A2 (part 2) - Cell Structure

Question 1

What domain do all eukaryotes belong to, and what defines them?

Answer 1

All eukaryotes belong to the domain Eukaryota. They are organisms whose cells have a nucleus, and they include animals, plants, fungi, and many unicellular organisms.

Question 2

What type of organisms are included in the kingdom Animalia?

Answer 2

All are multicellular eukaryotes without a cell wall. They are heterotrophs that ingest food, classified as holozoic — they eat other organisms using internal digestion.

Question 3

What is meant by “holozoic” nutrition in animals?

Answer 3

It refers to the ingestion of food followed by internal digestion and absorption of nutrients.

Question 4

What type of cell wall do fungi have, and what are fungi classified as?

Answer 4

Fungi are eukaryotes with a cell wall made of chitin.

Question 5

Are fungi multicellular or unicellular?

Answer 5

Most fungi are multicellular (e.g. mushrooms), but some are unicellular (e.g. yeast).

Question 6

What is saprotrophic nutrition, and which kingdom uses it?

Answer 6

Most fungi are saprotrophs: they secrete digestive enzymes into their environment and then absorb the digested nutrients into their bodies — a form of external digestion.

Question 7

What is a parasitic fungus?

Answer 7

A fungus that lives on or in another organism and derives nutrients from it, harming the host.

Question 8

What is the ecological role of fungi?

Answer 8

They are principal decomposers in ecosystems.

Question 9

What are the key features of Plantae?

Answer 9

• All are multicellular eukaryotes
• Have cellulose cell walls
• Most are autotrophs (use photosynthesis to make their own food)
• Estimated ~300,000 known species
• Provide food to nearly all heterotrophs

Question 10

What structures are shared among all eukaryotic cells?

Answer 10

• Nucleus
• Ribosomes (free & bound)
• RER
• SER
• Golgi apparatus
• Lysosomes
• Vesicles
• Cytoskeleton
• Mitochondria
(Note: not all eukaryotes have cell walls, centrioles, or vacuoles)

Question 11

What does MRS H GREN stand for in biology (Functions of Life)?

Answer 11

• Metabolism
• Reproduction
• Sensitivity (Response)
• Homeostasis
• Growth
• Respiration (often folded into metabolism)
• Excretion
• Nutrition

Question 12

Define metabolism in the context of cells.

Answer 12

Metabolism = all enzyme-catalyzed chemical reactions occurring in the cell.

Question 13

What is homeostasis?

Answer 13

The ability to maintain constant internal conditions within a narrow range.

Question 14

What is excretion in cells?

Answer 14

The disposal of metabolic waste products (e.g., removal of CO₂ or nitrogenous waste).

Question 15

How do cells obtain nutrition?

Answer 15

By absorbing or synthesizing energy and nutrients for growth and development. This can involve ingesting or absorbing organic molecules.

Question 16

What structures help unicellular organisms perform life functions?

Answer 16

• Mitochondria: provide energy via respiration
• Cell membrane: controls material movement, maintaining homeostasis
• Ribosomes: produce proteins
• Cytoplasm: contains enzymes and dissolved substances for reactions
• Vacuoles: for digestion and waste storage
• Cilia/Flagella: for movement in response to environment

Question 17

Are plastids found in all cell types?

Answer 17

No.
• Present in plant cells (e.g., chloroplasts, amyloplasts)
• Absent in animal and fungal cells

Question 18

What types of cell walls do different cell types have?

Answer 18

• Animal cells: No cell wall
• Fungal cells: Cell wall made of chitin
• Plant cells: Cell wall made of cellulose

Question 19

How do vacuoles differ between kingdoms?

Answer 19

• Animal cells: Small and temporary
• Fungi: Present but smaller than in plants
• Plant cells: Large and permanent; maintain turgor pressure

Question 20

Where are centrioles found?

Answer 20

• Animal cells: Present
• Fungal cells: Mostly absent (except some gametes)
• Plant cells: Present only in male gametes of mosses and ferns; absent in conifers and flowering plants

Question 21

Are cilia and flagella found in all cell types?

Answer 21

• Animal cells: Often present (e.g. sperm)
• Fungal cells: Rare; found in a few gametes
• Plant cells: Only in male gametes of mosses and ferns; absent in conifers and flowering plants

Question 22

What is a trend in biology?

Answer 22

A trend is a general tendency or pattern observed across many biological systems — e.g., all living organisms are made of cells.

Question 23

What is a discrepancy in cell biology?

Answer 23

Something that does not follow a trend, leading to new questions or discoveries. It deepens understanding of biology.

Question 24

Give 3 examples of cell structure discrepancies.

Answer 24

1. Red blood cells: No nucleus (during maturation)
2. Aseptate fungal hyphae: Continuous cytoplasm, many nuclei, not divided into individual cells
3. Skeletal muscle cells: Large cells with many nuclei from fusion of smaller ones
4. Phloem sieve tube elements: Lack nuclei and organelles to transport phloem sap efficiently

Question 25

What is a micrograph?

Answer 25

A photograph taken through a microscope, showing magnified images of cell structures.

Question 26

What is an electron micrograph used for?

Answer 26

To observe ultrastructure of cells — tiny cellular features not visible with light microscopes (e.g. in prokaryotes).

Question 27

Why are electron microscopes necessary for prokaryotes?

Answer 27

Prokaryotic cells are very small, and their ultrastructure (e.g. ribosomes, nucleoid) cannot be seen with a light microscope.