lab midterm review

Question 1

pepsin in stomach has _________ preferred pH

Answer 1

low

Question 2

effect of pH on enzyme activity

Answer 2

• each enzyme has optimal pH where activity is highest
• extremes of pH can denature enzyme by altering its structure and function

affects hydrogen bonding and enzyme changes shape, leading to reduced enzyme activity

Question 3

enzyme activity ___________ as temperature increases

Answer 3

increases

higher temps cause more effective collisions b/w enzymes & substrates

however, after certain point, enzyme activity levels out b/c loss of enzyme structure & function

Question 4

enzyme activity ___________ as substrate concentration increases

Answer 4

increases

• more collisions b/w substrate and enzyme
• as more active sites are filled with substrate, more product will form

reaction rate therefore increase as substrate concentration is increased but levels off

Question 5

maximum rate is achieved when ______________ (effect of concentration)

Answer 5

all active sites of an enzyme are filled with substrate

• increased substrate concentration after this point will not increase rate of reaction
• enzyme is saturated

Question 6

effect of concentration on enzyme activity

Answer 6

increasing amount of enzyme per amount of substrate = more enzyme-substrate complex formation

• once all substrate is bound to active site of enzyme, reaction will no longer accelerate with increasing enzyme concentration

Question 7

catalase

Answer 7

• involved in degradation reaction
• speeds up breakdown of hydrogen peroxide (H2O2)

Question 8

when catalase speeds up breakdown of hydrogen peroxide, __________ and ___________ are released

Answer 8

water and oxygen gas

Question 9

hydrogen peroxide

Answer 9

• harmful to cells
• powerful oxidizer that attacks and denatures cellular molecules such as DNA
• used as antiseptic to kill germs
• in reduced concentrations, used as whitening agent to bleach hair and teeth

Question 10

explain tonicity in plant cells (plant cell in isotonic, hypotonic, and hypertonic solution)

Answer 10

plant cell in isotonic solution: no net gain or loss of water

plant cell in hypotonic solution (fresh water): large central vacuole gains water and exerts pressure, cytoplasm including chloroplasts is pushed up against cell wall

plant cell in hypertonic solution (10% NaCl): central vacuole loses water, plasmolysis occurs (cytoplasm including chloroplasts pulls away from cell wall)

Question 11

effectiveness of antacids

Answer 11

• test the ability of OTC (over the counter) products to absorb excess H+
• for each antacid, use 100mL of phenol red solution diluted to a faint pink to wash antacid into a 250mL beaker
• add and count number of 0.1N Hal drops it takes for solution to turn light yellow

yellow = acid, red = base

Question 12

tonicity in animal red blood cells (RBCs)
- the concentrations of NaCl that make solution isotonic, hypotonic, and hypertonic

Answer 12

• solution of 0.9% NaCl is isotonic to RBC’s (RBC’s maintain their normal appearance)
• solution greater than 0.9% is hypertonic to RBC’S (RBC’s shrivel up = crenation)
• solution less than 0.9% NaCl is hypotonic to RBC’s (RBC’s swell and may burst = hemolysis)

Question 13

how many millimeters in one centimeter?-

Answer 13

10^-1

or 0.1

Question 14

how to measure liquid volume using a graduated cylinder?

Answer 14

• eyes have to be parallel to level
• measure at bottom of meniscus (lowest margin of water level)

Question 15

light microscope

Answer 15

also called compound microscope

• 2 sets of lenses focusing at the same time (compound) - ocular lens and objective lens
• total magnification from 40x - 1000x
• is par focal and par centric

Question 16

par focal & par centric (compound light microscope)

Answer 16

parfocal = once object is in focus with lowest power, it should remain mostly in focus with higher power

parcentric: object in focus remains near the center while changing objectives (magnification)

Question 17

function of the ocular lens

Answer 17

where you place your eyes to observe the specimen

monocular & binocular: monocular have single eye lens, binocular has double eye lens

• magnification of most ocular lenses is 10x

Question 18

function of the nosepiece

Answer 18

that rotating thing that contains all those different magnifications, turning it moves the magnification you want into place

Question 19

function of the objective lens & working distance definition

Answer 19

mounted on the nosepiece

longer the objective lens = greater the magnification power

working distance: distance between the tip of the lens and the top surface of the microscopic slide

Question 20

function of the stage, aperture, and mechanical stage

Answer 20

flat, horizontal shelf under objective lenses that support the microscope slide

center has aperture , or hole through which light passes to illumine specimen on the slide

mechanical stage: holds and moves the slide with more precision than is possible manually

Question 21

function of the coarse and fine adjustment knobs

Answer 21

coarse adjustment knob: large dial on the side of microscope, used ONLY at low magnification to find initial focus on specimen

fine adjustment knob: small dial on the side of microscope, moves the objective lens for precision focusing AFTER coarse focus. fine adjustment knob is used at all magnifications and is the only one used at magnifications greater than low

Question 22

function of the condenser & condenser adjustment knob

Answer 22

small lens under the stage that narrows the beam of light and directs it through the specimen on the slide

condenser adjustment knob: moves condenser vertically

Question 23

function of the iris diaphragm

Answer 23

series of flat metal plates at base of condenser that slide together and create an aperture in the condenser to regulate amount of light passing through

Question 24

list the steps for using the microscope

Answer 24

1. center specimen or cover slip directly over brightly-lit condenser lens (Do not look through ocular lens!)
2. using CA knob, move stage all the way up until it comes to a stop
3. Look into oculars (adjust them so that you can see one circle/field of view with both eyes open)
4. If light is too bright, use dimmer knob to lower it

**5. Slowly move CA knob downward/upward until you come into focus

6. Once you are in focus on 10x, you are automatically in focus on all other powers (this feature is called parfocalization)
7. DO NOT touch CA knob anymore! if you do, you will lose your focus
8. Using rotating nosepiece, simply dial-in any higher power objective you wish (high-power objectives will move closer to slide)
9. If you need to re-focus, use fine adjustment knob ONLY (FINE ADJUSTMENT ONLY ON HIGH POWERS)**

Question 25

steps for making a wet mount

Answer 25

1. place specimen on a slide and then add a drop of water or stain
2. place a cover slip at an angle so that it touches drop of water
3. slowly lower raised end of cover slip

Question 26

what is the test for protein and how does it work?

Answer 26

biuret reagent
- detects presence of protein and peptides
- Cu ions react w/ peptide bonds = color change

violet = proteins
light pink = peptides
clear-pale blue = no peptides

stronger color = greater concentration of proteins

Question 27

carbohydrates + 3 types

Answer 27

source of immediate energy for living organisms

• monosaccharides: simple sugars, ex. glucose
• disaccharides: composed of 2 monosaccharides linked together, ex. maltose, sucrose, lactose
• polysaccharides: polymers stored inside cell for further use, energy storage polysaccharides: starch and glycogen

Question 28

what is the test for starch and how does it work?

Answer 28

iodine potassium iodide
- reacts with starch (long coiled polymer of glucose molecules)

blue-black = presence of starch
yellow-brown = no starch

Question 29

what is the test for sugars and how does it work?

Answer 29

Benedict’s solution
- detects presence of monosaccharides & disaccharides in solution
- when heated, reducing sugars reduce Cu in Benedict’s

yellow/orange = sugars present
red= high amount of sugars present
green-blue = no sugars

Question 30

what is the Sudan test used for and how does it work?

Answer 30

detect lipids, one layer of red orange at the top

Question 31

chromosomes

Answer 31

carry genes

Question 32

ribosomes

Answer 32

make proteins

Question 33

cytoplasm

Answer 33

semi fluid medium inside cell

Question 34

plasma membrane

Answer 34

boundary that separates contents of cell from surrounding environment

• regulates entrance and exist of molecules into and out of cytoplasm

Question 35

what organelles are different in animal and plant cells?

Answer 35

plants have: cell wall & chloroplasts & large vacuoles

animals have: flagella & centrioles