Sample questions 1) Those cells which have a nucleus are classified as? a) prokaryotes b) eukaryotes 2) Name two organelles, other than a nucleus?

3) Where in a plant cell would you be able to find DNA? 4) The ER has what structures associated with it?

5) Is the plasma membrane composed only of lipids (fats)? 6) Which microscope has the greater resolution, light or electron?

7) Eukaryotic cells fall into 4 kingdoms. Finish the list A) Animal B) Protists C) Plants D) ?

8) Which organelle do animal cells get most of their energy? 9) Are viruses considered to be living?

10) Is glucose a protein, fat, or sugar? 11) DNA is made of a protein, fat, sugar, or nucleic acids? 12) Proteins are made of what?

13) Give an example of something with a high pH and another with a low pH. State which is which. 14) Name at least two types of atomic bond?

How Cells Work Chapter 5 Part 1 of 2

What you will learn. About energy and work Order and disorder

What Is Energy? Ability to do work Forms of energy Potential energy Kinetic energy Chemical energy

What Can Cells Do with Energy? Energy is used to make things, or move things, or break things Cells use energy for: Chemical work - making new stuff Mechanical work - moving around Electrochemical work - nerve impulses

One-Way Flow of Energy The sun is life’s primary energy source Food producers trap energy from the sun and convert it into chemical bond energy Plants and some types of bacteria All organisms use the energy stored in the bonds of organic compounds to do work All life forms including plants and photosynthetic bacteria

Endergonic Reactions Overall energy input required Energy is stored inside the final molecule glucose, a high energy product ENERGY IN low energy starting substances 6 + 6O

Exergonic Reactions Overall energy is released Products have less energy than starting substance This energy is used to power the cells glucose, a high energy starting substance + 6O 2 66 low energy products ENERGY OUT

The Role of ATP Cells “earn” ATP in energy releasing reactions Cells “spend” ATP in energy requiring reactions base sugar three phosphate groups

Basic Chemistry In the next few slide we need to recall our basic chemistry. WHY? Because it is important in our understanding of life...

Redox Reactions ‘OIL RIG’ Involves the movement of ELECTRONS OIL = Oxidation Is Loss RIG = Reduction Is Gain

Electron Transfer Chains Pass electrons from molecule to molecule In the process energy is made as ATP

Uncontrolled vs. Controlled Energy Release H2H2 1/2 O 2 Explosive release of energy as heat that cannot be harnessed for cellular work H2OH2O

Metabolic Pathways Defined as enzyme- mediated sequences of reactions in cells Biosynthetic Degradative

Enzyme Structure and Function Enzymes are catalytic molecules They speed the rate of chemical reactions (in some cases they speed them up billions of times)

What do I need to know about… ENZYMES

Four Features of Enzymes 1)Enzymes do not make anything happen that could not happen on its own. - They just make it happen much faster. 2) The enzyme is the same after the reaction as it was before the reaction - it comes out unchanged

Four Features of Enzymes 3) The same enzyme usually works for both the forward and reverse reactions. - forwards and backwards 4) Each type of enzyme is specific - it recognizes and binds to only certain substrates. - glucose to fructose can only be performed by one type of enzyme

Energy use inside cells

Activation Energy For a reaction to occur, an energy barrier must be surmounted Enzymes make the energy barrier smaller by bending the molecules to the optimal shape to react activation energy without enzyme activation energy with enzyme energy released by the reaction products starting substance

Things which Influencing Enzyme Activity Temperature of the cell pH of the cell Salt concentration in the cell

Effect of Temperature Small increase in temperature increases the speed of reactions High temperatures eventually destroy the protein - egg whites

Effect of pH - depends on where the enzyme is located!

Feedback Inhibition enzyme 2enzyme 3enzyme 4enzyme 5 enzyme 1 SUBSTRATE END PRODUCT (tryptophan) A cellular change, caused by a specific activity, shuts down the activity that brought it about

Lecture 7 Starts here!

Cell Membranes Show Selective Permeability

Concentration Gradient Means the number of molecules in one region is different than the number in another region A smell moves from an area of high concentration to one of low concentration

Diffusion - spreading out evenly The spreading of molecules evenly to fill a space

Factors Affecting Diffusion Rate Steepness of concentration gradient Steeper gradient, faster diffusion Molecular size Smaller molecules, faster diffusion Temperature Higher temperature, faster diffusion

Membrane Crossing Mechanisms - how to get into and out of a cell! 1) Diffusion across lipid bilayer 2) Passive transport 3) Active transport 4) Endocytosis - swallowing 5) Exocytosis - spitting

Membrane Crossing: Overview I

Membrane Crossing: Overview II

Span the lipid bilayer Interior is able to open to both sides Change shape when they interact with solute Play roles in active and passive transport Transport Proteins

Passive (without using energy) Transport Holes in the middle of the protein allow the molecules to pass through in either direction Does not require any energy to be spent

Passive Transport

Active (I must use energy) Transport Push material into or out of the cell Transport protein must be activated Energy is required to push and pull

Osmosis Diffusion of water molecules across a selectively permeable membrane Direction of net flow is determined by which side has the most water Side with the most solute molecules has the lowest water concentration

Tonicity Refers to relative solute concentration of a fluid Hypertonic - having more solutes Isotonic - having same amount Hypotonic - having fewer solutes

Tonicity and Osmosis 2% sucrose water10% sucrose 2% sucrose

Endocytosis and Exocytosis Exocytosis: A cytoplasmic vesicle fuses with the plasma membrane and contents are released outside the cell Endocytosis: A small patch of plasma membrane sinks inward and seals back on itself, forming a vesicle inside the cytoplasm – membrane receptors often mediate this process

Endocytosis and Exocytosis