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IB Bio > B2.2 Organelles & Compartmentalisation > Flashcards

B2.2 Organelles & Compartmentalisation Flashcards

1
Q
A
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2
Q

What does the nucleus store?

A

The genetic material of the cell as chromatin (DNA + histone proteins)

Chromatin is a complex of DNA and proteins that forms chromosomes within the nucleus.

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3
Q

What is the solution called that contains chromatin within the nucleus?

A

Nucleoplasm

Nucleoplasm is the semi-fluid matrix inside the nucleus, similar to cytoplasm.

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4
Q

What role does the nucleus play in the cell?

A

Acts as a control centre (regulates the expression of genetic instructions)

The nucleus regulates activities such as cell growth, metabolism, and reproduction through gene expression.

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5
Q

What is the nuclear envelope?

A

A double membrane surrounding the nucleus, embedded with pores

The nuclear envelope separates the contents of the nucleus from the cytoplasm.

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6
Q

Why is the nuclear envelope considered a double membrane structure?

A

Because it is part of the endomembrane system (connected to the ER network)

The endomembrane system includes various organelles that work together to modify, package, and transport lipids and proteins.

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7
Q

What advantage does the nuclear envelope provide regarding protein synthesis?

A

Allows proteins synthesized by the ER to access the nucleus without requiring vesicular transportation

This direct access facilitates efficient communication between the nucleus and the endoplasmic reticulum.

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8
Q

What processes does the nuclear envelope separate?

A

Transcription and translation

This separation is crucial for eukaryotic cells, unlike prokaryotes, where these processes occur simultaneously.

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9
Q

How does the presence of pores in the nuclear envelope affect gene expression?

A

Allows the cell to control the rate at which transcription and translation occur (coordinates gene expression)

Pores regulate the movement of molecules in and out of the nucleus, influencing gene expression and cellular responses.

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10
Q

Why is a double membrane beneficial for mitosis and meiosis?

A

Facilitates the disassembly of the nuclear envelope for chromosome sorting and separation

During cell division, the nuclear envelope must break down to allow chromosomes to be distributed to daughter cells.

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11
Q

What happens to the nuclear envelope during cell division?

A

It must be disassembled to allow chromosomes to be sorted and separated

This process is crucial for ensuring that each daughter cell receives the correct number of chromosomes.

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12
Q

What can the nuclear envelope break down into during division?

A

Vesicles

These vesicles can later reconstitute to reform the nuclear envelope after division.

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13
Q

What is the site of polypeptide synthesis within the cell?

A

The ribosome

The ribosome is essential for protein assembly.

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14
Q

What are the two main components of ribosomes?

A
  • Protein
  • Ribosomal RNA

Protein provides stability, while ribosomal RNA is responsible for catalytic activity.

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15
Q

What is the size of eukaryotic ribosomes?

A

80S

Eukaryotic ribosomes are larger than prokaryotic ribosomes.

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16
Q

What is the size of prokaryotic ribosomes?

A

70S

Prokaryotic ribosomes are smaller than eukaryotic ribosomes.

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17
Q

What are the two distinct subunits of ribosomes?

A
  • Small subunit
  • Large subunit

The small subunit binds to mRNA, while the large subunit binds to tRNA.

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18
Q

What occurs when the small and large ribosomal subunits form a complex?

A

Translation of an mRNA sequence

This is a key step in protein synthesis.

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19
Q

Where can ribosomes be located in eukaryotic cells?

A
  • Freely within the cytosol
  • Embedded within the rough endoplasmic reticulum

Their location influences the type of protein synthesized.

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20
Q

What do free ribosomes synthesize?

A

Proteins for use within the cytosol

These are also known as intracellular proteins.

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21
Q

What do ribosomes embedded within the rough endoplasmic reticulum synthesize?

A

Proteins that will be packaged into vesicles

These proteins are often transported to other organelles.

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22
Q

What happens to proteins transported to the Golgi apparatus?

A

They will be secreted from the cell for extracellular use

This process is crucial for cell communication and function.

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23
Q

What are mitochondria often referred to as?

A

The ‘powerplants’ of the cell

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24
Q

What do mitochondria synthesize via aerobic respiration?

A

Large amounts of ATP

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25
Do all eukaryotic cells possess mitochondria?
Yes
26
What do certain prokaryotes use to respire aerobically?
The cell membrane
27
What is the theory regarding the origin of mitochondria?
They were once independent prokaryotes internalised via endosymbiosis
28
What type of membrane structure do mitochondria have?
Double membrane structure
29
What type of DNA do mitochondria possess?
Circular and naked DNA
30
What type of ribosomes do mitochondria have?
70S ribosomes
31
What can affect the metabolic processes of mitochondria?
Certain antibiotics
32
What is contained in the outer membrane of the mitochondrion?
Transport proteins
33
What does the inner membrane of the mitochondrion contain?
The electron transport chain and ATP synthase
34
What is the function of ATP synthase in mitochondria?
Used for oxidative phosphorylation
35
What are the folds in the inner membrane of mitochondria called?
Cristae
36
What is the significance of cristae in mitochondria?
Increases the SA:Vol ratio
37
What is the intermembrane space in mitochondria?
Small space between membranes
38
What does the intermembrane space maximize?
Hydrogen gradient upon proton accumulation
39
What is found in the matrix of mitochondria?
Enzymes and a suitable pH for the Krebs cycle
40
Fill in the blank: Mitochondria have a _______ structure due to vesicular coating.
Double membrane
41
What are chloroplasts known as in a cell?
Solar energy plants
42
What type of energy do chloroplasts convert light energy into?
Chemical energy
43
What are the two forms of chemical energy produced by chloroplasts?
* ATP (light dependent) * Organic compounds (light independent)
44
Where are chloroplasts primarily found in plants?
In photosynthetic tissue, mainly in the leaves
45
Do roots of plants contain chloroplasts?
No
46
What is the theory about the origin of chloroplasts?
They were once independent prokaryotes that were internalised via endosymbiosis
47
What type of membrane structure do chloroplasts have?
Double membrane structure
48
What is the significance of the double membrane in chloroplasts?
It is due to vesicular coating as part of the endocytotic process
49
What type of DNA do chloroplasts possess?
Circular and naked DNA
50
What type of ribosomes do chloroplasts have?
70S ribosomes
51
Are chloroplast metabolic processes affected by antibiotics?
Yes
52
What are thylakoids?
Flattened discs in chloroplasts that maximise hydrogen gradient
53
What is the function of grana in chloroplasts?
Stacks of thylakoids to increase SA:Vol ratio of the thylakoid membrane
54
What is the role of photosystems in chloroplasts?
Organised pigments in thylakoid membrane to maximise light absorption
55
What is the stroma in a chloroplast?
The central cavity containing enzymes and suitable pH for the Calvin cycle
56
What do lamellae do in chloroplasts?
Connect and separate thylakoid stacks (grana) to maximise photosynthetic efficiency
57
What is the primary function of the Golgi apparatus?
Sorting, storing, modifying, and exporting cellular material ## Footnote The Golgi apparatus is also known as the Golgi complex or Golgi body.
58
What is the structural composition of the Golgi apparatus?
A series of flattened sacs called cisternae ## Footnote Cisternae are located between the rough ER (cis facing) and the plasma membrane (trans facing).
59
What types of molecules arrive at the Golgi apparatus in vesicles?
Proteins and lipids ## Footnote Proteins come from the rough ER and lipids from the smooth ER.
60
What types of chemical modifications occur in the Golgi apparatus?
Phosphorylation, glycosylation, etc. ## Footnote Different sacs in the Golgi are responsible for specific modifications based on the enzymes involved.
61
Which types of proteins pass through the Golgi apparatus?
* Secretory proteins * Glycoproteins * Cell membrane proteins * Lysosomal proteins * Some glycolipids ## Footnote In plant cells, much of the cell wall material also passes through the Golgi apparatus.
62
How are materials destined for secretion handled by the Golgi apparatus?
They are packaged into vesicles for extracellular release (exocytosis) ## Footnote This process involves either immediate release or storage in secretory vesicles.
63
What is the difference between constitutive secretion and regulatory secretion?
* Constitutive secretion: immediate release * Regulatory secretion: stored for sustained release and triggered by external signals ## Footnote Regulatory secretion is activated by a ligand binding to a specific receptor.
64
Fill in the blank: The Golgi apparatus is responsible for _______ cellular material.
modifying ## Footnote This includes various processes such as sorting and exporting.
65
True or False: The Golgi apparatus is only involved in protein modification.
False ## Footnote It is involved in both protein and lipid modification.
66
What are vesicles?
Membrane-wrapped containers involved in shuttling materials between cellular compartments ## Footnote Vesicles play a crucial role in transporting substances within cells.
67
Why are most molecules packaged into vesicles?
Most molecules are too large to pass directly through membranes ## Footnote This packaging allows for the transport of larger substances that cannot diffuse through lipid bilayers.
68
What is clathrin?
A coat protein that helps form some vesicles ## Footnote Clathrin has a triskelion shape and is essential for vesicle budding.
69
How is clathrin recruited to a membrane?
By adaptor proteins (adaptin) ## Footnote Adaptin acts as a bridge between the receptor and clathrin, facilitating vesicle formation.
70
What is the structure formed by clathrin proteins?
A rounded lattice that pulls the membrane into a bud ## Footnote This structure is crucial for the initial stage of vesicle formation.
71
What protein cleaves the bud to form a vesicle?
Dynamin ## Footnote Dynamin is responsible for the final detachment of the vesicle from the membrane.
72
What is receptor-mediated endocytosis?
A process where a specific ligand binds to a receptor, recruiting clathrin ## Footnote This mechanism ensures that only specific materials are taken up by the cell.
73
What is the advantage of receptor-mediated endocytosis?
It allows greater regulatory control over what materials enter a cell ## Footnote This enhances the cell's ability to selectively internalize necessary substances.
74
Fill in the blank: Clathrin is recruited to the membrane via _______.
adaptor proteins (adaptin) ## Footnote This recruitment is essential for the formation of clathrin-coated vesicles.
75
True or False: All vesicles are formed via the clathrin coating mechanism.
False ## Footnote While clathrin is common, other mechanisms also exist for vesicle formation.
76
What adaptations do cells specialized for material exchange possess?
They possess adaptations to increase their surface area. ## Footnote This is crucial for efficient transport of materials.
77
How does the shape of squamous cells affect their surface area to volume ratio?
Squamous cells have a higher SA:Vol ratio than larger or cuboidal cells. ## Footnote This facilitates more efficient material exchange.
78
What are the ruffled projections lining absorption surfaces called?
Villi. ## Footnote These projections increase the surface area for absorption.
79
What are microvilli?
Membranous extensions on cells that enhance absorption. ## Footnote They further increase the surface area of cells.
80
What is the shape and function of red blood cells?
Thin and flat (biconcave); they store hemoglobin to increase oxygen uptake. ## Footnote Their shape is optimized for gas exchange.
81
What adaptation do tubule cells in the kidney have?
They are folded into villi and possess microvilli to improve selective reabsorption. ## Footnote This structure enhances their function in reabsorption.
82
What are pneumocytes?
Cells that line the alveoli and comprise the majority of the inner surface of the lungs. ## Footnote They play a key role in gas exchange.
83
What are the two types of alveolar cells?
Type I pneumocytes and Type II pneumocytes. ## Footnote Each type has distinct functions in the lungs.
84
What is the role of Type I pneumocytes?
Involved in gas exchange between the alveoli and the capillaries. ## Footnote Their squamous shape minimizes diffusion distance.
85
What prevents leakage of tissue fluid into the alveolar air space?
Occluding junctions between Type I pneumocytes. ## Footnote This maintains the integrity of the air space.
86
What is the function of Type II pneumocytes?
Secrete pulmonary surfactant to reduce surface tension in the alveoli. ## Footnote This aids in alveolar inflation.
87
What is the shape of Type II pneumocytes?
Cuboidal. ## Footnote They also contain granules called lamellar bodies that store surfactant.
88
What are myofibrils?
Long protein filaments responsible for muscle contraction and relaxation. ## Footnote They are present in all muscle types.
89
What type of muscle is striated muscle?
Muscle that connects to the bones of the skeleton and is responsible for voluntary movement. ## Footnote It allows for locomotion.
90
What defines cardiac muscle cells?
They are short, narrow, and fairly rectangular in shape. ## Footnote They are responsible for the rhythmic beating of the heart.
91
How are cardiac muscle cells connected?
By gap junctions at intercalated discs. ## Footnote This allows for electrical conduction between cells.
92
What is a characteristic of skeletal muscle fibers?
They are multinucleate and formed from the fusion of individual cells. ## Footnote This structure allows them to function as a single unit.
93
What is the structure of a typical human spermatozoa?
Divided into head, mid-piece, and tail. ## Footnote Each section has specific functions related to fertilization.
94
What does the head region of sperm contain?
A haploid nucleus, an acrosome cap, and paired centrioles. ## Footnote The acrosome contains enzymes for penetrating the egg.
95
What is the function of the mid-piece of sperm?
Contains mitochondria that provide ATP for tail movement. ## Footnote This energy is essential for sperm motility.
96
What layers surround a typical egg cell?
Zona pellucida and corona radiata. ## Footnote These layers provide protection and nourishment.
97
What is the function of the zona pellucida?
Acts as a barrier to sperm entry. ## Footnote It is a glycoprotein matrix.
98
What do cortical granules in the egg cell do?
Release contents upon fertilization to prevent polyspermy. ## Footnote This is crucial for successful fertilization.
99
What is the state of the egg cell before fertilization?
Arrested in metaphase II. ## Footnote No nucleus forms until after fertilization.

IB Bio (14 decks)

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