Biochemistry Study Guide

 

Biochemistry Study Guide

 

1. Molecules with a slightly negative end and a slightly positive end are called ___________________  _____________________________.

2. A monomer of protein is called an __________________  __________________.

3. An attractive force between like particles is called ___________________________.

4. Organic molecules that catalyze reactions in living systems are ______________________.

5. The compound found in living things that supplies the energy in one of its chemical bonds directly to cells is ______________________.

6. Enzymes lower activation energy by___________ to the ____________________ and ______________________ bonds within the ________________________.

7. The monomers that make up nucleic acids are called __________________________.

8. The type of attraction that holds two water molecules together is called __________________________  __________________________.

9. The sharing of three pairs of electrons is called a ___________________  _____________.

10.  The structural building block that determines the characteristics of a compound is called the _____________________________  _______________________.

11.  Large carbon compounds are built from smaller molecules called ______________________________.

12.  What is the type of reaction that forms large molecules from smaller ones? _________________________________  _____________________________.

13.  What type of reaction breaks large molecules into smaller ones? _______________________

14.  What is the by product of a condensation reaction? __________________________

15.  The attractive force between unlike particles is called ____________________________.

16.  A compound that is stored as glycogen in animals and as a starch in plants is ____________________________________.

17.  Lipids are good energy storage molecules because they have many _________________-___________________ bonds.

18.  What are the components of many lipids? ________________________  ______________________

19.  What is the monomer of many polysaccharides? ______________________________

20.  What kind of reaction allows amino acids to become linked together? ________________________________  _____________________________.

21.  Nucleic acids function primarily to carry __________________________  ____________________ and direct _____________________  ______________________.

22. Tends not to react with water, “Water Fearing”  ________________________________

23. Attracted to water molecules, “Water Loving” _________________________________

24. Water is called a ___________________________  ___________________________.
DIRECTIONS: Read Chapter 3, Biochemistry, and Answer the questions below as completely and as thoroughly as possible. Answer the question in essay form (not outline form), using complete sentences. You may use diagrams or pictures to supplement your answers, but a diagram or picture alone without appropriate discussion is inadequate.

1. Describe the structure of a water molecule, and explain how the electrical charge is distributed over the molecule.

2. Describe the structure of amino acids and proteins.

3. What are the structural differences between monosaccharides, disaccharides, and polysaccharides?

4. What is capillarity? Include defining Adhesion and Cohesion.

5. How does a condensation reaction differ from a hydrolysis reaction?

6. Give Three reasons why water is an effective solvent.

7. What is an organic compound?

8. What property allows carbon compounds to exist in a number of forms?

9. The presence of four electrons in the outermost energy level of a carbon atom enables
carbon atoms to form what THREE Things.

10. Living things contain many different proteins of vastly different shapes and functions.
What determines the shape and thus the function of a particular protein?

11. How does the structure of a phospholipid, linear molecules with a polar end and a
nonpolar end, relate to their function in the cell membrane?

 

Biology First Semester


BiLogy I
Updated May 2007

Week of August 20 assignments:
Issue textbooks class rules, needed materials; Start answering chapter 1 worksheet; PowerPoint: Introduction to Biology; Set up notebooks

Week of August 27 assignments:
Explain website & work on & complete chapter 1 worksheet ; PowerPoint on scientific method; Scientific Method & Safety; Safety & equipment worksheet and TEST; Handout: Writing lab report

Week of September 3 assignments: 
Lab: Volume of an Irregular Object;  *Chapter 1 Test; Read & outline chapter 2 on Chemistry

Week of September 10 assignments:
PowerPoint: Chemistry; Symbols & Formula handout; chapter 2 outline due; Worksheet on atoms & molecules; *Symbol & Formula TEST

Week of September 17 assignments:    Interims    

Lab: Chromatography of Inks; Chapter 2 Chemistry TEST; Read & outline chapter 3 on Biochemistry; start PowerPoint: Biochemistry

Week of September 24 assignments:
Lab write up due!; Chapter 3 outline due; Assign nucleotide model; complete Biochemistry ppt

Parent-Teacher Conference – 3 to 7 pm!

Week of October 1 assignments:
Video: Organic Compounds; Lab: Building Organic Molecules; chapter 3 study guide; TEST on chapter 3 Biochemistry; Read & outline chapter 4 on Cells; Organic Model due!

Week of October 8 assignments:
Lab: Water Properties; Assign Chapter 4 Cell drawings; chapter 4 outline due; start PowerPoint on Cells

 

Week of October 15  assignments:
Continue ppt on Cells; Work on cell drawings


End of First Nine weeks

      Biology I


Week of October 22 assignments:     

Assign Cell Model; Cell drawings due; chapter 4 study guide; TEST on chapter 4 Cells; Lab: McMush; Read & outline chapter 5 on Homeostasis & Transport

 

 

Week of October 29 assignments:    

Cell models due; PowerPoint: Homeostasis & Transport; McMush lab write up due

 

Week of November 5 assignments:

Chapter 5 outline due; study guide for chapter 5 test; Lab: Egg Osmosis; TEST on chapter 5 Homeostasis & Transport; Read & outline chapter 6 on Photosynthesis

Week of November 12 assignments: Interims
PowerPoint: Photosynthesis; Video Photosynthesis; Chapter 6 outline due

Week of November 19 – 23:    

  Thanksgiving Break!     Thanksgiving Break!     Thanksgiving Break!

Week of November 26 assignments:
Lab:  Chromatography of Plant Pigments; chapter 6 study guide; Chapter 6 TEST on Photosynthesis; Read & outline Chapter 7 on cellular respiration, Start Cellular Respiration PowerPoint: Chromatography lab write up due

Week of December 3 assignments:
Lab: Making Root beer; Complete chapter 7 cell respiration PowerPoint; study guide for chapter 7 test; *TEST on Chapter 7 Cellular Respiration; Read & answer chapter 9 worksheet

Week of December 10 assignments:
Cover cell cycle, chromosomes, mitosis & meiosis; chapter 9 worksheet due; TEST on Chapter 9 Cell Division; Review for Semester Test

Week of December 17 assignments:
Monday review for semester test!

Semester Tests on   Wednesday, Thursday, and Friday!  

           End of First Semester

   Biology I

Arthropod

Arthropods
Non-Insects

Characteristics

  • Makes up 3/4’s of all animal species
  • Includes insects, spiders, scorpions, millipedes, centipedes, crabs, lobsters, & crayfish
  • Arthropod means “jointed foot”
  • Jointed appendages (legs, antenna, mouthparts)
  • Segmented body with paired appendages on each segment)
  • External exoskeleton made of chitin (carbohydrate) & protein for protection & support
  • Exoskeleton has 3 layers — outer waxy layer repels water, middle layer has calcium for extra strength, & inner layer has flexible joints for movement
  • Protostomes (blastopore develops into mouth)
  • Coelomate (mesoderm-lined body cavity)
  • Ventral nervous system
  • Open circulatory system
  • Specialized sensory receptors & high degree of cephalization
  • Have simple or compound eyes & segmented antenna

Movement & Growth

  • Muscles occur in bundles & are attached to inside of exoskeleton on each side of joints
  • Exoskeleton must be periodically molted (shed) for organism to grow
  • Molting called ecdysis
  • Molting hormone released & causes epidermal cells to secrete enzymes that digest & loosen inner exoskeleton
  • New exoskeleton secreted by epidermal cells flexible at first & must harden so arthropod not vulnerable to predators so often stay in hiding after molting
  • Arthropods go through numerous molts


Butterfly Molting Pupal Case

Evolution & Taxonomy

  • Evolved from ancestral arthropod with many body segments each with appendages
  • Modern arthropod segments fused into larger, specialized structures called tagmata
  • Four subphyla
    * Trilobita – extinct trilobites
    * Crustacea – shrimps, lobsters, crayfish, & barnacles
    * Chelicerata – spiders, scorpions, & ticks
    * Uniramia -centipedes, millipedes, & insects

Subphylum Trilobita
Characteristics

  • Includes extinct trilobite
  • Marine
  • Have a head & segmented trunk with one pair of legs on each segment
  • Breathe through gills
  • Single pair of antenna


TRILOBITE

Subphylum Chelicerata
Characteristics

  • Includes 2 classes — Xiphosura (horseshoe crab) and Arachnida (spiders, ticks, scorpions, & mites)
  • Have a cephalothorax (fused head& thorax) and abdomen
  • No antenna
  • Simple eyes or ocelli
  • Have 6 pairs of jointed appendages:
    * Chelicerae – claws or fangs (1 pair)
    * Pedipalps – used for feeding, walking, sensing, transferring sperm (1 pair)
    * Walking legs – movement (4 pairs)
  • Horseshoe crab
    * Marine
    * Not true crabs
    * Fanglike pincers or chelicerae
    * Use book gills to breathe


HORSESHOE CRAB

  • Arachnids
    * Terrestrial
    * Eight legs
    * Chelicerae or fangs with venom
    * Ocelli
    * No antenna
    * Breathe by book lungs &/or tracheal tubes
  • Spiders
    * Arachnid that feeds on insects (carnivores)
    *  Have oval shaped, unsegmented abdomen
    * Cephalothorax connected by narrow waist to abdomen
    * Have 8 simple eyes or ocelli
    * Fangs pierce prey, inject poison, & suck out body fluids
    * Pedipalps on head help sense prey & move it to the mouth
    * Open circulatory system
    * Ostia are openings in heart where blood reenters
    * Body cavity called hemocoel
    * Hemocycanin is oxygen-carrying pigment in blood
    * Have silk glands to make silk & spinnerets to release silk for webs
    * Breathe by book lungs & tracheal tubes
    * Malpighian tubules filter wastes & reabsorb water


GARDEN SPIDER

  • Ticks & Mites
    * Parasitic arachnid
    * Fused cephalothorax & abdomen
    * Most abundant arachnid
    * Need blood meal to molt
    * Mites can damage fruit & feed on dead skin at base of hair follicle
    * Ticks carry Lyme disease & Rocky Mountain Spotted Fever

 


MITE

TICK

 

  • Scorpions
    * Have a cephalothorax & long segmented abdomen curled over body
    * Prefer dry regions
    * Poisonous stinger on end of abdomen
    * Breathe through book lungs
    * Pedipalps modified into claws
    * Nocturnal predators


SCORPION

Subphylum Crustacea
Characteristics

  • Marine members include shrimp, lobster, copepods, barnacles, & crabs

 

CRAB SHRIMP

 

  • Terrestrial crustaceans called isopods include pillbugs & sowbugs


PILLBUG

  • Freshwater members include crayfish & Daphnia (water fleas)


DAPHNIA

  • All have jaws are mandibles for chewing or tearing
  • Known as mandibulates
  • Have cephalothorax & abdomen
  • Have 10 pairs of jointed appendages
  • Breathe through gills
  • Barnacles
    * Marine
    * Sessile crustaceans that live in limestone case
    * Filter plankton with 12 appendages called cirri


BARNACLE

  • Isopods (pillbugs & sowbugs)
    * Live on land in dark places
    * Have 7 pairs of legs on a segmented body
    * Can roll into a ball for protection
  • Crayfish
    * Cephalothorax made of 13 fused segments & covered by protective carapace
    * Antennules located on head help in balance, touch, & taste
    * Statocysts – balancing organs at the base of antennules
    * Antenna on head used for touch & taste
    * Maxillae – paired mouthparts that move side to side to tear food
    * Maxillipeds – help hold food
    * Chelipeds – claws used to capture food & for protection
    * Mandibles – jaws that move up & down to crush  food
    * Walking legs – 8 pairs used for movement
    * Swimmerets – under abdomen to swim, gas exchange, & protect eggs/young
    * Abdomen ends in flat segment called telson with flat uropods on each side


CRAYFISH

               * Compound eyes on stalks
* Chitinous teeth in stomach grind food
* Wastes leave through anus
*  Green glands filter wastes from blood & help with salt balance
*  Open circulatory system with heart to pump blood to gills & body cells
* Ostia – one way valves allowing blood from dorsal sinus to reenter heart
* Gills attached to walking legs
* Separate sexes that mate in fall & sperm stored in seminal receptacle
*  Eggs attach to swimmerets of female & hatch in several weeks

  • Copepods
    * Largest group of crustaceans
    *  Make up most of the marine plankton
    *  Serve as food for many marine animals
    *  Found in freshwater, marine, & moist terrestrial environments


COPEPOD

Subphylum Uniramia
Characteristics

  • All have antenna, mandibles (jaws), & unbranched appendages
  • Includes 3 classes — Chilopoda (centipedes), Diplopoda (millipedes), & Insecta
  • Known as myriapods
  • Most are terrestrial
  • Exoskeleton prevents desiccation (water loss)

Class Chilopoda

  • Terrestrial centipedes
  • Flattened body with longer legs for fast movement
  • Have 1 pair of legs per body segment
  • Predators
  • Mandibles & maxilla for chewing prey (insects & earthworms)
  • Claw-like appendages or pincers on 1st body segment that can inject venom
  • Can coil up for defense


CENTIPEDE

Class Diplopoda

  • Terrestrial millipedes
  • Have 2 pairs of legs per body segment
  • Rounded body
  • Scavengers on decaying vegetation as they burrow through soil
  • Roll into ball when threatened & spray noxious chemical containing cyanide


MILLIPEDE

BACK

 

Bacteria

KINGDOMS ARCHAEBACTERIA & EUBACTERIA


All Materials © Cmassengale

Bacterial Evolution & Classification 

  • Most numerous organisms on earth
  • Earliest life forms (fossils date 2.5 billion years old)
  • Microscopic prokaryotes (no nucleus nor membrane-bound organelles)
  • Contain ribosomes
  • Infoldings of the cell membrane carry on photosynthesis & respiration
  • Surrounded by protective cell wall containing peptidoglycan (protein-carbohydrate)
  • Many are surrounded by a sticky, protective coating of sugars called the capsule or glycocalyx (can attach to other bacteria or host)
  • Have only one circular chromosome
  • Have small rings of DNA called plasmids
  • May have short, hairlike projections called pili on cell wall to attach to host or another bacteria when transferring genetic material
  • Most are unicellular

  • Found in most habitats
  • Most bacteria grow best at a pH of 6.5 to 7.0
  • Main decomposers of dead organisms so recycle nutrients
  • Some bacteria breakdown chemical & oil spills
  • Some cause disease 
  • Move by flagella, gliding over slime they secrete ( e.g. Myxobacteria)
  • Some can form protective endospores around the DNA when conditions become unfavorable; may stay inactive several years & then re-activate when conditions favorable
  • Classified by their structure, motility (ability to move), molecular composition, & reaction to stains (Gram stain)
  • Grouped into 2 kingdoms — Eubacteria (true bacteria) & Archaebacteria (ancient bacteria)
  • Once grouped together in the kingdom Monera

 

STRUCTURE FUNCTION
Cell Wall protects the cell and gives shape
Outer Membrane protects the cell against some antibiotics (only present in Gram negative cells)
Cell Membrane regulates movement of materials into and out of the cell; contains enzymes important to cellular respiration
Cytoplasm contains DNA, ribosomes, and organic compounds required to carry out life processes
Chromosome carries genetic information inherited from past generations
Plasmid contains some genes obtain through genetic recombination
Capsule, and slime layer protects the cell and assist in attaching the cell to other surfaces
Endospore protects the cell against harsh environmental conditions, such as heat or drought
Pilus (Pili) assist the cell in attaching to other surfaces, which is important for genetic recombination
Flagellum moves the cell

 

Kingdom Archaebacteria

  •   Found in harsh environments (undersea volcanic vents, acidic hot springs, salty water)
  • Cell walls without peptidoglycan
  • Subdivided into 3 groups based on their habitat — methanogens, thermoacidophiles, & extreme halophiles

Methanogens

  • Live in anaerobic environments (no oxygen)
  • Obtain energy by changing H2 and CO2 gas into methane gas
  • Found in swamps, marshes, sewage treatment plants, digestive tracts of animals
  • Break down cellulose for herbivores (cows)
  • Produce marsh gas or intestinal gas (methane)

Extreme Halophiles

  •   Live in very salty water
  •   Found in the Dead Sea, Great Salt Lake, etc.
  • Use salt to help generate ATP (energy)

Thermoacidophiles (Thermophiles)

  • Live in extremely hot  (1100C) and acidic (pH 2) water
  • Found in hot springs in Yellowstone National Park, in volcanic vents on land, & in cracks on the ocean floor that leak scalding acidic water

Kingdom Eubacteria (true bacteria)

  • Most bacteria in this kingdom
  • Come in 3 basic shapes — cocci (spheres), bacilli (rod shaped), spirilla (corkscrew shape)

  • Bacteria can occur in pairs ( diplo– bacilli or cocci)
  •   Bacteria occurring in chains are called strepto- bacilli or cocci
  • Bacteria in grapelike clusters are called staphylococci
  • Most are heterotrophic (can’t make their own food)
  • Can be aerobic (require oxygen) or anaerobic (don’t need oxygen)
  • Subdivided into 4 phyla — Cyanobacteria (blue-green bacteria), Spirochetes, Gram-positive, & Proteobacteria
  • Can be identified by Gram staining (gram positive or gram negative)  

Gram Staining

  • Developed in 1884 by Danish microbiologist, Hans Gram
  •   Bacteria are stained purple with Crystal Violet & iodine; rinsed with alcohol to decolorize; then restained with Safranin (red dye)

  • Bacterial cell walls either stain purple or reddish-pink

Gram-positive bacteria (Gram +)

  • Thick layer of peptidoglycan (protein-sugar) complex in cell walls & single layer of lipids
  • Stain purple

  • Lactobacilli are used to make yogurt, buttermilk ….
  • Actinomycetes make antibiotics like tetracycline & streptomycin
  • Disease-causing gram + bacteria produce poisons called toxins
  • Clostridium causes tetanus or lockjaw
  • Streptococcus cause infections such as “strep” throat

  • Staphylococci cause “staph” infections

  • Also cause toxic shock, bacterial pneumonia, botulism (food poisoning), & scarlet fever
  • Can be treated with penicillin (antibiotics) & sulfa drugs

Gram-negative bacteria (Gram -)

  • Cell walls have a thin layer of peptidoglycan & an extra layer of lipids on the outside
  • Stain pink or reddish 

  • Lipid layer prevents the purple stain & antibiotics from entering (antibiotic resistant)
  • Some are photosynthetic but make sulfur, not oxygen
  • Rhizobacteria grow in root nodules of legumes (soybeans, peanuts…) & fix nitrogen form the air for plants
  • Rickettsiae are parasitic bacteria carried by ticks that cause Rocky Mountain spotted fever
  • Spirochetes can cause syphilis & Lyme disease

Phylum Cyanobacteria

  • Gram negative
  •   Carry on photosynthesis & make oxygen
  • Called blue-green bacteria
  • Contain pigments called phycocyanin (red & blue) & chlorophyll a (green)
  •    May be red, yellow, green, brown, black, or blue-green
  • Some grow in chains (e.g. Oscillatoria)  & have specialized cells called heterocysts that fix nitrogen


OSCILLATORIA

  •  First bacteria to re-enter devastated areas
  • Anabaena that live on nitrates & phosphates in water can overpopulate & cause “population blooms” or eutrophication
  •   After eutrophication, the cyanobacteria die, decompose, & use up all the oxygen for fish

Phylum Spirochetes

  •   Gram positive
  • Have flagella at each end so move in a corkscrew motion
  •   Some are aerobic (require oxygen); others are anaerobic
  • May be free-living, parasitic, or live symbiotically with another organism  

Phylum Gram Positive bacteria

  • Most are Gram +, but some are Gram –
  • Lactobacilli grow in milk & make lactic acid (forms yogurt, cottage cheese, buttermilk) & also found on teeth & cause tooth decay
  • Actinomycetes grow in the soil & make antibiotics
  • Gram + members are found in the oral & intestinal cavities & slow the growth of disease-causing bacteria

Phylum Proteobacteria

  • Largest & most diverse bacterial group
  • Subdivided into Enteric bacteria, Chemoautotrophic bacteria, & Nitrogen-fixing bacteria  

Enteric bacteria

  • Gram negative heterotrophs
  • Can live in aerobic & anaerobic environments
  • Includes E. coli that lives in the intestinal tract making vitamin K & helping break down food
  • Salmonella causes food poisoning

Chemoautotrophs

  • Gram negative bacteria that obtain energy from minerals  
  • Iron-oxidizing bacteria found in freshwater ponds use iron salts for energy

Nitrogen-Fixing bacteria

  • Rhizobium are Gram negative & live in legume root nodules

  • 80% of atmosphere is N2, but plants can’t use nitrogen gas
  • Nitrogen-fixing bacteria change N2 into usable ammonia (NH3)
  • Important part of the Earth’s nitrogen cycle

Methods of Nutrition

  •  Saprobes feed on dead organic matter
  •  Parasites feed on a host cell
  •  Photoautotrophs use sunlight for energy, but get carbon from organic compounds (not CO2) to make their own food  
  • Chemoautotrophs obtain food by oxidizing inorganic substances like sulfur, instead of using sunlight

Methods of Respiration

  •   Obligate aerobic bacteria can’t live without oxygen; (tuberculosis bacteria)
  •  Obligate anaerobes die if oxygen is present; (tetanus bacteria that causes lockjaw)
  • Facultative anaerobes do not need oxygen, but don’t die if oxygen is present; (E. coli)
  • Anaerobes carry on fermentation, while aerobes carry on cellular respiration 

Bacterial Reproduction & Genetic Recombination

  • Most bacteria reproduce asexually by binary fission (chromosome replicates & then the cell divides)  
  •   Bacteria replicate (double in number) every 20 minutes under ideal conditions  
  • Bacteria contain much less DNA than eukaryotes
  • Bacterial plasmids are used in genetic engineering to carry new genes into other organisms  
  • Bacteria recombine genetic material in 3 ways — transformation, conjugation, & transduction

Conjugation

  • Sexual reproductive method
  • Two bacteria form a conjugation bridge or tube between them

  •   Pili hold the bacteria together
  •   DNA is transferred from one bacteria to the other       

Transformation

  • Bacteria pick up pieces of DNA from other dead bacterial cells
  • New bacterium is genetically different from original

Transduction

  • A bacteriophages (virus) carries a piece of DNA from one bacteria to another

  • Human insulin is produced in the lab by this method

Pathogenic bacteria

  •   Known as germs or pathogens
  • Cause disease
  • Can produce poisonous toxins
  • Endotoxins are made of lipids & carbohydrates by Gram – bacteria & released after the bacteria die (cause high fever, circulatory vessel damage…)
  • E. coli  produce endotoxins
  • Exotoxins are made of protein by Gram + bacteria 
  • Clostridium tetani produce exotoxins
  • Antibiotics interfere with cellular functions (Penicillin interferes with synthesis of the cell wall; tetracycline interferes with protein synthesis)
  • Some antibiotics are made by bacteria or fungi
  • Broad-spectrum antibiotics affect a wide variety of organisms
  • Bacteria can mutate and become antibiotic resistant (often results from overuse of antibiotics)
BACK

 

Bacteria Culturing Activity

 

Where are Bacteria Found?  

 

 

Introduction:

They’re everywhere. Bacteria are the huddled masses of the microbial world, performing tasks that include everything from causing disease to fixing nitrogen in the soil. The estimated number of bacteria on Earth is five million trillion trillion — that’s a five with 30 zeroes after it.  When people think of bacteria, they likely first consider the nasty ones that cause disease, but the bacteria inside all animals combined — including humans — makes up less than one percent of the total amount. By far the greatest numbers are in the subsurface, soil and oceans.

 

Objectives:

  1. To take bacterial swabs from various places in the school
  2. To inoculate a petri dish with a bacterial culture
  3. To count bacterial colonies
  4. To determine what kind of environmental conditions influence bacterial growth

Materials: 

Petri dish,  pencil,  incubator, hot water bath, nutrient agar, thermometer

Procedure (Part A): Petri Dish Preparation

  1. Set up a hot water bath at 95oC.
  2. Loosen the caps and place nutrient agar bottle in hot water bath until agar liquefies. (Agar melts above 95oC and remains liquid until cooled to about 45oC.)
  3. Remove agar bottles and allow the agar to cool to about 50-55oC.
  4. Partially lift the cover of the petri dish and pour about 15-20ml of liquid to cover 2/3 of the plate surface.
  5. Lower the lid of the dish and gently swirl the plate to spread the media over all the bottom surface.

  1. Repeat step 5 to fill other petri dishes.
  2. DO NOT MOVE the covered plates until the nutrient agar has solidified.
  3. Once the plates are solidified, turn the plates upside down (presents condensation from getting on the agar surface).
  4. From this moment on, keep the plates upside down (condensation will disappear) in a dark, dust-free place in the room until ready to add bacteria. If plates will not be used for several days, refrigerate them.
  5. Check plates for contamination before proceeding to Part B. Discard contaminated plates.

Materials: 

Petri dish with nutrient agar, sterile cotton swabs, permanent marker, index card with sample location, pencil,  incubator

 

Procedure (Part B): Collecting Bacteria

  1. Choose an index card to determine your sample location
  2. Turn the petri dish upside down, and using your marker, place your initials, date and sample location along the bottom perimeter of the dish, NOT in the middle
  3. Get your sterile Q-tip, being very careful not to touch the side that will collect your sample. Go to your assigned area and quickly swab and return with your sample! (Sample locations included door handles, water faucets, desk tops, etc.)
  4. Carefully open your dish just enough to lightly rub your Q-tip in a zigzag pattern across the agar.

  1. Draw what your dish looks like in Figure 1 and record the number of bacterial colonies, if any, present on the agar surface in table 1
  2. Place your petri dish upside down in the incubator to be examined again in a few days.
  3. Recheck the plates after 1 day, 2 days, and 5 days. Count and record the number of bacterial colonies on each plate. If the plate is  completely covered with bacteria, record “lawn” in the data table.
  4.  Ignore “fuzzy” appearing colonies that are actually fungi!

Example of Bacterial Colonies on Plate

Data:

Reminder — Fuzzy Colonies = Fungus not Bacteria

Figure 1 

Day 1                Day 2                Day 5

   

Table 1:   Number of Colonies on petri dish 

    Location:
Day Number of Colonies

 

Analysis:  

  1. Compare the number of colonies on your plate on day 5 with the plates collected from other locations. Did any of the areas show a greater number of bacteria? How many clusters of bacteria appear to be growing in each petri dish?
  2. Which petri dish had the most growth? The Least?
  3. Why was the agar sterilized before this investigation?
  4. What kind of environmental conditions seem to influence where bacteria are found?
  5. How can you control the amount of bacteria that you will encounter?
  6. Check the plate that the teacher has had open, exposed to the air for several days. What did you observe and why?

Dispose of the petri dishes carefully!  Place them in a biohazard bag to be autoclaved.

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