Micro - organism

Question 1

Prokaryotes

Answer 1

unicellular entities
lack a nucleus and membrane bound organelles unlike eukaryotes
genetic material is usually in
the nucleoid region of the cytoplasm
some prokaryotes contain a single circular chromosome of double stranded DNA also known as a plasmid.

Question 2

Examples of prokaryotes

Answer 2

Bacteria and Archaea

Question 3

Prokaryotes reproduce

Answer 3

via binary fission
other processes such as
transduction, transformation, conjugation are forms of reproduction that also takes place in a prokaryote

Question 4

Prokaryotic Cell Features

Answer 4

Capsule: polysaccharides that aid prokaryotes such as bacteria to adhere to surfaces and to each other also prevent desiccation of the microbe.
Cell wall: located below the capsule, maintains the cells shape and plays in a role protection and withstanding pressures within the cell.
Cell membrane: lies underneath the cell wall, containing phospholipids which are arranged in a bilayer conformation where the hydrophobic tails (fatty acids) are in the interior with the hydrophilic heads (glycerol plus phosphate) out on the exterior
Appendages: prokaryotic cells contain a few appendages which are protrusions on the cell surface such as fimbriae, pili and flagella. Fimbriae are thin filaments that aid adhesion. Pili are longer structures that play a role in conjugation and in some cases movement, whilst flagellum is a structure that helps the cell to move around.
Ribosome: the site of protein synthesis
Nucleoid region: region in the cell where the double stranded circular chromosomal materials are found.
Chromosome: genetic material found within the nucleoid region
Plasmid: small circular rings of extrachromosomal double stranded DNA which carry non-essential genes and are duplicated independent of chromosomes

Question 5

Eukaryotes

Answer 5

Cells that possess a clearly defined nucleus, the nucleus has a membrane around it.
The nucleus holds chromosomes, and the cellular compartment holds organelles, some of which are membrane bound.
The membrane bound eukaryotic organelles are the nucleus, mitochondria, Golgi apparatus, lysosomes and endoplasmic reticulum

Question 6

4 Main types of eukaryotes

Answer 6

animals
plants
fungi
protists

Question 7

Eukaryotes reproduce

Answer 7

Some eukaryotes reproduce asexually whilst some reproduce sexually.

Question 8

Eukaryotic Cell Features

Answer 8

Mitochondria: powerhouse of the cell, ATP is synthesized here
Lysosomes: contains enzymes that break down pathogens, old organelles etc.
Peroxisome: aids in metabolizing wastes
Endoplasmic reticulum: synthesizes, stores and transports lipids and carbohydrates
Golgi apparatus: area where proteins are modified
Nucleus: stores genetic material
Nucleolus: ribosomes are formed in this region
Cytoplasm: the area of the cell where the organelles are found

Question 9

Differences Between Prokaryotes and Eukaryotes

Answer 9

1. Genetic material is usually circular and
   located in nucleoid region
   Genetic material are linear chromosomes
   situated in the nucleus
2. Lack organelles, small ribosomes
   Contains a few organelles such as mitochondria, Golgi apparatus, large ribosomes
3. Usually unicellular, generation/growth time is fast
   Can be multicellular, generation/growth
   time is slow
4. Cell wall found in all
   Cell wall only in plants and fungi

Question 10

Binary fission

Answer 10

asexual reproduction that bacteria uses to divide creating 2 identical daughter cells

Question 11

Conjugation

Answer 11

direct contact is used to transfer genetic material between bacteria

Question 12

Transformation

Answer 12

exogenous DNA is transferred into host cells

Question 13

Transduction

Answer 13

process by which viruses transfer genetic material between bacteria. This is performed by bacteriophage

Question 14

Archaea

Answer 14

single-celled prokaryote whose cell wall lacks peptidoglycan, ether linked lipids are in their cell wall as opposed to ester linked lipids in bacteria

Question 15

Phospholipid bilayer

Answer 15

vital component of a cell membrane made of a hydrophobic tail and hydrophilic heads

Question 16

Viruses

Answer 16

small parasites that lack the capacity to undergo replication, transcription, or translation outside of a host cell. Viruses that infect bacteria are known as bacteriophages. Viruses lack the concept of homeostasis which is the capacity to regulate and sustain their internal environment. Almost all viruses rely on the host cell for translation, and to a certain extent for transcription and replication.

Question 17

Viruses may contain

Answer 17

nucleic acid either
double stranded DNA or single stranded RNA surrounded by capsid (virus encoded protein coat). Viruses also have an outer membrane lipoprotein envelope which is obtained via the process of budding from the host cell.

Question 18

Glycoprotein

Answer 18

found on the viral surface play a role in the structure of the virion as well as interact with receptors on the host cell.

Question 19

Nucleocapsid

Answer 19

genome and the capsid together

Question 20

Some RNA and DNA viruses contain

Answer 20

non- structural proteins which are integral for immediate transcription or replication after infection of the host cell

Question 21

Virus Replication Strategies

Answer 21

Some viruses utilize the host cell machinery for replication.
Large DNA viruses with bigger genomes encode their own replication and transcription factors.
RNA viruses require RNA polymerase for transcription and these enzymes are not present in the host cell thus must be encoded by the virus.
Retroviruses are RNA viruses which utilize RNA-dependent DNA polymerase to replicate the RNA genome through a DNA intermediate (reverse transcription).

Question 22

Viral Replication Cycle

Answer 22

1. Attachment: virus binds to host cell surface receptors via its glycoproteins
2. Viral entry: viral genome enters host cell after attachment.
3. Synthesis: host cell machinery manufactures the viral proteins and copies viral nucleic acid.
4. Assembly: new viruses are produced from viral components
5. Release: newly synthesized viruses are released and may leave with a layer of the host cells surface which is the envelope layer

Question 23

Oncoviruses

Answer 23

viruses linked with the development of cancer
can produce proteins that inhibit or deteriorate the function of tumour suppressor genes which are known to play a key role in cell division
inactivation of tumour suppressor genes, cells grow uncontrollably thus forming tumours

Question 24

Cancer (human papillomavirus)

Answer 24

Cervical cancer is induced by oncogenic proteins produced by special types of human papillomavirus.

Question 25

HIV

Answer 25

A retrovirus that causes a severe dampening of the immunity by depleting T-lymphocytes thus opening the sufferer to opportunistic infections.

Question 26

Virion

Answer 26

complete, infective form of a virus outside a host cell, with a core of RNA and a capsid

Question 27

Glycoproteins

Answer 27

structures found on the surface of the cell

Question 28

Budding

Answer 28

the process by which viruses exit the host cell and may obtain an envelope to evade the immune system

Question 29

Virulence

Answer 29

the degree of pathology caused by a pathogen