Review:Scientific Method and Cells

The Scientific Method• O = observe• P = problem• H = hypothesis• E = experiment and record data• A = analyze data• C = conclusions• R = repeat and continue research

“OPHEACR”

Hypothesis & Experiment• Propose a hypothesis: an educated guess to predict possible

answer to problem based on research, previous knowledge, observations, and information from studying a problem

• Test a hypothesis: design an experiment to test hypothesis with repeated trial, large sample size* and collection of data

• Controlled experiment = tests only one* changing factor or variable and other parts remain the same or controlled

– control group* = does not change during testing, compared to experimental results

– experimental group = contains change being tested– Manipulated or independent variable = what you change (becomes

experimental group)– Responding or dependent variable = what you measure, depends on

other variable

Data Tables

• To record and organize observations

Line Graphs

• To show change over time

DependentVariable

Independent Variable

0

Analyze Data & Valid Conclusions

• Inference: your judgment based on an observation• Interpret what the data means for example by

graphing or using calculations• Review data from observations to determine if data

supports hypothesis and to develop additional hypotheses, generalizations or explanations

• Hypothesis is either supported or rejected (not proven!)

Repeat the experiment

• many scientists repeatedly test the experiment to ensure conclusions are supported and may become a scientific law – a. Facts = based on experiments and careful observations– b. Theories = scientific hypotheses that have been tested

many times and confirmed by many scientists– c. Scientific law = result of many scientists repeatedly

reaching the same conclusions

Metric Conversions

Kilo-Hecto-

Deca-

deci-centi-

milli-

Kilo (K) = Thousand, so 1km = 1000m

Centi (c) = Hundredth, so 1cm = 1/100m or 0.01m

Milli (m) = Thousandth, so 1mm = 1/1000m or 0.001m

Micro (µ) = 1µm = 1/1000000 or 0.000001m

pH• The pH scale ranges from 0 to 14 and increases by a factor of 10

– pH of 7 = neutral because there’s an equal number of H+ & OH- ions

– pH < 7 = acids because there’s more H+ ions than OH- ions– pH > 7 = bases because there’s less H+ ions than OH- ions

Organic Compounds• Contain carbon and hydrogen• Ex: C6H12O6

CH4

Chemical Reactions• A process that changes a set of chemicals into

another set of chemicals• Reactants = the set of chemicals that enters

into a chemical reaction• Products = the set of chemicals produced by a

chemical reaction• Chemical reactions break bonds in the

reactants and form new bonds in the products• When chemical bonds break or form, energy is

released or absorbed• Organisms need to carry out reactions that

require energy– Plant get energy from sunlight– Animals get energy from plants or other

animals and release energy by breaking down food

Catalysts

• A catalyst is a substance that speeds up the rate of a chemical reaction by lowering the activation energy.

• Enzymes are proteins that act as biological catalysts to speed up chemical reactions in cells.

• Enzymes are very specific and they are usually named after the reaction they catalyze and end in -ase

Enzyme Action• Reactants must collide with enough energy to break bonds and form

new ones• Enzymes provide a site for the substrates (reactants) to react, reducing

the energy needed for the reaction to occur• Enzymes are specific having an active site that is complementary to the

shape of the substrates it catalyzes = “lock and key” • This forms an enzyme-substrate complex• Enzymes activity can be affected by any variable that influences a

chemical reaction– pH– Temperature

Unicellular vs. Multicellular Organisms

• One-celled organism is able to function despite lacking the levels of organization present in more complex organisms.

• The structures present in some single-celled organisms act in a manner similar to the tissues and systems found in multicellular organisms, thus enabling them to perform all of the life processes needed to maintain homeostasis.

• Ex: yeast

• The cells in a multicellular organism are interdependent (can not live on their own) (they depend on each other like players on a team)

• Cell specialization = each type of specialized cell performs separate roles or functions within the organism, has a different number of each organelle depending on function

• Ex: red blood cells, nerve cells, muscle cells, pancreatic cells – have enormous amounts of organelles involved in their functions

HOMEOSTASIS• THE PROCESS OF MAINTAINING A CONSTANT

INTERNAL ENVIRONMENT DESPITE CHANGING EXTERNAL CONDITIONS

Levels of Organization

• Cell: specialized to obtain food & oxygen, and carry out specific functions

• Tissue: a group of similar cells that perform a particular function– Four types of tissue in living things: epithelial (skin), muscle,

nerve, & connective (bone, blood, cartilage & lymph)• Organs: many tissues working together to perform a function

(ex. Muscle = muscle tissue, nerve tissue & connective tissue)• Organ systems: group of organs working together to perform

a specific task (ex. Digestive system, nervous system, & circulatory system)

The Cell Theory

• All living things are composed of cells.• Cells are the basic units of structure and

function in living things.• New cells are produced from existing cells.• Cells have particular structures that perform

specific jobs. These structures perform the actual work of the cell. Just as systems are coordinated and work together, cell parts must also be coordinated and work together. These structures are called organelles.

Plant Cell

Nuclearenvelope

Ribosome(attached)

Ribosome(free)

Smooth endoplasmicreticulum

Nucleus

Rough endoplasmic reticulum

Nucleolus

Golgi apparatus

Mitochondrian

Cell wall

CellMembrane

Chloroplast

Vacuole

Section 7-2

Go to Section:

Animal Cell

Centrioles

NucleolusNucleus

Nuclearenvelope

Rough endoplasmic reticulum

Golgi apparatus

Smooth endoplasmicreticulum

Mitochondrian

CellMembrane

Ribosome(free)

Ribosome(attached)

Section 7-2

Go to Section:

Cell Membrane• Thin, flexible barrier around cells

(inside cell wall on plant cells)• Provides protections and support• Helps maintain homeostasis with

a chemical balance between materials inside and outside the cell by removing wastes from the cell

• Selectively permeable = allows only certain material in or out of the cell

• Made up of a lipid bilayer with some proteins scattered throughout

PASSIVE TRANSPORT

• MOVEMENT OF MOLECULES FROM AN AREA OF HIGHER CONCENTRATON TO AN AREA OF LOWER CONCENTRATION

• KINDS:– DIFFUSION– OSMOSIS– FACILITATED DIFFUSION

• DOES NOT REQUIRE THE USE OF ENERGY

Diffusion• Movement from an area of higher concentration to an area of lower

concentration to reach equilibrium without using energy to cross the cell membrane

• CONCENTRATION GRADIENT:exists when particles are in higher concentration in one area and lower in concentration in another. Causes movement of the molecules

• EQUILIBRIUM:when the rate of particle spreading is even throughout a given area.

• http://www.northland.cc.mn.us/biology/BIOLOGY1111/animations/active1.swf

Osmosis

• The diffusion of water through a selectively permeable lipid bilayer membrane without the use of energy

• FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION

• When the transfer of water molecules into and out of the cell reaches the same rate, a state of equilibrium is reached.

• Cell shrinks, because water moves out of cell, because there’s more water in cell than in solution.

start end

Salt water: 15% salt, 85% pure water

Cell: 95% water

• Cell swells (can burst), because water moves into cell, because there’s more water outside cell than in solution

start end

Water: 100% pure water Cell:

95% water

Facilitated Diffusion

• movement across the membrane through protein channels from an area of high concentration to an area of low concentration

HighConcentration

LowConcentration

CellMembrane

Glucosemolecules

Active Transport• movement from an area of

lower concentration to an area of higher concentration against the concentration gradient using energy– Endocytosis – taking in materials

by forming pockets• Phagocytosis – taking in large

particles• Pinocytosis – taking in liquid/fluids

– Exocytosis – removing materials by fusing vacuoles

Molecule tobe carried

LowConcentration

CellMembrane

HighConcentration

LowConcentration

CellMembrane

HighConcentration

Energy Energy

Nucleus• Large structure that contains the

cell’s genetic material or hereditary information (DNA - holds instructions for making proteins)

• Controls the cell’s activities– Chromatin – granular material visible

with nucleus made up of DNA bound to protein

– Chromosomes – formed by chromatin during cellular reproduction to be passed on to the next generation

– Nucleolus – small, dense region within the nucleus where ribosome assembly begins

– Nuclear Envelope – double membrane around the nucleus with nuclear pores to allow material to move through (including RNA)

Ribosomes

• Made of RNA and protein• Build proteins on ribosome from proteins and

RNA (coded instructions from the nucleus)

Chloroplasts• Use energy from sunlight

with carbon dioxide and water to make food (carbohydrates) and oxygen through photosynthesis in plant cells and some other cells (not in animal/fungi cells)

• Double envelop membrane• contain the green pigment

chlorophyll• Contain some of its own

genetic information (DNA)

Mitochondria

• Use food to make energy (ATP) for growth, development, and movement

• Double envelop membrane

• Contain some of its own genetic information (DNA)

Photosynthesis• Photosynthesis is a process used by green plants• The is a type of autotrophic nutrition.• Photosynthesis is carried out by chloroplasts, which contain

chlorophyll• In the chloroplasts, CO2 and H2O are used to form C6H12O6 and O2

• Stomata = pore-like opening on the bottom of plant leaf that allows carbon dioxide to diffuse in or oxygen to diffuse out only when the plant has enough water to open the guard cells and perform photosynthesis

light energy trapped in the chloroplast makes this process happen

6CO6CO22 + 6H + 6H22O O CC66HH1212OO66 + 6O + 6O22

carbon carbon waterwater sugar oxygen sugar oxygen

dioxidedioxide (glucose) (glucose)

Cellular Respiration• Cellular respiration is the process of breaking down food

(glucose) in cells in the presence of oxygen to release energy.• In the presence of oxygen, food is broken down through the

processes of glycolysis, the Krebs cycle and the electron transport chain = cellular respiration

• It uses oxygen taken in as you breath = aerobic• Carbon dioxide, water, energy, and some heat are given off as

waste products.

CC66HH1212OO66 + 6O + 6O22 6CO 6CO22 + 6H + 6H22O + energyO + energy sugarsugar oxygenoxygen carbon carbon waterwater

(glucose)(glucose) dioxide dioxide

Energy Transfer & Food Chains

• All energy comes from the Sun!

• Energy Transfer:Sunlight Autotroph Heterotroph other heterotrophs

(herbivore) (carnivore)• Food Chain:Autotroph Heterotroph other heterotrophs

(herbivore) (carnivore)

Cellular Reproduction• Reproduction – the life process by which living things

produce other living thing of the same species• It is necessary for the survival for the species• Two types of Reproduction through cell division:

– Sexually reproducing organisms go through mitosis and meiosis– Asexually reproducing organisms only go through mitosis

Genetically identical to parent

Genetic variability in gametes

Uncontrolled Cell Growth• Internal Regulators = Proteins that respond to events inside the cell.• External Regulators = Proteins that respond to events outside the cell

and direct the cell to slow down or speed up the cell cycle.• Cancer: cells lose the ability to control growth or don’t respond to

signals that regulate cell growth.• Tumor: cancer results in masses of cells that damage surrounding

tissues.• Cancer cells can break loose from tumors and spread throughout the

body, disrupting normal activities and causing serious medical problems or even death.