A2.1 and A2.2 Cells

Question 1

Cell theory

Answer 1

All cells are formed from preexisting cells.

All living things are composed of cells.

The cell is the basic unit of life

Question 2

In which of Pasteer’s experiments is bacteria present?

Answer 2

When heat is applied and the neck of the flask is broken off.
When heat is applied and the flask is tilted as the bacteria attaches to the bacteria and cannot move.

Question 3

What are the four processes needed for spontaneous origin cells on earth?

Answer 3

1. Synthesis of simple organic molecules from inorganic compounds. Also known as catalysis.

Example: Photosynthesis, a global process, involves the reaction of inorganic compounds CO₂ and H₂O with sunlight to produce organic sugars within green plant parts.

2. The self-assembly of these organic molecules (monomers) into polymers. This is polymerisation.
3. The formation of a polymer that can self replicate (enabling inheritance). Usually RNA.
4. Packaging of molecules into membranes with an internal chemistry different from surroundings

Question 4

Monomers (examples)

Answer 4

Amino acids, nitrogenous bases, fatty acids and simple sugars.

Question 5

What was the miller-Urey experiment

Answer 5

The Miller–Urey experiment (or Miller experiment) was an experiment in chemical synthesis carried out in 1952 that simulated the conditions thought at the time to be present in the atmosphere of the early, prebiotic Earth.

Question 6

Mrs Engh

Answer 6

Metabolism
Reproduction
Sensitivity (responsiveness)

Excretion
Nutrition
Growth
Homeostasis

Question 7

Why aren’t viruses considered living?

Answer 7

Lack of metabolism and reliance on a host cell metabolic events for replication.

Question 8

LUCA

Answer 8

last universal common ancestor

Question 9

What does LUCA represent?

Answer 9

The immediate antecessor of the three current domains of life which are: bacteria, archaea and eukaryotes

Question 10

What is the evidence for LUCA?

Answer 10

• Genetic code is universal and all life shows a common mechanism of transcription and translation.
• Certain genes are broadly distributed across all cellular organisms e.g) instructions for DNA replication

Question 11

Are fatty acids hydrophilic or hydrophobic

Answer 11

They have hydrophilic heads and hydrophobic tails.

Question 12

What will happen with non-polar fatty acids in water?

Answer 12

They will arrange to form micelles as the hydrophobic tails coalesce to avoid contact with the polar solution.

Question 13

How can RNA be the first genetic material?

Answer 13

• Can self-replicate - RNA can form complementary template sequences that can be used to produce new identical molecules.
• Can act as a catalyst - RNA catalysts (ribozymes) are involved in peptide bond formation and intron splicing in modern cells

Question 14

What are used of staining when using a microscope

Answer 14

Iodine - starch will be shown as brown or blue-black and glycogen will be shown as red

Methylene blue - useful for identifying DNA or the nucleus

Gram stain - divides bacteria into two types. Gram positive or negative depending on size and composition of cell wall.

Question 15

How do you calculate actual size, magnifications and image size?

Answer 15

I
A. M

Question 16

Difference between prokaryotic and eukaryotic cells?

Answer 16

Prokaryotic cell - Has no nucleus.

Eukaryotic cell - Has a nucleus.

Question 17

Organelle

Answer 17

Non living unit found inside a cell e.g.) mitochondria

Question 18

What are the components found in a prokaryotic cell?

Answer 18

Cell wall
Plasma membrane
Cytoplasm
Naked DNA in a loop
70s ribosomes
Plasmid

(See books for DEFS)

Question 19

Compartmentalisation and advantages

Answer 19

Allows for the interior of organelles to have separate conditions to the cytoplasm of the cell.

Advantages
- The ability to create higher concentrations of certain substances within organelles.
- The ability to separate toxins and potentially damaging substances from the rest of the cell.
- Control over conditions inside organelles (such as pH) to maintain the optimal conditions for the enzymes that function in those parts of the cell.

Question 20

What’s in a eukaryotic cell?

Answer 20

Plasma membrane
Cytoplasm
Mitochondria
80s ribosomes (same as 70s but look slightly different)
Nucleus
SER
RER
Golgi apparatus
Vesicle
Vacuole
Cytoskeleton

Question 21

Describe the characteristics of paramecium that allow it to perform functions of life.

Answer 21

Movement - can control beating of cilia to move in different directions.

Reproduction - cell will grow until it reaches a maximum volume to surface area ratio and will then divide via mitosis.

Excretion - waste products from digestion are excreted through the anal pore

Nutrition - is an heterotroph and therefore eats smaller organisms to obtain energy and matter.

Question 22

Characteristics which allow the chlamydomonas to perform functions of life.

Answer 22

Movement - swim using its flagella

Reproduction - asexual reproduction after cell division via mitosis to make another nuclei

Sensitivity - a light sensitive “eyespot” allows it to sense light and swim to it

Excretion - oxygen byproduct of photosynthesis diffuses out the cell membrane

Nutrition - is an autotroph and makes its own food via photosynthesis diffuses

Growth - will grow until it reaches a maximum volume to surface area ratio

Question 23

Differences in eukaryotic structures including animal,fungal and plant cells

Answer 23

Look in revision book as I can’t be bothered writing all that out

Question 24

What does atypical mean and what are examples of an atypical cell structure?

Answer 24

Atypical - unusual from other cells

Examples:
Skeletal muscle cells - have multiple nuclei because it’s technically multiple cells with multiple nucleus

Red blood cells - don’t contain a nucleus so there is a greater capacity for haemoglobin transport

Aseptate fungal hyphae - sometimes don’t divide causing a continuous cytoplasm

Phloem sieve tube elements - contain very little cytoplasm and few organelles including no nucleus

Question 25

What is a micrograph?

Answer 25

A photograph taken by means of a microscope. (Light micrographs and electron micrographs).

Question 26

What is endosymbiosis?

Answer 26

Whereby one cell was engulfed by another and became assimilated into its cellular structure.

Question 27

Evidence for endosymbiosis?

Answer 27

Mitochondria and chloroplasts are both organelles suggested to have arisen via endosymbiosis.

Both have a double membrane

Both organelles display susceptibility to certain antibiotics which target prokaryotic features

Both possess their own DNA which is naked and circular

Both divide by a process similar to binary fission

Both contain 70s ribosomes which are found in prokaryotic cells