1.2 Ultrastructure of cells

Question 1

What is resolution?

Answer 1

The ability to distinguish between two points of an object.

Question 2

When is resolution better?

Answer 2

When the wavelength of light is shorter

Question 3

How are electron microscopes different?

Answer 3

• Uses electron beam as illumination
• Gives black and white image
• Higher resolution
• Cannot view any living material or processes due to vacuum

Question 4

Ultrastructure

Answer 4

Architecture of cells and biomaterials that are only visible at high resolution

Question 5

Prokaryotes

Answer 5

Single-celled organisms that lack a nucleus and membrane bound organelles

Question 6

What does 70S mean?

Answer 6

It is the sedimentation rate in centrifugation

Question 7

Pilli

Answer 7

Enable cell to attach to other surfaces and exchange DNA

Question 8

Flagellum

Answer 8

Used for cell locomotion

Question 9

Nucleoid/Plasmid

Answer 9

Contains DNA not enclosed by a nucleus

Question 10

Process of binary fission

Answer 10

1. Circular DNA is copied in response to replication signal
2. 2 DNA loops attach to membrane
3. Membrane elongates and pinches off to form 2 cells. Cytokinesis

Question 11

Binary fission: Asexual or sexual?

Answer 11

Asexual as genetic content is exactly the same as circular DNA is replicated. (Except for mutations)

Question 12

Eukaryote

Answer 12

Complex cell which contains a clearly defined nucleus

Question 13

Advantages of compartmentalization

Answer 13

• Greater efficiency of metabolism as enzymes and substrates are enclosed in membrane for specific functions
• Internal conditions like pH and temp can be regulated separately
• Isolation of toxic or damaging substances in cytoplasm
• Flexibility in number and positions of organelles

Question 14

Nucleus

Answer 14

Contains genetic material and controls cell activity.

Question 15

Mitochondrion

Answer 15

Site of ATP production by aerobic respiration.

Question 16

Nucleus structure

Answer 16

• Densely stained areas are chromatin

- Double membrane with pores in between

Question 17

Mitochondria structure

Answer 17

• Smooth outer membrane
• Folded inner membrane
• Folds = cristae
• Matrix= Space in the middle of the cristae

Question 18

Free ribosomes (80S)

Answer 18

Synthesizes protein and releases it into the cytoplasm as enzymes. Constructed in nucleolus

Question 19

Ribosome structure

Answer 19

Usually appear as darkened granules in cytoplasm and not surrounded by a membrane. Often 20nm in diameter

Question 20

Rough endoplasmic reticulum

Answer 20

Synthesizes protein for secretion from cell (Note: Doesn’t package or carry)

Question 21

rER structure

Answer 21

• Cisternae: Flattened membrane sacs

- Ribosomes: Attached to cisternae

Question 22

Golgi Apparatus

Answer 22

Processes proteins brought in by vesicles and sends to membrane for secretion

Question 23

Golgi apparatus structure

Answer 23

• Cisternae: Not as long as rER, often curved
• No ribosomes
• More vesicles nearby

Question 24

Vesicles

Answer 24

Small vacuoles that transport materials inside a cell

Question 25

Vesicles structure

Answer 25

Small with single membrane and fluid inside. Often near Golgi apparatus

Question 26

Lysosomes

Answer 26

Formed from Golgi vesicles and contain a lot of protein. Enzymes can be used to break down food, organelles or even entire cell

Question 27

Lysosome structure

Answer 27

• Spherical with single membrane.

- Densely stained because of high conc. of proteins

Question 28

Vacuoles

Answer 28

Used in plant cells for storage, in animal cells for digestion of absorbed food and in prokaryotes, maybe for expulsion of water

Question 29

Vacuole structure

Answer 29

Often occupy more than half the space in plant cells. Most animal cells have tiny vacuoles

Question 30

Cilia

Answer 30

Used for locomotion and can be used to create current in fluid next to cell

Question 31

Cilia structure

Answer 31

Small and multiple present. Contain rings of nine double microtubules plus two central microtubules

Question 32

Microtubules and centrioles

Answer 32

Cylindrical fibers that can be used in cell division and centrioles form anchor point for microtubules during division. Centrioles are combination of 9 microtubules and 2 extra microtubules

Question 33

Chloroplast

Answer 33

Produce glucose and other organic compounds by photosynthesis

Question 34

Chloroplast structures

Answer 34

• Double membrane
• Thylakoids: Flattened sacs of membranes, usually spherical or ovaloid
• Starch grains: Present when they photosynthesize rapidly
• Stroma: Fills center of chloroplast

Question 35

Function of cell wall

Answer 35

They provide shape and structural support to cell. They also act as a filtering mechanism and are fully permeable

Question 36

Are cell walls organelles?

Answer 36

They are not usually considered organelles as they are not specialized and only provide support

Question 37

What is cell wall composed of?

Answer 37

Primarily made of cellulose fibers and pectin

Question 38

Difference between animal and plant cell

Answer 38

• Plant cells have cell walls and chloroplast
• Plants cells have much larger vacuoles
• Plants have starch grains as glucose is converted to starch but in animal cells it is converted to glycogen