Organelles

Question 1

Describe the structure of the nucleus.

Answer 1

It has a double membrane boundary called the nuclear envelope, which contains nuclear pores that allows some substances to move into or out of the nucleus. Within the nucleus is one or more nuclei and DNA (chromosomes).

Question 2

Describe the function of the nucleus.

Answer 2

Controls all cellular activity, regulating the transcription of genes and directs protein synthesis.

Question 3

Describe the structure of the nucleolus.

Answer 3

Composed of RNA and proteins.

Question 4

Describe the function of the nucleolus.

Answer 4

Synthesises ribosomal RNA (rRNA) and the assembly of ribosomes.

Question 5

Describe the structure of mitochondria.

Answer 5

Consists of a double membrane. The inner membrane is folded into cristae to increase surface area, allowing for the efficient synthesis of ATP (energy). It contains its own circular DNA (mtDNA).

Question 6

Describe the function of mitochondria.

Answer 6

Site of latter stages of aerobic respiration, which synthesises ATP molecules that provide energy for the cell. Cells requiring significant energy have an increased abundance of mitochondria.

Question 7

Describe the structure of the chloroplast.

Answer 7

Consists of a double membrane which encloses a system of membranous flattened sacs (thylakoids). It has fluid (stroma) that surrounds each stack of sacs (granum). The stacks of thylakoids contain the photosynthetic pigment chlorophyll, and it contains its own circular DNA (cpDNA).

Question 8

Describe the function of the chloroplast.

Answer 8

Site of photosynthesis, usually in the cells of the leaves of a plant. Produces glucose and oxygen for plant and other organisms.

Question 9

Describe the structure of the vacuole.

Answer 9

Consists of a single membrane-bound sac, typically containing solutes such as salts (in the form of ions), simple sugars and amino acids. Large central vacuoles in plant cells store water and small molecules such as ions, enzymes and harmful/waste molecules.

Question 10

Describe the function of the vacuole.

Answer 10

• Contributes to the balance of salt and water by taking in water and enlarging
• In regard to plant cells, its large central vacuole helps to maintain cellular shape
• Nutrient and water storage
• Some unicellular fresh water organisms contain contractive vacuoles which are able to remove excess water that enters the cell

Question 11

What is the difference between plant and animal cells in relation to vacuole?

Answer 11

Vacuoles found in animal cells are usually much smaller and more numerous than those of plant cells.

Question 12

What are food vacuoles?

Answer 12

They are formed when a cell engulfs a particle by phagocytosis.

Question 13

What is a small vacuole?

Answer 13

A vesicle that is used in endocytosis and exocytosis.

Question 14

Describe the structure of the Golgi body.

Answer 14

A stack of flattened, membrane-bound sacs (cisternae) that are not connected to each other.

Question 15

Describe the function of the Golgi body.

Answer 15

Modification, processing and packaging of proteins into vesicles for storage within the cell or secretion out of the cell by exocytosis.

Question 16

Describe the structure of the rough endoplasmic reticulum.

Answer 16

Network of interconnected flattened membrane sacs that span from the nuclear envelope to the cell membrane. It contains ribosomes attached to its surfaces (hence rough).

Question 17

Describe the function of rough endoplasmic reticulum.

Answer 17

Increases surface area for cellular processes. Attached ribosomes synthesise proteins that RER packages into vesicles and secretes to the Golgi body.

Question 18

Describe the structure of smooth endoplasmic reticulum.

Answer 18

Network of interconnected flattened membrane sacs that does not contain ribosomes attached to its surface (hence smooth).

Question 19

Describe the function of smooth endoplasmic reticulum.

Answer 19

Synthesis of lipids.

Question 20

Describe the structure of ribosomes.

Answer 20

Consists of two subunits which are both made up of ribosomal RNA (rRNA) and proteins. It can be attached to RER or free-floating in the cytoplasm.

Question 21

Describe the function of ribosomes.

Answer 21

It is the site for translation in protein synthesis, assembling amino acids to form a polypeptide chain.

Question 22

Describe the structure of lysosomes.

Answer 22

Small, spherical organelle with a single membrane. It contains digestive enzymes.

Question 23

Describe the function of lysosomes.

Answer 23

Serves as the ‘digestive system’ of the cell by breaking down cellular waste - they may also be used to engulf and destroy foreign particles.

Question 24

Describe the structure of the cytoskeleton.

Answer 24

Composed of three main components: microfilaments intermediate filaments and microtubules.

Question 25

Describe the function of the cytoskeleton.

Answer 25

Microfilaments: used in movement of organelles (such as chloroplast orientation), pinching in of the cell to form daughter cells and phagocytosis. Microtubules: allows movement of the flagella and cilia, and also used to hold organelles in place. Intermediate filaments: provides strength for cells, and are especially found in cells prone to 'wear and tear'.

Question 26

Describe the structure of the centriole.

Answer 26

Small structure composed of protein microtubules.

Question 27

Describe the function of the centriole.

Answer 27

Duplicates prior to cell division so that each daughter cell receives one. Microtubules extend from centrioles at opposite poles of cells to attach to centromeres of chromosomes and align them along a metaphase plate. They also assist in separation of sister chromatids (mitosis) and homologous chromosomes (meiosis).

Question 28

How does the cytoskeleton change its shape?

Answer 28

The filaments and microtubules of the cytoskeleton are made up of subunits which can be rapidly removed or inserted into the existing structure to change its shape. It is a dynamic structure.

Question 29

Plant, animal and fungal cells are all examples of what type of cell?

Answer 29

Eukaryotes.

Question 30

What characteristics do both plant and animal cells share?

Answer 30

Cell membrane, nucleus, nucleolus, mitochondria, Golgi body, endoplasmic reticulum, ribosomes, lysosomes and a cytoskeleton.

Question 31

What characteristics do only plant cells contain?

Answer 31

Cell wall, chloroplast (may be present), large central vacuole.

Question 32

What characteristic(s) do only animal cells contain?

Answer 32

Small vacuoles.