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CCEA AS Biology Units 1, 2 And 3 > (U1) Cells > Flashcards

(U1) Cells Flashcards

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1
Q

What is a chromosome? (3)

A
  • A long strand of DNA
  • located in the nucleus
  • and bound by histones
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2
Q

What is in a eukaryotic cell? (7)

A
  • a membrane-bound nucleus,
  • chromosomes,
  • mitochondria,
  • endoplasmic reticulum, (smooth and rough)
  • ribosomes,
  • Golgi apparatus,
  • vesicles,
  • lysosomes and
  • microtubules
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3
Q

What size is a eukaryotic cell?

A

10 - 200 µm

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4
Q

What size is a prokaryotic cell?

A

Usually less than 5 µm

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5
Q

Where is the site of DNA in a eukaryotic cell?

A

The membrane bound nucleus

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6
Q

Where are the sites of DNA in a prokaryotic cell? (2)

A
  • Loop of DNA sprawled in cytoplasm
  • also plasmids which are circular
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7
Q

How is DNA organised in a eukaryotic cell? (2)

A
  • DNA is linear and in chromosomes
  • chromosomes contain DNA in a helical shape and histones
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8
Q

How is DNA organised in a prokaryotic cell?

A

In loops without histones

Also in plasmids

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9
Q

What size are ribosomes in a eukaryotic cell?

A

Large compared to prokaryotic - 25 nm (80S)

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10
Q

What size are ribosomes in a prokaryotic cell?

A

Small compared to eukaryotic - 20 nm (70S)

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11
Q

What does synthesis mean?

A

Creation

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12
Q

What is chromatin also known as?

A

Uncondensed DNA

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13
Q

What are spindle fibres made of?

A

Microtubules made of tubulin (a protein)

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14
Q

In centrioles, how are microtubules arranged?

A

Perpendicularly

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15
Q

What 3 substances are contained within a nucleus?

What is also found in a nucleus?

A
    • heterochromatin (heavily condensed around histones)
    • euchromatin (less condensed around histones)
    • nucleoplasm
  2. Nucleoli - most densely packed (with rRNA)
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16
Q

What size is a nucleus usually?

How are they enclosed? (2)

A
  • 10-30µm
  • within an envelope, with some nuclear pores
  • continuing into rough endoplasmic reticulum studded with ribosomes
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17
Q

What are the functions of ribosomes? (2)

A
  • translates mRNA into an amino acid sequence
  • formation of polypeptide chains (primary proteins)
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18
Q

What are ribosomes (not functions)?

What size are they usually?

A
  • bodies of protein and rRNA either in cytoplasm or on the rough endoplasmic reticulum
  • 20-25µm
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19
Q

How is the rough endoplasmic reticulum structured? (3)

A
  • flattened cavities known as cisternae
  • covered with ribosomes
  • maze like folding
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20
Q

What is the structure of the cell surface membrane? (2)

in broad terms - not including glycocalyx etc.

A

Phospholipid bilayer with:

  • hydrophilic phospho-glycerol heads and
  • hydrophobic hydrocarbon fatty acid tails

  • The bilayer consists of polar phospholipid heads facing the extracellular fluid or cytoplasm,
  • while non-polar fatty acid tails are in the center.
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21
Q

What model describes the arrangement of proteins in the cell membrane?

A

Fluid-mosaic model

This model illustrates how proteins are embedded within the phospholipid bilayer.

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22
Q

What types of proteins are found in the cell membrane?

A

Intrinsic (transmembrane) and extrinsic proteins

Intrinsic proteins span the membrane, while extrinsic proteins are attached to the surface.

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23
Q

What role does cholesterol play in the cell membrane?

A
  • Regulates fluidity
  • and maintains permeability of the membrane

Cholesterol is located among the hydrocarbon tails in animal cell membranes.

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24
Q

Can non-polar molecules diffuse through the cell membrane?

A

Yes

Non-polar molecules can easily pass through the phospholipid layers.

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25
Q

What types of molecules can move through the membrane besides non-polar molecules?

A

Smaller molecules such as water and oxygen

These smaller molecules can also diffuse through the membrane.

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26
Q

How do larger molecules (too big for facilitated diffusion) move through the cell membrane?

A

Through cytosis or bulk transport

Larger molecules cannot diffuse directly through the membrane.

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27
Q

Can polar molecules pass through the phospholipid bilayer?

A

No

The non-polar fatty acid tails prevent polar molecules from traveling through.

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28
Q

What process allows polar molecules to cross the membrane?

A

Facilitated diffusion

This process involves channel and carrier proteins.

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29
Q

How do carrier proteins assist in the movement of polar molecules?

A

By attaching to polar molecules and changing shape

Carrier proteins have receptor regions for polar molecules.

30
Q

What is simple diffusion?

A

Movement from higher concentration to lower concentration

This process occurs with lipid-soluble substances.

31
Q

When is active transport required?

A

When moving substances against the concentration gradient

Active transport requires ATP for energy - also proteins

32
Q

What is the relationship between the number of carrier proteins and the rate of facilitated diffusion?

A

Greater number of carrier proteins increases the rate

More carrier proteins enhance the movement of polar molecules.

33
Q

How is a mitochondrion structured? (5)

A
  • outer membrane
  • inner membrane folded into cristae
  • fluid-filled matrix (site of the Krebs cycle)
  • ribosomes (70S)
  • mitochondrial DNA
34
Q

What are mitochondria responsible for?

Where does this occur?

A
  • Production of ATP by aerobic respiration
  • cristae
35
Q

How are chloroplasts structured? (4)

A
  • outer envelope
  • inner membrane folded into lamellae
  • lamellae consist of thylakoids (attached to chlorophyll molecules) stacked into grana
  • jelly like stroma - contains lipid droplets and starch grains
36
Q

In which type of organism are chloroplasts found?

A

Plants (largely)

37
Q

Why are thylakoids stacked into grana? (2)

A
  • supports efficient packing of chlorophyll molecules attached to thylakoids
  • increasing area for light absorption
38
Q

What are plasmodesmata?

In what organisms is it found?

What is its purpose?

A
  • cytoplasm continuous between 2 cells
  • plants
  • facilitates transport of substances
39
Q

How is the nuclear envelope structured? (3)

A
  • nuclear pores throughout
  • rough endoplasmic reticulum continuous with envelope
  • ribosomes encrust the RER
40
Q

What is the purpose of nuclear pores?

A

Allow large molecules in and out (e.g. rRNA to go to RER)

41
Q

What is the primary purpose of the:

  • nucleus
  • nucleolus
A
  1. Nucleus: Houses DNA which codes for synthesis of polypeptides (base triplets)
  2. nucleolus: synthesises rRNA, which make up over half the mass of ribosomes
42
Q

How is the Rough Endoplasmic Reticulum structured? (2)

A
  • flattened cavities continuous with nuclear envelope
  • studded with ribosomes
43
Q

What are the purposes of the Rough Endoplasmic Reticulum? (2)

A
  • primary proteins (synthesised by ribosomes) folded to form secondary proteins
  • then packed into vesicles to go to the Golgi
44
Q

How is the Smooth Endoplasmic Reticulum structured? (2)

A
  • interconnecting tubules
  • not studded with ribosomes
45
Q

What is the purpose of the Smooth Endoplasmic Reticulum?

A

Synthesis of lipids and/or carbohydrates

46
Q

How is the Golgi apparatus structured? (3)

A
  • consist of membrane-bound cavities - cisternae
  • cis face accepts vesicles from RER,
  • trans face has vesicles pinching off - usually a bent shape
47
Q

What is the purpose of the Golgi apparatus? (3)

A
  • modifies, processes and packages proteins
  • polypeptides combined (forming quaternary structure) or a prosthetic group is added,
  • then packed into vesicles for secretion by exocytosis (secretory vesicle) or delivery somewhere in cytoplasm (e.g. as a lysosome)
48
Q

What is the purpose of ribosomes?

A
  • translate mRNA into an amino acid sequence
  • polypeptide synthesis (primary protein)
49
Q

What are ribosomes made of? (2)

A
  • rRNA and
  • protein / amino acids
50
Q

What are lysosomes?

How are they structured?

A
  • A form of vesicle used to carry hydrolytic enzymes to breakdown worn out organelles
  • thick membrane - phospholipid bilayer
51
Q

What are vesicles used for?

Where do they come from?

A
  • storage or transport of substances e.g. structural proteins.
  • Either to site in cytoplasm or cell surface membrane (where they fuse with membrane and release substance out of cell)
  • bud off from trans face of Golgi apparatus
52
Q

What is the name of the membrane of a vacuole?

A

The tonoplast

53
Q

How do fungal cells reproduce?

A

Budding

54
Q

Give the equation between magnification and lengths.

What unit should lengths be in?

A
  • M = I/A
    Magnification = image length / actual length
    I
    M A
  • µm (micrometers) (1mm = 1000 µm)
55
Q

What is resolution? (2)

A
  • the ability to discriminate fine detail
  • between 2 separate neighbouring points
56
Q

Why are some organelles not always visible when using a microscope?

A

Some in different section / not in plane

57
Q

What is the difference between a:

  • scanning electron microscope (SEM)
  • transmission electron microscope (TEM)
A

TEM =

  • more expensive
  • higher resolution
  • images not 3d - SEM opposite
58
Q

What is the main advantage of using a light microscope instead of an electron microscope?

A
  • can be used to view living cells
  • images are in colour
59
Q

What is the main advantage of using an electron microscope instead of a light microscope?

A
  • higher resolution images
  • higher magnification
60
Q

What is the cell wall made of in:

  • bacteria
  • fungi
  • plant cells
A
  1. Bacteria = peptidoglycan
  2. Fungi = chitin
  3. Plant = cellulose
61
Q

How do fungi feed?

A

Fungi are heterotrophic:

  • Saprophytic digestion
  • then absorb breakdown products
62
Q

What are microfilaments?

What size are they?

What is their role in cells?

A
  • rod-like structures made of contractile Actin and Myosin proteins
  • 7nm
  • provide support and aid movement.
63
Q

What is the primary purpose of microtubules in cells?

A

Structural support as part of the cytoskeleton

64
Q

What is a vacuole?

Where is it found? (generally)

What is its purpose?

A
  • large vesicles which hold cell sap
  • plant cells (central and permanent) and fungal cells
  • provides structural support through turgor pressure
65
Q

What substance is not seen in a prokaryotic cell envelope?

A

Cholesterol

66
Q

What is different about how plant cells feed compared to animal and fungal cells?

A
  • plant cells are photoautotrophic
  • animal and fungal cells are heterotrophic
67
Q

How is energy stored in:

  • plant cells
  • animal cells
  • fungal cells?
A
  • plant = starch grains
  • animal = glycogen granules
  • fungal = glycogen granules
68
Q

Where are microtubules found in:

  • prokaryotic
  • eukaryotic organisms?
A
  • prokaryotic = only in flagella
  • eukaryotic = centrioles in animal and plant cells + cytoskeleton
69
Q

Name 3 structures which contain microtubules

State the arrangement of these microtubules.

A
  • flagella - 9+2 arrangement
  • cilia - 9+2 arrangement
  • centrioles - 9 triplets arrangement
70
Q

What are microvilli and what is their function?

A
  • finger-like folds of the cell-surface membrane
  • increases surface area for diffusion of molecules and ions
71
Q

What happens when a vesicle reaches another membrane?

A

The membrane of the vesicle fuses with the membrane

72
Q

What is the structure formed when a lysosome fuses to a membrane called?

A

A secondary lysosome / phagolysosome

CCEA AS Biology Units 1, 2 And 3 (15 decks)

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