Cell structure

Question 1

Starch granules

Answer 1

Carbohydrates stored in amyloplasts (plastids specialised in storage)

Question 2

Chloroplasts

Answer 2

2-5 micrometers. Contain the green pigment chlorophyll. They contain dense stacks of membrane (grana) within a colourless fluid, much like cytosol. They are the site of photosynthesis and are mainly in leaves. Contain 70s ribosomes

Question 3

Cell wall

Answer 3

A semi rigid structure outside the plasma membrane, 0.1 to several micrometers thick. Composed mainly of cellulose. It supports the cell and limits its volume.

Question 4

Mitochondria

Answer 4

1.5 to 2.8 micrometers. They are the cells energy transformers, converting chemical energy into ATP. It contains 70s ribosomes. It is bounded by a double membrane system, the number in a cell depends on its metabolic activity.

Question 5

Large central vacuole

Answer 5

Filled with an aqueous solution of ions. Its function is storage, waste disposal and growth. It is surrounded by a membrane called a tonoplast

Question 6

Cell surface membrane

Answer 6

Located inside the cell wall in plants. It is 3 to 10 nanometers thick. It is semi-permeable and controls what substances enter or leave the cell

Question 7

Cytoplasm

Answer 7

A watery solution containing dissolved substances, enzymes and the cells organelles and structures. It is the site of many chemical reactions.

Question 8

Ribosomes

Answer 8

80s. These small 20nm structures manufacture proteins. They may be free in the cytoplasm or associated with the surface of an endoplasmic reticulum.

Question 9

Endoplasmic reticulum (ER)

Answer 9

A network of tubes and flattened sacs. The ER is continuous with the plasma membrane and the nuclear membrane.

Question 10

Smooth endoplasmic reticulum (ER)

Answer 10

The ER without ribosomes. The site of lipid and carbohydrate metabolism, including hormone synthesis.

Question 11

Rough endoplasmic reticulum (ER)

Answer 11

Site of protein synthesis, also synthesises new membranes by adding proteins and phospholipids

Question 12

Golgi apparatus

Answer 12

A series of flattened disk shapes sacs stacked on top of each other and connected with the ER. The Golgi stores, modifies and packages proteins. It “tags” them so that they go to the right location.

Question 13

Centrioles

Answer 13

Structures associated with nuclear division. Composed of microtubules, but appear as small featureless particles. 0.25 micrometers in diameter

Question 14

Lysosomes

Answer 14

A sac bounded by a single membrane. They are pinched off from the Golgi apparatus and contain and transport enzymes. They have little internal structure but contain fragments of material being broken apart

Question 15

Plasmodesmata

Answer 15

Connects plant cells with fine strands of cytoplasm. They pass through pore like structures in the cell wall

Question 16

Nucleus

Answer 16

Contains the nucleolus which is a dense, solid structure composed of crystalline protein and nucleic acid. Is involved in ribosome synthesis. The nuclear pore is a hole in the nuclear membrane which allows the nucleus to communicate with the rest of the cell. The nucleus is surrounded by a double layered nuclear membrane. It contains chromosomes which controls the cells activity

Question 17

Resolution

Answer 17

The ability to distinguish between two separate points

Question 18

Magnification

Answer 18

Actual size of image

Question 19

ATP

Answer 19

Produced by the mitochondria and chloroplasts. It is an energy store in cells. Energy is released when it is broken down into ADP.

Question 20

Prokaryotic cell

Answer 20

Diameter of cell is 0.5-5 micrometers. DNA is circular and lies free in the cytoplasm. DNA is naked. 70s ribosomes (smaller then in eukaryotes). Very few cell organelle - no separate membrane bound compartments unless formed by the infolding of the cell surface membrane. Cell wall containing murein which is a peptidoglycan.

Question 21

Eukaryotic cell

Answer 21

Up to 40 micrometers in diameter. DNA is contained within a nucleus, the nucleus is surrounded by an envelope of two membranes. DNA is associated with proteins forming chromosomes. 80s ribosomes. ER present. Many types of cell organelle (extensive compartmentalisation and division of labour). Cell wall sometimes present, in plants in contains cellulose and in fungi it contains chitin.

Question 22

Viruses

Answer 22

Has a protein coat (capid) made up of separate protein molecules called a capsomere. About 20-300nm. All viruses are parasitic and only reproduce by infecting and taking over living cells. The viruses DNA or RNA takes over the protein synthesising machinery of the hosts cell which can be used to make new virus particles. They are non-cellular

Question 23

Plant cell

Answer 23

Cell surface membrane, cytoplasm, nucleus, rough ER, smooth ER, mitochondria, Golgi apparatus, chloroplast, plasmodesmata, starch granules, cell wall and vacuole

Question 24

Animal cell

Answer 24

Cell surface membrane, cytoplasm, nucleus, rough ER, smooth ER, mitochondria, Golgi apparatus, centrioles and lysosomes