Eukaryotic Cells

Eukaryotic Cells

1. Nucleus

   • > Contains hereditary material and controls cell activity.
   • > Nuclear envelope - double membrane - controls entry & exit.
   • > Nuclear pores - allow passage of large molecules.
   • > Nucleoplasm - jelly-like material.
   • > Chromosomes - linear DNA.
   • > Nucleolus - manufactures RNA.

2. Mitochondria

   • > Double membrane. Inner two membranes is cristae.
   • > Cristae - large surface area for enzymes.
   • > Matrix - controls reproduction of proteins.
   • > Produce ATP, site of aerobic respiration.

3. Ribosomes

   • Site of protein-synthesis.
   • > 80s - eukaryotic cells.
   • > 70s - prokaryotic cells.

4. Cell Wall

   • > Cellulose - strong, stops cell from bursting. To give mechanical strength to the plant.

5. Lysosomes

   • Formed when vesicles produced by Golgi contain proteases and lipases.
   • > Hydrolyse material ingested by phagocytic cells.
   • > Digest worn out organelles so that the useful chemicals that they are made out of can be reused.
   • > Completely break down cells after they have become inactive.

6. Golgi Apparatus

   • Modifies and labels proteins.
   • > Add carbohydrates to proteins to form glycoproteins.
   • > Produce secretary enzymes.
   • > Transport, modify and store lipids.
   • > Form lysosomes.

7. Vacuoles

   • > Tonoplast - single membrane. Makes cells turgid. Sugars and amino acids act as a temporary store. Pigments may attract pollinating insects.

8. Endoplasmic reticulum

   • > RER: ribosomes, provide large surface area for protein-synthesis.
   • > SER: no ribosomes, synthesise, store and transport lipids. Synthesise, store and transport carbohydrates.

9. Chloroplasts

   • > Carry out photosynthesis.
   • > Chloroplast envelope - double membrane.
   • > Grana - stacks of thylakoids (contain chlorophyll)
   • > Stroma - second stage of photosynthesis. Contains starch grains.