Bio 112 Exam 2 study guide

Topics: 29 - Fungi 33 - Viruses 34 - Plant From and Function 35 - Water and Sugar Transport in plants

Organelles

originated from more primitive cells that become trapped in eukaryotic cells

Fungi

eukaryotes

single celled or multicellular filaments

most important decomposers

are mutualists

positive impacts of fungi

course of antibiotics

food

yeast for bread, cheese, soy sauce, beer, wine

improve characteristics of foods such as fruit juice, candy, and meat

mycorrhizal fungi

live close to plant roots

plants grow better in their presence

name for mycorrhizal fungi

mycorrhizae

saprophytes

fungi that digest dead plant material

cycle carbons through terrestrial systems

what do fungi do for the carbon cycle?

speed it up

cell wall

rigid

structural support and shape

made of chitin

cytoplasmic membrane

bilayer of phospholipids and protein molecules

contain sterols

reduces membrane fluidity and permeability

selective permeable barriers

controls what comes in and out of cell

two growth forms of fungi

single cell form (yeast)

multicellular, filamentous forms (mycelia or mycelium)

nature of mycelium

dynamic

grow in direction of food sources and die back in areas where food is running out

body shape can continuously change

Hyphae

long, narrow filaments of mycelium

septa

cross walls in hyphae

pores allows materials to flow between compartments

coenocytic

lacking septa (cross walls)

many nuclei are scattered throughout the mycelium

mycelia supports what type of digestion

external

swimming gametes and spores

sexually produced gametes and asexually produced spores (zoospores) or chytrids have flagella

zygosporangia

spore producing structures of zygomycetes

form from fusion of cells from joined together haploid hyphae from two individuals

basidia

basidiomycete (club fungi) form basidia

ends of hyphae

produces 4 spores

Asci

ascomycetes (sac fungi) form asci, reproductive sac like cells at ends of hyphae

produce 8 spores

conidia

asexual spores

dispersed by water or wind currents and grow into new hyphae

why are fungal infections in humans more difficult to treat?

similar cellular and molecular structures

drugs that disrupt fungal physiology are likely to damage humans as well

symbiotic relationship

living together (between plant and fungi)

mutualic relationship

benefit both species

parasitic relationship

one benefits other is harmed

commensal relationships

benefit one another is unaffected

types of plant mycorrhizal interactions

ectomycorrhizal fungi (EMF)

arbuscular mycorrhizal fungi (AMF)

Ectomycorrhizal Fungi (EMF)

found in tree species in temperate regions

form a dense network of hyphae that cover plant roots

enter soil but not root cells

penetrate decaying material

release peptidases

provide phosphate ions to host plant

peptidase

cleave proteins to release amino acids that hyphae transport

Arbuscular Mycorrhizal Fungi (AMF)

hyphae grows into the cells of root tissue

also called endomycorrhizal fungi

endophytes (inside plant)

organisms that live between and within plant cells

live in close association with roots or aboveground tissues of land plants

Lichens

mutualistic partnership usually between a specie of ascomycete and either a cyanobacterium or an alga

extracellular digestion

digestion that takes place outside the organism

simple compounds resulting from enzymatic action are absorbed by hyphae

what aids in lignin degradation?

enzyme called lignin peroxidase

what aids in cellulose digestion?

cellulases

what are the most fundamental reproductive cell in fungi?

spores

what do mating types also function as?

sexes

how does fertilization occur in fungi?

fusion or hyphae or fusion of nuclei from the fused hyphae

plasmogamy

occurs when the cytoplasm fuse

heterokaryotic

when two or more genetically distinct nuclei exist within a single mycelium

what are most heterokaryotic hyphae?

dikaryotic

karyogamy

occurs when the nuclei fuse to form a diploid zygote

cyrtid life cycle

alternation of generations

Key stages of the chytrid life cycle:

1. Haploid adults form gametangia: ▪ Mitosis produces male and female swimming gametes

2. Gametes fuse to form a diploid zygote

3. The zygote grows into a diploid sporophyte

4. Haploid spores, which disperse by swimming, are produced by meiosis inside the sporophyte’s sporangium

Zygomycete Life Cycle

hyphae from different mating types fuse

can also reproduce asexually by making sporangia, which produce haploid spores by mitosis

Basidiomycete Life Cycle

Mushrooms are sexual reproductive structures produced by basidiomycetes

originate from the dikaryotic hyphae of mated individuals:

Ascomycete Life Cycle

Hyphae or specialized structures from different mating types fuse:

Forms a heterokaryotic

Short dikaryotic hypha with cells containing two nuclei emerges:

asci at tips

production of eight haploid spores • When the ascus matures, the spores inside are forcibly ejected

Microsporidia

Single-celled and parasitic

polar tube

Chytrids

Largely aquatic and common in freshwater

digesting cellulose:

important decomposers of plant material in wet soils, ponds, and lakes

Many freshwater species are parasitic: – Likely culprit behind the decline of amphibian populations worldwide

Zygomycetes

Primarily soil-dwellers

responsible for rotting fruits and vegetables

Glomeromycota

All members (except for a single species) comprise the arbuscular mycorrhizal fungi (AMF)

Absorb phosphorus, nitrogen, other nutrients, and water into roots of most of plants living in grasslands and tropical forests

Host plant provides symbiotic fungi with sugars and other organic compounds

Basidiomycota

Form mycelia and produce basidia where meiosis and spore formation occur

Mushrooms

wood decomposition Some are ectomycorrhizal fungi (EMF) that improve the health of forests Some can also be parasitic

Ascomycota

Most form mycelia and produce spores in asci: – Mycelia also commonly reproduce asexually • yeasts

mutualistic association with cyanobacteria and/or single-celled green algae, forming structures called lichens

mutualistic EMF associations with tree roots

properties of viruses

not cells

active only inside host cell

multiply by taking control of host

lack enzymes for most metabolic processes

lack machinery for synthesizing proteins

contains a nucleic acid core

capsids

shell surrounds the nucleic acid

Nucleocapsid

capsid and nucleic acid together

Envelope

• Not found in all viruses

• Usually a modified piece of the host cell membrane

Spikes

• Found on both naked and enveloped viruses. Project from either the nucleocapsid or envelope

• Allow viruses to dock with their host cells

Virion

Fully formed virus able to establish infection in a host

Capsomeres

Identical protein subunits that spontaneously self assemble to form the capsid

Helical capsid

Rod-shaped capsomeres that form a continuous helix around the nucleic acid

Icosahedral capsid

Three-dimensional, 20-sided figure with 12 evenly spaced corners

Complex capsids

Found in bacteriophage, the viruses that infect bacteria

Have multiple types of proteins

Take shapes that are not symmetrical

Viral Envelope

• Composed of the membrane system of the host • Cell membrane or nuclear membrane

• Regular membrane proteins are replaced with viral proteins

• Spikes: protruding glycoproteins essential for attachment to the host cell

what type of genetic material can a virus have?

DNA or RNA but not both

general phases in the life cycle of animal viruses:

Adsorption

• Penetration

• Uncoating

• Synthesis

• Assembly

• Release from the host cell

Adsorption

Invasion begins when the virus encounters a susceptible host and adsorbs specifically to receptor sites on the cell membrane

•Endocytosis

entire virus is engulfed by the cell and enclosed in a vacuole or vesicle

Uncoating

enzymes in the vacuole dissolve the envelope and capsid, releasing the virus into the cytoplasm

where do RNA viruses replicate?

cytoplasm

where do DNA viruses replicate?

nucleus

exocytosis

Enveloped viruses are liberated by budding

Nucleocapsid binds to the membrane

• A small pouch is formed

• Pinching off of the pouch releases the virus with its envelope

• Viruses are shed gradually without destruction of the cell

Inclusion bodies

compacted masses of viruses or damaged cell organelles in the nucleus or cytoplasm

Syncytia

fusion of multiple host cells into single large cells containing multiple nuclei

Oncogenic viruses

Experts estimate that up to 13% of human cancers are caused by viruses

Transformation

Virus carries genes that directly cause cancer

• Virus produces proteins that induce a loss of growth regulation in the cell

Viruses That Infect Bacteria

bacteriophage

Lytic phase or lytic cycle

life cycle of bacteriophage that ends in destruction of the bacterial cell

Lysogenic cycle

bacteriophage becomes incorporated into the host cell DNA

Temperate phages

Have the ability to undergo adsorption and penetration but do not immediately undergo replication or release

Prophage

an inactive state in which phage DNA is inserted into the host chromosome

Induction

activation of a prophage in a lysogenic cell to progress directly into viral replication and the lytic cycle

lysogenic conversion

The acquisition of a new trait from a temperate phage

Responsible for the diphtheria toxin, cholera toxin, and botulism toxin

•Interferon (IFN)

–Naturally occurring human cell product

–Used with some success in preventing and treating viral infections

Viroid

Virus like agent that parasitizes plants

Composed only of naked strands of RNA—lack a capsid or other type of coating

what type of growth do most plants undergo?

indeterminate growth

Aboveground: – Shoot system

harvests light and carbon dioxide from atmosphere to produce sugars

Belowground: – Root system

anchors plant and takes in water and nutrients from soil

Root and shoot systems both function in what?

absorption

key functions of the root system:

– Roots anchor plant to the soil

– Roots absorb ions and water from soil

– Roots conduct water and ions to the shoot system

– Roots obtain energy from the sugar in the shoot system

– Roots store material produced in the shoot system for later use

Morphological Diversity in Root Systems

herbaceous

perennial

herbaceous

Seed plants that lack woody tissue

perennial

They live for many years

Phenotypic Plasticity in Root Systems

– Their form is changeable depending on environment

Modified Roots

formed by various types of plants

Adventitious roots

grow from shoot system: – In ivy, adventitious roots act to anchor the plant

Prop roots

brace the plant (corn)

tap root

originates from radicle

Pneumatophores

specialized lateral roots in genus Avicennia

Function in gas exchange

Oxygen in atmosphere can diffuse into root system through pneumatophores

storage roots

Thick taproot that stores carbohydrates during plant’s first two growing seasons

• Biennial plants, such as carrots and beets: