Ultrastructure of a generalised cell Flashcards
What are all membranes thought to have?
The same structure
What are membranes composed of?
They are composed of phospholipids and proteins
What type of phosphate and lipid groups do phospholipids have?
A water-hating lipid group and a water-loving phosphate group
How are phospholipids arranged?
They are arranged into double layers (bilayers) The phosphates are on the exposed outer surfaces with the lipids in the middle
Name four functions of membranes
- retain the cell contents
- Recognise molecules that touch them
- Control what enters and leaves the cell
- Give some support to the cell
What is the nucleus surrounded by?
It is surrounded by a double membrane with numerous nuclear pores.
What does the double membrane with numerous nuclear pores surrounding the nucleus do?
They allow the controlled entry and exit of molecules into and out of the nucleus.
What does the nucleus contain?
It contains strands of deoxyribonucleic acid (DNA). and it is arranged into structures called chromosomes
Why is the nucleus of a stained cell darker than the other parts of the cell?
As the DNA in the nucleus readily absorbs many stains and becomes darkly coloured under the microscope.
What does every organism have a definite number of in each nucleus? Give this number for humans nuclei
A definite number of chromosomes. (humans have 46)
Where are genes located?
They are located randomly along chromosomes
Define chromatin
Chromatin is the name given to chromosomes when they are elongated and not dividing
What are genes? What do they control?
Genes are the structures that inform the cell how to make certain proteins.
They control features such as the number of fingers, colour of eyes and production of enzymes
What are genes also known as?
Units of inheritance
When cells are not dividing what do they look like?
They are very elongated and interwoven. In this form they are called chromatin