Cytology

Cytology is the study of cells. There are two main types of cells; plant and animal cells. The microscope is used to view and study cellular structures. There two types of microscopes are the light microscope and the electron microscope.

Magnification is the process by which the appearance of a structure is enlarged. 
magnification = size of drawing /size of object(structure)

Resolution is the ability of a the microscope to distinguish between two points and visualize them as two points, even though they are extremely close together.

 Plant (onion cells) as seen under the Light Microscope

Animal (cheek cells) as seen under the Light Microscope

To Determine the effect of Increasing Enzyme Concentration on the Rate of Enzyme Catalysed Reaction

Lab#:6

Title: Enzymes

Aim: To determine the effect of increasing enzyme concentration on the rate of an enzyme catalysed reaction.

Apparatus and Materials: Potato extract, hydrogen peroxide, distilled water,measuring cylinder, ruler, beakers and timer.

Diagram:

Method:

1.      Label four beakers A,B,C and D respectively.

2.      Use the data in table below to prepare the respective mixtures for each of the above labeled beakers: (I do not want to see the table below in your lab books, you must write out each step described in the table below!!!!)

Beaker	Volume of Potato Extract	Volume of Hydrogen peroxide	Volume of Distilled water
A	25ml	15ml	0ml
B	20ml	15ml	5ml
C	15ml	15ml	10ml
D	10ml	15ml	15ml

3.      Allow each beaker to stand for three minutes , then measure the bubbles produced.

4.      Calculate the rate of reaction for each beaker.

5.      Record your results in a suitable table.

6.      Use your results to plot an appropriate graph.

Calclulations :

Discussion questions:

1.      Define enzymes.

2.      Account for your results.

3.      List two limitations of the experiment.

To Determine an Enzyme's Optimal Temperature

Lab#:

Title: Enzymes

Aim: To determine the optimal temperature of an enzyme.

Apparatus & Materials:

Diagram:

Method:

1.      Pour 10ml of potato extract in a clean, dry beaker and place beaker in water bath that is at 50⁰C.

2.      Immediately add 10ml of hydrogen peroxide to beaker with potato extract.

3.      Remove the beaker at the end of three minutes and use a ruler to measure the height of bubbles produced.

4.      Repeat the above steps at 40⁰C, 35^OC, 32⁰C , 20⁰C and 10⁰C.

5.      Use an appropriate equation to calculate the rate of reaction in m/s (standard form please)

6.      Record your results in a suitable table.

7.      Use your results to plot an appropriate graph.

Calculations:

Discussion questions:

1.      Define enzyme, optimum temperature and rate of reaction.

2.      State the importance of hydrogen peroxide degradation.

3.      Account for your results briefly. Identify the enzyme, substrates and products (write a chemical equation that summarizes the reaction). What factors were kept constant and why were they kept constant?

4.      Why did you blend potato?

5.      List two limitations.

The Cell Membrane

Anatomy of  The Cell Membrane

All living cells are surrounded by a cell or plasma membrane which form a barrier between the interior and exterior of cells. The cell membrane:

·         Regulates what enters and exits a cell

·         Consist of the structural units; phospholipids which forms a bilayer(a double layer). The hydrophilic heads of phospholipids are exposed to the watery exterior and watery interior of cell. The hydrophobic tails of phospholipids face each other in the middle.

·         Is fluid because the phospholipids are free to move around (though their movement is restricted by cholesterol) and the bilayer is interspersed with many proteins forming a mosaic pattern. The structure of the cell membrane is therefore described by the fluid mosaic model proposed by S.Singer and G.Nicolson. The Fluid Mosaic Model is shown below:

 

Component of Cell Membrane	Function
Phospholipid bilayer	Prevents loss of important watersoluble molecules as they cannot pass the hydrophobic layer.
Channel Protein (Transmembrane protein –spans membrane)	Provide a passage for transport of polar molecules and ions across membrane.
Carrier Protein (Transmembrane protein)	Transports molecules across membrane via a series of conformational changes.
Receptor Protein (Transmembrane protein)	Transmit information into cell by providing a specific binding site for a specific molecule or substrate.
Glycolipids (carbohydrate  attached to phospholipid)	Responsible for tissue recognition they form A,B,O blood group markers.
Glycoproteins (carbohydrate  attached to protein)	Prevents one’s immune system from attacking its own cells as they form the major histocmpatability complex protein.
Cholesterol (dispersed throughout membrane)	Stabilize membrane structure by restricting movement of phospholipids.

Table Listing The Functions of the different Components of the Cell Membrane

Glucose for Grade 12

Biochemistry of Glucose

Glucose is a carbohydrate and has the following properties:

·         It is a monosaccharide (a single sugar)

·         It has the chemical formula C₆H₁₂O₆

·         It is sweet and crystalline

·         It is small and is a monomer for polysaccharides.

·         It is a reducing sugar; it has the ability to reduce Cu²⁺ found in soluble copper II sulphate (blue) to Cu¹⁺ (brick red) found in insoluble copper I oxide. This is the basis of the Benedict’s test (a biochemical test used to detect reducing sugars). All monosaccharides are reducing sugars.

·         It exists in the straight chain (open chain) and Ring form (alpha ring and beta ring):

Structural Feature	Related Function
Many C-H bonds	When these bonds are broken energy is released, this makes glucose the ideal respiratory substrate.
Consists of only one sugar and it has many free OH (hydroxyl) groups hanging off its ring structure.	Small size and many OH groups makes it soluble, this makes glucose an excellent transport sugar in animals.

Table Listing The properties of Glucose and Its Related Function