POB lab 4

Explain the steps on how to accurately measure %T (7 steps)

1) turn on 2) set dial to desired wavelength (470nm) 3) toggle: %T for transmittance abs for absorbance 4) place blank in chamber 5) press R to set reference: 100% remove blank 6) insert sample in chamber 7) press T to read % sample transmittance or absorbance

Which of the following substances that were tested are acidic? A: soda B: sports drink (gatorade) C: antacid D: methanol

A&B. Both sodas and sports drinks are acidic, wile antacid is basic. Methanol was not one of the substances tested

If you did not use a blank of the correct solution/ concentration before taking your readings, what is likely to happen? A: your %T readings may be inaccurate as they were based on the max light transmittance through a different substance B: the colorimeter will beep to tell you a new substance has been detected C: your %T readings will still be accurate as long as the solution is clear D: the beet cell membranes will be further denatured

A. The blank ensures you are making a fair comparison as different solutions have different colors. Even if they are clear, they still have different densities and therefore different optical properties that may affect how much light is transmitted or absorbed. Errors with blanks do not alter reactions, but they do alter the accuracy of your data and interpretations

Classify the following as either acids, bases, or both 1: increase OH- 2: increase H+ 3: disassociate in water 4: when strong, can be caustic enough to eat through metals 5: NaOH is an example of a "strong" one 6: HCl is an example of a "strong" one 7: take up H+ 8: found in foods like lemon juice, vinegar, and coffee 9: commonly associated with milk of magnesia or bicarbonate soda which decrease stomach acid

ACIDS: 2,6,8 BASES: 1,5,7,9 BOTH: 4, 3

Most of the functions of a cell membrane, including transport and enzymatic function, are performed by... A: cholesterol B: proteins C: glycolipids D: phospholipids

B

In lab 4, what are banks used for? A: to neutralize the pH of solutions B: to calibrate the colorimeter C: to cut beet pieces of equal size D: to allow the colorimeter to have a short break between samples

B. A blank is used to calibrate the colorimeter. It has no contaminates (like beet pigment) so will give the highest possible reading. This serves at the basis to compare other samples to

What was the dependent variable in lab 4 during the temperature experiment? A: temperature B: household chemical C: %T at 470 nm D: length of the beet core

C

Which of the following passively diffuse across the plasma membrane? A: water B: oxygen C: carbon dioxide

C (idk check)

In this lab, you use a special ballon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur? A: water will enter the balloon B: sucrose will leave the balloon C: water will leave the balloon D: sucrose will enter the balloon

C. osmosis

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of... A: active transport B: exocytosis C: endocytosis D: facilitated diffusion

D

The lipids in a cell membrane are arranged... A: so that the hydrophilic components are arranged to face each other B: on either side of a single layer of protein C: between two layers of proteins D: so that the non-polar parts of two lipids points toward each other

D. A phospholipid bilayer can exist as a stable boundary between two aqueous compartments because the molecular arrangement shelters the hydrophobic tails of the phospholipids from water whole exposing the hydrophilic heads to water

True or False: Basic solutions have high pH

FALSE. basic solutions have a pH of 7

Molecules of _________ are embedded within the membrane to keep it from being too fluid, and _________ are embedded within the membrane to aid in the transport of molecules

cholesterol, proteins

Because of all the various molecules embedded within the membrane and because of its fluid nature, it is referred to as the _____________________.

fluid-mosaic model

Because the _________ heads are oriented towards the watery internal and external environments, this allows small water soluble substances to flow through the plasma membrane more freely

hydrophilic

In the inner layer of the membrane, the _________ head points inward towards the internal environment

hydrophilic

In the outer layer of the membrane, the __________ head points outward towards the external environment

hydrophilic

The means the __________ tail points towards each other

hydrophobic

The greater the %T, the __________ damage

less

Lipids are hydrocarbons that are mostly ___________ and ___________

non-polar, hydrophilic

The cell membrane is composed of a ____________, meaning there are two layers of ____________.

phospholipid bilayer, phospholipids

Why do we use replicates to test scientific hypotheses?

science is knowledge gained through repeated experiments or observations