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Lecture 2

BIOB32H3 Lecture Notes - Lecture 2: Enzyme Kinetics, Activation Energy, Cell Theory

Biological Sciences
Course Code
Dan Silver

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BIOB34H3- Lecture 2 September 13, 2012
Cellular Physiology
- cell processes govern physiology
Metabolism: biochemistry- metabolic pathways: substrates to products
-reactions govern by enzymes (catalyst= faster for synthesis (anabolic) or break
apart ( catabolic)
-sum of all metabolic pathways
-determined by how will enzymes are working
-If ATP deprived, no metabolic pathways
-speed or slow things down
-made of proteins (have confirmations (changes) allow enzymes to bind certain way)
-3 properties
1. Active at low concentrations
2. Increase rate of reactions without being altered itself
3. Do not change nature of product ( only break down or put together)
How they work?
- they bind to substrates
- changes activation energy ( reduces) in order to accelerate reaction
Enzymes accelerate reactions:
-without enzyme: Activation energy higher
-with enzyme: Activation energy lower
-enzyme: add more substrate= faster reactions= but reach plateau
-too much product=slow reaction
-no space for substrate
Enzyme kinetics:
- enzyme at first rapidly makes substrates to product
-fastest with lots of substrates and lot of enzyme
-plateau/equilibrium: run out of substrate
Michaelis Menten: add too much substrate> enzyme saturated, free floating substrate
until enzyme available
-half velocity> Km value- affinity of enzyme to its substrate
Biomolecules: 4 types
1. Proteins (like enzymes)
2. Carbohydrates
3. Lipids- hydrophobic
-energy metabolism, cell structure and signalling
4. Nucleic Acids > tells us our genetic info
-make important proteins
The cell: compartmentalization
Cell theory
1. Cells are the building blocks of plants and animals
2. Come from pre-existing cell
3. Smallest units, perform vital physiological functions
4. Each cell maintains homeostasis
Cell membrane > phospholipid bilayer
- physical isolation, regulates internal environment more than external environment
-regulation of exchange with the environment
-sensitive to environment
-structure support
Cell membrane
- made of lipids, carbs , proteins
-glycoproteins/lipids > made of sugar
-has functions
-glycoproteins has function of recognition: identifies/ fingerprint of each cell
Membrane proteins: cross membrane > integrate proteins
Different classification of proteins:
- Permeability: substances ( hydrophobic) go across
-impermeable: cannot go through the protein channels
-passive: diffusion, osmosis, water
- concentration from high to low
- easier, so many substates on the side > so it just flows
-active: need ATP
- move against concentration gradient
- concentration from low to high concentrations
-ATP is from mitochrondria
Passive Transport:
1. Diffusion:
-through lipid members > through lipid molecule
- large molecules need another way
Osmotic flow> aquaporins allow water to go through the cell
Helps facilitate diffusion
Hydophillic substances cannot go though > need ion channels, porins, permeases
Voltage gated : need change in voltage for gates to open
Ligand: need to bind to a ligand
-mechano gated : need confirmational change to open
- gated channels are not ATP depended
Active Transport : all need ATP
- Primary active transport
-sodium -potassium : need ATP
- ATP binds and change in confirmation occurs
- sodium expels from cell
- Second: have carrier channel
- hijack a gradient that uses ATP
- uses neighbouring molecules for ATP
-Endocytosis> big stuff cannot go through channel
- broken down