2. Eukaryotic Cells Flashcards
Define cell ultrastructure
Internal structure of a cell (organelles present AS WELL AS structure of the organelles)
Define eukaryotic cells
A larger cell with a nucleus and membrane-bound organelles in its cytoplasm
Examples of eukaryotic cells
All animal & plant cells
Fungi
Protoctists
Define prokaryotic cells
A smaller cell that doesn’t have a true nucleus or membrane-bound organelles
Examples of prokaryotic cells
All bacteria
Archaea
Examples of membrane-bound organelles
Mitochondria
Chloroplasts
Vacuoles
4 differences between plant and animal cells
- Plant cells have a cell wall made of cellulose
- Plant cells have a large permanent vacuole containing cell sap
- SOME plant cells have chloroplasts containing chlorophyll
- Plant cells store carbohydrates as starch; glycogen for animals
What does a cell surface membrane look like at very high magnification?
Two dark lines separated by a pale area (plasma membrane)
4 functions of cell surface membrane
- Controls what enters & leaves cell
- Cell recognition (e.g. for immune system)
- Adhesion (cells sticking together - important in tissues in multicellular organisms)
- Signalling (e.g. receptors on surface)
What is the cell surface membrane composed of
A phospholipid bilayer
How wide is the cell surface membrane?
Very thin (10 nm)
Cytoplasm function
Contains organelles & enzymes for reactions
Size of nucleus
10-20 micrometres in diameter (largest organelle!)
Structure of nucleus
Double membrane (nuclear envelope) with nuclear pores (100nm diameter) that allows movement of molecules such as mRNA
What is inside the nucleus?
Nucleoplasm - granular, jelly-like material
How do chromosomes behave?
Visible during cell division but at other times are dispersed as chromatin (unravelled chromosome)
The outer membrane of the nucleus is…
Continuous with the rough endoplasmic reticulum
Functions of the nucleus
- Enables protein synthesis through production of mRNA and tRNA
- Retains genetic material as chromosomes
Structure of nucleolus
One or more darkly staining spherical areas within the nucleus
Is the nucleolus membrane bound?
NO
Function of nucleolus
Site of manufacture of ribosomal RNA and assembly of ribosomes
Size of ribosomes
around 20 nm diameter (smallest organelle)
Where are ribosomes
Free in cytoplasm or bough to rough ER (in eukaryotes)
Are ribosomes surrounded by a membrane?
NO
What are ribosomes made of
rRNA and protein
Function of ribosomes
Site of protein synthesis
Size of ribosomes
80S in eukaryotes
70S in prokaryotes (slightly smaller)
Ribosomes have…
a large and small subunit
Structure of rough endoplasmic reticulum
System of membrane bound, flattened sacs (channels) called cisternae
The cisternae are…
interconnected throughout the cell
Why is the rough ER rough
It’s studded with ribosomes
Proteins and the rough ER
Proteins are synthesised on the ribosomes on the rough ER. They are then passed into the cisternae and carried by vesicles to the Golgi