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A Level Biology > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

What is the nucleus?

A

A large organelle surrounded by a nuclear envelope (double membrane), which contains chromatin and often a structure called the nucleolus.

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2
Q

What is the function of the nucleus?

A

The nucleus controls the cell’s activities by controlling the transcription of DNA. The pores allow substances (e.g. RNA) to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.

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3
Q

What is a lysosome?

A

A round organelle surrounded by a membrane, with no clear internal structure.

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4
Q

What is the function of lysosomes?

A

Contains digestive enzymes kept separate from the cytoplasm, used to digest invading cells or to break down worn out components of the cell.

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5
Q

What is a ribosome?

A

A very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. It’s made up of proteins and RNA and is not surrounded by a membrane.

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6
Q

What is the function of ribosomes?

A

The site where proteins are made.

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7
Q

What is the rough endoplasmic reticulum (RER)?

A

A system of membranes enclosing a fluid-filled space, covered with ribosomes.

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8
Q

What is the function of the rough endoplasmic reticulum?

A

Folds and processes proteins that have been made at the ribosomes.

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9
Q

What is the smooth endoplasmic reticulum (SER)?

A

Similar to rough endoplasmic reticulum, but with no ribosomes.

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10
Q

What is the function of the smooth endoplasmic reticulum?

A

Synthesises and processes lipids.

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11
Q

What is a vesicle?

A

A small fluid-filled sac in the cytoplasm, surrounded by a membrane.

Transports substances in and out of the cell and between organelles.

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12
Q

What is the function of the Golgi apparatus?

A

It processes and packages new lipids and proteins. It also makes lysosomes.

Vesicles are often seen at the edges of the sacs.

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13
Q

What is a mitochondrion?

A

It’s usually oval-shaped with a double membrane. The inner membrane is folded to form structures called cristae. Inside is the matrix, which contains enzymes involved in respiration.

The site of aerobic respiration, where ATP is produced.

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14
Q

What is a chloroplast?

A

A small, flattened structure found in plant cells, surrounded by a double membrane, with thylakoid membranes stacked to form grana.

The site where photosynthesis takes place.

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15
Q

What should you avoid saying about mitochondria in an exam?

A

Never say mitochondria produce energy in the exam.

They produce ATP or release energy (energy can’t be made).

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16
Q

What are centrioles?

A

Small, hollow cylinders made of microtubules found in animal cells and some plant cells.

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17
Q

What is the function of centrioles?

A

Involved with the separation of chromosomes during cell division.

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18
Q

What are cilia?

A

Small, hair-like structures found on the surface membrane of some animal cells.

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19
Q

What is the structure of cilia?

A

They have an outer membrane and a ring of nine pairs of protein microtubules inside, with a single pair of microtubules in the middle.

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20
Q

What is the function of cilia?

A

The microtubules allow the cilia to move, which is used by the cell to move substances along the cell surface.

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21
Q

What is a flagellum?

A

Flagella on eukaryotic cells are like cilia but longer, sticking out from the cell surface.

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22
Q

What is the structure of flagella?

A

They have two microtubules in the center and nine pairs around the edge, surrounded by the plasma membrane.

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23
Q

What is the function of flagella?

A

The microtubules contract to make the flagellum move, propelling cells forward.

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24
Q

What is the ‘9 + 2’ formation?

A

The formation of microtubules inside flagella and cilia, consisting of nine pairs of microtubules surrounding two central microtubules.

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25
What are the plural forms of 'cilium' and 'flagellum'?
'Cilia' is the plural of 'cilium' and 'flagella' is the plural of 'flagellum'.
26
Where can you find more about electron micrographs?
On pages 49-50.
27
What is the only example of a flagellum found in humans?
The 'tail' of a sperm cell.
28
What is the function of cilia in the trachea?
They are used to sweep dust and dirt out of the lungs.
29
What is the plasma membrane?
The membrane found on the surface of animal cells and just inside the cell wall of plant cells and prokaryotic cells. It's made mainly of lipids and protein.
30
What is the function of the plasma membrane?
Regulates the movement of substances into and out of the cell. It also has receptor molecules on it, which allow it to respond to chemicals like hormones.
31
What is the cell wall?
A rigid structure that surrounds plant cells. It's made mainly of the carbohydrate cellulose.
32
What is the function of the cell wall?
Supports plant cells.
33
Can organisms other than plants have cell walls?
Yes, other organisms (e.g. fungi and bacteria) can have cell walls too but they aren't made of cellulose.
34
Where are proteins made in the cell?
Proteins are made at the ribosomes.
35
What type of proteins do ribosomes on the rough endoplasmic reticulum (RER) produce?
They make proteins that are excreted or attached to the cell membrane.
36
What type of proteins do free ribosomes in the cytoplasm produce?
They make proteins that stay in the cytoplasm.
37
What happens to new proteins produced at the RER?
They are folded and processed in the RER.
38
How are proteins transported from the RER?
They are transported in vesicles to the Golgi apparatus.
39
What occurs at the Golgi apparatus?
Proteins may undergo further processing.
40
What is an example of a protein processed at the Golgi apparatus?
Glycoproteins, such as those found in mucus, move to the cell surface and are secreted.
41
What is the cytoplasm?
The cytoplasm is a network of protein threads surrounding organelles.
42
What are the two types of protein threads in the cytoskeleton?
Microfilaments and microtubules.
43
What are the four main functions of the cytoskeleton?
1. Support organelles in position. 2. Strengthen the cell and maintain its shape. 3. Responsible for transport of organelles. 4. Respond to changes.
44
What are the proteins that play a role in the movement of vesicles around the cell?
Cytoskeletal proteins ## Footnote Cytoskeletal proteins are essential for intracellular transport.
45
The movement of vesicles in a cell depends on the contraction of _______.
Microtubules ## Footnote Microtubules are part of the cytoskeleton and are crucial for cell division.
46
What is one function of the proteins of the cytoskeleton?
Cause the cell to move ## Footnote The cytoskeleton provides structural support and enables cellular movement.
47
True or False: The prokaryotic cytoskeleton contains the same proteins as the eukaryotic cytoskeleton.
False ## Footnote Prokaryotic cytoskeletons contain different proteins than eukaryotic cytoskeletons.
48
What type of cells rely on cytoskeletal proteins for movement?
Both prokaryotes and eukaryotes ## Footnote While both types of cells utilize cytoskeletal proteins, their composition differs.
49
What is the typical size of prokaryotic cells?
Less than 2 um in diameter
50
What type of DNA do prokaryotic cells have?
Circular DNA
51
Do prokaryotic cells have a nucleus?
No nucleus; DNA is free in cytoplasm
52
What is the composition of the cell wall in prokaryotic cells?
Polysaccharide, but not cellulose or chitin
53
What type of organelles do prokaryotic cells have?
Few organelles; no membrane-bound organelles
54
How are flagella in prokaryotic cells structured?
Made of the protein flagellin, arranged in a helix
55
What is the ribosome size in prokaryotic cells?
Small ribosomes (20 nm or less)
56
Give an example of a prokaryotic cell.
E. coli bacterium or Salmonella bacterium
57
What is the typical size of eukaryotic cells?
About 10-100 um in diameter
58
What type of DNA do eukaryotic cells have?
Linear DNA
59
Do eukaryotic cells have a nucleus?
Yes, nucleus present; DNA is inside nucleus
60
What is the composition of the cell wall in eukaryotic cells?
No cell wall (in animals), cellulose cell wall (in plants), or chitin cell wall (in fungi)
61
What type of organelles do eukaryotic cells have?
Many organelles; mitochondria and other membrane-bound organelles present
62
How are flagella in eukaryotic cells structured?
Made of microtubules arranged in a '9 + 2' formation
63
What is the ribosome size in eukaryotic cells?
Larger ribosomes (over 20 nm)
64
Give an example of a eukaryotic cell.
Human liver cell, yeast, or amoeba
65
True or False: Prokaryotic cells are larger than eukaryotic cells.
False
66
Fill in the blank: Prokaryotic cells are roughly a tenth the size of _______ cells.
eukaryotic
67
What type of microscope is needed to view the internal structure of prokaryotic cells?
Electron microscope
68
What is a plasmid?
Ring of DNA in bacterial cells
69
What is the definition of Resolution?
The ability to distinguish between two separate points or how detailed an image is.
70
What is the definition of magnification?
Refers to how many times larger the image is compared to the object
71
Dry Mount
When thin slices or whole specimens are viewed with just the coverslip placed on top e.g hair
72
Wet mount
When water is added to the specimen before lowering the coverslip with a mounted needle to avoid air bubbles from forming. E.g aquatic organisms
73
Squash slides
Wet mount which are then pushed down on the cover slip to squash the sample and ensure you have a thin layer to enable light to pass through. E.g root tip for mitosis
74
Smear slides
Created by placing a drop of a sample on one end of the slide and using the edge of another slide to create a smear across the first slide to create a smooth thin specimen. A cover slip to be placed after.
75
Differential Staining
A technique which involves many chemical stains being used to stain different parts of a cell in different colours.
76
Electron microscopes (EM)
Advantages: beam of electrons has with s a short wavelength=high resolution enables small organelles and internal structures to be seen. Image is created sing an electromagnet to focus the beam of negatively charged electrons Disadvantages: this must be in a vacuum therefore only dead specimen can be viewed The image is also in black and white needing stains.
77
Transmission Electron Microscopes (TEM)
Extremely thin specimens are stained and placed in a vacuum. Electron gun produces a beam of electrons that passes through the specimen. Some parts of the specimen absorb the electrons and this makes them appear darker. 2D image and shows detailed images of the internal structures of cells
78
Scanning Electron Microscope (SEM)
Specimen does not need to be thin as the electrons are bouncing not transmitting. Electrons are beamed onto the surface and electrons are scattered in different ways depending on the contour. 3D image of the surface of the specimen

A Level Biology (2 decks)

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