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A LEVEL BIOLOGY > Chapter 2: Cell Structure > Flashcards

Chapter 2: Cell Structure Flashcards

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1
Q

What are advantages of Light Microscopes

A
  • can be used on living cells. Means we can explore processes such as cell division or movement of cells
  • inexpensive
  • small and portable
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2
Q

What is resolution ?

A

Resolution is the minimum distance between two objects where they can still be seen as two separate objects

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3
Q

What are disadvantages of Light Microscopes ?

A
  • low resolution , due to the nature of light . The wavelength of visible light is too large to allow us to resolve objects closer than that
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4
Q

What are the advantages of Laser Scanning Confocal (LSC) microscopy ?

A
  • higher resolution than conventional light microscopy
  • we can produce 3D images of cells
  • We can visualise specific proteins and structures within cells and watch them move
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5
Q

What is the equation for magnification ?

A

Magnification = image size/object size

I = A x M
Always keep units the same

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6
Q

What does Electron microscopy use ?

A

This uses electrons instead of light - electrons have a very short wavelength so resolution is 2000x better than a light microscope

Electrons have properties of both particles and waves so they can have a wavelength

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7
Q

How do EM’s work ?

A
  1. Electron gun produces a beam of electrons
  2. These electrons pass down the microscope
  3. Inside of an EM contains a vacuum so electrons can pass through without bouncing off the molecules in air
    4.can focus the electron beam by using electromagnets (electromagnetic lenses)
  4. The specimen is placed in the path of the electron beam
  5. The final image is produced on a fluorescent screen
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8
Q

Electron microscopy advantages

A
  • electron microscopes can have a 2000x better resolution than light microscopes , can achieve a greater level of magnification before image becomes blurred
  • because of high resolution electron microscopes have made huge discoveries - ribosomes and the structure of cell membrane
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9
Q

Electron microscopy disadvantages

A
  • the interior of an electron microscope is a vacuum . We cannot view living specimens in electron microscopes
  • electron microscopes requires very careful staining and the specimen often has to be very thin
  • electron microscopy can lead to artefacts (false images) created by the staining process or the conditions inside the EM
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10
Q

2 different types of electron microscopes

A
  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
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11
Q

Transmission electron microscope

A
  • in a TEM the electron beam passes through the specimen
  • produces flat 2D images
  • only works if specimen is very thinly sliced
  • has a very high resolution
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12
Q

Scanning electron microscopes

A
  • in a SEM the electron beam does not pass through the specimen - electrons are scattered from surface of specimen and detected
  • produces 3D images
  • does not require specimen to be thinly sliced
  • has a lower resolution than the TEM
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13
Q

What two categories can all living organisms be divided into?

A
  • Eukaryotes (animal,plants and fungi)
  • prokaryotes (bacteria and archaea)
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14
Q

Key features of eukaryotic cells

A
  • The DNA is contained in a membrane-bound nucleus
  • Their DNA is tightly wrapped around proteins called histones . The DNA and histone proteins form chromosomes
  • their DNA is a linear molecule
  • presence of membrane-bound organelles
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15
Q

What organelle does eukaryotic cells contain that are not membrane-bound ?

A

Ribosomes (protein synthesis)

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16
Q

What are eukaryotic cells surrounded by?

A

Cell-surface membrane - helps to control the molecules that can pass in and out of the cell

In plants and fungi the cell-surface membrane is surrounded by a cell wall - helps to maintain the structure of these cells

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17
Q

What is plant cell wall made from ?

A

The polysaccharide cellulose

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18
Q

What is the fungal cell wall made from ?

A

The polysaccharide chitin

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19
Q

What do animal cells not have ?

A

Cell wall

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20
Q

Key features of Prokaryotic cells

A
  • much smaller than eukaryotic cells
  • have no membrane-bound organelles at all - in prokaryotes DNA is found in the cytoplasm rather than in a nucleus
  • The DNA is arranged into a circular chromosome with no free ends - the DNA is prokaryotes are not bound to histone proteins
  • contain plasmids (small loops of DNA) which contain genes
  • contain ribosomes - much smaller than eukaryotic ribosomes (70s >80s)
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21
Q

What are prokaryotic cells surround by ?

A

Cell wall

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22
Q

What is the cell wall made from in bacterial cells ?

A

Peptidoglycan - A polymer formed between peptides and polysaccharide molecules

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23
Q

What does the bacterial cell wall help do ?

A

Maintain the structure of the cell wall - e,g, if water moves in the bacterial cell by osmosis, the cell wall prevents the cell from bursting

24
Q

What do some bacterial cells contain ?

A

A slime capsule on the outside of the cell wall - helps protect the bacteria from phagocytosis by white blood cells

25
Q

Structure in prokaryotic cells

A
  • flagellum - helps them to move
  • Pili - fine protein strands on surface , help bacteria to attach to surfaces and other bacteria
26
Q

What can happen when two bacteria are attached ?

A

DNA can be transferred from one bacterium to another

27
Q

What does bacteria cells also contain ?

A

Lipid droplets and glycogen granules - act as nutrient stores for the bacteria cell

28
Q

What are mesosomes ?

A

Unfolding in the cell membrane of prokaryotic cells when viewed under an electron microscope
Scientists now believe mesosomes are artefacts

29
Q

Describe the structure of the Nucleus

A

• surrounding the nucleus there is a double membrane, known as the nuclear envelope
• Nuclear pores (within the nuclear envelope) allow molecules to enter and leave the nucleus
• Inside the nucleus there is a region that is darker than the rest - The nucleolus.
Where a special type of RNA is produced-ribosomal RNA (forms part of the structure of ribosomes)

30
Q

What is assembled In the nucleolus ?

A

Ribosome subunits

31
Q

Describe the function of the nucleus

A

• The nucleus contains a dark material known as chromatin - chromatin consists of DNA coiled around proteins called histones.
Together the DNA and histone proteins form chromosomes.
• Controls cellular processes
• The DNA in a chromosome is a Linear molecule - the ends of the DNA are not joined to form a loop

32
Q

What is protein synthesis ?

A

The process cells use to create proteins

33
Q

How to calculate the magnification of a light microscope ?

A

Eyepiece lens magnification x objective lens magnification

34
Q

What is the structure of the Rough ER ?

A

• The RER consists of sheets of membranes forming flattened sacs called cisternae. The membrane of the cisternae are covered in ribosomes

35
Q

What is the function of the Rough ER ?

A

Site of protein synthesis

36
Q

What is the structure of the smooth ER ?

A
  • similar to Rough ER but is not covered in ribosomes
37
Q

What is the function of the smooth ER ?

A

The job of the SER is to make and store both lipids and carbohydrates. These can then be passed through the Golgi apparatus where they can be modified and then transported

38
Q

What is the structure of the Golgi apparatus?

A

Sheets of flattened sacs called cisternae . These are continuously formed from the ER at one end

39
Q

What is the function of the Golgi apparatus ?

A

-Receives proteins from the RER
-Modifies and processes molecules and packages them into vesicles.
-Makes lysosomes
-Lipid synthesis

40
Q

What is the structure of lysosomes ?

A

-They are spherical sacs surrounded by a single membrane
-Contain powerful digestive enzymes such as proteases - these digest larger molecules into smaller soluble molecules
- the internal fluid in a lysosome is acidic

41
Q

What is the function of lysosomes ?

A

-Play a key role in phagocytosis e.g. in WBC’S
- their role is to break down worn out components of the cell or digest invading cells

42
Q

What is the structure of mitochondria?

A

• oval shaped
• have a double membrane (outer and inner membrane)
• within the mitochondria there is a fluid called the matrix (creates enzymes for respiration)
• loop of mitochondrial DNA - contains genes required some of the enzymes involved in aerobic respiration
• contain mitochondrial ribosomes - these synthesis the protein encoded by the mitochondrial DNA

43
Q

What is the function of mitochondria?

A

Site of aerobic respiration. To produce the energy carrying molecule ATP

44
Q

What is the structure of chloroplast ?

A

-Chloroplasts are surrounded by a double membrane - theses membranes control which molecules enter and leave the cell
- inside the chloroplast there is membrane-bound flattened discs - these discs are called thylakoids
- thylakoids are stacked on top of eachother - this is called a grana
- contain a fluid materials called the stroma

45
Q

What is the function of chloroplast ?

A

Photosynthetic reactions

46
Q

What is the structure of Cilia ?

A

Hair like projections out of cell

47
Q

What is the function of Cilia ?

A

Can be mobile or stationary. Mobile cilia help move substances in a sweeping motion. Stationary cilia are important in sensory organs, such as the nose.

48
Q

What is the structure of flagella ?

A

Whip-like structure

49
Q

What is the function of flagella ?

A

For mobility, and sometimes as a sensory organelle
for chemical stimuli.

50
Q

What is the structure of centrioles ?

A

Made of microtubules. Occur in pairs to form a centrosome.

51
Q

What is the function of centrioles ?

A

-Involved in the production of spindle fibre and organisation of chromosomes in cell division.

52
Q

What is the structure of Cytoskeleton ?

A

A network of fibres found within the cytoplasm all over a cell. Consists of microfilaments, microtubules and intermediate fibres.

53
Q

What is the function of the Cytoskeleton ?

A

Provides mechanical strength to cells, and helps maintain the shape and stability of
a cell. Many organelles are bound to the cytoskeleton. Microfilaments are responsible for cell
movement.

54
Q

What is the structure of the cell wall ?

A

Found in plants, algae and fungi. Consists of polysaccharides, cellulose in plants and chitin
in fungi. There is a thin boundary layer between adjacent cells called the middle lamella.

55
Q

What is the function of the cell wall ?

A

Provides structural strength to cells and prevents cells from bursting when water enters by
osmosis.

56
Q

Production and secretion of proteins

A

1.
Polypeptide chains are synthesised on the RER (ribosomes on
the outside).
2.These polypeptide chains move to the cisternae in the RER and are packaged into vesicles to be sent
to the Golgi apparatus via the cytoskeleton.
3.In the Golgi apparatus, the proteins are modified and packaged into vesicles.
4. The secretory vesicles carry the proteins to the cell surface membrane, where it fuses and releases
the protein by exocytosis.

57
Q

What is magnification?

A

A LEVEL BIOLOGY (2 decks)

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