The Living Cell (1)

Question 1

What are the fundamental cell activities?

Answer 1

1. to maintain integrity
2. store info for building + reproduction
3. convert info to activators
4. use proteins for metabolism
5. transduce energy for cell activities
6. transport proteins to their destination
7. change shape and create movement
8. divide to produce new cells
9. interact with the environment

Question 2

Definition of a cell.

Answer 2

A membrane-bound compartment that brings into close proximity all the biochemical and metabolic reactions necessary for the maintenance, replication and propagation of the genome.

Question 3

What are the 3 major domains?

Answer 3

1. Bacteria
2. Archaea
3. Eukaryotes

Question 4

What do cells contain?

Answer 4

1. organelles
2. organic macromolecules
3. small molecules and ions in solution

Question 5

What does the cell membrane allow the cell to do?

Answer 5

It means the cells can concentrate nutrients from the environment and retain products that they synthesise, while expelling waste products.

Question 6

Describe a gram-positive bacterium.

Answer 6

Has a single membrane with a thicker cell wall on the outside (readily accessible to the gram stain).

Question 7

Describe a gram-negative bacterium.

Answer 7

Has 2 membranes surrounding the cell with a thin cell wall lying between them.

Question 8

Describe plant cell walls.

Answer 8

Cellulose fibres embedded in a matrix of pectin.

Question 9

Plant cell walls are strong and rigid, with great mechanical strength. Why?

Answer 9

1. tensile fibres (polysaccharides) provide strength

2. they are embedded in a matrix of pectin, which provides resistance to compression

Question 10

Describe fungal cell walls.

Answer 10

made of 3 layers including chitin

Question 11

The store of biological information must:

Answer 11

1. be incredibly stable yet readily accessible

2. the info has to be replicated rapidly but without introducing errors.

Question 12

How does DNA fulfil the criteria for the store of biological information?

Answer 12

Hydrogen bonds between the bases of the 2 strands are weak compared with the sugar phosphate links, meaning the 2 strands can be separated without damaging their backbones. Therefore, the sequence of bases remains very stable, but readily accessible.

Question 13

What happens in DNA replication?

Answer 13

Each strand of DNA acts as a template for the synthesis of a complementary strand.

Question 14

What is a chromosome?

Answer 14

A single molecule of DNA that carries the genetic information of an organism.

Question 15

How do prokaryotes carry their genetic material?

Answer 15

On a single circular chromosome and smaller circular molecules called plasmids.

Question 16

Why are plasmids useful?

Answer 16

Means genetic material can spread rapidly through a population.

Question 17

What is chromatin?

Answer 17

chromosome + packaging protein

Question 18

What is the nuclear envelope?

Answer 18

2 concentric membranes separated by the perinuclear space

Question 19

the nuclear pore complex regulates the passage of…

Answer 19

..molecules larger than about 60,000 Daltons. (small molecules can diffuse through the nuclear pore)

Question 20

How does ribose differ from deoxyribose?

Answer 20

Hydroxyl group on the second carbon atom instead of hydrogen.

Question 21

How do amino acids differ?

Answer 21

Amino acids differ according to the side chain attached to the alpha-carbon atom.

Question 22

What regulates the exit of mRNA from the nucleus via nuclear pores?

Answer 22

nuclear export receptors

Question 23

What are ribosomes made of?

Answer 23

2 chains of rRNA and proteins

this rRNA accounts for approx 80% of total cell RNA

Question 24

rRNA is synthesised and its proteins added in the nucleolus. Where does final assembly occur?

Answer 24

In the cytoplasm.

Question 25

What are the functions of the RNA subunits?

Answer 25

1. smaller subunit–provides a framework for protein assembly
2. larger subunit–provides the catalytic activity to link amino acids into a polypeptide chain

Question 26

What is catabolism?

Answer 26

When complex molecules are broken down into smaller molecules and energy is released.

Question 27

What is anabolism?

Answer 27

When energy and simple molecules are used to synthesise larger molecules.

Question 28

Why are metabolic pathways highly conserved?

Answer 28

All cells make DNA, RNA and proteins, and the majority metabolise the same type of small molecules (e.g. simple sugars; nucleotides; amino acids)

Question 29

How can enzyme efficiency be maximised?

Answer 29

By organising enzymes into arrays in or on membranes.

Question 30

What is the purpose of subdividing eukaryotic cells into multiple compartments?

Answer 30

1. provides additional membrane to act as a platform for metabolic activity
2. the contents of each compartment can become very specialised.

Question 31

What is a peroxisome?

Answer 31

A specialised compartment for oxidative reactions.

Question 32

What is a lysosome?

Answer 32

An acidic compartment rich in digestive enzymes. (these enzymes are optimally active at a pH ~5, therefore are virtually inactive if they escape into the cell)