Monday, February 25th

Monday, February 25thThank 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

Enzyme LabQuestion: 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)

VariablesVariables are all of the factors involved in a reaction.

Examples:Time, amount, size, temperature, weight, height, type

of chemicalIn 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.

Variables cont’dIndependent VariableIs the factor that is isolated from all other variablesIt is manipulated or changed in order to observe an

expected result.There should only ever be ONE independent variableControl VariablesRemain the same for every trial or test in the

experimentThere are always several variables that must be

controlled.

Cell Structure and Function

Cell StructuresJust 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

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

Nuclear EnvelopeDouble membraneConsists of two lipid bilayers folded

togetherThe 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

NucleolusA dense and

irregularly shaped region

Creates subunits of ribosomes from proteins and RNA

The Endomembrane SystemA 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

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

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

MitochondriaProduce 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

Mitochondion

PlastidsUsed 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

Chloroplast: Type of Plastid

Cell MembraneSemipermeable 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

Role of the PhospholipidsPolar (hydrophilic)

heads stick together on both sides

Non-polar (hydrophobic) tails stay in the middle to spontaneously form a bilayer

Role of Membrane ProteinsLipid 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