Cell Biology: Cell Structure

Question 1

What are prokaryotic cells?

Answer 1

Prokaryotic cells are cells of bacteria.

Question 2

What are eukaryotic cells?

Answer 2

Eukaryotic cells are cells of animals, plants and fungi.

Question 3

What are the sizes of eukaryotic cells and prokaryotic cells?

Answer 3

Eukaryotic cell: 5μm- 100μm

Prokaryotic cell: 0.2μm- 2.0μm

Question 4

What are the outer layers of eukaryotic and prokaryotic cells?

Answer 4

Eukaryotic: Cell membrane- surrounded by cell wall in plants and fungi

Prokaryotic: Cell membrane- surrounded by cell wall

Question 5

What cell contents do eukaryotic and prokaryotic cells have?

Answer 5

Eukaryotic: Cytoplasm, cell organelles include mitochondria, chloroplasts in plants and ribosomes

Prokaryotic: Cytoplasm, ribosomes, no mitochondria or chloroplast

Question 6

What genetic materials do eukaryotic and prokaryotic cells have?

Answer 6

Eukaryotic: DNA in nucleus

Prokaryotic: DNA found free in cytoplasm. May contain extra small rings of DNA called plasmids.

Question 7

What type of cell division does an eukaryotic and prokaryotic cell have?

Answer 7

Eukaryotic: mitosis

Prokaryotic: binary fission

Question 8

What is the definition of cell membrane?

Answer 8

Contains genetic material, including DNA, which controls the cell’s activities.

Question 9

What is the definition of a cell wall?

Answer 9

Made of cellulose and strengthens cell.

Question 10

What is the definition of cytoplasm?

Answer 10

Contains dissolved nutrients and salts and structures called organelles. It is where many of the chemical reactions happen.

Question 11

What are cell organelles?

Answer 11

A structure or part that is enclosed within its own membrane inside a cell and has a particular function.

Question 12

What is the definition of mitochondria?

Answer 12

Organelles that contains the enzymes for respiration, and where most energy is released in respiration.

Question 13

What is the definition of mitosis?

Answer 13

Mitosis is a type of cell division in which a diploid body cell copies itself and finally divides into two identical diploid daughter cells . The daughter cells are clones of each other. Every base pair of their DNA is identical.

Question 14

What is the definition of binary fission?

Answer 14

Asexual reproduction, single organism becomes two independent organisms

Question 15

What is the definition of a ribosome?

Answer 15

A tiny organelle where protein synthesis occurs.

Question 16

What is the definition of DNA?

Answer 16

A molecule that contains the genetic code of organisms

Question 17

What are the adaptations of a sperm cell?

Answer 17

• The head contains a nucleus which contains half the normal number of chromosomes (haploid, no chromosome pairs)
• The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
• The mid-piece is packed with mitochondria to release energy (via respiration) for the tail
• The tail rotates, propelling the sperm cell forwards (allowing it to move/swim)

Question 18

What is a muscle cell and what is it’s function?

Answer 18

A muscle cell contains layers of fibre that allow them to contract. Function is the contraction for movement.

Question 19

What are the adaptations for muscle cells?

Answer 19

• There are three different types of muscle in animals: skeletal, smooth and cardiac (heart)
• All muscle cells have layers of protein filaments in them. These layers can slide over each other causing muscle contraction
• Muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
• Skeletal muscle cells fuse together during development to form multi nucleated cells that contract in unison

Question 20

What is a root hair cell and what is it’s function?

Answer 20

A root hair cell is an extension of cytoplasm, increasing the surface area of the cell in contact with soil in order to maximise the absorption of soil and nutrients.

Question 21

What are the adaptations of a root hair cell?

Answer 21

• Root hair cells increase surface area (SA) so the rate of water uptake by osmosis is greater (can absorb more water and ions than if SA were lower)
• Thinner walls than other plant cells so that water can move through easily (due to shorter diffusion distance)
• Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient
• Mitochondria for active transport of mineral ions
• Remember that chloroplasts are not found in these cells – there’s no light for photosynthesis underground

Question 22

What is the function of a xylem cell?

Answer 22

A xylem cell transports tissue for water and dissolved ions.

Question 23

What are the adaptations of xylem cells?

Answer 23

• No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
• Cells are essentially dead, without organelles or cytoplasm, to allow free passage of water
• Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant

Question 24

What is the function of a phloem cell?

Answer 24

A phloem cell transports dissolved sugars and amino acids.

Question 25

What are the adaptations of a phloem cell?

Answer 25

* Made of living cells (as opposed to xylem vessels which are made of dead cells) which are supported by companion cells * Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation) * Cells also have very few sub-cellular structures to aid the flow of materials

Question 26

What is translocation?

Answer 26

Translocation is the the movement of sugars made in photosynthesis from the leaves of plants.