2.1.1 Cell Structure

Question 1

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what can microscopes be used for?

Answer 1

to observe and investigate cell structure

Question 2

what are the two types of microscope?

Answer 2

• light microscope
• electron microscope

Question 3

what is the maximum resolution of a light microscope?

Answer 3

around 0.2 micrometers

Question 4

what are the advantages of light microscopes?

Answer 4

• they are small and relatively cheap
• specimen preparation is relatively straightforward enough to perform in a school laboratory

Question 5

what is the maximum resolution of an electron microscope?

Answer 5

around 0.0002 micrometers

Question 6

what are the downsides of electron microscopes?

Answer 6

• they are very large and expensive
• specimens have to be prepared using a highly complex process

Question 7

what are the two types of electron microscopes?

Answer 7

• transmission electron microscopes (TEMs)
• scanning electron microscopes (SEMs)

Question 8

how does a TEM work?

Answer 8

electromagnets transmit a beam of electrons through a specimen, and denser parts of the specimen absorb more electrons

Question 9

what are the images produced by TEMs like?

Answer 9

• high resolution
• can see internal structures of cells
• are 2D

Question 10

how do SEMs work?

Answer 10

a beam of electrons pass across the surface of a specimen and detect the rate at which the electrons bounce back

Question 11

what are the images produced by SEMs like?

Answer 11

• 3D
• show the surface of specimens

Question 12

which type of electron microscope has a lower maximum resolution?

Answer 12

a SEM

Question 13

what does the endosymbiotic theory propose?

Answer 13

that mitochondria and chloroplasts originated as aerobic prokaryotic cells engulfed by the anaerobic ancestors of eukaryotic cells

Question 14

what is the evidence for the endosymbiotic theory?

Answer 14

• mitochondria have thir own DNA, which is similar to bacterial DNA
• mitochondrion contain their own ribosomes, which are the 70s bacterial type

Question 15

what is the function of the cell wall in a plant cell?

Answer 15

• maintains the shape of the cell
• prevents the cell bursting

Question 16

what is the role of the nucleus?

Answer 16

contains genetic material, which controls the activity of the cell

Question 17

what is the function of the nuclear envelope?

Answer 17

compartmentalises the DNA from the rest of the cell

Question 18

what is the function of the nucleolus?

Answer 18

contains DNA that controls the manufacture of ribosomes

Question 19

what is the function of the cell surface membrane?

Answer 19

controls which substances can enter and leave the cell (is selectively permeable)

Question 20

what does the cytoskeleton consist of?

Answer 20

a network of protein fibres that give the cell stability and allow it to move

Question 21

how is the cytoskeleton arranged?

Answer 21

• microfilaments
• microtubules
• intermediate filaments

Question 22

what is the role of microfilaments in the cytoskeleton?

Answer 22

to provide support and mechanical strength to the cell

Question 23

what are microfilaments?

Answer 23

small, solid strands made of actin

Question 24

what is the role of microtubules in the cytoskeleton?

Answer 24

• support, shape and to help move substances
• can form a track that motor proteins can walk on to drag organelles

Question 25

what are **microtubules**?

Answer 25

very small **protein cylinders** made of **subunits called tubulin**

Question 26

what is **magnification**?

Answer 26

how much **bigger an image appears** compared with the original object

Question 27

what is the function of the **cell surface membrane** in a eukaryotic cell?

Answer 27

* **controls the exchange of materials** between the internal and external environment

Question 28

what is the **cell membrane** fromed from in eukaryotic cells?

Answer 28

a phospholipid bilayer

Question 29

where is a **cell wall** found in eukaryotic cells?

Answer 29

in **plant cells** but not animal cells

Question 30

where are **cell walls** formed?

Answer 30

**outside** of the **cell membrane**

Question 31

what is the function of a **cell wall** in eukaryotic cells?

Answer 31

offers **structural support** to the cell

Question 32

how is **structural support** provided by the **cell wall** in plant cells?

Answer 32

by the polysaccharide **cellulose**

Question 33

what eukaryotic cell **does not** contain a **nucleus**?

Answer 33

red blood cells

Question 34

how is the nucleus **seperated** from the cytoplasm?

Answer 34

by a double membrane (**the nuclear envelope**) which has pores

Question 35

how can you describe the scale of an **eyepiece graticule**?

Answer 35

abritrary | it represents different lengths at different magnifications

Question 36

what is used to **calibrate** the eyepiece graticule?

Answer 36

the stage graticule

Question 37

what does each division on a **stage graticule** represent?

Answer 37

0.01mm

Question 38

what is the value of one **eyepiece division** on x4 magnification?

Answer 38

25 micrometers

Question 39

what is the value of one **eyepiece division** on x10 magnification?

Answer 39

10 micrometers

Question 40

what is the value of one **eyepiece division** on x40 magnification?

Answer 40

2.5 micrometers

Question 41

what does the **nucleus** contain in all eukaryotic cells?

Answer 41

DNA organised and wound into linear chromosomes

Question 42

where are the **ribosomes** produced in a eukaryotic cell?

Answer 42

nucleolus

Question 43

where are the organelles suspended in a eukaryotic cell?

Answer 43

cytoplasm

Question 44

what is the **cytoskeleton**?

Answer 44

a network of protein filaments within the cytoplasm

Question 45

what are the **functions** of the cytoskeleton?

Answer 45

* **move organelles** from place to place **within the cell** * allow some cells to **move** * allow the **contraction** of **muscle cells**

Question 46

where are the proteins **assembled** in a eukaryotic cell?

Answer 46

ribosomes

Question 47

name the **structures** in a eukaryotic animal cell

Answer 47

* nucleus * nucleolus * nuclear envelope * mitochondria * ribosomes * rough endoplasmic reticulum * smooth endoplasmic reticulum * lysosomes * golgi apparatus * plasma membrane

Question 48

why are some organelles **membrane-bound**?

Answer 48

so that they are seperate to the rest of the cell

Question 49

which type of cells do **not** feature membrane-bound organelles?

Answer 49

prokaryotic cells

Question 50

what is the **structure** of the rough endoplasmic reticulum (RER)?

Answer 50

* **a system of membranes**, containing **cisternae** that are **continuous with the nuclear membrane** * coated with **ribosomes**

Question 51

what is the **function** of the rough endoplasmic reticulum (RER)?

Answer 51

* the **intracellular transport system** (the cisternae form channels) * provides a **large surface area for ribosomes**, which assemble proteins. * the **proteins** are **transported into the cisternae** to be transported.