Biology 1002B Study Guide - Final Guide: Alternative Splicing, Polysome, Horizontal Gene Transfer
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Bio 1002B Final Exam Review
Cycle 1
Defining Life and its Origins
• Cell is the fundamental unit of life – all life is composed of cells
• Seven characteristics of life
o Display order
o Use energy
o Reproduce
o Respond to stimuli
o Homeostasis
o Grow and develop
o Evolve
• Cells arise from the growth and division of other cells – but the first cells could not have
o Life must have come from a mixture of primordial molecules
• EARTH’S TIMELINE
o 0 – present
o 1.2 - multicellular eukaryotes
o 2.1 – unicellular eukaryotes
o 2.5 – rapid increase in oxygen in atmosphere
o 3.3-3.7 – prokaryotic cells, oxygenic photosynthesis
o 4 – first evidence of life
o 4.5 – organic molecules
o 4.6 – formation of earth
• prokaryotes gave rise to eukaryotes
o endocytosis – membranous pockets fell in
o endosymbiosis – mito and chlo went inside eukaryotes
• How were building block molecules formed in the absence of life?
o Reducing atmosphere
▪ Water vapour, ammonia, hydrogen, carbon dioxide, methane (no oxygen)
▪ Can form complex molecules as oxygen is not present
▪ UV light could have provided the energy
▪ Miller-Urey – proved organic molecules could be formed by this atmosphere
o Deep sea vents
▪ Organic molecules have originated from deep sea vents in the ocean floor
• How polymers were made?
o Reducing atmosphere only makes monomers, polymers are what makes life
o Requires enzymes
• Macromolecules to life
o Shifts in temp and energy – can create organic from inorganic
o Life evolved in steps
▪ RNA, protein, DNA
▪ Self-replication of RNA
▪ Association between amino acids and nucleotides
▪ Formation of membrane-enclosed compartments
▪ Development of metabolic pathways
• Lipid spheres may have led to the development of cells
o Membrane defines compartment
• RNA can carry info and catalyze reactions
o Central dogma – DNA to RNA to protein
o RNA can hold information like DNA – but degrades faster
▪ Unstable uracil not found in DNA
▪ DNA is double stranded – error in one strand does not mean mutation
o Ribozymes – RNA molecules that act as catalysts
▪ Single stranded, can fold into 3D shapes like proteins
o Could have evolved – RNA to protein to DNA
• The first cells relied on anaerobic metabolism
o Heterotroph – obtain carbon from organic molecules
o Autotroph – obtain carbon from the environment in an inorganic form (carbon dioxide)
▪ Anoxygenic photosynthesis – hydrogen sulfide was used instead of water
• Oxygenic photosynthesis led to the rise in oxygen in the atmosphere
o Cyanobacteria – use water as an electron donor
o Oxygenic photosynthesis – relies on the oxidation of water for electrons
• All life shares common characteristics
o Cells made up of lipid molecules forming a bilayer
o Genetic system based on DNA
o System of information transfer – central dogma
o System of protein assembly from a pool of amino acids by translation using mRNA and tRNA
and ribosomes
o Reliance on proteins as the major catalytic molecule
o Use of ATP as chemical energy
o Breakdown of glucose by the metabolic pathway of glycolysis to make ATP
The Cell
• Cell theory
o All organisms are composed of one or more cells
o The cell is the basic structural and functional unit of all living organisms
o Cells arise only from the division of pre-existing cells
• Unicellular – functionally independent organism
o Yeasts, bacteria, archaea
• Multicellular – activities of life divided among cells
o Plants, animals
• Why are cells small?
o Surface area must be enough for the volume it contains
o Some may fold their membranes to increase SA
• Parts of the cell – main
o Plasma membrane – lipid bilayer with proteins
▪ Transport proteins – channels that allow
selective substances to enter
o Cytoplasm
o Organelles
o Cytosol – aqueous solution containing ions and
organic molecules
o Cytoskeleton – protein based framework to maintain shape
o Nucleus – only present in eukaryotes
▪ Nucleoid – DNA containing region with no membrane (pro)
• Prokaryotic cells
o Spherical, rodlike, spiral
o Genetic material in the nucleoid
▪ Chromosomes – singular, circular
o Plasma membrane surrounded by cell wall
o Most have flagella to allow them to move – protein fibres that extend from the surface
• Eukaryotic cells
o Have a nucleus enclosed by a membrane – holds genetic information
▪ Nuclear envelope – two membranes
▪ Nuclear pores – membrane proteins
▪ Chromosome – many single, linear chromosomes
▪ Nucleoli – contained in nucleus, forms around genes for rRNA
o Plasma membrane (plants also have a cell wall
o Endomembrane system – interrelated membranous sacs that divide the cell into functional and
structural components
▪ Nuclear envelope, ER, Golgi, lysosomes, vesicles, plasma membrane
o Endoplasmic reticulum – formed by single membrane
▪ Rough – has ribosomes on surface
• Attach and fold into their final form
• Chemical modifications
• Proteins then delivered to other regions of the cell
o To golgi complex
▪ Smooth – no ribosomes
• Creation of lipids
• Breaks down toxins
o Golgi complex – membranous sacs
▪ Receive proteins from the ER
▪ Chemically modified
▪ Regulates movement of several proteins
▪ Secretory vesicles
▪ Exocytosis – release of contents to exterior
• Can fuse with the membrane, allow surface to grow
▪ Endocytosis – bringing of molecules into the cell
• Pinching off of the plasma membrane
o Lysosomes – membrane bound vesicles that contain enzymes for digestion
▪ Only in animals, not plants
▪ pH is more acidic – if it is broken, proteins will not function
▪ autophagy – digest organelles not functioning properly
▪ phagocytosis – some types of cells engulf bacteria to break them down
o Mitochondria – cellular respiration
▪ Energy molecules broken down into water and carbon dioxide to release energy
▪ Requires oxygen
▪ Double membrane bound
• Inner membrane – ETC
• Inner compartment – matrix
o Contains DNA and ribosomes
o ATP generating reactions occur here
o Cytoskeleton – connected system of protein fibres
▪ Microtubules
• Tubulin
• Hollow cylinder of monomers
• Polar
• Radiate towards the centrosome
• Create centrioles
• Separation of chromosomes