Regents Biology

Monday, 12/8Today’s Agenda:1. Turn in HW (Cell Craft)

2. Go over Limits To Cell Size lab

3. Lecture on viruses and bacteria

4. Time to work on HW or project

Bell Ringer (Answer in your notes WITHOUT looking back at them!):5. What are the 3 main jobs of organelles? Which

organelles carry out these functions?

Regents Biology

Cells have 3 main jobs make energy

need food + O2

cellular respiration & photosynthesis need to remove wastes

make proteins need instructions from DNA need to chain together amino acids & “finish”

& “ship” the protein make more cells

need to copy DNA & divide it up to daughter cells

Cell Summary

Our organellesdo all those

jobs!

Regents Biology

cell membranecell boundarycontrols movementof materials in & out

recognizes signals

cytoplasmjelly-like material holding organelles in place

mitochondriamake ATP energy

from sugar + O2

nucleusprotects DNAcontrols cell

ribosomesbuilds proteins

ERhelps finish proteinsmakes membranes

Golgi apparatusfinishes, packages

& ships proteins

lysosomefood digestiongarbage disposal &recycling

vacuole & vesiclestransport inside cellsstorage

centriolescell division

Regents Biology

Limit To Cell Size Lab5 questions were graded: 1, 4, 5, 7, and 8

1. As the cube increases in size the increase in volume is greater than the increase in surface area, therefore the SA:V ratio decreases.

4. The greater the SA:V ratio, the less time it takes for diffusion to occur.

5. As cells get larger they become less efficient at transporting essential nutrients/molecules to the center and have difficulty eliminating waste products and may essentially starve or become too toxic to survive.

Regents Biology

7. Oddly worded question – 2 points depending on your response

8. Discuss

Regents Biology

Ch. 19 - Viruses

Overview: A Borrowed Life Viruses called bacteriophages can infect and

set in motion a genetic takeover of bacteria, such as Escherichia coli

Viruses lead “a kind of borrowed life” between life-forms and chemicals

The origins of molecular biology lie in early studies of viruses that infect bacteria

© 2011 Pearson Education, Inc.

Regents Biology

Figure 19.1

0.5 mm

Regents Biology

Concept 19.1: A virus consists of a nucleic acid surrounded by a protein coat

Structure of Viruses Viruses are not cells A virus is a very small infectious particle

consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope

© 2011 Pearson Education, Inc.

Regents Biology

Viral Genomes

Viral genomes may consist of either Double- or single-stranded DNA, or Double- or single-stranded RNA

Depending on its type of nucleic acid, a virus is called a DNA virus or an RNA virus

© 2011 Pearson Education, Inc.

Regents Biology

Capsids and Envelopes

A capsid is the protein shell that encloses the viral genome

Capsids are built from protein subunits called capsomeres

A capsid can have various structures

© 2011 Pearson Education, Inc.

Regents Biology

Figure 19.3

Capsomereof capsid

RNA CapsomereDNA

Glycoprotein Glycoproteins

Membranousenvelope RNA

CapsidHead

DNA

Tailsheath

Tailfiber

18 250 nm 80 225 nm70–90 nm (diameter) 80–200 nm (diameter)

20 nm 50 nm 50 nm 50 nm(a) Tobacco

mosaic virus(b) Adenoviruses (c) Influenza viruses (d) Bacteriophage T4

Regents Biology

Some viruses have membranous envelopes that help them infect hosts

These viral envelopes surround the capsids of influenza viruses and many other viruses found in animals

Viral envelopes, which are derived from the host cell’s membrane, contain a combination of viral and host cell molecules

© 2011 Pearson Education, Inc.

Regents Biology

Bacteriophages, also called phages, are viruses that infect bacteria

They have the most complex capsids found among viruses

Phages have an elongated capsid head that encloses their DNA

A protein tail piece attaches the phage to the host and injects the phage DNA inside

© 2011 Pearson Education, Inc.

Regents Biology

Overview: Masters of Adaptation Utah’s Great Salt Lake can reach a salt

concentration of 32% Its pink color comes from living prokaryotes

Ch. 27 - Prokaryotes

© 2011 Pearson Education, Inc.

Regents Biology

Thrive almost everywhere, including places that are too: Acidic Salty Cold/Hot

Most are microscopic, but what they lack in size they make up for in #s

There are more in a handful of fertile soil than the number of people who have ever lived

Prokaryotes are divided into two domains: Bacteria Archaea

© 2011 Pearson Education, Inc.

Prokaryotes

Regents Biology

Concept 27.1: Structural and functional adaptations contribute to prokaryotic success Most likely 1st organisms on Earth Most are unicellular, although some species

form colonies Sizes are usually 0.5–5 µm

Eykaryotic cells are usually 10–100 µm Come in a variety of shapes, the 3 most

common shapes are: spheres (cocci) rods (bacilli) spirals

© 2011 Pearson Education, Inc.

Regents Biology

Cell-Surface Structures

Cell wall: Maintains cell shape Protects the cell Prevents cell from bursting in a hypotonic

environment A eukaryotic cell wall is made of cellulose or

chitin Bacterial cell walls contain peptidoglycan

A network of sugar polymers cross-linked by polypeptides

© 2011 Pearson Education, Inc.

Regents Biology

Archaea contain polysaccharides and proteins but lack peptidoglycan

Scientists use the Gram stain to classify bacteria by cell wall composition Gram-positive bacteria have simpler walls with

a large amount of peptidoglycan Gram-negative bacteria have less

peptidoglycan and an outer membrane that can be toxic

© 2011 Pearson Education, Inc.

Regents Biology

Figure 27.3

(a) Gram-positive bacteria: peptidoglycan traps crystal violet.

Gram-positivebacteria

Peptido-glycanlayer

Cellwall

Plasmamembrane

10 m

Gram-negativebacteria

Outermembrane

Peptido-glycanlayer

Plasma membrane

Cellwall

Carbohydrate portionof lipopolysaccharide

(b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye.

Regents Biology

Many antibiotics target peptidoglycan and damage bacterial cell walls

Gram-negative bacteria are more likely to be antibiotic resistant

A polysaccharide or protein layer called a capsule covers many prokaryotes

© 2011 Pearson Education, Inc.

Regents Biology

Figure 27.4

Bacterialcell wall

Bacterialcapsule

Tonsilcell

200 nm

Regents Biology

Some prokaryotes have fimbriae, which allow them to stick to their substrate or other individuals in a colony

Pili (or sex pili) are longer than fimbriae and allow prokaryotes to exchange DNA

© 2011 Pearson Education, Inc.

Regents Biology

Figure 27.5

Fimbriae

1 m

Regents Biology

Motility

In a heterogeneous environment, many bacteria exhibit taxis: the ability to move toward or away from a

stimulus Chemotaxis is the movement toward or away

from a chemical stimulus Towards nutrients Away from toxins

© 2011 Pearson Education, Inc.

Regents Biology

Most motile bacteria propel themselves by flagella scattered about the surface or concentrated at one or both ends

Flagella of bacteria, archaea, and eukaryotes are composed of different proteins and likely evolved independently

© 2011 Pearson Education, Inc.

Regents Biology

Figure 27.6

Flagellum

Hook

Motor

Filament

RodPeptidoglycan

layerPlasma

membrane

Cell wall

20 nm

Regents Biology

Evolutionary Origins of Bacterial Flagella

Bacterial flagella are composed of a motor, hook, and filament

Many of the flagella’s proteins are modified versions of proteins that perform other tasks in bacteria

Flagella likely evolved as existing proteins were added to an ancestral secretory system

This is an example of exaptation, where existing structures take on new functions through descent with modification

© 2011 Pearson Education, Inc.

Regents Biology

Internal Organization and DNA

Prokaryotic cells usually lack complex compartmentalization

Some prokaryotes do have specialized membranes that perform metabolic functions

These are usually infoldings of the plasma membrane

© 2011 Pearson Education, Inc.

Regents Biology

The prokaryotic genome has less DNA than the eukaryotic genome

Most of the genome consists of a circular chromosome

The chromosome is not surrounded by a membrane; it is located in the nucleoid region

Some species of bacteria also have smaller rings of DNA called plasmids

© 2011 Pearson Education, Inc.

Regents Biology

Figure 27.8

Chromosome Plasmids

1 m

Regents Biology

There are some differences between prokaryotes and eukaryotes in DNA replication, transcription, and translation

These allow people to use some antibiotics to inhibit bacterial growth without harming themselves

© 2011 Pearson Education, Inc.

Regents Biology

Reproduction and Adaptation

Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours

Key features of prokaryotic reproduction: They are small They reproduce by binary fission They have short generation times

© 2011 Pearson Education, Inc.

Regents Biology

Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries

© 2011 Pearson Education, Inc.

Regents Biology

Figure 27.9

Coat

Endospore

0.3 m

Regents Biology

Their short generation time allows prokaryotes to evolve quickly

For example, adaptive evolution in a bacterial colony was documented in a lab over 8 years

Prokaryotes are not “primitive” but are highly evolved

© 2011 Pearson Education, Inc.