IB Biology HL Unit 1

Redi’s Experiment

• Demonstrated that maggots do not spontaneously arise from decaying meat but rather from eggs laid by flies

• Jars with varying degrees of exposure

• Prove spontaneous generation false

Pasteur’s Experiment

• Bacteria could only grow in sterile broth when exposed to air

• Disproved spontaneous generation

• Introduced the concept of sterilization and pasteurization

3 Tenets of Cell Theory

1. All living organisms are composed of cells

2. Cells are the basic unit of structure and function in living things

3. All cells come from pre-existing cells

Conditions of Early Earth

• Little oxygen

• No ozone

• Lots of carbon dioxide and methane

• High temperature

Miller-Urey Experiment

• Simulated early conditions to test the origins of life

• Used H2O, CH4, NH3, H2, heat, electricity

• Created organic simple molecules including amino acids

• Criticism: assumption of these conditions to be true

Protocells

• Simple cell-like structures that may have formed the basis of early life

• Have genetic material

• Exhibit basic metabolic functions

Spontaneous Formation of Vesicles

• Phospholipids in primordial soup spontaneously form due to hydrophilic/hydrophobic ends

• Created membranes

Reasons for RNA being considered the first genetic material

• Catalytic properties

• Stores genetic information

Last Universal Common Ancestor (LUCA)

• Unicellular, autotrophic microbe

• Formed 2.5-3.5B years ago in hydrothermal vents of the ocean floor

Evidence for LUCA

• Universal genetic code

• Universal machinery for protein synthesis (like ribosomes)

• ATP for energy

• Universally shared genes for processes like DNA replication

• Ribosome structure

• Enzymes that synthesize

Metabolism

Chemical reactions take place in their cells

Response to Stimuli

Respond to environmental change

Homeostasis

Maintain constant internal conditions

Movement

Control their position in space

Growth

Increase in size or number of cells

Reproduction

Produce offspring asexually or sexually

Excretion

Facilitate removal of waste

Nutrition

Obtain energy or nutrients from their environment

All cells have…

• Cell membrane

• Cytoplasm

• Ribosomes

• DNA

Formula for magnification

image/actual

Differences between prokaryotes and eukaryotes

• Prokaryotes

  • No membrane bound organelles

  • No nucleus

  • Older and simpler

  • Cell wall

  • 70s ribosomes

  • Naked DNA

• Eukaryotes

  • Membrane bound organelles

  • 80s ribosomes

  • Mitochondria

  • Nucleus

Plant VS Animal VS Fungal Cells

Plant

• Cell wall of cellulose

• 1 large, permanent central vacuole

• Chloroplasts

Animal

• No cell wall

• Small, temporary vacuoles

• Centrioles

• Undulipodia: flagella and cilia

Fungal

• Large vacuoles

• Cell wall of chitin

Tradeoffs of a cell wall

• Limited flexibility

• Affected nutrient absorbtion

Atypical cells: Aseptate Fungal Hyphae

Lack compartmentalization and internal membranes

Atypical cells: Red Blood Cells

No nucleus or DNA

Atypical cells: Phloem Sieve Tube Elements

No nucleus and few organelles

Atypical cells: Striated Muscle Tissue (Skeletal Tissue)

Multiple nuclei

Compartmentalization

Functions are split up for benefit

• Efficiency

• Protection of cellular parts

• Organizes cellular processes

Endomembrane System

• Parts: nucleus, ribosomes, ER, golgi, vesicles, lysosomes, membrane

• Process of producing and transporting proteins: Protein synthesis →mRNA travel to ribosomes on rough ER →transport vesicles go to golgi →golgi vesicles direct protein to final destination

Endosymbiosis

Beneficial relationship inside a cell

Endosymbiotic Theory

Explains origins of eukaryotes

• Process: 1 bacteria engulfed another, and it lived inside and got passed down through generations

• Likely engulfed in the order of mitochondria then chloroplast

Evidence for the Endosymbiotic Theory

• Double membrane

• Naked and circular DNA

• 70S ribosomes

• Independent replication

4 Biological Macromolecules

• Nucleic Acids

• Carbohydrates

• Lipids

• Proteins

Anabolic Pathway

• Synthesizes molecules

• Monomers → Polymer

• Uses condensation reactions (dehydration synthesis) AKA the removal of water

• Endergonic: Requires energy

• Catalyzed by enzymes

Catabolic Pathways

• Breaks down molecules

• Polymer→ Monomers

• Uses hydrolysis AKA addition of water

• Exergonic: Releases energy

• Catalyzed by enzymes

Monomer and Polymer of Nucleic Acids

• Monomer: Nucleotide

• Polymer: Polynucleotide

Monomer and Polymer of Carbohydrates

• Monomer: Monosaccharides

• Polymer: Polysaccharides

Monomer and Polymer of Proteins

• Monomer: Amino acids

• Polymer: Polypeptide

Monomer and Polymer of Lipids

TRICK QUESTION they have no true monomer or polymer

2 Types of Nucleic Acids

DNA and RNA

Phosphodiester Bonds

The covalent bonds between nucleotides

3 Parts of a Nucleotide

• Phosphate Group

• Pentose Sugar (Deoxyribose in DNA, Ribose in RNA)

• Nitrogenous Base (AGTCU)

Elements found in nucleic acids

C, H, O, N, P

How are polynucleotides synthesized?

Anabolic pathway, condensation

Sugar Phosphate Backbone

Repeating pattern of pentose Sugar then phosphate along the nucleotide

• Held by phosphodiester bonds

DNA VS RNA: Similarities and Differences

Similarities

• Contain adenine, guanine, cytosine

• Monomers: nucleotides

• Polymer: polynucleotide

• Contain phosphodiester bonds

Differences

• DNA has 2 strands, RNA has 1 strand

• DNA has deoxyribose, RNA has ribose

• DNA has thymine, RNA has uracil

Purines

• Adenine (A) and guanine (G)

• 2 Rings

Pyramidines

• Cytosine (C), thymine (T), uracil (U)

• 1 ring

Base pairings

• A and T/U

• G and C

Antiparallel

• 2 strands which are parallel but in opposite directions

• Describes DNA strands

Describe a polynucleotide strand

5’ end is the end with the phosphate

3’ end is the end w/o phosphate

What bonds form between two bases?

Hydrogen bonds

Hershey & Chase

• DNA is the genetic material of the cell

• Knowledge: Bacteriophages infect bacteria by injecting DNA

• Method: labeled proteins with radioactive sulfur and DNA with radioactive phosphorus in the phages →infected bacteria → put through centrofuge to separate cells into pellet

• Results: Phosphorus was found in cell pellets and sulfur was in the supernatent (where the bacteriophages were)

Rosalind Franklin

• Researched and took x-ray of double helix of DNA

• Used x-ray crystallography

Watson & Crick

• Used Franklin’s data

• Used it and Chargraff’s data to create double-helix model of DNA and base pairings

Erwin Chargraff

• Discovered base pairing ratios

• Tetranucleotide Hypothesis: all 4 bases occur in equal amounts

  • Disproved by Chargraff

• Showed that A and T occurred in similar % and C and G occur in similar %

Nucleus

• Contains DNA in chromosomes

• Has double nuclear membrane with nuclear pores

• Central dot called nucleolus which produces ribosomes

Rough Endoplasmic Reticulum

• Contains ribosomes which produce proteins for out of cell use

Smooth Endoplasmic Reticulum

• Produces and stores lipids

• No ribosomes

Vesicles

• Modify and assist in transport of substances produces by the cell

• Fuse with membranes in the cell

Golgi Apparatus

• Processes and packages proteins which are released to vesicles

80S Ribosomes

• Where protein synthesis occurs

• Higher mass than 70S ribosomes

• in eukaryotes

Cytoskeleton

• Not and organelle

• System of protein fibers called microtubules and microfilaments

• Hold organelles in place and maintains shape and structure of the cell

Plasma Membrane

• Separates internal and external environments

• Controls entering and exiting

• Semipermeable

• Phospholipids bilayer

Lysosomes

• Contain enzymes that break down cellular components

Cytoplasm

• Water-based, jelly-like fluid filling the cell

• Site of metabolic reactions

• Not an organelle

Cell Wall

• Made of polysaccharides in plants and or chitin in fungus

• Protects and provides support

• Not and organelle

Vacuole

• Maintains osmotic balance

• Stores substances

• Hydrolytic functions

Chloroplasts

• Double membrane

• Photosynthesis location

DNA

• Not an organelle

• Codes for protein

• Genetic material

Undulipodia (Cilia and Flagella)

Cilia

• Movement

• Shorter and more abundant

• Made of microtubules

Flagella

• Movement

• Longer and less abundant

• Made of microtubules

Microtubules and Centrioles

Microtubules

• Move chromosomes during cell division

Centrioles

• Form anchor point for microtubules

Intermembrane Space (Mitochondria)

• Creates H+ concentration gradient

• Small gap between inner and outer membranes

Matrix (Mitochondria)

• Holds enzymes

Cristae (Mitochondria)

• Folds on the inner membrane

• Increase surface area

Inner Membrane (Mitochondria)

• Proteins for electron transportation

Outer Membrane (Mitochondria)

• Protection

Thylakoid (Chloroplast) and Granum

• Has chlorophyll

• Absorbs light to produce ATP

• Stacks of thylakoid = granum

Stroma (Chloroplast)

• Has enzymes for the Calvin cycle

Immunofluorescence Staining

• Uses fluorescently labeled antibodies to bind to target molecules, detecting them within cells.

Light Microscope

• Uses light to form images

• Magnifies up to 1500x

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How to make a wet mound

• Place a thin slice of your sample on a slide →Place one drop of water on it →Cover with coverslip at 45 degree angle

Fluorescent Staining

• Uses fluorescent dyes to attach to specific cellular structures, making them visible under UV light.