Summary OCR A/AS-Level Biology 2.1.1 Cell Organelles

Cell Organelles
Nucleus
 The nucleus stores the organism’s genome
and transmits genetic information and is
found exclusively in eukaryotic cells
 The nucleolus in the centre of the nucleus is
responsible for ribosome synthesis
 The nuclear envelope is a double membrane
made from phospholipids, separating the
contents of the nucleus from the rest of the
cell
 Nuclear pores are where the inner and outer
membranes fuse together, allowing
ribosomes and messenger RNA to pass
through
 The nucleoplasm is like a cytoplasm but
inside the nucleus
 Chromosomes and Chromatin are genetic
material inside the nucleus. When the cell is
not dividing, chromatin is spread out. When
it is dividing, the chromatin coils and
condense into chromosomes

Endoplasmic Reticulum
 Endoplasmic Reticulum, or ER, is a system of
membranes containing fluid-filled cavities
known as cisternae
 Rough ER is adjacent to the nuclear
envelope and is covered in ribosomes which
are responsible for protein synthesis
 The rough ER is also an intercellular
transport system and transports the proteins
to the Golgi apparatus
 Smooth ER has no ribosomes and contains
enzymes that catalyse lipid reactions
 Smooth ER is involved in lipid absorption,
synthesis and transport

Golgi Apparatus
 The Golgi Apparatus is a complex of
flattened sacs, consisting of cisternae
surrounded by a lumen
 Transport vesicles, also called secretory
vesicles, bring materials to and from the
Golgi apparatus
 Incoming transport vesicles enter via the cis
face
 Outgoing transport vesicles leave via the
trans face
 Inside the Golgi apparatus, proteins are
modified and packaged before being sent of