IB biology [HL] A2.1.2 ​Cells are the Smallest Units of Self-Sustaining Life; A2.2.1 ​Cells as the Basic Structural Unit of all Living Organisms; A2.2.4 ​Structures Common to Cells in all Living Organisms; A2.2.3— Developments in microscopy; A2.2.2— Microscopy skills.

Textbook definition of life

Textbook definition of life

• Physical structures of life such as cells and DNA

• Physiological processes of life like growth and reproduction

Cell

Smallest living structure

They are not made out of ______. They cannot keep themselves in a ______. They do not ______. They cannot ______. They cannot perform independent _______.

cells, stable state, grow, replicate themselves, metabolism.

The cell theory

1. Living things are composed of cells

2. Cell is the basic unit of life

3. Cells arise from pre-existing cells

Inductive reasoning

Using specific observations to form general conclusions. Such as theories, cell theory, etc.

Deductive reasoning

Using a general premise to form a specific conclusion.

Plasma membrane

A barrier separating the interior of a cell from its surroundings, and controlling what goes in and out of the cell.

What is plasma membrane made of

its a bilayer fromed from phospholipids by its hydrophobic and hydrophilic regions/components

Cytoplasm

Gel like fluid substance of water that is rich with dissolved substances like salts, fatty acids, sugars, amino acids, proteins(enzymes). This is where all metabolic reactions happen.

DNA

Genetic material. All living organisms use this.

Eukaryotic DNA

Wraps around histone proteins

Ribosome

Catalyzes the synthesis of polypeptides during translation. Composed of 2 subunits.

Microscopes

Devices that produce a magnified image of objects too small to be seen directly by eyes. 

Magnification

How much an object appears compared to its actual size.

Resolution

The smallest interval distinguishable by the microscope, which is proportionate to the amount of detail shown.

Total magnifying power =

Ocular x Objective

Staining

Chemicals that bind to certain structures within a sample and that shows things more clearly.

FOV (field of view)

Diameter of the area visible through a microscope

Determining FOV:

1. Use transparent metric ruler and measure (only works on low power)

2. (diameter of LP X magnification of LP objective) / magnification of HP objective = HP diameter — (used for high power)

Estimating size of specimen

METHOD 1:  To estimate the size of an object seen with a microscope:

1. Estimate the fraction of the field of view that the specimen occupies. 

2. Multiply the FOV diameter by that estimated fraction.

   METHOD 2: To estimate the size of an object seen with a microscope:

   1. Estimate (or count) how many of the specimen would fit across the FOV. 

   2. Divide the FOV diameter by that estimated count. 

Calculating the magnification

size of image / actual size of specimen

Calculating the image size

Magnification x actual size of specimen

Calculating the actual size of specimen

size of image / magnification