2.1 Cell Structure

Question 1

Name the 10 parts of a eukaryotic cell.

Answer 1

Ribosomes
Rough endoplasmic reticulum
Nuclear envelope
Lysosome
Golgi apparatus
Cell membrane
Smooth endoplasmic reticulum
Nucleus 
Nucleolus 
Mitochondrion

Question 2

Define Eukaryotic organisms

Answer 2

Eukaryotic organisms are multi-cellular organisms made up of eukaryotic cells. E.g animal and plant cells.

Question 3

Define prokaryotic organisms

Answer 3

Prokaryotic organisms are prokaryotic cells (i.e. they are single celled organisms). E.g. bacteria.

Question 4

Define “A eukaryote”.

Answer 4

A eukaryote is any organism consisting of one or more cells that contain DNA in a membrane-bound nucleus, separate from the cytoplasm.

Question 5

Name four types of eukaryotes.

Answer 5

Animals
Plants
Fungi
Protocists

Question 6

Name the three structural components of the cytoskeleton.

Answer 6

Microfilaments
Microtubules
Intermediate fibres

Question 7

Name the 7 functions of the cytoskeleton

Answer 7

1. ) Whole cell, support, stability, scaffolding.
2. ) Maintains the shape of the cell.
3. ) Allows movement of cilia/flagella.
4. ) Changing shape of cell / cytokinesis / pseudopodia / phagocytosis / endocytosis / exocytosis / muscle contraction.
5. ) Organelles can be moved or held in place.
6. ) Controls movement of chromosomes/ chromatids /(m)RNA .
7. ) Controls movement of vesicles along microtubules

Question 8

Describe the structure and function of microfilaments.

Answer 8

Fibres made from the protein actin. They are responsible for movement of the cell and cytoplasm during Cytokinesis.

Question 9

Describe the structure and function of microtubules.

Answer 9

Formed by the globular protein tubulin. They polymerise to form tubes that determine the shape of the cell. They also act as tracks for organelles moving around the cell.

Question 10

Describe the structure and function of intermediate fibres.

Answer 10

It gives strength to cells and helps maintain integrity.

Question 11

Name the 4 structures of the nucleus.

Answer 11

Double Nuclear envelope
Nuclear pores
Nucleolus
Chromatin

Question 12

Describe the functions of the nucleus.

Answer 12

1) Controls all the activity of the cell.
2) Where the (DNA) of the cell is stored, replicated, and copied into RNA (transcribed).
3) The Nucleus is attached to the Rough ER so the mRNA can easily get to ribosomes.

Question 13

Describe the structure of the rough endoplasmic reticulum.

Answer 13

Stacks of membrane bound (fluid filled) sacs which form sheets called cisternae.

Attached to the nucleus and covered with ribosomes.

Consists of an interconnected system of flattened sacs.

Question 14

Describe the function of the rough endoplasmic reticulum.

Answer 14

Site of protein synthesis.

Question 15

Describe the structure of the smooth endoplasmic reticulum.

Answer 15

It is similar to rough endoplasmic reticulum but is not attached to ribosomes- it is a system of interconnected tubules.

Question 16

Describe the function of smooth endoplasmic reticulum.

Answer 16

It is responsible for carbohydrate & lipid synthesis, and storage.

Question 17

What is the structure of ribosomes?

Answer 17

• A 2 subunit organelle.
• Made from RNA and protein.
• Not membrane bound.
• Very small organelles: about 22nm in diameter.
• Found free floating in the cytoplasm or attached to the rough ER.

Question 18

What is the function of the ribosomes?

Answer 18

• It is where proteins are made.

- The ribosomes assemble amino acids into proteins in chains using mRNA.

Question 19

What is the structure of the mitochondria?

Answer 19

• Oval shaped.
• Surrounded by two membranes (double membrane).
• The inner membrane forms finger-like structure called cristae which increases the surface area.
• The solution inside is called a matrix which contains enzymes for respiration.
• Mitochondrial DNA – Small amounts of DNA, enable mitochondrion to reproduce and create enzymes.

Question 20

What is the function of the mitochondria?

Answer 20

• Site of aerobic respiration.

- As a result of respiration, they release ATP (energy carrier in cells).

Question 21

What is the structure of the golgi apparatus?

Answer 21

• It has stacks of flattened, membrane bound sacs (cisternae).
• These are continuously formed from the ER at one end and budding off as Golgi vesicles at the other.

Question 22

What is the function of the golgi apparatus?

Answer 22

• It allows internal transport.
• It receives proteins from the rough endoplasmic reticulum.
• It modifies and processes molecules (such as new lipids and proteins) and packages them into vesicles.
• The molecules into packages may be secretory vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell).
• Make lysosomes.
• Lipid synthesis.

Question 23

Describe the structure of lysosomes.

Answer 23

They are spherical sacs surrounded by a single membrane.

Question 24

Describe the function of lysosomes.

Answer 24

They contain powerful hydrolytic digestive enzymes known as lysozymes.

Their role is to break down worn out components of the cell or digest invading cells.

Question 25

Describe the structure of centrioles.

Answer 25

- A component of the cytoskeleton, composed of many microtubules. - Small hollow cylinders that occur in pairs next to the nucleus in animal cells only. - Each centriole contains a ring of 9 triplet microtubules.

Question 26

Describe the function of centrioles.

Answer 26

It makes a copy of itself during cell division and then helps to form the spindle in cell division.

Question 27

Describe the structure of the cilia.

Answer 27

- ‘Hair like’ extensions that protrude from some animal cell types. - In cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle. - Known as a 9 +2 arrangement. - Arrangement allows movement.

Question 28

Describe the function of the cilia.

Answer 28

- Sensory function (e.g. nose), beat creating a current to move fluid/mucous/objects - For locomotion (movement of one place to another).

Question 29

Describe the structure of the flagella.

Answer 29

- Similar to cilia but longer. - They protrude from the cell surface and are surrounded by the plasma membrane. - Like cilia they have a 9 +2 arrangement.

Question 30

Describe the function of the flagella.

Answer 30

- (Whip-like) enables the mobility of a cell. - The microtubules contract to make the flagellum move. - Propel cells forward e.g. sperm cells.

Question 31

Describe the structure of the cell surface membrane (or plasma membrane).

Answer 31

- The membrane found on the surface of animal cells and inside the cell wall of plant and prokaryotic cells. - A phospholipid bilayer. - Composed of proteins and lipids.

Question 32

Describe the function of the cell surface membrane (or plasma membrane).

Answer 32

- Regulates the movement of substances into and out of the cell. - Contains receptor molecules that allow it to respond to chemicals like hormones.

Question 33

Describe the structure of the chloroplasts.

Answer 33

- Double membrane which encloses the stroma. - Stroma contains: Starch grains, lipid stores, DNA, RNA, ribosomes. - Series of membrane-bound flattened sacs called thylakoids in the stroma. Thylakoids stacked together are called grana. - Grana are linked together by lamellae. - The grana contain chlorophyll.

Question 34

Describe the function of the chloroplasts.

Answer 34

Photosynthetic reactions.

Question 35

Describe the structure of the cellulose cell wall.

Answer 35

Made of B-cellulose microfibrils– complex carbohydrate Cell wall is fully permeable to substances Thin layer called the middle lamella which marks the boundary between adjacent cell walls and ‘cements’ adjacent cells together.

Question 36

Describe the function of the cellulose cell wall.

Answer 36

- Gives the plant mechanical strength. - Gives the plant cell support and it's shape. - Contents of a plant cell can ‘push’ against the cell wall (turgid cell). This gives the cell (and the whole plant) good support.

Question 37

Describe the structure of the large permanent vacuole.

Answer 37

- Single membrane bound (membrane is called a tonoplast). - Contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc). - Selectively permeable barrier.

Question 38

Describe the function of the large permanent vacuole.

Answer 38

- Stores cell cap. - Support herbaceous plants by making cells turgid. - Helps maintain shape and gives support by maintaining turgor pressure. - Sugars and amino acids act as a temporary food store.