Cells and Organelles - Class notes 4

Question 1

Know the basic structure of a cell

Answer 1

See diagram

Question 2

What are organelles?

Answer 2

organelles are a cell’s way of making chemical reactions, and hence activity, more efficient.

organelles compartmentalise a cell (i.e., divide the cell into compartments). this compartmentalisation isolates different chemical processes that occur within a cell, e.g., protein synthesis, lipid synthesis, respiration, enzyme production etc.

Question 3

What is the nucleus?

Answer 3

the nucleus contains:
> DNA (in the form of chromatin)
> RNA.
> the nucleus is surrounded by the nuclear membrane.
>the nuclear membrane has tiny pores throughout.

DNA and RNA are responsible for:
>regulation of cell activity via protein synthesis.

Question 4

what is the nucleolus?

Answer 4

the nucleolus is contained within the nucleus. its function is to produce RNA.

Question 5

What is the R.E.R?

Answer 5

the rough endoplasmic reticulum.
>The R.E.R is responsible for protein synthesis activity - as it is associated with *ribosomes (the actual organelle directly responsible for protein synthesis).

Synthesises proteins that are:
>destined to be intergrated into the plasma membrane (e.g., cell membrane or organelle membrane)
> destined for export from the cell (e.g., protein-based hormones like insulin and digestive enzymes)
> produces glycoproteins

*PLEASE NOTE - Ribosomes in the cytoplasm are responsible for making proteins that typically are not destined to leave the cell.

Question 6

What is the S.E.R?

Answer 6

the smooth endoplasmic reticulum.the S.E.R is responsible for:
> lipid synthesis
   -produces fatty acids
   -oils
   -phospholipids
   -steroids - including the sex hormones
>detoxification of drugs (in the liver)
>storage site for calcium (in muscle) 
> metabolism of carbohydrates.

Question 7

What is the golgi apparatus?

Answer 7

primarily modifies and sorts proteins,
>makes proteins functional by adding various substances
-carbohydrate groups
-phosphate groups
-or ‘signal sequences’ (which determine a protein’s final destination).

It is in the golgi apparatus, for instance, where carbohydrate groups might be added in order to modify glycoproteins produced in the R.E.R

Question 8

What is the golgi apparatus involved in?

Answer 8

it is primarily involved in the transport of modified proteins that arrive from the R.E.R

the golgi apparatus is also involved with the transport of lipids to various destinations within the cell.

Question 9

What is the mitochondria?

Answer 9

the mitochondria is the primary site of ATP synthesis. ATP is a key energy source in all cells.