OCR Biology Unit 1

Resolution is the ability to distinguish between 2 objects very close together.

Higher Resolution, greater detail can be seen

Resolution for the human eye is 100 um

The scale of the eyepiece graticule is arbitary(represents different lengths at different magnifications)

Eye piece scale has to be calibrated for each objective lens.

There is a relationship between actual size magnification and image size where :

Actual Size = Image size(measured with ruler) / Magnification

1mm=1000 um

A cytoskelton is a network of microtubules and microfibres that provides support in Eukaryotic cells.

Functions of Cytoskeleton as a whole:

>Provide an internal framework which supports the cell

>Organises and moves organelles within the cell

>Moves the whole cell

>Constructs the spindle during cell division

>Provides the components of Cilia and Flagella

Microtubules
made of the protein tubulin,forms the spindle in division,long thin tubes of protein,unbranched that helps cytoskeleton in a eukaryotic cell, it can join to form complex stuctures such as Cilia. They are linear an hollow.

Function-spindle pulls chromosomes around,moves granules.

Microfilaments
A network of protein filaments,thinnest filamenst of the cytoskeleton. Found in cytoplasm of Eukaryotic cells, flexible and strong versatile solid ,branches.

Function-Helps support the cells shape,allows a dividing cell to become 2 cells,generates forces needed in contraction and basic cell movements.

Division of Labour:
Sharing of tasks that need to be performed between specialists in each of the tasks
>In cells, different organelles perform different functions
>Each function is performed well by the organelle responsible and the organelle performin its function contributes to the overall life of the cell

Proteins

Collagen Keratin Insulin Elastin Haemoglobin

Rough Endoplasmic Reticulum: Protein synthesis takes place on the ribosomes that are attatched to the membranes. protein leaves in vesicle. Packaging and processing of proteins take place here.

As protein molecules are made ,they collect in the CISTERNAE(enclosed spaces formed by membranes).

Smooth Endoplasmic Reticulum: do not have ribosomes .This is where the production of Steroids and lipids take place e.g testosterone and oestrogene.