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Cell structure Flashcards

1
Q

What is the first stage of cell fractionation?

A

Cells are placed on a cold, buffered solution at the same water potential

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2
Q

What is the supernatant?

A

Solution formed when denser components form pellets whilst others remain in suspension above

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3
Q

Why do electron microscopes have a higher resolution?

A

Shorter wavelength

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4
Q

Why can’t living cells be used in an electron microscope?

A

A near vacuum has to be created so the electrons aren’t absorbed or deflected by air

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5
Q

How are electron beams focused?

A

Electromagnets

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6
Q

What’s the resolving power of TEM?

A

0.1nm

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7
Q

What’s the resolving power of SEM?

A

20nm

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8
Q

What are the main limitations of TEM?

A

Vacuum so no living specimens
Complex staining but no colour
Extremely thin
May contain artefacts
2D image

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9
Q

What are the limitations of SEM?

A

All of TEM, but the specimens don’t need to be thin

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10
Q

What does the nucleolus do?

A

rRNA production- the RNA then creates proteins
Produces ribosomes

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11
Q

In what form does DNA exist inside the nucleus?

A

Chromatin

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12
Q

What are the holes in the nuclear envelope called?

A

Pores

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13
Q

What’s the diameter of the nucleus?

A

10-20 micrometers

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14
Q

What do nuclear pores do and how many are there?

A

Allow passage of large molecules such as mRNA
3000, 40-100nm

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15
Q

What is the nuclear envelope?

A

Double membrane, outer is continuous in ER
Controls entry and exit of substances

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16
Q

What’s the shape and size of mitochondrion?

A

Rod-shaped and 1-10 micrometers in length

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17
Q

What is the cristae?

A

Inner membrane of mitochondria containing enzymes for respiration

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18
Q

What’s inside the matrix of the mitochondria?

A

Proteins, lipids, ribosomes and DNA, many of the enzymes for respiration

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19
Q

What are they typical sizes of chloroplasts?

A

Disc-shaped 2-10micrometers in length and 1 micrometer in diameter

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20
Q

What’s the chloroplast envelope?

A

Highly selective, double plasma membrane

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21
Q

What are grana?

A

Stacks of up to 100 disc-like structures called thylakoids, containing chlorophyll

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22
Q

What links grana together?

A

Some thylakoids have tubular extensions that join thylakoids inn adjacent grana

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23
Q

Where do the first stages of photosynthesis occur?

A

The grana (light absorption)

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24
Q

What is the stroma?

A

A fluid-filled matrix, where stage 2 of photosynthesis occurs (synthesis of sugars)

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25
How are chloroplasts adapted to their function?
Granal membranes- large SA- attach chlorophyll, electron carriers and enzymes Stroma fluid possesses all enzymes needed for stage 2 Contains DNA and ribosomes so they can quickly manufacture proteins for photosynthesis
26
What is the cisternae?
The membrane of ER enclose a network of tubules and flattened sacs
27
What are the functions of the RER?
Provide large SA for synthesis of proteins and glycoproteins Pathway for transport of materials, especially proteins, throughout the cell
28
What are the functions of the SER?
Synthesise, store and transport lipids and carbohydrates
29
What are vesicles?
Structures consisting of liquid or cytoplasm enclosed by a lipid bilayer which transport materials in the plasma membrane
30
How do vesicles form?
Naturally by secretion and uptake (exocytosis and endocytosis)
31
What do Golgi vesicles do?
Stores lipids and proteins and transports them into and out of the cell
32
What does the Golgi apparatus consist of?
Stacks of membranes that make up flattened sacs, cisternae with small rounded hollow vesicles
33
What does the Golgi apparatus do?
Modifies proteins by adding non-protein components such as carbs. 'Labels' them, allowing to be accurately sorted and sent to the correct place
34
What are the functions of the Golgi apparatus?
Form glycoproteins Produce secretory enzymes Secrete carbohydrates Transport, modify and store lipids Forms lysosomes
35
When are lysosomes formed?
Golgi vesicles contain digestive enzymes such as proteases and lipases and they also contain lysozymes
36
What do lysozymes do?
Hydrolyse the cell wall of certain bacteria
37
How many enzymes may be contained in a lysosome?
Up to 50
38
Where do lysosomes release enzymes?
Outside the cell or into phagocytic vesicle
39
What are the functions of lysosomes?
Hydrolyse material ingested by phagocytic cells Exocytosis of enzymes to destroy material outside the cell Digest old organelles Autolysis
40
What are ribosomes made of?
Protein and RNA
41
What are the two types of ribosomes and where are they found?
80S- eukaryotic cells (25nm) 70S- prokaryotic cells, mitochondria and chloroplasts
42
How many ribosomes are there in each cell?
Accounts for up to 25% of the dry mass
43
What's the main characteristic of plant cell cell wall?
Microfibrils of the polysaccharide cellulose, embedded in a matrix
44
What is the middle lamellae and what does it do?
Thin layer, marks the boundary between adjacent cell walls and cements adjacent cells together
45
What are the functions of the cell wall?
Mechanical strength for support and allows osmosis as water can pass along it
46
What are the cell walls of algae made up of?
Cellulose and/or glycoproteins
47
What are fungi cell walls made up of?
Nitrogen containing polysaccharide chitin, the polysaccharide glycan and glycoproteins
48
What is a vacuole?
Fluid-filled sac bounded by a single membrane
49
What's the membrane around the vacuole called?
Tonoplast
50
What's in the solution of the vacuole?
Mineral salts, sugars, amino acids, wastes and some pigments
51
What's the function of the vacuole?
Support herbaceous plants Sugar and amino acids may act as a temporary food store Pigments colour petals to attract pollinating insects
52
What does the centriole do?
Spacial arrangement: organise microtubules, position of the nucleus and moves chromosomes in cell division Formation and movement of cilia and flagella
53
What are peroxisomes?
Membrane-enclosed organelles containing enzymes involved in metabolic reactions (oxidative)
54
What's the cell wall of bacteria made of?
Murein
55
What's the normal size range of bacteria?
0.1-10micrometers
56
What is the role of the cell wall in bacteria?
Physical barrier excludes certain substances and protects against mechanical damage and osmotic lysis
57
What is murein?
Polymer or polysaccharides and peptides
58
How thick is the cell wall of bacteria?
10-80nm
59
What is the role of plasmids in bacteria?
Possesses genes that may aid the survival of bacteria in adverse conditions, produces enzymes that break down antibiotics
60
What is the role of circular DNA in bacteria?
Possesses the genetic information for the replication of bacterial cells
61
What is the role of the cell surface membrane in bacteria?
Acts as a differentially permeable membrane layer, which controls the entry and exit of chemicals
62
What is the role of the capsule in bacteria?
Protects bacterium from other cells and helps groups of bacteria stick together for further protection
63
What are cilia and flagella made of?
Microtubules
64
What's the difference between the plant cells and fungal cells?
Can be multicellular (mushrooms) or unicellular (yeast) Cell wall is made of chitin No chloroplasts
65
What's the difference between cilia and flagella?
Their length
66
What's the difference between algae and plants?
Can be unicellular (chlorella) or multicellular (seaweed) Chloroplasts are different shapes and sizes, some algae have one long chloroplasts
67
What are some eukaryotic organisms?
Animal, plant, fungal and algal
68
What are the receptors on plasma membranes?
Glycoproteins and glycolipids
69
What size are bacteria?
20-300nm
70
What does the capsid on the viruses do?
Protein coat which contains attachment proteins
71
When does cell specialisation initially begin?
The first group of cells in an embryo are identical and as it matures, each cells takes on its own individual characteristics
72
How does a cell become specialised?
Every cell contains the same genes needed for it to develop into any one of the many different cells in an organism, but only some of the genes are expressed at any one time
73
What is a tissue?
Aggregation of similar cells that perform a specific function
74
What do epithelial tissues do?
Line the surface of organs and often have protective or secretory function
75
What are the two types of epithelial cells?
Thin, flat cells that line organs of diffusion such as the alveoli Ciliated epithelium cells line ducts such as trachea
76
Whats the function of the cilia in the trachea's epithelial cells?
Moves mucus over the surface
77
What are the functions of the xylem?
Transport water and mineral ions throughout the plant and also give mechanical support
78
What is an organ?
An aggregation of tissues that combine to provide a variety of functions, although they often have one predominant major function
79
What tissues are in the stomach?
Muscular tissue to churn and mix the contents Epithelial tissue to protect the stomach wall and produce secretions Connective tissue holds together other tissues
80
What tissues make up a leaf?
Palisade mesophyll, spongy mesophyll, epidermis, phloem and xylem
81
Are blood vessels organs?
Capillaries aren't as they are only made up of epithelial cells, veins and arteries are as they have many tissues such as muscular and epithelial
82
What are organ systems?
A group of organs working together in a single unit to perform particular functions efficiently
83
What protein is DNA associated with in eukaryotic cells?
Histones
84
What cells have a capsule?
Some prokaryotic cells

Biology (22 decks)

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