Chapter 1 Cell Structure

Question 1

Magnification formula:

Answer 1

M= I/A (Magnification= Image length/Actual length).

Question 2

1mm=____μm?

Answer 2

1000μm.

Question 3

1μm=____nm?

Answer 3

1000nm.

Question 4

Define resolution

Answer 4

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

Question 5

Define magnification

Answer 5

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

Question 6

Maximum resolution of a light microscope:

Answer 6

200nm (400nm÷2=200nm).

Question 7

Maximum resolution of an electron microscope:

Answer 7

0.5nm.

Question 8

Cell surface membrane SIZE, STRUCTURE AND FUNCTION:

Answer 8

S: The cell membrane is formed from a phospholipid bilayer and spans a diameter of around 10 nm.
F: Cell surface membranes controls the exchange of materials between the internal cell environment and the external environment.

Question 9

Smooth endoplasmic reticulum STRUCTURE AND FUNCTION:

Answer 9

S: The SER does not have ribosomes on the surface. Made up of a series of membranes that form flattened sacs within the cell cytoplasm.
F: It is involved in the production of lipids, and of steroid hormones such as oestrogen and testosterone.

Question 10

Nuclear envelope STRUCTURE AND FUNCTION:

Answer 10

S: The nuclear membrane is known as the nuclear envelope, and contains many pores.
F: Nuclear pores are important channels for allowing mRNA and ribosomes to travel out of the nucleus, as well as allowing enzymes and signalling molecules to move in.

Question 11

Rough endoplasmic reticulum STRUCTURE AND FUNCTION:

Answer 11

S: Continuous folds of membrane that are linked with the nuclear envelope. The surface of the RER is covered in ribosomes. Made up of a series of membranes that form flattened sacs within the cell cytoplasm.
F: The role of the RER is to produce and process proteins that are produced on the ribosomes.

Question 12

Nucleolus STRUCTURE AND FUNCTION:

Answer 12

S: Smaller deeply stained structure inside a nucleus.
F: The site of ribosome production, rRNA synthesis.

Question 13

Nucleus STRUCTURE AND FUNCTION:

Answer 13

S: The nucleus is a large organelle that is separated from the cytoplasm by a double membrane.
F: The nucleus contains the DNA, which is arranged into chromosomes.

Question 14

Golgi body STRUCTURE AND FUNCTION:

Answer 14

S: It consists of a series of flattened sacs of membrane. Has a distinctive ‘wifi symbol’ appearance.
F: Its role is to modify proteins and package them into vesicles.

Question 15

Mitochondria STRUCTURE AND FUNCTION:

Answer 15

S: Relatively large organelles surrounded by a double-membrane. The inner membrane is folded to form cristae. Matrix contains enzymes and small circular DNA.
F: Mitochondria are the site of aerobic respiration within eukaryotic cells.

Question 16

Ribosomes STRUCTURE AND FUNCTION:

Answer 16

S: Complex of ribosomal RNA (rRNA) and proteins. 80S ribosomes (composed of 60S and 40S subunits) are found in eukaryotic cells. Smaller, 70S ribosomes (composed of 50S and 30S subunits) are found in prokaryotes, mitochondria and chloroplasts.
F: Site of translation during protein synthesis.

Question 17

Lysosomes FUNCTION:

Answer 17

Lysosomes are specialised vesicles which contain hydrolytic enzymes.

Question 18

Centrioles STRUCTURE AND FUNCTION:

Answer 18

S: Centrioles are hollow fibres made of microtubules. Two centrioles at right angles to each other form a centrosome. F: The centrosome organises the spindle fibres during cell division. (MTOC)

Question 19

Microtubules STRUCTURE AND FUNCTION:

Answer 19

S: Microtubules are hollow tubes made of tubulin protein. α and β tubulin proteins combine to form dimers, which are then joined into protofilaments. Thirteen protofilaments in a cylinder make a microtubule.
F: Microtubules make up the cytoskeleton of the cell. The cytoskeleton is used to provide support and movement of the cell. Intracellular transport of organelles and spindle formation as well.

Question 20

Cilia STRUCTURE AND FUNCTION:

Answer 20

S: Cilia are hair-like projections made from microtubules.
F: Allow the movement of substances over the cell surface.

Question 21

Microvilli STRUCTURE AND FUNCTION:

Answer 21

S: Microvilli are cell membrane projections.
F: Increase the surface area for absorption.

Question 22

Chloroplasts STRUCTURE AND FUNCTION:

Answer 22

S: Surrounded by a double-membrane. Membrane-bound compartments called thylakoids stack together to form structures called grana. Grana are joined together by lamellae. Chloroplasts contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis.
F: Photosynthetic pigments such as chlorophyll are found in the membranes of the thylakoids, where their role is to absorb light energy for photosynthesis.

Question 23

Cell wall STRUCTURE AND FUNCTION:

Answer 23

S: Made of cellulose in plants, chitin in fungi, and peptidoglycan in bacteria.
F: Structural support.

Question 24

Plasmodesmata STRUCTURE AND FUNCTION:

Answer 24

S: Plasmodesmata are bridges of cytoplasm between neighbouring plant cells.
F: They allow the transfer of substances between plant cells.

Question 25

Large permanent vacuole STRUCTURE AND FUNCTION:

Answer 25

S: Vacuoles are surrounded by the tonoplast, which is a partially permeable membrane. Large permanent vacuoles are found in plant cells. F: They store cell sap and provide additional structural support to cells (Vacuoles are sometimes found in animal cells, but these will be small and temporary).

Question 26

Common structures found in both animal and plant cells:

Answer 26

Cell surface membrane Cytoplasm Nucleus Mitochondria Rough and smooth endoplasmic reticulum Golgi bodies Vesicles and lysosomes Ribosomes Microtubules

Question 27

Structures found only in animal cells:

Answer 27

Centrioles Microvilli

Question 28

Structures found only in plant cells:

Answer 28

Cellulose cell wall Large permanent vacuoles Chloroplasts Plasmodesmata

Question 29

Key structural features and size of a prokaryotic cell:

Answer 29

unicellular generally 1–5 µm diameter peptidoglycan cell walls circular DNA 70S ribosomes absence of organelles surrounded by double membranes

Question 30

Differences (Size, genetic material, cell division, ribosomes, organelles, cell wall) Prokaryotic cells vs Eukaryotic cells:

Answer 30

Size: 0.5-5 μm vs Up to 100 μm. Genetic material: Circular DNA not associated with proteins vs Linear chromosomal DNA associated with histone proteins. Cell division: Binary fission vs Mitosis/Meiosis. Ribosomes: 70S vs 80S. Organelles: No membrane-bound organelles vs Multiple membrane-bound organelles. Cell wall: Made of peptidoglycan vs Made of cellulose in plants, or chitin in fungi.

Question 31

Key Features and size of Viruses:

Answer 31

1. They are much smaller than prokaryotic cells, with a diameter of 20-300 nm. 2. Structurally they have: A nucleic acid core made of either DNA or RNA. A protein coat called a capsid. 3. Some viruses have an outer layer called an envelope (this forms from the membrane phospholipids of the host cell in which they were produced) and envelope proteins.