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cell structure Flashcards

1
Q

What defines a eukaryotic cell?

A

A eukaryotic cell has a nucleus and membrane-bound organelles such as mitochondria, the Golgi apparatus, and the endoplasmic reticulum.

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2
Q

What are the key differences between eukaryotic and prokaryotic cells?

A

Eukaryotic cells have a nucleus, membrane-bound organelles, and larger ribosomes (80S), while prokaryotic cells lack a nucleus, have no membrane-bound organelles, and have smaller ribosomes (70S).

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3
Q

What is the function of the nucleus?

A

Stores genetic material (DNA), regulates gene expression, and controls cell activities.

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4
Q

What is the nucleolus, and what does it do?

A

A dense region in the nucleus where ribosomal RNA (rRNA) is synthesised and ribosome subunits are assembled.

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4
Q

What is the function of ribosomes?

A

Synthesising proteins by translating messenger RNA (mRNA) into polypeptides.

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5
Q

What is chromatin?

A

DNA and histone proteins found within the nucleus.

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5
Q

What is the structure of the nuclear envelope?

A

A double membrane surrounding the nucleus with nuclear pores allowing molecule exchange between the nucleus and cytoplasm.

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6
Q

What are the two types of endoplasmic reticulum (ER)?

A

Rough ER (RER): Covered with ribosomes, synthesises and transports proteins.

Smooth ER (SER): Lacks ribosomes, synthesises lipids & transports lipids & steroids.

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7
Q

How does the Golgi apparatus function?

A

Structure: single membrane organelle with a fluid filled space (cisternae)
Membranes are arranged into a stack.
Surrounded by vesicles

  • Production of lysosomes
  • packages and modifies proteins
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8
Q

What is the role of lysosomes?

A

Contain hydrolytic enzymes that break down waste, cellular debris, and invading pathogens.

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8
Q

What is the function of mitochondria?

A

Site of aerobic respiration, producing ATP via oxidative phosphorylation.

Contains its own DNA and 70s ribosomes for protein synthesis.

Inner (fores cristae) and outer membrane

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9
Q

What is the structure of mitochondria?

A

Double-membraned; inner membrane folds into cristae, increasing surface area for ATP production. The matrix contains enzymes for respiration

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10
Q

What is the function of centrioles?

A

Organise microtubules to form the spindle fibers necessary for chromosome separation during mitosis and meiosis.

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11
Q

What is the cytoskeleton?

A

A network of protein filaments that provides structural support, aids intracellular transport, and enables cell movement.

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12
Q

What are the three components of the cytoskeleton?

A

Microfilaments: Made of actin, involved in movement and shape changes.

Microtubules: Provide support, act as tracks for vesicle movement, form spindle fibers.

Intermediate filaments: Provide mechanical strength to cells.

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13
Q

What is the role of vesicles?

A

Small membrane-bound sacs that transport substances within the cell.

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14
Q

What is the function of cilia and flagella?

A

Used for movement; cilia move substances along surfaces, while flagella propel cells (e.g., sperm cells).

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15
Q

What are the key differences between plant and animal cells?

A

Features Unique to Plant Cells
Cell Wall – Made of cellulose
Chloroplasts– Site of photosynthesis, contain chlorophyll.
Large Permanent Vacuole – Filled with cell sap, maintains turgor pressure.
Carbohydrate Storage – Stores carbohydrates as starch.
Fixed Shape – Rigid structure due to the cell wall.

Features Unique to Animal Cells
No Cell Wall – Allows flexibility in shape.
No Chloroplasts – Cannot photosynthesise.
Small, Temporary Vacuoles – If present, do not provide structural support.
Centrioles – Involved in spindle fibre formation during mitosis.
Carbohydrate Storage – Stores carbohydrates as glycogen.

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16
Q

What distinguishes prokaryotic cells from eukaryotic cells?

A

Prokaryotic cells lack a nucleus and membrane-bound organelles; they have a single circular DNA molecule, ribosomes (70S), and a cell wall made of peptidoglycan.

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17
Q

What is the function of the bacterial cell wall?

A

Provides structural support and protection, composed of peptidoglycan.

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18
Q

What is the role of plasmids in prokaryotic cells?

A

Circular DNA molecules carrying additional genes, such as antibiotic resistance genes.

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19
Q

What is the function of flagella in prokaryotic cells?

A

tail-like structures used for locomotion, rotating to propel the cell forward.

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20
Q

What are pili, and what is their function?

A

Hair-like projections aiding attachment to surfaces and involved in conjugation (DNA transfer between bacteria).

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21
Q

How do prokaryotic ribosomes differ from eukaryotic ribosomes?

A

Prokaryotic ribosomes are smaller (70S) compared to eukaryotic ribosomes (80S).

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22
What is the nucleoid region in prokaryotic cells?
An area in the cytoplasm where the single circular DNA molecule is found, not enclosed by a membrane.
23
How do prokaryotic cells reproduce?
By binary fission, a process where the DNA replicates, and the cell splits into two identical daughter cells
24
What is the function of the capsule in prokaryotic cells?
A protective layer preventing desiccation, phagocytosis, and aiding in adhesion to surfaces.
25
What are the differences between light and electron microscopes?
Light microscopes: Lower magnification and resolution, can view live cells. Electron microscopes: Higher magnification and resolution, require dead specimens.
26
What are the two types of electron microscopes?
Transmission electron microscope (TEM): Provides detailed internal structures. Scanning electron microscope (SEM): Produces 3D images of surface structures.
27
What is magnification?
The ratio of an object's image size to its actual size.
28
How do you calculate magnification?
Magnification = Image size ÷ Actual size.
29
What is the purpose of cell fractionation?
To separate cellular components by centrifugation for detailed study.
30
What are the steps of cell fractionation?
Homogenization: Breaking open cells. Filtration: Removing debris. Ultracentrifugation: Spinning at different speeds to separate organelles by density.
31
What organelles are separated at different centrifugation speeds?
Low speed: Nuclei. Medium speed: Mitochondria/chloroplasts. High speed: Ribosomes and cytosolic fragments.
32
What are the advantages of confocal laser scanning microscopy?
Produces high-resolution 3D images of fluorescently labeled specimens, used in live cell imaging.
33
What is the standard unit for measuring cells under a microscope?
Micrometers (µm).
34
Convert 1 mm to µm
1 mm = 1000 µm.
35
Convert 1 µm to nm.
1 µm = 1000 nm.
36
Convert 0.002 mm to µm.
0.002 mm = 2 µm.
37
If a cell is 50 µm long, how many mm is this?
50 µm = 0.05 mm.
37
Convert 500 nm to µm.
500 nm = 0.5 µm.
38
What is an eyepiece graticule?
A small scale inside the eyepiece of a microscope used to measure objects under the microscope.
39
Why do you need to calibrate an eyepiece graticule?
The scale has no fixed units, so it must be calibrated with a stage micrometer at each magnification.
40
What is a stage micrometer?
A microscope slide with a precise scale (usually 1 mm divided into 100 µm sections) used to calibrate the eyepiece graticule.
41
How do you calibrate an eyepiece graticule?
Line up the eyepiece graticule with the stage micrometer. Count how many graticule divisions match a known distance on the micrometer. Calculate the size of one graticule division using: Size of one division = distance on stage micrometer/ number of graticule divisions
42
If 20 graticule divisions align with 100 µm on a stage micrometer, what is the size of one graticule division?
5 mircometers
43
What is the maximum magnification of a light microscope?
×1500 (some can reach ×2000).
44
What is the resolution of a light microscope?
200 nm (0.2 µm).
45
What are the advantages of a light microscope?
Can view living specimens. Easy to use and relatively cheap.
46
How does a light microscope work?
1. Lenses focus rays of light and magnify the view of a thin slice of specimen. 2. Different structures absorb different amounts and wavelengths of light. 3. Reflected light is transmitted to the observer via the objective lens and eyepiece.
47
What is the maximum magnification of a TEM?
×500,000 – 2,000,000.
48
What is the resolution of a TEM?
0.1 nm (highest resolution of all microscopes).
49
What are the disadvantages of a light microscope?
Low resolution (can’t see organelles like ribosomes). Limited magnification.
50
How does a TEM work?
1. Pass a high energy beam of electrons through a thin slice of specimen. 2. More dense structures appear darker since they absorb more electrons. 3. Focus image onto fluorescent screen or photographic plate using magnetic lenses.
51
What are the advantages of a TEM?
Highest resolution (can see internal cell structures like ribosomes and membranes). Produces detailed 2D images.
52
What are the disadvantages of a TEM?
Specimen must be dead (vacuum required). Expensive and requires expert use. Specimen must be very thin.
53
What is the maximum magnification of an SEM?
×100,000 – 500,000.
54
What is the resolution of an SEM?
3 – 10 nm.
55
How does an SEM work?
Uses electrons to scan the surface of a specimen. Electrons bounce off the specimen and are detected. Produces a 3D image of the surface.
56
What are the disadvantages of an SEM?
Specimen must be dead. Lower resolution than TEM. Expensive and requires skill to operate.
56
What is the resolution of a laser scanning confocal microscope?
≈200 nm (similar to a light microscope).
57
What are the advantages of an SEM?
Produces detailed 3D images. Can view the surface of specimens in high detail.
58
What is the maximum magnification of a laser scanning confocal microscope?
×2000.
59
How does a laser scanning confocal microscope work?
Uses laser beams to scan the specimen. A pinhole aperture ensures only in-focus light is detected. Produces high-contrast images and allows for 3D reconstruction.
60
What are the advantages of a laser scanning confocal microscope?
Can view living cells in real-time. High contrast and detailed images. Can create 3D images by scanning different layers.
61
What are the disadvantages of a laser scanning confocal microscope?
Expensive and complex to use. Slower than other microscopes.
62
What is the function of the plant cell wall?
Provides structural support, prevents excessive water uptake, and protects the cell from mechanical damage.
63
What is the composition of the plant cell wall?
Mainly composed of cellulose, with hemicellulose and pectin for additional strength and flexibility.
64
What is the middle lamella?
A pectin-rich layer between plant cell walls that cements adjacent cells together.
65
What are plasmodesmata?
Small channels in plant cell walls that allow communication and transport of substances between adjacent cells.
66
What is the function of chloroplasts?
Conduct photosynthesis by converting light energy into chemical energy (glucose).
67
What are the main structures within a chloroplast?
Thylakoids: Flattened sacs containing chlorophyll for the light-dependent reactions of photosynthesis. Grana: Stacks of thylakoids that increase surface area for photosynthesis. Stroma: The fluid-filled space where the light-independent reactions (Calvin cycle) occur.
68
What is the function of the large central vacuole?
Stores nutrients, maintains cell turgor pressure, and contains waste products.
69
What is the tonoplast
The selectively permeable membrane surrounding the vacuole, controlling substance movement in and out.
70
Smooth and Rough ER general structure
Single membrane organelle with a fluid filled cisternae Rough ER: 80s Ribosomes on the outside Usually connected to the nuclear membrane. Not visible under light microscopes because they are too small and thin.
71

biology (8 decks)

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