IB DP Biology HL B2.2 Organelles and compartmentalization Flashcards

[q] B2.2.1—What are organelles? 

Which cell parts are considered organelles?

Which are not?

[a] Organelles as discrete (separate) subunits of cells that are adapted to perform specific functions;

nuclei, vesicles, ribosomes and the plasma membrane are considered organelles;

cell wall, cytoskeleton and cytoplasm are not considered organelles

[q] B2.2.2—Why are the nucleus and cytoplasm separated into different compartments?

What is the advantage of this?

[a] Separation allows for distinct processes in different compartments of Eukaryotic cells;

Gene Transcription: Occurs in the nucleus.

Translation: Happens in the cytoplasm.

Post-transcriptional modification of mRNA can occur before it reaches ribosomes in the cytoplasm;

in contrast with prokaryotes there is No separation, leading to immediate interaction between mRNA and ribosomes.

[q] B2.2.3—What are the advantages of compartmentalization in the cytoplasm of cells?

What structures are compartmentalized?

[a] The advantage of compartmentalization is that the concentration of specific metabolites and enzymes in particular areas can be increased;

biochemical processes can be separated where they would negatively affect each other; enhancing efficiency and safety.

examples Lysosomes: Digestive enzymes are kept separate from other cell parts.

Phagocytic Vacuoles: Contain enzymes for engulfing and digesting foreign substances; which are kept separate;

[q] AHL Only – B2.2.4 What are the adaptations of the mitochondrion for production of ATP by aerobic cell respiration?

[a] Studied in Unit 4

Double Membrane: Allows optimum concentrations of enzymes used in respiration e.g. Krebs cycle 

Small Intermembrane Space: Allows buildup of high concentration of protons (H+) ions 

Cristae: Large surface area and increases space for electron transport and ATP synthesis;

Matrix Compartmentalization: Houses enzymes and substrates for the Krebs cycle, optimizing conditions for ATP production;

[q] AHL Only – B2.2.5—What are the adaptations of the chloroplast for photosynthesis?

[a] Studied in Unit 4

Thylakoid Membranes: Large surface area with embedded photosystems for light absorption.

Thylakoid Fluid: Small volume allows for buildup of high concentration of protons (H+ ions)

Stroma Compartmentalization: Contains enzymes and substrates for the Calvin cycle, facilitating glucose synthesis.

[q] AHL Only – B2.2.6—What are the functional benefits of the double membrane of the nucleus?

[a] Nuclear Pores: Allow selective exchange of materials between nucleus and cytoplasm;

Allows mRNA to leave and for DNA to be protected within nucleus;

Allows environment to be different than in the cytoplasm, with a different concentration of nucleotides; and for DNA to be protected;

Vesicle Formation: Membrane breaks into vesicles during mitosis and meiosis for chromosome segregation.

[q] AHL Only – B2.2.7—What is the structure and function of free ribosomes?

[a] Free ribosomes are made of a small and large subunit;

they are protein and RNA;

they synthesize proteins which are kept within the cell; not for export;

[q] AHL Only – B2.2.7—What is the structure and function of the rough endoplasmic reticulum?

[a] Made of a series of flattened membranes;

with ribosomes bound to it;

Responsible for processing and secretion of proteins; 

Modifies proteins received from the rough endoplasmic reticulum and prepares them for export;

creates vesicles containing proteins which bud off;

[q] AHL Only – B2.2.8—What is the structure and function of the Golgi apparatus?

[a] Made up of stacked, flat pouches; made of membrane;

Modifies and sorts proteins and lipids;

Packages materials for different cell parts or for release from the cell; through exocytosis;

[q] AHL Only – B2.2.9—What is the structure and function of vesicles in cells?

What is clathrin?

[a] Vesicles are small, single membrane-bound sacs within the cytoplasm; 

they transport materials within the cell and to the cell membrane; 

they are involved in processes like endocytosis and exocytosis;

they help store and move nutrients, enzymes, and waste;

Clathrin is a protein used in vesicle formation in cells. 

Clathrin aids in vesicle budding;

it forms a Cage-like Structure around membrane areas destined to become vesicles; 

creating a Clathrin-Coated Pit;

allowing the shaping and pinching off of the membrane to create a vesicle;

after, the clathrin coat disassembles through hydrolysis into individual molecules.

[q] identify one of the main advantages of compartmentalization in cells

[a] increased efficiency and specificity of cellular processes

[q] the cell wall is not considered an organelle.

identify the reason why

[a] it does not have a specific metabolic function

[q] why are the cytoplasm and nucleus separated in eukaryotic cells?

[a] to prevent protein synthesis before post-transcriptional modification of mRNA

[q] what is a possible disadvantage of compartmentalization in cells?

[a] it can delay a cells ability to respond to the environment

[q] identify the main function of the thylakoid membranes in photosynthesis

[a] to increase surface area for photosynthesis

[q] identify the role of the space surrounded by the inner membrane of the thylakoid in photosynthesis

[a] to contain all the enzymes and substrates required for photosynthesis

[q] what is the role of the cristae in the inner membrane in cell respiration?

[a] to increase the surface area of the inner membrane

[q] identify the purpose of the enclosed space called the ‘matrix’ in cellular respiration

[a] to contain high concentrations of enzymes for cell respiration

[q] identify the role of clathrin in vesicle formation

[a] it acts as a scaffold and brings together the machinery needed to shape and pinch off a piece of the membrane

[q] identify the function of the Golgi apparatus

[a] sorting of proteins

[q] where are bound ribosomes located?

[a] on the cytosolic side of the endoplasmic reticulum membrane

[q] identify the type of vesicles that would be involved in the breakdown of a poisonous substance

[a] peroxisomes

[q] how could you describe the structure of the Golgi apparatus?

[a] multiple stacked, flattened membrane-bound structures

[q] which of the following statements is correct about the structure of mitochondria?

[a] the matrix contains enzymes vital for the link reaction and Krebs cycle

[q] where are carbohydrates made in the chloroplast?

[a] in the stroma

[q] what is the role of clathrin in the formation of vesicles?

[a] to help the vesicle form more efficiently

[q] which of the following is an advantage of the organelles being separated from the cytoplasm?

[a] the organelle can maintain its own internal environment

[q] which statement is correct about chloroplasts?

[a] the thylakoid membrane has a large surface, for more light-dependent reactions to occur

[q] in the diagram of a chloroplast below, where will the Calvin cycle take place?

[a] I, the stroma

[q] what is the destination of a protein synthesized by free ribosomes?

[a] cytoplasm

[q] what is the purpose of the double membrane in the mitochondrion?

[a] to separate the intermembrane space from the cytoplasm

[q] which of the following is correct with regard to the free ribosomes found in eukaryotic cells?

[a] they synthesize proteins for use primarily within the cell

[q] what is the benefit of the double membrane of the nucleus in maintaining the stability of genetic information?

[a] it prevents the loss of DNA to the cytoplasm

[q] what is the function of the photosystems I and II in the thylakoid membranes of the chloroplast?

[a] to produce glucose

[q] what is the significance of the separation of the nucleus and the cytoplasm in eukaryotic cells?

[a] it allows for better regulation of gene expression

[q] where do the Krebs cycle take place in the cell?

[a] mitochondria

[q] Mitochondrion

[a] Bean-shaped or round organelle that supplies energy to the cell.

Has its own ribosomes and DNA.

Requires oxygen in its processes (aerobic).

[q] Aerobic Respiration

[a] Respiration that requires oxygen

[q] Intermembrane Space

[a] Fluid filled space between the inner and outer mitochondrial membranes.

Allows rapid accumulation of protons/hydrogen ions.

[q] Cristae

[a] Infoldings of the inner membrane of a mitochondrion that houses the electron transport chain and the enzyme catalyzing the synthesis of ATP.

Folded for more surface area.

[q] Matrix

[a] Innermost compartment of the mitochondrion.

Contains DNA and ribosomes which carry out the Krebs Cycle.

[q] Krebs Cycle

[a] Second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions

[q] Chloroplast

[a] An organelle found in plant and algae cells where photosynthesis occurs.

[q] Photosynthesis

[a] Conversion of light energy from the sun into chemical energy.

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