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What are serological pipettes used for?

To accurately dispense volumes of liquids.


5 Procedure Steps

1. Choose smallest pipette suitable for volume you intend to deliver.
2. Double check using correctly labelled pipette to avoid cross contamination.
3. Attach pipette to pump or bulb.
4. Draw the liquid into the pipette slowly.
5. Dispense liquid into receiving container slowly.


2 Warnings with serological pipette

#'s start with 9 on bottom and count to 0 on top
1mL pipette has #'s for every 0.1 mL and mark for every 0.01mL


What are pasteur pipettes used for

To dispense liquids when accuracy is less important & gently mix liquid mixtures by pipetting in and out


4 step procedure for pasteur pipettes

1. Double check labels to avoid cross contamination
2. Attach pipette to pump or bulb
3. Draw liquid into pipette slowly
4. Dispense liquid into receiving container slowly


Use of wet mounts on glass slide?

To spread a sample thin enough to view clearly under a microscope


4 step procedure for wet mounts

1. Place small drop of sample in middle of glass slide
2. Gently place one edge of cover slip on slide so that cover slip touches sample
3. Gently lower opposite edge of slip using pencil or pasteur pipette to avoid forming bubbles under cover slip
4. Use tissue to soak up excess liquid until cover slip does not move when slide is tilted


Use of iodine starch test

To determine whether a sample contains starch


3 step procedure for iodine starch test

1. Obtain iodine and clean dry spot plate with depressions
2. Add 2-3 drops of sample to one depression and add 2 drops of iodine in same depression
3. Observe colour changes. Iodine binds with starch to form a purplish-blue colour


Use of cheesecloth filter

To filter out large solids while allowing liquids and smaller particles to pass through


3 step procedure for cheesecloth

1. Label clean test tube and place in rack
2. Place funnel on top of tube, then place cheesecloth on top of funnel
3. Pour sample slowly into middle of cheesecloth and wait for sample to pass through into tube


Warning for cheesecloth

Cloth absorbs 4.5mL of liquid. Make sure sufficient enough homogenate to get enough filtrate despite what is absorbed by cloth


What are compound microscopes used for

To view objects at 40x, 100x, or 400x magnification


10 step procedure for microscope

1. Rotate objective lens on 4x magnification. Place slide on stage of microscope.
2. Hold metal spring clip on stage aside and set slide so that corner of slide sits snugly in metal slide holder. Gently release clip to hold slide in place.
3. Move slide using stage movement controls until object centred under lens. Upper dial adjusts up/down, lower dial adjusts left/right
4. Turn light intensity adjustment dial down to 5 and turn on microscope lamp. Move substage condenser (under stage_ all the way up using small adjustment knob on left. Close diaphragm of substage condenser using small black diaphragm level.
5. Use coarse focus knob to focus object clearly.
6. To put both eyepieces in focus, close left eye and focus image in right eye with fine focus until in focus. Close right eye and focus left eyepiece with focusing ring without altering focus knob settings
7. Adjust eye distance by pushing or pulling apart eyepieces.
8. Do not use coarse focus knob at higher magnifications, can smash lens.
9. Reset light intensity to 5 and lens to 4x when done


Go pg 21 and Label parts of microscope



What are spectrophotometers used for

To measure how much light (of each specific wavelength/colour) is absorbed by a sample. Prism is used to split light to test one wavelength at a time across wide range of possible wavelengths.


What are the 4 wavelengths used to test the unknown homogenate in class

470 nm blue, 545 nm green, 580 nm yellow, 680 nm red


6 steps to use spectrophotometer

1. Turn on spectrophotometer. Set wavelength to 470 nm blue with wavelength knob 4.
2. Locate "blank tube" (colorimeter tube with ethanol in it). Ethanol absorbs light differently at each wavelength, must use blank tube to set spectrophotometer to zero every time change wavelength
3. Wipe blank tube with tissue to remove fingerprints.
4. Place blank tube in holder under cover 3 and replace cover. Adjust absorbance reading to read zero using knob 2
5. Replace blank tube with tube of extract. Record absorbance reading (measure of how much light of particular wavelength is absorbed).
7. Change to next wavelength with knob 4 and repeat steps to obtain absorbance reading at that wavelength.


2 details about absorbance

Absorbance is a logarithmic scale from 0 to infinite so intervals between units not equal. Has no units.


What are centrifuges used for

Separate particles within mixture into layers according to their relative densities, by spinning at extremely high speeds. Densest particles found at bottom of tube.


10 step procedure for centrifuge

1. Label 2 clean falcon tubes
2. Add a volume of sample to one tube and equal volume of liquid to second tube.
3. Turn POWER switch on
4. Press OPEN button. Place tubes diagonally opposite each other.
5. Close lid and wait for lock.
6. Press SPEED until reads ref value. Use arrow bottoms to set speed at 1,300.
7. Press TIME button and set time to 10 mins.
8. Press START.
9. After 10 mins press OPEN.


Imagine that you need to pipette 5.2 mL of a urine sample into a test tube for analysis. Your lab has clean 10mL, 5mL, and 1mL serological pipettes available. Which Pipette(s) would you use to accurately transfer this volume of urine?



A reddish tint to the urine may indicate the presence of blood. Which equipment would you use to test presence of reddish tint in urine?



Describe one common mistake that students make when using the above equipment

Not blanking the machine after each colour test, not wiping the tube of fingerprints


Imagine that you are analyzing two ocean water samples for the presence of "red tide" which is caused by high concentrations of red coloured microscopic algae. Choose one piece of lab equipment you would use to accurately compare the concentrations of red tide algae in your two samples.



Briefly explain the steps you would take to compare your two samples using this piece of equipment.

- Use spectrophotometer to test the two samples on wavelengths blue, red, green and yellow separately. To test first sample, set machine to 470 nm blue. Take "blank tube" (tube that contains the ethanol) and wipe off all fingerprints. Place blank tube into holder under cover 3 and replace cover. Adjust absorbance reading to read zero using knob 2. Once machine is zeroed, replace with tube of extract, remembering to wipe off fingerprints with this tube as well. Record absorbance reading at this wavelength. This is a measure of how much light this particular wavelength has absorbed. Change machine to next wavelength with knob 4 and repeat steps.


Imagine you have already focused on a specimen at 100x magnification. Describe in detail the steps you would take to view the sample at 400x magnification

Rotate to 40x magnification. Refocus using fine focus knob. More powerful lens capture less light, increase light intensity by either opening diaphragm level on substage condenser or adjusting light intensity.


A simple way to determine dehydration level is by observing how clear your urine is. Imagine you want to compare the clarity of several urine samples using a spectrophotometer. Describe the steps you would take to prepare a spectrophotometer for this measurement.



Name two tools that you can use to separate some of the components of your unknown homogenate for further analysis

Cheesecloth and centrifuge


Which of these tools do you think is the better choice? Two reasons for answer

Centrifuge. Cheesecloth absorbed 4.5 mL of your homogenate, if you do not have enough volume you won't have any left to test. Cheesecloth is less accurate as it only filters out large solids, certain midsized particles can still pass. Centrifuges separates the homogenate into layers relative to their densities, you will get a more precise measurement and able to test different particles accurately.