Structure of eukaryotic cells

What are the structures present in a eukaryotic cell
(animal cell only)?

• Cell surface (plasma) membrane

• Nucleus

• Mitochondria

• Golgi bodies

• Smooth endoplasmic reticulum

• Rough endoplasmic reticulum

• Ribosomes

• Lysosomes

What are the structures present in a eukaryotic cell
(plant cell only) ?

• Cellulose cell wall

• Permanent vacuole

• Chloroplasts

Describe the structure and function of the cell surface (plasma) membrane

• Composed of hydrophilic heads which face outwards towards water, and the hydrophobic tails face inwards away from the water - forming a bilayer.

• The centre of the bilayer is also hydrophobic

• So the membrane doesn't allow large, water-soluble or polar substances to pass in and out of the cell

• Also contain extrinsic proteins in the membrane, which act as receptors and intrinsic proteins which act as channel/carrier proteins

Describe the structure and function of the nucleus

• Contains the nuclear envelope, which is a double membrane that separates genetic material in the nucleolus from the cytoplasm

• Nuclear envelope contains pores called nuclear pores which allow the mRNA to exit

• Nucleoplasm is a jelly-like substance within the nuclear envelope that suspends chromatin and the nucleolus and molecules for DNA transcription and replication

• Nucleolus is a dense, non-membrane-bound region found inside the nucleus responsible for the synthesis of ribosomal RNA and ribosomes

• It also contains chromatin, which is linear DNA that is wrapped around histones

Describe the structure and function of the mitochondria

• Mitochondria has a double membrane structure with a highly folded inner membrane called the crystae

• Massively increase surface area, allowing more ATP synthase enzymes to attach (to stalks which are attached to the crystae)

• This leads to a lot of ATP being produced in respiration

• Also contains the matrix which contains DNA, ribosomes and enzymes involved in aerobic respiration

Describe the structure and function of the golgi bodies

• Contain fluid filled membrane bound sacs called cistarnae

• These have specific enzymes that modify and process proteins and lipids as they move from trans to cis phase

• Have vesicles at the end which store proteins and lipids and transport them out of the cell

• Also produce lysosomes

Describe the structure and function of the lysosomes

• They are vesicles containing lysozymes

• These are nzymes are used to break down or damaged pathogens.

• They are also enclosed in a double membrane to prevent self-digestion and to isolate the hydrolytic enzymes from the rest of the cytoplasm

Describe the structure and function of the SER (smooth endoplasmic reticulum)

• Surface is not covered in ribosomes

• Synthesises and processes lipids and carbohydrates

Describe the structure and function of the RER (rough endoplasmic reticulum)

• Surface is covered in ribosomes

• Synthesises and processes proteins

Describe the structure and function of the cell wall

• Rigid outer structure made of cellulose which provides mechanical strength (prevents bursting in osmotic balances)

• Contains plasmodesmata which are channels in plant cell walls that connect cytoplasm of adjacent cells allowing for a direct transport of substances

• Freely permeable so allows water to pass across it

Describe the structure and function of the chloroplast

• Enclosed by a double membrane structure and contains its own DNA

• Contains thylakoids (flattened fluid filled sacs from from extensions of the chloroplast membrane) which contain chlorophyll

• Stacked into grana which increase the surface area for photosynthesis

• Lamallae connect grana (further increasing the surface area) and forming a long network of grana allowing for the transport of molecules between them

• Contains stroma which contain aqueous fluid containing enzymes for chemical reactions - dark reactions occur in the stroma

Describe the structure and function of the vacuoles

• Membrane bound organelle that contains an outer membrane called tonoplasts which controls passage of substances in and out of vacuole

• Contains cell sap - weak solution of sugars, salts and other dissolved molecules which maintains turgor pressure inside the cell

• Also acts as a temporary food storage

How are algal and fungal cells different/same?

Algal cells:

Same as the plant cell in term of organelles

Fungal cells:

Similar to plant cells, but cell wall is made of chitin not cellulose
No chloroplasts