloric acid, and activates enzymes., continues to breakdown food and kill off any pathogens. Stores and churns food. Enzyme pepsin digests protein.

• Liver: The largest organ inside the body. Makes bile (fluid that helps break down fats and gets rid of wastes in the body); changes food into energy; and clears alcohol, some medicines, and poisons from the blood. Stores vitamins and iron. Destroys old blood cells.

• Gallbladder: Stores the bile made in the liver, then empties it into the small intestine to help digest fats. Stones can form within.

• Pancreas: A gland that makes enzymes for digestion, and bicarbonate to neutralize stomach acid. Also makes the hormone Insulin ,which helps the body turn food into energy,and regulates blood sugar levels.

• Small intestine: Digests protein, fats and carbohydrates. Bacterial metabolism plus nutrient and excess water absorption. Surface is covered in villi for greater absorption. Site of fructose malabsorption and Coeliac disease.

• Large intestine: Also called the colon. It absorbs water and electrolytes from stool. It also contains beneficial bacteria which help produce certain vitamins. Forms and stores faeces.

• Appendix: A pouch attached to the first part of the large intestine. No one knows its function

• Rectum: The lower end of the large intestine, leading to the anus. Stores and expels faeces.

• Anus: The opening at the end of the digestive tract where bowel movements leave the body.

Oral Cavity

• Point of entry for food.

• Mastication breaks food down into smaller particles.

• All mammals have teeth for chewing.

• Saliva begins the digestion process.

  • Produced by salivary glands (parotid, submandibular, sublingual).

  • Watery substance that contains mucus, immunoglobulins, lysozymes, and salivary amylase (breaks down carbohydrates).

Types of Saliva

• Parotid: Located near your ears, these produce saliva rich in enzymes like amylase, which helps break down starches during digestion.

• Submandibular: Found under your jaw, they produce a mix of watery and mucous saliva, aiding in lubrication and swallowing.

• Sublingual: Situated under your tongue, these produce mostly mucous saliva, keeping your mouth moist and comfortable.

Dentition

• Dentition differs with mode of nutrition

• Omnivores

  • Variety of specializations

  • Accommodate both vegetation and meat

• Herbivores

  • Incisors for clipping

  • Premolars and molars for grinding

• Carnivores

  • Pointed incisors and enlarged canines

  • Shear off pieces small enough to swallow

Bolus

• Lipase is produced by cells in the tongue and begins the breakdown of triglycerides.

• Bolus = wettened mass of food produced in the mouth

• Tongue aids in swallowing, which moves the bolus to the pharynx.

• Soft palate closes off nasopharynx.

• In the trachea, the epiglottis directs food into the esophagus.

Swallowing

• Hard palate, Soft palate, Nasopharynx, uvula, Bolus, Epiglottis, Glottis, Esophagus, Trachea

Esophagus

• Tubular organ that connects the mouth to the stomach.

• Smooth muscles create a wavelike motion called peristalsis.

  • Involuntary response to swallowing.

  • Unidirectional motion that moves bolus to stomach.

Peristalsis

• Esophagus: Takes food to stomach by peristalsis

• Peristalsis - Rhythmical contraction to move contents in tubular organs

Gastro-esophageal Sphincter

• Gastro-esophageal sphincter provides entry into the stomach.

  • Circular smooth muscles that relax in response to swallowing and pressure.

  • Not a true sphincter in humans. (Esophagus remains closed when there is no swallowing.)

  • Acid reflux occurs when stomach acids escape into the esophagus.

Sphincters

• Esophagus, Stomach, Lower esophageal sphincter, Pyloric sphincter

Stomach

• Saclike organ that secretes gastric digestive juices.

• Highly acidic for the chemical breakdown of food and extraction of nutrients.

• Can expand up to 20 times its resting size due to folds within (rugae).

• A major site for protein digestion (except in ruminants).

  • Chief cells secrete pepsinogen, which changes into pepsin within the stomach acid.

  • Parietal cells secrete hydrogen and chloride, which becomes hydrochloric acid.

• High acidity kills many microorganisms.

• Chemical digestion is facilitated by churning action.

• Chyme = mixture of partially digested food and gastric juices

• Pyloric sphincter allows small amount of chyme to enter small intestine.

  • Gastric emptying takes about two to six hours.

• Stomach is protected from extreme acidity by…

  • Thick lining of mucous containing bicarbonate.

  • Chief cells secrete inactive form of pepsin (pepsinogen).

Stomach Wall

• Stomach: Stomach wall has deep folds, folds disappear as the stomach fills to an approximate volume of one liter, Epithelial lining of the stomach has millions of gastric pits, which drain gastric glands, Pepsin is a hydrolytic enzyme that acts on protein to produce peptides

Small Intestine

• Digestion of proteins, carbohydrates, and fats is completed.

• Has enormous surface area because…

  • Long tube with many folds.

  • Villi = fingerlike projections on internal surface

  • Microvilli = fingerlike projections on apical surface of villi

• Villi are lined with epithelial cells that allow for the absorption of simple food molecules.

• Regions include the duodenum, jejunum, and ileum.

Villi

• Villi are folds on the small intestine lining that increase the surface area to facilitate the absorption of nutrients.

Human Digestive Tract

• Accessory organs: Liver, Gallbladder, Pancreas, Salivary glands

• Digestive tract organs: Mouth, Pharynx, Esophagus, Stomach, Small intestine, Large intestine, Rectum, Anus

Duodenum

• Chyme mixes with bile, pancreatic juices, and intestinal juices.

  • Bile (Liver):

    • Emulsifies lipids.

  • Pancreatic juices (Pancreas):

    • Contains variety of digestive enzymes.

  • Intestinal juices (Small Intestine):

    • Adds alkalinity (bicarbonate).

    • Contains variety of digestive enzymes.

• Absorption of fatty acids occurs here.

Liver, Gallbladder, and Pancreas

Jejunum

• Hydrolysis of nutrients continues.

• Most absorption of carbohydrates and amino acids.

• Bulk of chemical digestion and absorption.

Ileum

• Bile salts and vitamins are absorbed.

• Undigested foodstuff passes through the ileocecal valve into the large intestine.

Anatomy of Small Intestine

Large Intestine

• Reabsorbs water and processes waste material.

• Smaller in length but larger in diameter.

• Regions include the cecum, colon, and rectum.

Cecum

• Initial segment.

• Receiving pouch for waste matter.

• Site of attachment for appendix.

Cecum (cont.)

• About 1/3 of the fecal matter is bacteria (live or dead)

Colon

• Houses many bacteria (intestinal flora) that aid in further digestion.

• Regions include the ascending, transverse, descending, and sigmoid colon.

• Main function is to extract water and mineral salts.

• Carnivores have a shorter colon than herbivores.

Rectum and Anus

• Terminal end of large intestine.

• Rectum = store feces until defecation

• Anus = exit point for feces

  • Has inner involuntary and outer voluntary sphincters.

• Feces is propelled via peristaltic movements.

Colon (cont.)

• Transverse colon, Ascending colon, Descending colon, Cecum, Vermiform appendix, Anus, Sigmoid colon, Rectum

Accessory Organs

• Salivary glands

  • Produce saliva.

• Liver

  • Produce bile.

  • Absorbed nutrients from small intestine are processed.

  • Delivered via the hepatic portal vein.

  • Important in detoxification.

Pancreas

• Exocrine gland.

• Assists in reducing the acidity of chyme.

• Produces pancreatic juice and digestive enzymes.

• Pancreatic amylase digests starch to maltose.

• Trypsin digests protein to peptides.

• Lipase digests fat droplets to glycerol and fatty acids.

Liver, Gallbladder, and Pancreas

Digestive System Processes

• Obtaining nutrition and energy from food is a multistep process.

• Ingestion and propulsion.

• Digestion

• Absorption

• Elimination

Steps of Digestion

1. Stage 1: Cephalic: Mechanical chewing, wetting food with saliva in mouth and swallowing of food. Saliva starts digesting carbohydrates.

2. Stage 2: Swallowing: After swallow, food enters esophagus. Peristaltic propulsion of food through the esophagus into stomach.

3. Stage 3: Stomach Digestion: Digestion of proteins using gastric acid and other digestive juices in the stomach. Evacuation of food into the duodenum.

4. Stage 4: Small Intestine: Liver and pancreas produce digestive juices and enzymes to digest food. Digestion of carbohydrates, fats, polypeptides, nucleic acids. Absorption of amino acids, peptides, glucose, fructose, glycerin. Peristaltic propulsion of food in along towards the large intestine

5. Stage 5: Absorption: In the large intestine fermentation of the digestible substances by intestinal flora, synthesis of vitamins. Absorption of water and glucose, fructose, vitamins and minerals.

6. Stage 6: Waste Elimination: Solid waste products from digestion move into the colon and leave body via bowel movements.

Ingestion

• Taking in food through the mouth.

• Teeth, saliva, and tongue play an important role in vertebrates.

• Food is modified into a soft mass that can be swallowed.

Mechanical and Chemical Digestion

Digestion

• Food must be broken down into smaller particles to allow for absorption.

  • Carbohydrates

    • Digestion begins in mouth with salivary amylase (breaks down starches).

    • Acidic environment in stomach stops amylase action.

    • Digestion continues in the duodenum.

      • Pancreatic amylase breaks down starch and glycogen.

      • Brush border enzymes (maltase, sucrase, and lactase) break down disaccharides into monosaccharides.

    • Absorption occurs across the intestinal epithelium.

• Protein * Large amount of digestion occurs in the stomach. * Pepsin breaks down proteins into peptides (four to nine amino acids). * Digestion is continued in the duodenum. * Trypsin, elastase, and chymotrypsin reduce peptides into smaller peptides. * Peptidases (carboxypeptidase, dipeptidase, and aminopeptidase) reduce peptides to free amino acids. * Absorption occurs across the intestinal epithelium.

  • Lipids

    • Digestion begins in the stomach with lingual lipase and gastric lipase.

    • Bulk of digestion occurs in the small intestine.

      • Entrance of chyme triggers hormonal response to release bile.

        • Aids in the digestion of triglycerides.

        • Emulsifies large lipids globules into several small lipid globules.

      • Pancreatic lipase breaks down lipids into fatty acids and glycerides.

    • Absorption sends chylomicrons into lymphatic vessels that enter the bloodstream via the subclavian vein.

      • Bile salts surround long-chain fatty acids and monoglycerides forming micelles.

      • Micelles move into the brush border of the small intestine absorptive cells.

      • Fatty acids and monoglycerides enter the absorptive cells and form triglycerides.

      • Triglycerides aggregate and become coated with proteins to become chylomicrons.

      • Chylomicrons leave the absorptive cells via exocytosis.

  • Vitamins

    • Fat-soluble vitamins are absorbed in the same manner as lipids.

    • Water-soluble vitamins can be directly absorbed into the bloodstream form the intestine.

Carbohydrate Digestion

• Digestion of carbohydrates is performed by several enzymes.

• Starch and glycogen are broken down into glucose by amylase and maltase.

• Sucrose (table sugar) and lactose (milk sugar) are broken down by sucrase and lactase, respectively.

Protein Digestion

Lipid Digestion and Absorption

Absorption

• Mucous membrane of small intestine

• Has ridges and furrows that give it a corrugated surface

• Villi are ridges on the surface, which contain even smaller ridges, microvilli

• Greatly increase absorptive area

• Each villus contains blood capillaries and a lymphatic capillary (lacteal)

Elimination

• Final step in digestion.

• Removes undigested food material.

• Water is reabsorbed in the colon.

• Intestinal flora can perform some further digestion.

• Semi-solid waste is moved via peristalsis.

• As rectum expands in response to storage it triggers the neural signals required to set up the urge to eliminate.

• Feces is eliminated out the anus.

• Common Problems with Elimination

  • Constipation = hardened feces due to excess water removal in colon

  • Diarrhea = insufficient removal of water in colon

  • Emesis (vomiting) = elimination of food via forceful expulsion through the mouth

Lesson 2: Nutrition and Food Processing in Plants

Objectives

1. Describe how plants obtain the nutrients they need to grow and develop

2. Identify the macronutrients and micronutrients needed by plants for growth and development

3. Describe the process of photosynthesis

Plant Nutrition

• Unlike animals, plants can produce their own food. Plants also need nutrients to survive, grow, and continue manufacturing food. Plants get the nutrients they need from several sources.

• Plants need nutrients from the soil:

  • Mineral nutrients

  • Home for several bacteria and fungi (nitrogen- fixers)

• By-products of photosynthetic activities (Oxygen and glucose)

Nutrients obtained from soil

• Organic compost (consists largely of decayed organic matter)

• Minerals (nitrogen, phosphorus, potassium)

• Water

• Soil gases (nitrogen, carbon dioxide, oxygen)

• Microorganisms (bacteria, fungi)

Plant Requirements

• Macronutrients – molecules that plants need in relatively large amounts

  • carbon, oxygen, hydrogen, nitrogen, potassium, calcium, magnesium, phosphorus, and sulfur

• Micronutrients – required in relatively small quantities

  • chlorine, iron, manganese, boron, zinc, molybdenum, and copper

  • Deficiency can generate severe effects on plant growth and development

Overview: The Process That Feeds the Biosphere

• Photosynthesis is the process that converts solar energy into chemical energy

• Directly or indirectly, photosynthesis nourishes almost the entire living world

  • Autotrophs sustain themselves without eating anything derived from other organisms

    • Autotrophs are the producers of the biosphere, producing organic molecules from $CO_2$ and other inorganic molecules

    • Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules from $H<em>2O$ and $CO</em>2$

• Photosynthesis occurs in plants, algae, certain other protists, and some prokaryotes

  • These organisms feed not only themselves but also most of the living world

Autotrophs

• Plants

• Multicellular alga

• Unicellular protist

• Cyanobacteria

• Purple sulfur bacteria

• Heterotrophs obtain their organic material from other organisms

• Heterotrophs are the consumers of the biosphere

• Almost all heterotrophs, including humans, depend on photoautotrophs for food and $O_2$

  • Characterized as parasitic, saprophytic, or holozoic, depending on the mode of food intake

• PARASITIC - Organisms (parasites) obtain organic compounds from another living organism of a different species (host)

  • Parasite is benefited

  • Host is harmed

• SAPROPHYTIC
  Organisms feed on dead organisms or non- living organic matter (saprophytes)
  Decomposers

• HOLOZOIC

  • Ingest food that is mechanically broken down and is subsequently digested by enzymes produced within organisms. *Types of animals taking holozoic nutrition

    1. Herbivores – feed on plants only

    2. Carnivores – feed on animals only

    3. Omnivores – Feed on both plants and animals

Photosynthesis

$6CO<em>2 + 6 H</em>2O <br>ewline Sunlight <br>ewline C<em>6H</em>{12}O<em>6 + 6O</em>2 +Chlorophyl<br>Concept Photosynthesis converts light energy to the chemical energy of food</p><ul><li><p>Chloroplasts are structurally similar to and likely evolved from photosynthetic bacteria</p></li><li><p>The structural organization of these cells allows for the chemical reactions of photosynthesis</p></li></ul><h5 id="2f070287-0828-43d2-bf19-bc34b26d53c0" data-toc-id="2f070287-0828-43d2-bf19-bc34b26d53c0" collapsed="false" seolevelmigrated="true">Chloroplasts: The Sites of Photosynthesis in Plants</h5><ul><li><p>Leaves are the major locations of photosynthesis</p></li><li><p>Their green color is from chlorophyll, the green pigment within chloroplasts</p></li><li><p>Light energy absorbed by chlorophyll drives the synthesis of organic molecules in the chloroplast</p></li><li><p>CO<em>2$ enters and $O</em>2 exits the leaf through microscopic pores called stomata<br>*Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf</p></li><li><p>A typical mesophyll cell has 30–40 chloroplasts</p></li><li><p>The chlorophyll is in the membranes of thylakoids (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana</p></li><li><p>Chloroplasts also contain stroma, a dense fluid</p></li><li><p>Tracking Atoms Through Photosynthesis: Scientific Inquiry</p><ul><li><p>Photosynthesis can be summarized as the following equation:<br>*6CO<em>2 + 12H</em>2O + Light energy \rightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2 + 6H_2O<br>The Two Stages of Photosynthesis: A Preview</p></li></ul></li><li><p>Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis part)</p></li><li><p>The light reactions (in the thylakoids):</p><ul><li><p>Split$H_2O$</p></li><li><p>Release$O_2$</p></li><li><p>Reduce NADP+ to NADPH (Nicotinamide adenine dinucleotide phosphate)</p></li><li><p>Generate ATP from ADP by photophosphorylation (splitting of the water molecule in oxygen and hydrogen protons <br>*The Calvin cycle (in the stroma) forms sugar from$CO_2$, using ATP and NADPH (Nicotinamide Adenine Dinucleotide Phosphate)</p></li></ul></li><li><p>The Calvin cycle begins with carbon fixation, incorporating$CO_2$into organic molecules</p></li></ul><h5 id="fcdf7d01-e372-4111-bd52-306c62a0cb2d" data-toc-id="fcdf7d01-e372-4111-bd52-306c62a0cb2d" collapsed="false" seolevelmigrated="true">Photosynthesis Steps</h5><ol><li><p>Light</p></li><li><p>$H_2O$</p></li><li><p>Light Reactions</p></li><li><p>NADP+</p></li><li><p>ADP</p></li><li><p>$O_2$</p></li><li><p>$CO_2$$

Special Nutritional Strategies in Plants

• Symbiotic relationship with Rhizobium species – bacteria provides ammonia and nitrate in exchange for carbohydrates
  *Symbiotic relationship with Mycorrhizal fungi – increases surface area of roots for Phosphorous uptake (other micronutrients)

• Some carnivorous plants (Nepenthes, Dionaea, and Drosera) capture and digest insects to obtain nitrogenous nutrients

• Parasitic plants (Dodder) lacking chlorophyll tap into nutrient reserves a host plants

Natural Adaptations in plants

• Epiphytes – grow on other plants, but do not harm their host

• Parasitic Plants – absorb water, minerals, and sugars from their host
  *Carnivorous Plants – photosynthetic but supplement their mineral diet with insects and small animals; found in nitrogen poor soils

Nutritional Adaptations in Plants

• Epiphytes- grow on other plants, but do not harm their host

• Parasitic Plants-absorb water, minerals, and sugars from their host

• Carnivorous Plants- photosynthetic but supplement their mineral diet with insects and small animals; found in nitrogen poor soils