CH:1 - Cell Structure

Question 1

Cell

Answer 1

The basic unit of all living organisms; it is surrounded by a cell surface membrane and contains genetic material (DNA) and cytoplasm containing organelles.

Question 2

Organelle

Answer 2

A functionally and structurally distinct part of a cell, e.g. a ribosome or mitochondrion.

Question 3

Nucleus

Answer 3

A relatively 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 which together form the nuclear envelope.

Question 4

Eukaryote

Answer 4

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

Question 5

Prokaryote

Answer 5

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

Question 6

Cell Surface Membrane

Answer 6

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

Question 7

Chromatin

Answer 7

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

Question 8

Chromosome

Answer 8

In the nucleus of the cells of eukaryotes, a structure made of tightly coiled chromatin (DNA, proteins and RNA) visible during cell division; the term ‘circular DNA’ is now also commonly used for the circular strand of DNA present in a prokaryotic cell.

Question 9

Nucleolus

Answer 9

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 10

Protoplasm

Answer 10

All the living material inside a cell
(cytoplasm + nucleus).

Question 11

Cytoplasm

Answer 11

The contents of a cell, excluding the nucleus.

Question 12

Mitochondrion

Answer 12

The organelle in eukaryotes in which aerobic respiration takes place.

Question 13

Cell Wall

Answer 13

A wall surrounding prokaryote, plant and fungal cells; the wall contains a strengthening material which 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.

Question 14

Plasmodesma (Plural: Plasmodesmata)

Answer 14

A pore-like structure found in plant cell walls; plasmodesmata 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 the other; the pores contain ER and are lined with the cell surface membrane.

Question 15

Vacuole

Answer 15

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; temporary vacuoles, such as phagocytic vacuoles (also known as phagocytic vesicles), may form in animal cells.

Question 16

Tonoplast

Answer 16

The partially permeable membrane that surrounds plant vacuoles.

Question 17

Chloroplast

Answer 17

An organelle, bounded by an envelope (i.e. two membranes), in which photosynthesis takes place in eukaryotes.

Question 18

Photosynthesis

Answer 18

The production of organic substances from inorganic ones, using energy from light.

Question 19

Granum (Plural: Grana)

Answer 19

Stacks of membranes inside a chloroplast.

Question 20

Magnification

Answer 20

The number of times larger an image of an object is than the real size of the object;

Magnification = Image size ÷ Actual (real) size of the object

Question 21

Eyepiece Graticule

Answer 21

Small scale that is placed in a microscope eyepiece.

Question 22

Stage Micrometer

Answer 22

Very small, accurately drawn scale of known dimensions, engraved on a microscope slide.

Question 23

Micrograph

Answer 23

A picture taken with the aid of a microscope; a photomicrograph (or light micrograph) is taken using a light microscope; an electron micrograph is taken using an electron microscope.

Question 24

Resolution

Answer 24

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 25

Microvilli

Answer 25

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

Question 26

Nuclear Envelope

Answer 26

The two membranes, situated close together, that surround the nucleus; the envelope is perforated with nuclear pores.

Question 27

Nuclear Pores

Answer 27

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

Question 28

Endoplasmic Reticulum (ER)

Answer 28

A network of flattened 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

Ribosome

Answer 29

A tiny organelle found in large numbers in all cells; prokaryotic ribosomes are about 20 nm in diameter while eukaryotic ribosomes are about 25 nm in diameter.

Question 30

Golgi Apparatus/Body/Complex

Answer 30

An organelle found in eukaryotic cells; the Golgi apparatus consists of a stack of flattened sacs, constantly forming at one end and breaking up into Golgi vesicles at the other end.

Question 31

Golgi Vesicles

Answer 31

Carry their contents to other parts of the cell, often to the cell surface membrane for secretion; the Golgi apparatus chemically modifies the molecules it transports, e.g. sugars may be added to proteins to make glycoproteins.

Question 32

Lysosome

Answer 32

A spherical organelle found in eukaryotic cells; it contains digestive (hydrolytic) enzymes and has a variety of destructive functions, such as removal of old cell organelles.

Question 33

Crista (Plural: Cristae)

Answer 33

Folds of the inner membrane of the mitochondrial envelope on
which are found stalked particles of ATP synthase and electron transport chains associated with
aerobic respiration.

Question 34

Matrix

Answer 34

The space between the two membranes is called the intermembrane space.

Question 35

ATP

Answer 35

The molecule that is the universal energy currency in all living cells; the purpose of respiration is to make ATP.

Question 36

ATP - full form?

Answer 36

Adenosine Triphosphate

Question 37

ADP

Answer 37

The molecule that is converted to ATP by addition of phosphate (a reaction known as phosphorylation) during cell respiration; the enzyme responsible is ATP synthase; the reaction requires energy.

Question 38

ADP - full form?

Answer 38

Adenosine Diphosphate

Question 39

Microtubules

Answer 39

Tiny tubes made of a protein
called tubulin and found in most 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 40

Centriole

Answer 40

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

Question 41

Centrosome

Answer 41

The main microtubule organising centre (MTOC) in animal cells.

Question 42

Cilium (Plural: Cilia)

Answer 42

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 43

Flagellum

Answer 43

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 43

Thylakoid

Answer 43

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

Question 44

Bacteria

Answer 44

A group of single-celled prokaryotic microorganisms; they have a number of characteristics, such as the ability to form spores, which distinguish them from the other group of prokaryotes known as Archaea.

Question 45

Peptidoglycan

Answer 45

A polysaccharide combined with amino acids; it is also known as murein; it makes the bacterial cell wall more rigid.

Question 46

Pilus (Plural: Pili)

Answer 46

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

Question 47

Virus

Answer 47

A very small (20–300 nm) 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 48

Phospholipid

Answer 48

A lipid to which phosphate is added; the molecule is made up of a glycerol molecule, two fatty acids and a phosphate group; a double layer (a bilayer) of phospholipids forms the basic structure of all cell membranes.