Chaper 2 Flashcards Preview

Biology AS oxford AQA > Chaper 2 > Flashcards

Flashcards in Chaper 2 Deck (19):

What is a cell?

The smallest unit of all living organisms.


What is a tissue?

A group of similar cells


What is an organ?

Different tissues working together to carry out a function.


What is an organ system?

A group of organs working together to carry out a function.


Why are microscopes needed?

To discover microorganisms
To obtain a detailed image of cells
Study cell biology


What does a light microscope consist of?

A series of lenses and an eyepiece.


How does a light microscope work?

The light from the bulb travels through the condenser lens, then the specimen, up through the objective lens, and finally through the eyepiece lens into your eye.


How do you calculate total magnification?

eyepiece X objective


What is magnification?

How much larger an object appears compared to the actual size of the object.


What is resolution?

The ability to distinguish between two points that are very close together. The higher the resolution, the more detailed an image will appear.


Why do specimen need to be stained before using a microscope?

to better visualize cells and cell components under a microscope.


How does a TEM work?

Electron beam passes through very thinly prepared sample. More dense areas of the sample don't allow the electrons through as easily. this allows the 2D image to be created.
magnification of x500,000
short wavelength


How does a SEM work?

Electrons directed onto the sample don't pass through, but bounce off which creates a 3D image.
magnification of 100,000
short wavelength


How large are cells?

5-500 micrometers


How is actual size calculated?

image size/magnification


What is cell fractionation?

The process by which cells are broken up and the different components they contain are separated out.


Why does the solution used for cell fractionation have to be cold, isotonic, and buffered?

Cold - to reduce enzyme activity that might break down organelles
Isotonic - to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water.
Buffered - to maintain a constant pH


What is the role of the golgi apparatus?

Modifies proteins


List structures that are found in a bacterial cell.

Cell wall - [physical barrier that protects against mechanical damage]
capsule - [protects bacterium from other cells and helps groups of bacteria stick together]
cell-surface membrane - [controls the entry and exit of chemicals]
flagellum - [aids movement of bacterium]
circular DNA - [possesses the genetic information for the replication of bacterial cells]
Plasmid - [possesses genes that aid the survival of bacteria in adverse conditions]