3.1.4Unit 3: Practical Skills in Biology I
The Rough Endoplasmic Reticulum and Golgi — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 4 parts Lesson 6 of 27 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 4Organelles Involved in Protein Secretion
Extracellular enzymes are proteins made inside the cell and then released from it.
Nucleus
- Nucleus The DNA code for the protein is transcribed here, and mRNA leaves through a nuclear pore.
Ribosomes on the RER
- Ribosomes on the RER These carry out translation and pass the new polypeptide into the lumen of the rough endoplasmic reticulum.
Rough endoplasmic reticulum
- Rough endoplasmic reticulum Proteins are folded and processed inside the lumen, which is the space inside the flattened sacs.
Vesicles
- Vesicles Small membrane-bound sacs that bud off one organelle and carry their contents to the next one.
Golgi apparatus
- Golgi apparatus This stack of flattened sacs further modifies proteins and prepares them for secretion or delivery.
Cell surface membrane
- Cell surface membrane A vesicle fuses with this membrane and releases its contents to the outside by exocytosis.
Part 2 of 4Pathway of a Secreted Protein
1
A gene is transcribed in the nucleus, and the mRNA leaves the nucleus to attach to a ribosome on the rough endoplasmic reticulum.
2
The polypeptide is made by translation and enters the lumen of the rough endoplasmic reticulum, where it is folded and processed.
3
Vesicles carrying the processed protein bud off from the rough endoplasmic reticulum and move to the Golgi apparatus.
4
The vesicles fuse with the Golgi, which modifies the protein, and new vesicles then bud off carrying the finished product.
5
The vesicles move to the cell surface membrane, fuse with it and release the enzyme outside the cell.
Part 3 of 4Destinations of Golgi Products
Destinations of Golgi Products
Export
- Export Proteins such as extracellular enzymes are packaged in vesicles and released outside the cell.
Lysosomes
- Lysosomes Hydrolytic enzymes are packaged by the Golgi into vesicles that become lysosomes.
Other organelles
- Other organelles Some modified proteins are delivered to other membrane-bound organelles within the cell.
Free ribosomes
- Free ribosomes Ribosomes in the cytoplasm make proteins that stay in the cytoplasm and are not exported.
Part 4 of 4Exam Checklist & Tips
3.1.4 – Key Points for the Exam
- Rough endoplasmic reticulum Membrane-bound sacs studded with ribosomes where proteins are made and folded.
- Golgi apparatus A stack of flattened sacs that modifies and packages proteins.
- Vesicle A small membrane-bound sac used to transport substances inside cells.
- Extracellular enzyme An enzyme made inside a cell that acts outside it.
- Lumen The space inside an organelle such as the rough endoplasmic reticulum.
- Exocytosis The process in which a vesicle fuses with the cell surface membrane and releases its contents outside the cell.
Common Mistakes
- Saying that the ribosome makes the protein in the Golgi apparatus, when translation occurs at ribosomes.
- Writing that the smooth endoplasmic reticulum has ribosomes and makes proteins.
- Forgetting that vesicles carry proteins between the rough endoplasmic reticulum and the Golgi.
- Stating that proteins diffuse out of the cell, when they leave by vesicles.
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