Biology Test/Quiz #2

characteristics that all living things share

• made up of units called cells

• reproduce

• based on universal genetic code

• grow and develop

• obtain and use materials and energy

• respond to their environment

• maintain homeostasis

• change over time/ evolve

what is a virus

• a noncellular particle of nucleic acids, protein, and in some cases, lipids

• can only reproduce by infecting living cells

what is a virus composed of

• a core of nucleic acids (RNA or DNA)

• surrounded by a protein coat (capsid)

• come in a variety of shapes

• vary in size (10-400 nanometers)

how does a virus enter an a cell

the capsid proteins bind to the receptors on the surface of the cell and “trick” the cell into allowing it inside

bacteriophage

viruses that infect only bacteria

two types of infections

• lysogenic infection

• lytic infection

characteristics of a lytic infection

• enters the cell

• uses the cell to make copies of itself

• cause the cell to lyse or burst releasing new viruses and killing the cell

characteristics of a lysogenic infection

• a virus integrates its DNA into the DNA of the host cell

• the viral genetic information replicates along with the new host cell’s DNA possibly for many generations

• viral DNA eventually becomes active and creates new virus particles and lyses the cell wall releasing new viruses

why is a retrovirus different from a regular virus

it contains RNA instead of DNA as its genetic information

how do retroviruses work

• by infecting cells and making a DNA copy of their RNA

• the DNA is then inserted into the DNA of the host’s cells

what is a prokaryote

unicellular organism that lacks a nucleus

** also the smallest and most common microorganisms

Eubacteria

• have a cell wall that protects the cell and determines its shape

• cell walls contain peptidoglycan

• have a cell membrane that surrounds the cytoplasm

what kind of environments do eubacteria live in

• fresh water

• on land

• the human body

Archaebacteria

• cell walls do not contain peptidoglycan

• have different membrane lipids

• the DNA sequences are more like eukaryotes than eubacteria

• live in extreme environments

where do archaebacteria live

• methanogens live in oxygen-free environments, such as thick mud and animal digestive tracts

• others live in salty environments or in hot springs where water temperatures approach the boiling point

how can scientists identify prokaryotes

• shape

• chemical nature of their cell walls

• the way they move

• the way they obtain energy

rod shaped prokaryote

bacilli

spherical shaped prokaryote

cocci

spiral and corkscrew shaped prokaryotes

spirilla

two types of cell walls

• gram-positive

• gram-negative

gram-positive cell walls

bacteria have thick cell walls with large amounts of peptidoglycan (take up crystal violet)

gram-negative cell walls

bacteria have thinner cell walls inside an outer lipid layer (take up safranine)

how can scientists identify what kind of cell wall they are dealing with?

gram staining- tells them apart by using crystal violet and safranine

types of movement for prokaryotes

• flagella

• lash, snake, or spiral forward

• glide along a layer of slime

• or don’t move at all

what are the two main groups of prokaryotes obtaining energy

• heterotrophs

• autotrophs

heterotroph

get their energy by consuming organic molecules made by other organisms

autotroph

make their own food from inorganic molecules

chemoheterotrophs

• take in organic molecules for both energy and a supply of carbon

  • most animals

  • most bacteria

photoheterotrophs

• use sunlight for energy but take in organic compounds

  • cant use carbon dioxide as sole carbon source

photoautotrophs

• use sunlight to convert carbon dioxide and water to carbon compounds and oxygen

  • similar to plants

chemoautotrophs

• make organic compounds from carbon dioxide but do not require light as energy instead use inorganic molecules including hydrogen sulfide, ammonia, and sulfur

how is needed energy released

cellular respiration or fermentation

respiration

involves breaking down food molecules to release energy

fermentation

enables cells to carry out energy production without the use of oxygen

obligate anaerobes

must live without the presence of oxygen because they may be killed by it (EX// food poisoning)

facultative anaerobes

can survive with or without oxygen

how does bacteria reproduce through binary fission

also known as asexual reproduction, bacteria doubles in size, replicates its DNA, and divides in half

how does bacteria reproduce through sexual reproduction

• a hollow bridge forms between two bacterial cells, and genes move from one cell to another

• when done each cell has a different set of genes

• increases genetic diversity

when does an endospore form?

when bacterium produces a thick internal wall that encloses its DNA and some of its cytoplasm

shapes of bacteria

• rod-shaped

• tadpole-shaped

• many sided

• helical

• cube-like

obligate aerobe

organism that requires a constant supply of oxygen in order to live

types of important bacteria we need

• decomposers

• nitrogen fixers

decomposers

• bacteria recycle nutrients and maintain equilibrium in the environment

• bacteria also help in the treatment of sewage

nitrogen fixers

• atmosphere is approximately 80 percent nitrogen

• plants can’t use nitrogen gas but need nitrogen

• many plants have symbiotic relationships with nitrogen fixing bacteria which take nitrogen gas from the air and convert it to a form plants can use

humans uses for bacteria

• foods

• removal of waste

• clean up oil spills

• synthesis of drugs and chemicals via genetic engineering

• production is vitamins in human intestines