B2.2 Organelles and Compartmentalisation Flashcards
What are organelles?
Discrete structures within a cell and perform a specific function
Examples include the nucleus, Golgi apparatus, mitochondria, lysosomes, chloroplasts, rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER)
What is compartmentalisation in cells?
The use of membranes to isolate certain parts of the cell to form separate organelles. This allows reactions to occur without interference from other cellular processes.
Internal conditions (E.g. pH) can be differentiated in the cell to maintain optimum conditions for different enzymes;
What is the function of the nucleus?
Houses nearly all the cell’s genetic material and makes ribosomes
The nucleus contains chromatin, which consists of DNA and proteins. Also contains nucleolus and the nuclear envelope
What is the role of the nucleolus?
Part of Nucleus. Produces RNA, which is made into ribosomes
Ribosomes move out of the nucleus to the rough endoplasmic reticulum to produce proteins.
What is the structure of the Nuclear envelope?
A dense, spherical structure which surrounds the nucleolus, and is made up of an inner and outer membrane, separated by a fluid.
It is marked with pores which allow for exchange of relatively large molecules.
What is the function of the Cell membrane?
Semi-permeable layer that controls movement in and out of the cell.
What is the function of the Golgi apparatus?
Processes and packages proteins, which are released in Golgi vesicles
The Golgi apparatus modifies proteins received from the rough endoplasmic reticulum.
What are lysosomes and their function?
Contain hydrolytic enzymes for the destruction of microbes engulfed by white blood cells, and old organelles
Lysosomes are not present in plant cells.
What is the advantage of compartmentalisation in cells?
Allows for optimal internal conditions, isolation of toxic substances, and flexibility in organelle positioning
Example: Phagocytic vacuoles isolate ingested materials.
What is the structure of mitochondria?
Contains an inner and outer membrane, with the inner membrane folded into cristae
This structure increases surface area for ATP production.
What is the role of vesicles in cells?
Transport and release substances produced by the cell by fusing with the cell membrane.
Vesicles can include transport vesicles, secretory vesicles, lysosomes, and peroxisomes.
What does the chloroplast do?
Responsible for photosynthesis and contains pigments such as chlorophyll. Double-membrane bound organelle.
Chloroplasts are not present in animal cells.
What is the function of clathrin?
Plays a role in the formation of vesicles in cells
Clathrin stabilizes membrane invaginations during processes like endocytosis and phagocytosis.
What are the membranes in Chloroplasts?
Outermembrane, innermembrane, thylakoid membrane.
Compartment (space) between innermembrane and thylakoid membrane is called stroma.
What is the role and structure of Chloropolasts?
Absorb light to create ATP. Disc-shaped structure increases surface area to hold chlorophyll and other enzymes needed for photosynthesis; this increases rate of photosynthesis.
Stack to form grana.
What is the significance of the double membrane around the nucleus?
Acts as a barrier. Protects genetic material, prevents damage to DNA. Regulates the entry and exit of molecules
The nuclear pores allow for the exchange of substances.
Describe the function of vacuoles.
Helps in osmotic balance and storage of substances
Vacuoles may also have hydrolytic functions similar to lysosomes.
How does compartmentalisation aid in protein synthesis?
Allows mRNA to be modified before binding to ribosomes
This ensures functional proteins are produced.
What is the matrix in mitochondria?
The enclosed space between the membranes (inner and outer) contains enzymes and other substances for respiration. Allows for high concentration gradients, which is required for respiration.
High concentration gradients form in the matrix, aiding respiration.
What is the main function of the outer membrane of mitochondria?
Permeable to small molecules and ions. Contains transport proteins (porins), to assist transport of larger molecules into the mitochondria.
These transport proteins help larger molecules enter the mitochondria.
What does the stroma in chloroplasts contain?
Enzymes and substrates required for the Calvin cycle
Compartmentalisation maximizes the efficiency of chemical reactions.
What drives membrane curvature and the budding off of a vesicle?
Clathrin
Clathrin forms a lattice-like structure that is crucial for vesicle formation.
What happens to the clathrin coat once the vesicle is internalized?
The clathrin coat disassembles
This allows the vesicle to be transported to its target destination.
Through what process are low-density lipoprotein (LDL) particles internalized?
Clathrin-mediated endocytosis
This process provides cholesterol for cellular processes.
What role does clathrin play in phagocytosis?
Stabilizes membrane invaginations
Clathrin aids in the final stages of vesicle formation during phagocytosis.
Which type of cells use clathrin-mediated vesicles to engulf and digest bacteria?
Macrophages
Macrophages are immune cells that perform phagocytosis.
What is the function of clathrin-coated vesicles in lysosome formation?
Transport enzymes like acid hydrolases
This ensures the proper functioning of lysosomes in breaking down macromolecules.
What is a key example of an enzyme transported to lysosomes by clathrin-coated vesicles?
Mannose-6-phosphate-tagged enzymes
These enzymes are crucial for lysosomal function.
What is the significance of compartmentalisation in cells?
Development of specialised cell structures
This allows for the concentration of reactants and separation of damaging chemicals.
Which structures are not considered organelles?
Cytoskeleton, cell wall, and cytoplasm
While they are important for cell function, they do not fit the definition of organelles.
Which organelles have highly folded membranes to increase surface area?
Mitochondria and chloroplasts
This adaptation allows for more efficient production of ATP and glucose.
What is the protective role of the double membrane of the nucleus?
Serves as a barrier for genetic material
It regulates the entry and exit of molecules critical for gene expression.
What is the function of the rough endoplasmic reticulum (ER)?
Produces proteins for export outside the cell
It has attached ribosomes that facilitate this process.
What are vesicles?
Small membrane-bound structures that transport and store materials
They include proteins, lipids, and RNA.
Outline the difference between bound and free ribosomes.
Bound ribosomes produce proteins for export; free ribosomes produce proteins for internal use
This distinction is important for understanding protein targeting.
List solid organelles (no membrane), single-membrane enclosed organelles and double-membrane enclosed organelles.
Solid: Ribosomes
Single membrane: ER, Golgi apparatus, Lysosomes, and Vacuoles.
Double membrane: Nucleus, mitochondria, cytoplasm.
Why are cytoplasm, cel wall and cytoskeleton not considered organelles?
They do not fit the definition of an organelle: do not perform a specific function. Doesn’t do anything to aid in carrying out of 7 life functions.
Cytoplasm is medium; provides space for organelles to perform functions.
Cell wall: provide support and regulate movement of substances in and out.
Advantages of Compartmentalization of DNA in nucleus from cytoplasm
In Eukaryotic cells, compartmentalization of nucleus allows post-transcriptional changes to occur before translation.
