Hypothesis & Scientific Theory

Hypothesis

• A proposed explanation for a phenomenon is a hypothesis
• It can lead to predictions that can be tested
• Hypothesis can be supported or revised based on the test results

Scientific Theory

• A theory is a hypothesis for natural phenomena exceptionally well-supported by data
• It becomes scientific theory when a hypothesis is supported by many experimentations using many different variables

Scientific Theories vs. Everyday Theories

• Scientific theories are supported by evidence and describe universal natural phenomena
• Everyday theories are not supported by evidence, and describe only specific situations

Important Theories in Biology

• Cell Theory states all organisms are composed of cells, and all cells come from preexisting cells
• Theory of Evolution states species change over time and are all related through common ancestry

Limitations of the Scientific Method

• The scientific method cannot provide answers to artistic and creative processes
• It does not answer value judgements such as religion and faith
• It is not used for moral judgements or social or ethical problems

Pseudoscience

• Pseudoscience manipulates with misleading "scientific sounding" language

Debunking Pseudoscience

• Avoid drawing conclusions from anecdotes
• Be skeptical if something seems too good to be true
• Always demand scientific evidence

Relying on Source Material

• Read the original source instead of trusting statements by news media
• News media reporting can be inaccurate due to sensationalism
• Press releases from companies or academic institutions may be biased due to financial motivations

Google Scholar

• Google Scholar is a search engine designed for academic articles
• Peer-reviewed research articles are the most reliable source
• Peer-reviewed review articles are also reliable
• Book chapters are not as reliable

Drugs vs Dietary Supplements

• Prescription and over-the-counter drugs undergo rigorous testing
• FDA or Health Canada closely monitor drug quality and safety
• All new drugs must pass Phase 3 clinical trials before hitting the market
• Dietary supplements are not regulated and lack quality/safety testing
• Government intervention for dietary supplements occurs only when safety concerns are raised
• Dietary supplements are sold without proper clinical trials

MMR Vaccine and Autism

• The MMR vaccine is a combination vaccine for measles, mumps, and rubella
• The MMR vaccine does not associate with autism
• Anti-vaxxers continue to spread misinformation despite scientific evidence
• Anti-vaxxing leads to revival of childhood illnesses, long-term complications, and unnecessary deaths
• New media focused on sensationalism about Wakefield's study
• Wakefield's press conference statements were motivated by financial gain
• Anti-vaccine campaigners continue to fund Wakefield

Evaluating Science

• Consider study types when evaluating science

Observational vs Hypothesis-Testing

• Observational studies establish possible correlations, but cannot establish causation
• Hypothesis-testing studies aim to establish causation through comparison between treatment and control groups
• Observations should yield testable hypotheses

Cohort Studies

• Cohort studies observe two or more groups over time to track disease frequencies
• Example: Comparing lung cancer frequencies between smokers and non-smokers

Case-Control Studies

• Case-control studies observe people with and without a disease to determine factors associated with disease occurrence
• Example: Comparing smoking habits between lung cancer patients and healthy individuals

Retrospective Studies

• Retrospective studies rely on recall, which may not be reliable
• Asking lung cancer patients about exposure to secondhand smoke as an example

Prospective Studies

• This observes people before disease appears, then assesses disease frequency over time
• Doll and Hill surveyed 40,000 medical doctors about their smoking habits in 1951, following mortality rates for 10 years

Correlation vs. Causation

• Correlation does not equal causation
• Hypothesis-testing experiments can determine causation, but are not always possible

Types of Clinical Trials

• In Open-Label trials, subjects know the treatment being received which may reduce the reliability of conclusions
• "Blind" trials conceal treatment from subjects
• "Double-Blind" trials conceal treatment from both subjects and experimenters
• Randomized trials assign subjects randomly to experimental and control groups
• Randomized double-blind studies are the "Gold Standard" for clinical trials

Clinical Trial Stages for Drugs

• Pre-Clinical trials establish scientific base and safety testing, studying human cells, animals, and models
• Phase 1 trials test safety and determine dosage/administration, using an open-label format and fewer than 30 participants
• Phase 2 trials test efficacy, determine side effects, using a randomized double-blind format and 30-100 participants
• Phase 3 trials assess efficacy and side effects, using a randomized double-blind format and 300+ participants, before FDA approval

Cell Theory

• All organisms are composed of cells that come from preexisting cells
• Scientific theories have been tested many times and are supported by all experimental data available to date
• Scientific theories are unlikely to change in the future

Prokaryotes vs Eukaryotes

• Prokaryotic cells are smaller, and eukaryotic cells are bigger
• Eukaryotic cells have a nucleus that contains DNA
• Eukaryotic cells have more structures surrounded by membranes called organelles

Cell Structures Common to Both

• Plasma Membrane: Separates cell contents from environment
• Cytoplasm: Thick jelly-like fluid that fills inside of cell
• DNA: Molecule storing genetic information; prokaryotes store it in the cytoplasm, eukaryotes store it in the nucleus
• Ribosomes: Granular structures in cytoplasm that synthesize proteins

Prokaryotic Cell Structure

• Contains plasma membrane, cytoplasm, ribosomes, and DNA
• Cell Wall: Rigid protective layer surrounding plasma membrane
• Capsule: Gelatinous layer outside of the cell wall
• Pili: Hair-like structures for attachment
• Flagellum: Whip-like projection for propulsion

Membrane-Bound Organelles

• Eukaryotic cells contain many organelles surrounded by membrane

Membrane-Bound Organelle Formation

• Are derived from membrane invagination, with the plasma membrane folding in on itself to create inner compartments
• Are derived from Endosymbiosis, as a situation where 2 organisms co-exist and benefit from each other

The Endosymbiotic Theory

• Theory explains bacteria-like organelles origin such as mitochondrion and chloroplast
• Bacteria-like organelles are derived from bacteria-like organisms
• Mitochondrion and chloroplast ancestors were engulfed by eukaryotic organism ancestors

All Cells

• All eukaryotic cells contain mitochondria, which were created by endosymbiosis, and retain bacteria-like characteristics

Plant Cells

• Plant cells contain mitochondria and chloroplasts as bacterial-like organelles
• Endosymbiosis happened twice, first with Mitochondria and second with Chloroplast

Endosymbiosis Observed Through

• Mitochondrion and Chloroplast own DNA
• Genes in mitochondrion and chloroplast resembling bacteria genes
• Mitochondrion and Chloroplast having double membranes (inner and outer membranes), with the inner membrane looking like a bacterial membrane

Summary

• Endosymbiosis created mitochondrion and chloroplast
• Membrane invagination created the Nucleus, Endoplasmic reticulum (ER), Golgi apparatus, Lysosome, Vacuole/Vesicles

Plasma Membrane

• Plasma Membrane is found in all cells
• A membrane that separates cell content from its environment

Plasma Membrane Components

• Receptor Proteinsdetect signals in the environment, such as flavour chemicals, hormones, and light
• Adrenaline response and sweet receptors are also signals in the environment
• Recognition proteins on membrane surface serve as molecular fingerprints, which are used to distinguish self vs. non-self cells, and to tell cell types apart
• Transport proteins provide a passage for molecules to enter into the cell, like the glucose transporter
• Some enzymes embedded in the plasma membrane, performing chemical reactions either inside or outside of the cell, like cellulose synthase in plants

Gate Keeper

• The plasma membrane is the gatekeeper of the cell
• Some molecules enter easily, some are blocked, and some enter only through transport proteins

Molecule Movement

• Vesicles move the small membrane bound organelles inside the cells Small molecules do not use Vesicles; large molecules/particles use Vesicles.

Concentration Gradient

• Different areas of a solution have different concentrations of the solute
• The larger the concentration difference, the larger the concentration gradient

Diffusion

• Solutes spread from the area of high concentration to an area of low concentration until the elimination of all gradient
• Molecules move "down" the concentration gradient

Simple Diffusion

• Small molecules move across the plasma membrane by simple diffusion
• Example: Oxygen, carbon dioxide, and water
• Ex: oxygen dissolved in blood move by simple diffusions→ From outside to inside the cell

Plasma Membrane Permeability

• Not all molecules can pass the plasma membrane
• The hydrophobic layer resists charged molecules
• Glucose and ion aren't able to pass through the plasma membrane

Facilitated Diffusion

• Molecules that do not pass the plasma membrane use transport proteins
• Proteins facilitate the movement of ions and other molecules
• Molecules move down the concentration gradient
• Glucose transporters provide a passage for glucose
• it's still a type of diffusion

Diffusion

• Facilitated Diffusion uses transport proteins to allow the movement of the molecule
• Simple diffusion moves molecules directly across the plasma membrane
• In both cases, the movement follows the law of diffusion to move molecules down the gradient from high to low concentration

Passive Transport

• Diffusion is a type of passive transport

Passive Transport Vs Active Transport

• Passive transport - Molecules move down, no energy needed
• Active Transport - Molecules move against, Transport that needs energy input

Osmosis

• A type of passive transport that does not require energy input
• The cell is exposed to molecules that do not pass the membrane
• Solutes can't move across the Plasma Membrane, but Water can cross
• Water moves to reduce the concentration gradient
• The cell may shrink or expand as a result

Solution Terminology

• Hypertonic Solution: The environment has a higher solute concentration than the cell
• Isotonic Solution: Solute concentration - Environment is the same as the cell
• Hypotonic Solution: The environment has a lower solute concentration than the cell

Environmental Conditions

• Isotonic Environment - Solute concentrations and Water movement are balanced, cell maintains the same size, body cells are maintained in this
• Hypertonic Environment - Salt or Sugar solution, Cell in this Hypertonic environment Body must be dehydrated, To equalize concentrations between inside and outside, water molecules will move out of the cell.
• Hypotonic Environment - Water is overhydrated, Cell in hypotonic solution is filled with ions, Ions do not pass the plasma membrane, to equalize concentrations between inside and outside, water molecules will move into the cell.

Plant Cells

• Plant Cell is surrounded by a rigid cell wall
• A rigid cell wall keeps cells from bursting open
• Plant cells become turgid, which is necessary for support and growth

Water Intake

• Drink when you are thirsty - don't over hydrate
• Don't forget to replenish Salts after periods of sweating
• Get advice from experts

Isotonic Solutions

• Isotonic Solutions given intravenously correct imbalances
• Hypertonic solutions intravenously damage body cells, causing them to shrink
• Hypotonic solutions intravenously damage body cells, as cells will lyse

Active Transport

• Active transport can move molecules against the concentration gradient
• Requires energy input

Stomach Acidity

• Gastric juice in the stomach helps digestion
• Acidity is maintained by H+ ions produced by stomach cells
• Active transport helps maintain acidity of stomach - works against the concentration gradient
• H+ pump moves H+ ions against the concent gradient, and requires energy usage
• ATP is used as a portable chemical energy in living organisms

Neurons and Potassium/Sodium Concentrations

• Neurons maintain a low concentration of Na+ in the cells
• Neurons are stimulated, Na+ enters into cells, with both active transport and facilitation diffusion use transporter proteins
• Neurons maintain a low concent of Na+ and a high concentration of K+ in the cells, Gradient maintained by Na+/K+ pump, Pumps out Na+ from the cell and Pumps in K+

Facilitated vs. Active Transport

• Both involve transporter proteins and moving molecules against a concent gradient
• Facilitated diffusion can only move molecules down the concentration gradient

Cell Processes

• Active transport is needed to move cell molecules move against the concentration gradient
• Cells produce carbon dioxide when they harvest energy from food
• Simple diffusion moves carbon dioxide across the plasma membrane into the extracellular space

Vesicles

• Vesicles help cells create sphereical, bubble-like structures
• They pinch off other membranes

Vesicle Mediated Transit

• Endocytosis transports vesicles for importing molecules in cells
• Exocytosis exports vesicles to transport molecules outside of cells

Types of Endocytosis

• Phagocytosis eats cells (phago is eat) Cells eat other organisms
• Plinocytosis cells drink and absorbs Liquid
• Receptor-Mediated Endocytosis Incorporate a molecules Surface receptors binds to signature molecules, where Endocytosis is initiated

Liver Cells Transport

• Liver Cells Carry LDL Receptors
• Binding occurs
• LDL Cholesterol Clears by Liver Cells Forms Plasma Membranes & Engulfts LDL,
• Removes LDL Cholesterol

Genetic LDL Disorder

• Familial LDL Disorder leads to deficiency
• Low LDL Receptors causes blood clots
• High LDL causes cardio disease

Exocytosis Secretion

• Releases vesicles to form plasma membranes to transfer elements to its surroundings
• Communicates from 2 neurons cell structure

1. Genetic Control Centers

• Genetic Centers Creates Nuclear membranes to molecules & has chromosomes
• Nucleic Synthesis creates Ribosomes

2. Lysosomes

• Lysosome waste is the cell
• Digesting Enzymes
• Cell parts and recyclers
• Invaders digesting

3. Rough ER Synthesizers & Smooth ER

• Endoplasmic and reticulums which synthesizes
• Create and Modify Protien synth

4: The Apparatus

• The Packaging Centers of the Cell
• Contains Protien, Lypids & Other Ship Cell Elements
• Contains Mitocondrites

What Makes It Special

• The organells that are Bactria Like
• Harvests Food & Harvests ATP
• Inner Membrane Folds & Contains Its DNA
• Has Cytoskeleton

Cyto Skeleten

• The cell provides cells shape
• The sperm whipping is created with cytoskeleton Movement

Specialized Cell Wall Structure

• Helps with stress & mech support
• Wards off pests & bugs
• Made from cellulous
• Also Known as the Chloroplast organelle

Chloraplast Fun Facts

• HArvest Energy, Has DNA, Synthesizes
• Has inner + Outer layers which Harvest Elements
• This is required for photosynthesis