Monday, February 25th

1. Monday, February 25th • Thank you for submitting your quizzes! • Friday’s Enzyme Lab: You must have your Question, Prediction, Hypothesis, Materials and Procedure by Thursday (see chart paper posted around the room) • Today: Lecture #5

2. Enzyme Lab • Question: How does temperature affect enzyme function? • Prediction: Temperature will have a negative effect on enzyme function. • Hypothesis: As temperature increases, enzymes will begin to denature. • Tests/Experiments (Procedure): Design a procedure that is based on your prediction, hypothesis and prior knowledge to observe an expected result. If we increase the temperature of this liquid, the enzyme will not function. (need to know the variables)

3. Variables • Variables are all of the factors involved in a reaction. Examples: • Time, amount, size, temperature, weight, height, type of chemical • In order to understand how a variable influences a reaction, it must be isolated from all other variables. • Dependent Variable: is the measureable or observed outcome of the experiment. It depends on what happens to the independent variable. There is the possibility of multiple variables, but not if an experiment is controlled properly.

4. Variables cont’d Independent Variable • Is the factor that is isolated from all other variables • It is manipulated or changed in order to observe an expected result. • There should only ever be ONE independent variable Control Variables • Remain the same for every trial or test in the experiment • There are always several variables that must be controlled.

5. Cell Structure and Function

6. Cell Structures • Just as our organs complement each other in both form and function, so do the organelles in eukaryotic cells • We will focus on the organelles inside eukaryotic plant and animal cells • All organelles are found within the cytosol of the cell and it’s all held in by the plasma membrane

7. Nucleus • Consists of two main parts: the nuclear envelope and the nucleolus • Contains ALMOST all the DNA in a cell • The nucleus protects the DNA from the metabolic reactions that happen in the cytosol that could damage it

8. Nuclear Envelope • Double membrane • Consists of two lipid bilayers folded together • The outer layer is connected to the rough endoplasmic reticulum • Two kinds of membrane proteins are embedded in the lipid bilayers (receptors and transporters) which work to transport molecules across the membrane

9. Nucleolus • A dense and irregularly shaped region • Creates subunits of ribosomes from proteins and RNA

11. The Endomembrane System • A group of interacting organelles found between the nucleus and the plasma membrane • Main function is to make lipids, enzymes and other proteins that are found in cell membranes • Also specializes in destroying toxins and recycling wastes

13. Endomembrane System Organelles • Rough Endoplasmic Reticulum: translates RNA in the cytosol into polypeptide chains by ribosomes found on the rough ER • Vesicles: bud off of the rough ER and carry some of the new proteins to the golgi body

14. Endomembrane System Organelles • Smooth Endoplasmic Reticulum: take some polypeptide chains from the rough ER as enzymes which produce most of the cell’s membrane lipids, as well as breaking down carbohydrates, fatty acids and some drugs and poisons • Golgi Body: modifies proteins arriving from the rough ER into their final form, then sorts and sends them to the plasma membrane or lysosomes

16. Mitochondria • Produce ATP (Adenosine triphosphate – a coenzyme used in cells containing chemical energy) in a series of reactions that require oxygen • Contain their own DNA and ribosomes and divide independently of the cell – making scientists believe they evolved from aerobic bacteria that took up permanent resident in a host cell

17. Mitochondion

18. Plastids • Used for photosynthesis or storage in plant cells for example: • Chloroplasts specialize in photosynthesis by catching light energy • Chromoplasts make and store pigments (other than chlorophyll) that colour flowers, leaves, fruits and roots • Amyloplasts store starch grains in stems and seeds

19. Chloroplast: Type of Plastid

20. Cell Membrane • Semipermeable membrane allows the uptake of nutrients and the elimination of wastes • Current views of membrane structure are based on the fluid mosaic model – membranes are not rigid with molecules locked into place, but consist of lipid molecules in which proteins are embedded and float freely

22. Role of the Phospholipids • Polar (hydrophilic) heads stick together on both sides • Non-polar (hydrophobic) tails stay in the middle to spontaneously form a bilayer

23. Role of Membrane Proteins • Lipid molecules are the backbone of the membrane, but the proteins associated with it determines function and makes it unique • Proteins are responsible for: transport, enzymatic activity, triggering signals, attachment and recognition