Microorganisms

Question 1

What is a vector

Answer 1

Transfer pathogens from one host to the next

Question 2

What is a pathogen

Answer 2

Disease causing microorganisms (protists, bacteria, viruses, fungi)

Question 3

Ways diseases can be spread

Answer 3

Sharing bodily fluids(blood, saliva, semen), physical contact, uncooked and contaminated food, droplet infection through coughing and sneezing, vectors eg mosquito, animal bites, contaminated water

Question 4

Key points of external structure of bacteria

Answer 4

-peptidoglycan cell wall
-capsule
-pili
-flagellum
-cell surface membrane

Question 5

Size of bacteria cells

Answer 5

Between 0.5 and 5 micrometres

Question 6

Key points of internal structure of bacteria

Answer 6

-no nucleus or membrane-bound organelles
-mesosome
-plasmids
-ribosomes

Question 7

Method of replication for bacteria

Answer 7

Reproduce asexually by binary fission, after replication of DNA they divide into two identical cells

Question 8

Size of virus cells

Answer 8

Vary in size between 20nm and 400nm, smaller than bacteria

Question 9

Key points of external structure of viruses

Answer 9

-enclosed within protein coat
-outer envelope taken from host membrane, have glycoproteins and antigens which help attach to cell and penetrate membrane

Question 10

Key points on internal structure of viruses

Answer 10

-have strand of nuclei acid (RNA/DNA) surrounded by protein coat called capsid
-lack some internal structures for growth and reproduction so must infect host
-lack internal membranes, cytoplasm and ribosomes
-some viruses carry proteins inside their capsid eg HIV carries enzyme reverse transcriptase

Question 11

Method of replication for viruses

Answer 11

-virus attaches to host cell
Inserts nucleic acid
Viral nuclei acids replicate using reverse transcriptase
Viral protein coats synthesised
New virus particles formed
Viral particles released due to cell lysis (cell splitting)

Question 12

How ears prevent infection

Answer 12

Ear wax is bacteriacidal

Question 13

How respiratory tract prevents infection

Answer 13

Mucus membranes (goblet cells) secrete mucus which traps particles and pathogens, cilia sweeps mucus towards throat which prevents entry of pathogens into lungs

Question 14

How does skin prevent infection

Answer 14

Dry keratin outer layer, can’t be digested easily, large number of naturally occurring bacteria live on skin which outcompete pathogenic bacteria, impermeable to skin
-blood clotting seals wounds

Question 15

How does sebum prevent infection

Answer 15

Lowers pH which inhibits growth of microorganisms

Question 16

How do microbes on the skin and in gut prevent infection

Answer 16

Skin flora better adapted to salty conditions on skin, they are harmless and reduce colonisation by other bacteria as outcompete them for nutrients and space. Those in gut secrete toxins which help to destroy pathogens

Question 17

How does vagina prevent infection

Answer 17

Vaginal secretions are acidic

Question 18

How does stomach prevent infection

Answer 18

HCl in stomach destroys ingested bacteria

Question 19

How do sweat and tears and saliva prevent infection

Answer 19

Contains lysozyme which digests cell wall of bacteria causing cells to burst

Question 20

What is cell wall made of in bacteria

Answer 20

Glycoprotein-usually murein

Question 21

Purpose of capsule in bacteria and what it is made up of

Answer 21

Made up of secreted slime, helps protect the bacterium from attack by cells of the immune system

Question 22

What is a bacterial chromosome

Answer 22

One long, circular, coiled up strand floating freely in cytoplasm