What is the sequence of organisation in a multicellular organism?

Cells form tissues, tissues form organs, organs form organ systems.

What is the function of the nucleolus?

It makes ribosomal RNA and assembles ribosomal subunits.

What are nuclear pores for?

They allow mRNA and other molecules to pass between the nucleus and the cytoplasm.

What do ribosomes do?

They are the site of protein synthesis (translation).

What is the function of the rough endoplasmic reticulum?

Ribosomes on its surface make proteins that enter the lumen to be folded and transported.

How does smooth ER differ from rough ER?

It has no ribosomes; it makes lipids and carries out detoxification.

What does the Golgi apparatus do?

It modifies proteins, packages them into vesicles and forms lysosomes.

What is the function of a lysosome?

It contains hydrolytic enzymes that digest worn-out organelles and material taken in by the cell.

Describe a mitochondrion in an electron micrograph.

Oval or rod-shaped, double membrane, with the inner membrane folded into cristae.

Why do cristae matter?

They give the inner membrane a large surface area for ATP production in aerobic respiration.

What is the function of centrioles?

They are involved in forming the spindle in animal cell division.

Describe the route of a secreted protein.

Ribosome on rER, rER lumen, transport vesicle, Golgi, secretory vesicle, fusion with the surface membrane (exocytosis).

What is an extracellular enzyme?

An enzyme made inside a cell and secreted to act outside it, such as amylase.

Eukaryotic cell ultrastructureEdexcel International A Level Biology: Flashcards

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List three features common to all cells.

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List three features common to all cells.: Cell surface membrane, cytoplasm, genetic material (DNA) and ribosomes.
What is the sequence of organisation in a multicellular organism?: Cells form tissues, tissues form organs, organs form organ systems.
What is the function of the nucleolus?: It makes ribosomal RNA and assembles ribosomal subunits.
What are nuclear pores for?: They allow mRNA and other molecules to pass between the nucleus and the cytoplasm.
What do ribosomes do?: They are the site of protein synthesis (translation).
What is the function of the rough endoplasmic reticulum?: Ribosomes on its surface make proteins that enter the lumen to be folded and transported.
How does smooth ER differ from rough ER?: It has no ribosomes; it makes lipids and carries out detoxification.
What does the Golgi apparatus do?: It modifies proteins, packages them into vesicles and forms lysosomes.
What is the function of a lysosome?: It contains hydrolytic enzymes that digest worn-out organelles and material taken in by the cell.
Describe a mitochondrion in an electron micrograph.: Oval or rod-shaped, double membrane, with the inner membrane folded into cristae.
Why do cristae matter?: They give the inner membrane a large surface area for ATP production in aerobic respiration.
What is the function of centrioles?: They are involved in forming the spindle in animal cell division.
Describe the route of a secreted protein.: Ribosome on rER, rER lumen, transport vesicle, Golgi, secretory vesicle, fusion with the surface membrane (exocytosis).
What is an extracellular enzyme?: An enzyme made inside a cell and secreted to act outside it, such as amylase.

Exam questions on Eukaryotic cell ultrastructure

A student examines an electron micrograph of an acinar cell from the pancreas, which secretes the digestive enzyme amylase. The cell has a large amount of rough endoplasmic reticulum, a prominent Golgi apparatus and many small vesicles close to the cell surface membrane.
Explain why this cell having a large amount of rough endoplasmic reticulum is an advantage.2 marks
Tay-Sachs disease is an inherited disorder in which a lysosomal enzyme that breaks down a lipid is missing. The lipid builds up inside nerve cells, which swell and become damaged.
Explain why the lipid builds up inside the nerve cells.2 marks
Pancreatic cells were given a short pulse of a radioactively labelled amino acid and then transferred to a medium containing only unlabelled amino acids. After 3 minutes most radioactivity was in the rough endoplasmic reticulum. After 20 minutes most was in the Golgi apparatus. After 60 minutes most was in vesicles near the cell surface membrane and in the medium surrounding the cells.
Describe the pathway taken by the labelled protein, as shown by these results.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).