Cell structure and function

Question 1

Outline the cell theory

Answer 1

1. All living things are composed of one or more cells
2. The cell is the smallest unit of life
3. All cells come from pre-existing cells

Question 2

What are the 2 main types of cell?

Answer 2

Eukaryotic cells (plants and animals)

Prokaryotic cells (bacteria)

Question 3

How are organelles in a cell separated by ultracentrifugation?

Answer 3

Densest to least dense : Nuclei, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus, ribosomes

Question 4

List out double membrane-bound organelles

Answer 4

1. Nucleus
2. Chloroplast
3. Mitochondria

Question 5

List out single membrane-bound organelles

Answer 5

1. Endoplasmic reticulum (RER/SER)
2. Golgi apparatus
3. Lysosome

Question 6

List out non membrane-bound organelles

Answer 6

1. Ribosome
2. Centrioles

Question 7

What is the structure of nucleus? (7 features)

Answer 7

1. Spherical/ ovoid
2. Enclosed by a nuclear envelope that consists of a double membrane
3. Nuclear pores are found in the nuclear envelope
4. Outer membrane is studded with ribosomes and continuous with the membrane of the RER
5. Nucleoplasm contains enzymes (proteins), nucleotides
6. Nucleoplasm contains nucleolus, which contains DNA that codes for rRNA
7. Nucleoplasm contains chromatin (eu + hetero) which is composed of DNA and histone proteins

Question 8

How does the feature of double-membraned nuclear envelope help the nucleus?

Answer 8

Helps to separate the nucleoplasm from the surrounding cytoplasm -> prevent chromatin from coming into contact with the cytoplasm and being mutated

Question 9

How does the feature of double-membraned nuclear envelope help the nucleus?

Answer 9

Helps to separate the nucleoplasm from the surrounding cytoplasm -> prevent chromatin from coming into contact with the cytoplasm and being mutated

Question 10

How does the feature of nucleoplasm containing enzymes help the nucleus?

Answer 10

Allows for processes of DNA replication and transcription

Question 11

How does the feature of
nucleolus help the nucleus?

Answer 11

Synthesis of rRNA

Assembly of ribosomal subunits in nucleolus

Question 12

How does the feature of nucleoplasm containing chromatin help the nucleus?

Answer 12

Contains most of the genetic material in the form of chromatin that will condense to form visible chromosomes during cell division

Question 13

What does the nucleolus contain?

nucleolus- region which appears most densely stained

Answer 13

• DNA genes coding for rRNA

Question 14

What does the nucleoplasm contain?

Answer 14

enzymes (proteins), nucleotides, chromatin, nucleolus

Question 15

What are the structures of chloroplast?

Answer 15

1. Biconcave, disk-shaped
2. Enclosed by a double-membraned
3. Stroma (inner membrane) contains circular DNA and 70S ribosomes
4. Stroma contains enzymes

*5. Stroma contains grana (plural) (singular: granum), which are stacks of flattened sacs (thylakoid) connected by tubes (intergrana (p)) to adjacent grana

6. Stroma contains starch granules
7. Photosynthetic pigments, electron carriers, and ATP synthase are embedded in the thylakoid membranes <photosynthesis></photosynthesis>

Question 16

How does the feature of double-membrane help the chloroplast?

Answer 16

Provides a compartment for the the reactions of photosynthesis (Calvin cycle in the stroma) -> physically separate chemical reactions since many of them are incompatible

Question 17

How does the feature of stroma containing 70S ribosomes and circular DNA help the chloroplast?

Answer 17

Circular DNA molecule contains genes which code for the same chloroplast proteins involved in photosynthesis

70S ribosomes are responsible for the synthesis of the chloroplast proteins encoded by the chloroplast DNA

Question 18

How does the feature of the stroma containing enzymes help the chloroplast?

Answer 18

Enzymes catalyse the light- independent reactions (Calvin cycle)

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