Practical Skills Rennin and - PowerPoint Presentation

Slide1

Practical SkillsSlide2

Rennin and Cheese

making

Rennin (AKA Rennet,

chymosin) – Enzyme found in the stomachs of young mammalsRennin’s substrate is casein (protein found in milk)Video - Cheese makingSlide3

Lab Practical Skills

In papers 2 and 3 (esp. 3), you will be expected to demonstrate mastery of collecting, organizing, and displaying data

Plotting points

Creating a tableMeasuringDrawingSlide4

Plotting points

Independent var.: x-axis

Variable being manipulated (ex: temperature, concentration, pH)

Dependent (response) var.: y-axisVariable being measured (ex: reaction rate, products formed)

D

ISlide5

Plotting points

Always

plot

points with a small x or small dot inscribed in a circleAlways connect data points with a rulerDifferent data sets should use different points OR different lines (solid, dashed, dotted)Slide6
Slide7

Creating a table

ALWAYS USE A RULER!!!

Tables

should be drawn in pen onlyUnits go on column headingsFirst column = always independentSlide8

Units of Measurement

Kilometer (km) 10

3

Meter (m) 1Centimeter (cm) 10-2Millimeter (mm) 10-3Micrometer (µm) 10-6Nanometer (nm) 10-9Picometer

(pm) 10

-12Slide9

Units of measurement

Important for measuring cells!

BIG

to SMALL: decimal to the rightSMALL to BIG: decimal to the left1. Convert 10 μm to mm2. Convert 10 µm to nmSlide10

Drawing – Cells

We will cover this in more detail in Chapter 1!Slide11

Drawing Cells

Do’s

Don’ts

pencil only

Clear, continuous lines

Accurate proportions

Tissues completely enclosed by lines

Label all tissues

Correctly identified parts

Representative portions or cells

Scale bar

Shading

Textbook versions

Individual cells on low power

Nucleus

as a solid blob on high power

Drawing different tissues:

Shape, Size, and Shading Slide12
Slide13

Visualizing Animal and Plant Cells

Every plant and animal cell is surrounded by a very thin

cell surface membrane

(aka plasma membrane)All have a nucleus which is very large and stains very darkly (especially chromatin)The nucleolus located within the nucleus stains even more deeply (variable amount, can be ~1-5)Slide14

Visualizing Animal and Plant Cells

The most numerous organelles seen with light microscopes are usually

mitochondria

(single mitochondrion)Golgi apparatus can only be seen with silver containing stainsSlide15

Plant Cells Only

Usually

larger than animal cells

All surrounded by cell wallLinked to neighboring cells by plasmodesmata (single plasmodesma)Slide16

Plant Cells Only

Large central vacuole, surrounded by

tonoplast

Chloroplasts: show grana (single granum) at high magnificationSlide17

There is a limit to how much can be seen w/light

Magnification

is the number of times larger an image is, compared with the real size of the object.

Or

I=observed size of the image

A= actual size

Light MicroscopesSlide18

Magnification

I

A

M

×Slide19

This length of the displayed lymphocyte is 36mm. The actual length of the lymphocyte is 6µm. What is the magnification?

Check Your UnderstandingSlide20

This length of the displayed lymphocyte is 36mm. The actual length of the lymphocyte is 6µm. What is the magnification?

1.) Convert mm

→

µm2.) Use the equation

to calculate magnification

(M=magnification, I= image size, A=actual size)

Check Your UnderstandingSlide21

This length of the displayed lymphocyte is 36mm. The actual length of the lymphocyte is 6µm. What is the magnification?

1.) Convert mm

→

µm

2.) Use the equation

to calculate magnification

(M=magnification, I= image size, A=actual size)

= 6000 x

Check Your UnderstandingSlide22

Measuring CellsSlide23

Measuring Cells

Cells and organelles can be measured with a microscope by means of an

eyepiece

graticuleThis is a transparent scale with 100 divisions that is placed in the eyepiece so it can be seen at the same time and the sample on the slideSlide24

Using an eyepiece graticule

This figure shows the scale over a human cheek epithelial cell.

The cell lies between 40 and 60 on the scale, therefore we say it measures 20 eyepiece units in diameter

We will not know the actual size of the cell until the eyepiece graticule scale is calibratedSlide25

Calibrating an eyepiece

graticule

scale

To calibrate the eypiece graticule scale, a miniature transparent ruler called a

stage micrometer scale

is placed on the microscope stage and is brought into focus

This scale may be etched onto a glass slide or printed on transparent film

It commonly has subdivisions of 0.1 and 0.01 mm

The images can then be super imposed to calibrate the

graticule

8 cm

?? cm

What is the value of 1

epu

? Slide26

Complete the Calibration problem and paste in notebook! Slide27

Calibrating an eyepiece graticule

scale

In the eyepiece

graticule shown, 100 units measure 0.25 mm.Hence, the value of each eyepiece unit is

0.0025 mm.

Converting mm to µm:

for each

epu

 Slide28

Calibrating an eyepiece graticule

scale

The diameter of the cell measures 20 eyepiece units, so the actual diameter is

 Slide29

Find the size of the nucleusSlide30

Nucleus measures 10 eyepiece units (from 40 to 50)

In the eyepiece

graticule

shown, 100 units measure .25mm. Hence, the value of each eyepiece unit is

0.0025 mm.

The diameter of the nucleus measures 10 eyepiece units, so the actual diameter is

 Slide31
Slide32
Slide33

Solution

Distance between X and Y is approximately

27 eyepiece units (epu) 27 units x 0.0025 mm = 0.0675 mm 0.0675 mm x 1000 = 67.5