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Biology > B2.2: Organelles and Compartmentalization > Flashcards

B2.2: Organelles and Compartmentalization Flashcards

1
Q

What is an organelle

A

A discrete structure within a cell that’s adapted to perform a specific function

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2
Q

Is the plasma membrane itself considered an organelle

A

Yes

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3
Q

3 examples of solid organelles (no membrane)

A
  • Ribosomes
  • Centrioles
  • Nucleolus
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4
Q

What is meant by single membrane

A

Single Phospholipid Bilayer

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5
Q

What is meant by double membrane

A

Double phospholipid bilyaer

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6
Q

4 examples of single membrane bound organelles

A
  • Vesicles and Vacuoles
  • rER & sER
  • Golgi apparatus
  • Lysosomes
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7
Q

3 examples of double membrane bound organelles

A
  • Nucleus
  • Chloroplasts
  • Mitochondria
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8
Q

Why is the cell wall not considered to be an organelle

A
  • Outside of the cell membrane hence, meaning it’s extracellular - it’s not in the cell so the cell wall isn’t an organelle
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9
Q

Why is the cytoplasm not considered to be an organelle

A
  • Not specialised to perform a specific function
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10
Q

Why is the cytoskeleton not considered to be an organelle

A
  • It’s not a discrete structure as it’s composed of many different types of filaments and tubules
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11
Q

Why do some membrane-bound organelles need double membranes

A

Prevents cells with interacting with one another

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12
Q

What is compartmentalisation

A

separation from organelles via their membranes to provide them an area for itnernal chemistry

  • kinda like rooms in a house
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13
Q

What are the benefits of DNA in the nucleus being compartmentalised from the cytoplasm

A
  • Allows for specialised and compartmentalisation control of major DNA functions like Transcription and Translation, Replication and repair of damaged DNA
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14
Q

Compare the location and timing of initiation of transcription and translation between prokaryotic and eukaryotic cells

A

Eukaryotic cells:
- Transcription first occurs in the nucleus and translation occurs in the cytoplasm

Prokaryotic cells:
- Both transcription and translation occur in the cytoplasm

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15
Q

Outline why post-transcriptional modification of RNA isn’t possible in prokaryotic cells

A
  • Eukaryotic cells:
    Post transcriptional modification is a common occurrence. Compartmentalising the nucleus and cytoplasm allows the post-transcriptional changes to occur before translation
  • Prokaryotic cells
    Transcription and Translation occur in the cytoplasm at the same time and a separation is not possible due to the lack of a nucleus
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16
Q

Why are the cytoplasm and nucleus separated in eukaryotic cells

A
  • To prevent proteins synthesis before post-transcriptional modification of mRNA
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17
Q

Define compartmentalisation within cells

A
  • The membrane around an organelle creates a compartment with controlled conditions inside
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18
Q

List advantages of compartmentalisation within cells

A
  • Enzymes & Metabolites can be concentrated in a small space which increases chances for collisions between active site and substrate
  • Substances that can damage cells can be isolated within a membrane which can protect remaining structure from degradation
  • Conditions can be maintained at optimal value for reactions
  • Large areas of membranes can become dense with proteins for a specific process
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19
Q

What’s a possible disadvantage of compartmentalisation in cells?

A

It can delay a cell’s ability to respond to the environment

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20
Q

Outline the benefit of compartmentalisation of lysosomes and phagocytic vacuoles in cells

A

Lysosomes:
- Hydrolyses (breaks down) and recycle waste materials within the cell

Phagocytic vacuoles in cells:
- Break down pathogens into parts to develop an immune response

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21
Q

What type of process occurs in phagocytosis

A

endocytosis

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22
Q

How does phagocytosis work in lysosomes

A
  • The hydrolytic enzymes from the lysosome digest the object
  • The engulfed object is enclosed within a membrane bound vacuole called phagosome
  • The phagosome fuses with the lysosome to become a phagolysome
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23
Q

Why does the outside of the Lysosome have a lower pH than the inside

A
  • Prevents hydrolytic enzyme leakage therefore causing the enzymes to denature
  • The hydrolytic enzymes function optimally at a lower, acidic pH
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24
Q

Describe how outer membranes of mitochondria are adapted to their function:

A

Separates contents of mitochondria from the rest of the cell

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25
Q

Describe how inner membranes of mitochondria are adapted to their function:

A
  • Highly folded to form a large area to maximise number of reactions
  • This is covered in ATPase enzymes which are required for ATP Production
  • Contains electron transport proteins
26
Q

Describe how intermembrane spaces of mitochondria are adapted to their function:

A

The small space allows mitochondria to quickly generate a high concentration gradient

27
Q

Describe how cristae of mitochondria are adapted to their function:

A

Increase surface area and allow more of the enzymes needed for ATP production to be present on the membranes

28
Q

How is ATP made

A

Through a series of oxidation and reduction reactions that occur in the final stage of the process at the e- transport chain
- Oxidation: Remove H or Add Oxygen & loss of e-
- Reduction: Add H or Remove Oxygen & gain of e-

29
Q

Describe how matrix of mitochondria are adapted to their function:

A

Contains lots of enzymes in high concentration needed for the Krebs Cycle and for cellular respiration

30
Q

Describe how ribosome of mitochondria are adapted to their function:

A

Site for protein synthes

31
Q

Describe how DNA of mitochondria (mtDNA) are adapted to their function:

A

Regulates cellular metabolism

32
Q

Describe how double membrane of chloroplasts are adapted to their function:

A

Acts as a barrier between the genetic material inside the nucleus and the rest of the cell.

33
Q

Describe how Thylakoid membrane of chloroplasts are adapted to their function:

A
  • They are where the light-dependent reactions of photosynthesis take place as they contain photosystems and increase surface area of chloroplasts
  • Proteins for e- transport chain in thylakoid membranes establish concentration gradients.
34
Q

Describe how Compact Thylakoid Lumen of chloroplasts are adapted to their function:

A

Contains photosynthetic pigments within their memranes

35
Q

Describe how Stroma of chloroplasts are adapted to their function:

A
  • contains all the enzymes and substrates required for the Calvin cycle that will make glucose molecules in the light dependent stage
36
Q

Describe how Ribosomes of chloroplasts are adapted to their function:

A

Site of photosynthesis

37
Q

Describe how DNA of chloroplasts (cpDNA) are adapted to their function:

A

Codes part of the genetic info to fulfil photosynthesis

38
Q

Describe the structure and function of the pores in the nuclear membrane

A

Structure:
- A double protein’s used to make a larger pore for the assemblages of rRNAs and proteins

Function:
- Creates a selective passageway through which only specific molecules are able to travel between the nucleus and the cytoplasm

39
Q

Describe the breakdown and reformation of the nucleus during mitosis

A
  • Nuclear membrane breaks down to allow the chromosomes to be moved to the poles of the cell
  • Nuclear membranes reform around the new groupings of chromosomes
  • This can be easily achieved with a double membrane
40
Q

Outline the structure of ribosome

A
  • Ribosomes are made of dozens of proteins arranged on scaffold of ribosomal RNA (rRNA)
  • Consist of a large subunit with 3 tRNA binding sites and a small subunit with 3 mRNA binding sites
41
Q

Where are bound ribosomes located in the cell

A
  • On the cytosolic side (fluid portion of cytoplasm) of the rER
42
Q

Compare the structure and function of free ribosomes and those bound to the rER

A

Structure:
- Free ribosomes float in cytoplasm whereas those bound to the rER

Function:
- Free ribosomes are synthesizing polypeptides that are used in the cell whereas those bound to the rER are secreted from the cell or become integral proteins in the cell membrane

43
Q

Where is the endomembrane system and what’s its function

A
  • The ER is part of the endomembrane system
  • The compartmentalisation sacs within the eukaryotic cell work together to modify, process and ship molecules within and out of the cell
44
Q

Compare the ultimate destination(s) of proteins synthesized at free ribosomes to those synthesized at ribosomes bound to the rough endoplasmic reticulum.

A

Ultimate destination of protein synthesized free ribosomes:
- Ultimately released into cytoplasm and remain there or they enter the nucleus or they are absorbed by mitochondria or chloroplasts

Ultimate destination of those synthesized at ribosomes bound to the rER
- Initial destination is golgi apparatus with many of them ultimately secreted from the cell

45
Q

Outline the structure and function of the Golgi Apparatus

A

Structure:
- Composed of flattened membrane-enclosed

Function:
- in Golgi cisternae, polypeptides are modified into their functional state

46
Q

What is the vesicle transport model

A
  • Where the transport vesicles carry proteins between the cisternae of the Golgi compartments
47
Q

What is the cisternal maturation model

A
  • Where the golgi cisternae gradually mature and progressively move through the Golgi in the cis to trans direction
48
Q

Outline the general flow of protein to, through and from the Golgi Apparatus

A

General flow:
- Each protein gradually moves through cisternae from the cis side (side nearest to the rER) to the trans side (opposite side) of the Golgi which sorts, concentrates and packs the proteins into vesicles that transport the protein elsewhere

49
Q

What are some examples as to where the protein is transported

A

Lysosomes or vacuoles for digestive enzymes, the plasma membrane for integral proteins or the cell exterior for proteins secreted via exocytosis

50
Q

Describe the formation of vesicles in cells from phospholipid membranes, including the role of clathrin.

A
  • Fluidity of the membrane allows for constant formation of vesicles during endocytosis
  • Clathrin assembles into a lattice structure on the inner surface of the plasma membnrane. It bends the membrane and begins the process of vesicle budding
  • Clathrin coated vesicles are produced by this process and this structure helps to overcome the positive hydrostatic pressure which tends to prevent vesicle formation
51
Q

What is the movement of vesicles

A
  • Vesicles move through the cell along the cytoskeleton track
52
Q

List functions of vesicles in cells.

A
  • Transport vesicles: Transport proteins and lipids from one location to another within the cell (from ER to golgi then from golgi to vacuoles for digestive enzymes)
  • Secretory vesicles: Transport proteins and lipids from inside the cell to the plasma membrane
  • Endocytic vesicles: Formed by invagination of plasma membrane around an extracellular substance during endocytosis. They deliver the cargo to other organelles for further sorting/digestion.
53
Q

Outline the consequence of vesicle fusion.

A
  • Vesicle fusion is the merging of a vesicle with another organelle/part of a cell membrane
  • This adds phospholipids to the target structure which makes it larger
54
Q

What types of vesicles are involved in the breakdown of a poisonous substance

A
  • Preoxisomes which contain a different set of enzymes from lysosomes and detoxify harmful compounds. They are also involved in lipid metabolism
55
Q

Where does the Krebs cycle take place in the cell

A

Mitochondria

56
Q

Where does the Calvin cycle take place in the plant cell

A

Stroma

57
Q

Correct description of free ribosomes and bound ribosomes?

A

Free ribosomes:
- Produce polypeptides to make proteins for use in the cell

Bound ribosomes:
- Located on the rER

58
Q

What happens to ribosomes once translation is completed

A
  • Large subunit and Small subunit separate to be reused again later
59
Q

Explain how compartmentalisation is beneficial during phagocytosis

A
  • Compartmentalisation is the separation of cellular components into regions by membrane
  • Engulfed object gets surrounded by a vacuole with a membrane called a phagosome
  • Lysosomes contains digestive enzymes
  • Phagosome binds to lysosome to make a phagolysome
60
Q

Predict how might a cell be affected if the enzymes present in lysosomes were not stored within a phospholipid bilayer

A
  • Prediction: digestive enzymes can digest other organelles
  • Reason: Because digestive enzymes in lysosomes would diffuse through cytoplasm
61
Q

In eukaryotic cells, transcription occurs in the nucleus and translation occurs in the cytoplasm. Explain the benefits to the cell of this physical separation (7 marks)

A
  • Post-transcriptional changes occur in mRNA before protein synthesis in cytoplasm
  • Nucleus provides a controlled environment for transcription
  • DNA is protected within Nucleus
  • Separation allows for more control over when and where genes are transcribed
  • Accuracy of gene expression is maintained
  • Ribosomes are in the cytoplasm
  • Transcription factors can enter nucleus
62
Q

Outline the adaptations of chloroplasts for their functions (4 marks)

A
  • outer membrane provides protection
  • Ribosomes to allow chloroplasts to undergo protein synthesis
  • Stroma contains high conc. of enzymes allowing for calvin cycle to occur
  • Contains chlorophyll to absorb and convert light energy to chemical energy
  • chDNA codes a part of the genetic info to fulfill photosynthesis
  • Thylakoid membranes increase SA for chloroplasts for light absorption

Biology (20 decks)

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