Cell structures

Question 1

What are the two types of cells? Which one of them have nucleus?

Answer 1

Prokaryotic cell and Eukaryotic cell. Eukaryotic cell has a nucleus.

Question 2

Eukaryote

Answer 2

An organism whose cells contain a nucleaus and other membrane-bound organelles.

Question 3

Prokaryote

Answer 3

An organism whose cells do not contain a nucleus or any membrane-bound organelles.

Question 4

What are the two fundamentally different types of microscopes?

Answer 4

Light microscope and Electron microscope.

Question 5

Electron Microscope:

• Source of radiation
• Wavelength of radiation used
• Maximum resolution
• Lenses
• Specimen
• Stains
• Image

Answer 5

• Electron
• about 0.0005nm
• 0.5nm in practice
• electromagnets
• non -living or dead
• contain heavy metal atoms
• black and white

Question 6

Light microscope

• Source of radiation
• Wavelength of radiation used
• Maximum resolution
• Lenses
• Specimen
• Stains
• Image

Answer 6

• Light
• 400nm - 700nm
• 200nm
• glass
• living, non-living, dead
• Coloured dyes
• Coloured

Question 7

Magnification and the formula.

Answer 7

Magnification is the number of times larger an image of an object is than the real size object. M=I/A.

Question 8

Microvilli

Answer 8

small, finger-like extensions of a cell which increase the surface area of the cell for more efficient absorption or secretion.

Question 9

Nucleus

Answer 9

a large organelle found in eukaryotic cells but absent from prokaryotic cells, the nucleus contains the cell’s DNA and therefore controls the activities of the cell, it is surrounded by two membranes that together form the nuclear envelope.

Question 10

Cell surface membrane

Answer 10

a very thin membrane (about 7nm) diameter surrounding all cells, it is partially permeable and controls the exchange of materials between the cell and its environment.

Question 11

Chromatin

Answer 11

the material of which chromosomes are made, consisting of DNA, proteins and small amounts of RNA, visible patches or fibres within the nucleus when stained.

Question 12

Nucleolus

Answer 12

a small structure, one or more of which is found inside the nucleus, the nucleolus is usually visible as a densely stained body, its function is to manufacture ribosomes using the information in its own DNA.

Question 13

Protoplasm

Answer 13

all the living material inside a cell

Question 14

cytoplasm

Answer 14

the contents of a cell, excluding the nucleus. It is an aqueous watery material, varying from a fluid to a jelly-like consistency. organises cell activities in separate compartments is essential for a structure as complex as an animal or plant cell to work efficiently.

Question 15

Mitochondrion

Answer 15

The organelle in eukaryotes in which aerobic respiration take place.

Question 16

Golgi Apparatus

Answer 16

collects and processes molecules within the cell, particularly proteins. is a stack of flattened sacs called cisternae. More than one GA can be present in a cell.

Question 17

Cell walls

Answer 17

a wall surrounding prokaryote, plant and fungal; cells, the wall contains a strengthening material (cellulose) that protects the cell from mechanical damage, supports it and prevents it from bursting by osmosis if the cell is surrounded by a solution with a higher water potential. Freely permeable.

Question 18

Plasmodesma

Answer 18

a pore-like structure found in plant cell walls, plasmodesma of neighbouring plant cells line up to form tube-like pores through the cell walls, allowing the controlled passage of materials from one cell to another, the pores contain ER and are lined with the cell membrane.

Question 19

Vacuoles

Answer 19

are sac-like structures that are surrounded by a single membrane. an organelle found in eukaryotic cells, a large, permanent central vacuole is a typical feature of plant cells, where it has a variety of functions, including storage of biochemicals such as salts, sugars and waste products. Usually found in plant cells. In animal cells, they’re not permanent.

Question 20

Tonoplast

Answer 20

the partially permeable membrane that surrounds plant vacuoles which controls exchange between the vacuole and the cytoplasm.

Question 21

chloroplast

Answer 21

an organelle, bounded by an envelope, in which photosynthesis takes place in eukaryotes

Question 22

Grana

Answer 22

stacks of membranes inside a chloroplast. These are the parts of the chloroplast that contain chlorophyll.

Question 23

Transmission electron microscope (TEM)

Answer 23

scanning inside the cells.

Question 24

Scanning Electron micrograph (SEM)

Answer 24

see the surface of the cell. cannot be achieved with the same resolution as a TEM.

Question 25

Resolution

Answer 25

the ability to distinguish between two objects very close together, the higher the resolution of an image, the greater the detail that can be seen.

Question 26

The nuclear envelope

Answer 26

the two membranes, situated close together, that surrounded the nucleus, the envelope is perforated with nuclear pores

Question 27

Nucleus pores

Answer 27

pores found in the nuclear envelope which controls the exchange of materials, e.g. mRNA, between the nucleus and the cytoplasm.

Question 28

Endoplasmic Reticulum (ER)

Answer 28

a network of flatted sacs running through the cytoplasm of eukaryotic cells, molecules, particularly proteins, can be transported through the cell inside the sacs separate from the rest of the cytoplasm, ER is continuous with the outer membrane of the nuclear envelope.

Question 29

Rough ER

Answer 29

covered with many tiny organelles called ribosomes. Ribosomes are the sites of protein synthesis as well as on the RER. It makes proteins for the cells.

Question 30

Smooth ER

Answer 30

has a smooth appearance because it lacks ribosomes. It makes lipids and steroids, such as cholesterol and the reproductive hormones oestrogen and testosterone. Is also a major storage site for calcium ions.

Question 31

Ribosomes

Answer 31

a tiny organelle found in large numbers in all cells, prokaryotic ribosomes are about 20nmin diameter while eukaryotic ribosomes are about 25nm in diameter. Eukaryotic ribosomes are 80S ribosomes. The ribosomes of prokaryotes are 70S ribosomes, slightly smaller. They allow all the interacting molecules involved in protein syntheses, such as mRNA, tRNA, amino acids and regulatory proteins to gather together in one place.

Question 32

Golgi vesicles

Answer 32

carry their contents to other parts of the cells, often to the cell membrane for secretion, the GA chemically modifies the molecules it transports, e.g sugars may be added to proteins to make glycoproteins.

Question 33

Lysosomes

Answer 33

are simple sacs, surrounded by a single membrane. A spherical organelle found in eukaryotic cells, it contains digestive (hydrolytic) enzymes and has a variety of destructive functions, such as the removal of the old organelles.

Question 34

Microtubules

Answer 34

long, rigid, hollow tubes found in the cytoplasm. They are tiny tubes made of a protein called tubulin and found in eukaryotic cells, microtubules have a large variety of functions including cell support and determining cell shape, the ‘spindle’ on which chromatids and chromosomes separate during nuclear division is made of microtubules.

Question 35

Centrioles

Answer 35

one of two small, cylindrical structures, made from microtubules, found just outside the nucleus in animal cells, in the region known as the centrosomes, they are also found at the bases of cilia and flagella.

Question 36

Cilia

Answer 36

whip-like structures projecting from the surface of many animal cells and the cells of many unicellular organisms, they beat, causing locomotion or the movement of fluid across the cell surface.

Question 37

Flagella

Answer 37

whip-like structures projecting from the surface of some animal cells and the cells of many unicellular organisms, they beat, causing locomotion or the movement of fluid across the cell surface, they are identical in structure to cilia, but longer.

Question 38

Thylakoid

Answer 38

a flattened, membrane-bound, fluid-filled sac which is the site of the light-dependent reactions of photosynthesis in a chloroplast

Question 39

Circular DNA

Answer 39

the DNA molecule in bacteria is circular. it is found in a region called the nucleoid, which also contains proteins and small amounts of RNA. It is not surrounded by a double membrane.

Question 40

Infolding of cell surface membrane

Answer 40

in some bacteria, the cell membrane folds into the cell forming an extra structure on which certain biochemical reactions can take place.

Question 41

Capsules

Answer 41

some bacteria are surrounded by an extra layer outside the cell wall. This may take the form of a capsule or a slime layer. It is a definite structure, made mostly of polysaccharides. Both help to protect the bacterium from drying out and may have other protective functions.

Question 42

Plasmid

Answer 42

a small circular piece of DNA in a bacterium (not its main chromosome), plasmids often contain genes that provide resistance to antibiotics.

Question 43

Pili

Answer 43

are fine protein rods. They are used for attachment and interactions with other cells or surfaces. They allow the transfer of genes, including plasmids, from one bacterium to another during conjugation.

Question 44

viruses

Answer 44

a very small (20-300nm) infectious particle which can replicate only inside living cells, it consists of a molecule of DNA or RNA (the genome) surrounded by a protein coat, an outer lipid envelope may also be present.

Question 45

Are you satisfied with yourself today?

Answer 45

You should be!