Cell Theory

• Every organism is composed of one

or more cells

• Cell is smallest unit with properties of

life

• Continuity of life arises from growth

and division of single cells

• Smallest unit of life

• Is highly organized for metabolism

• Senses and responds to environment

• Has potential to reproduce

Cell

The cell theory states that _____.

1 2 3 4

0% 0%0%0%

1. every organism consists of one or more cells

2. the cell is the smallest unit of organization that displays all the properties of life

3. the continuity of life arises directly from the growth and division of single cells

4. all of the choices

Structure of Cells

All start out life with:– Plasma membrane – Region where DNA

is stored– Cytoplasm

Two types:– Prokaryotic– Eukaryotic

DNA innucleoid

cytoplasm

plasma membrane

Bacterial cell (prokaryotic)

Fig. 3-1a, p.39

Types of Cells

The DNA of a prokaryotic cell is located in the _____.

1 2 3 4

0% 0%0%0%

1. nucleus2. plasma

membrane3. nucleoid4. cell wall

DNA in nucleus

cytoplasm

plasma membrane

Plant cell (eukaryotic)

Fig. 3-1b, p.39

Types of Cells

Fig. 3-4, p.41

Most Cells Are Really Small

• Create detailed images of something that is too small to see

• Light microscopes– Simple or compound

• Electron microscopes– Transmission EM or Scanning EM

Microscopes

Limitations of Light Microscopy

• Cells must be thin enough for light to pass through

• Structures are usually stained

• Light microscopes can see details 200 nm in size

Fig. 3-2a, p.40

Microscopes

Ocular lens enlargesprimary image formedby objective lenses.

Path of light rays(bottom to top) to eye

Prism (directs rays to

ocular lens)

Objective lenses (closestto specimen) form primary image.

Stage (holds microscope slide in position)

Condenser lenses focus light rays through specimen.

Illuminator

Fig. 3-2a, p.40

Electron Microscopy

• Uses beams of electrons rather than light

• Electrons are focused by magnets rather than glass lenses

• Can resolve structures down to 0.5 nm

Different Views

Structure of Cell Membranes

• Fluid mosaic model

• Mixed composition:– Phospholipid bilayer – Glycolipids– Sterols– Proteins

• Archaebacteria and eubacteria

• DNA is not enclosed in nucleus

• Generally the smallest, simplest cells

Prokaryotic Cells

Fig. 3-8b, p.44

The DNA of a typical prokaryote is organized into _____.

1 2 3 4

0% 0%0%0%

1. a single circular chromosome

2. many rod-shaped chromosomes

3. a corkscrew shaped chromosome

4. a spherical jellylike mass in the nucleoid region

Eukaryotic Cells

• Have a nucleus and other organelles

• Eukaryotic organisms– Plants– Animals– Protistans– Fungi

Eukaryotic Cell Features

• Plasma membrane• Nucleus• Endoplasmic

reticulum• Golgi body• Vesicles• Mitochondria• Ribosomes• Cytoskeleton

Fig. 3-9b-c, p.46

ribosome vesicle

rough ER

The Nucleus

Endoplasmic Reticulum

• Starts at nuclear membrane and

extends throughout cytoplasm

• Rough ER: ribosome covered,

processes proteins

• Smooth ER: no ribosomes, builds lipids

Fig. 3-9e-f, p.46

budding vesicle

Golgi body

plasma membrane

Secretory pathway ends.

Endocytic pathway begins.

Golgi Body

Vesicles

• Membranous sacs that

move through cytoplasm

• Lysosomes

• Peroxisomes

Cogito ergo….

sum

non s

um

0%0%

1. sum

2. non sum

• ATP-producing powerhouses

• Membranes form two distinct

compartments

• ATP-making machinery embedded

in inner mitochondrial membrane

Mitochondria

Fig. 3-10, p.48

outer membrane

outer compartment

inner compartment

inner membrane

FOOD

complex carbohydrates

simple sugars

pyruvate

acetyl-CoA

glycogenfats proteins

amino acids

carbon backbones

fatty acids

glycerol

NH3

PGAL

glucose-6-phosphate

GLYCOLYSIS

KREBS CYCLE

urea

Krebs cycle

Fig. 3-9a, p.46

chromatin

nucleolus

nuclear envelope(two lipid bilayers)

The Nucleus

Figure 6.5Page 87

2 ATP

4 ATP

glucose

2 PGAL

2 pyruvate

2 ATP

2 acetyl-CoA

36 ATP

ATP

ATP

Krebscycle

NAD+

2 NADH

2 NADH2

2 FADH2

6 NADH

2 NADH

2 CO2

4 CO2

ADP+Pi

electrontransfer

phosphorylation

H+

H+

H+

H+

H+

H+

H+

H+

H+

The function of a mitochondrion is to _____.

1 2 3 4

0% 0%0%0%

1. produce protein

2. make ATP3. attach sugar

side chains to some proteins and lipids

4. degrade toxins

Chloroplasts

• Convert sunlight energy to ATP through photosynthesis

• Found in plants and some protistans

Fig. 3-11, p.48

two outermembranes

thylakoids(inner membranesystem folded intoflattened disks)

Griffith Discovers Transformation

• 1928

• Attempting to develop a vaccine

• Isolated two strains of Streptococcus pneumoniae– Rough strain was harmless– Smooth strain was pathogenic

Griffith Discovers Transformation

1. Mice injected with live cells of harmless strain R

2. Mice injected with live cells of killer strain S

3. Mice injected with heat-killed S cells

4. Mice injected with live R cells plus heat-killed S cells

Mice die. Live S cells in their blood

Mice live. No live R cells in their blood

Mice die. Live S cells in their blood

Mice live. No live S cells in their blood

Transformation

• Harmless R cells were transformed by material from dead S cells

• Descendents of transformed cells were also pathogenic

What Is the Transforming Material?

• Avery found protein-digesting enzymes did not change results– extracts still transformed bacteria

• But treated with DNA-digesting enzymes– extracts lost transforming ability

• Concluded that DNA, not protein, transforms bacteria

If DNA from a disease-causing bacterium is added to the nucleus of a bacterium that normally does not cause disease, _____.

1 2 3 4

73%

8%7%12%

1. the new bacterium will cause the disease

2. the new bacterium will not cause the disease

3. the bacterium will die

4. the bacterium will be resistant to the disease

Bacteriophages

• Viruses that infect bacteria

• Consist of protein and DNA

• Inject their hereditary material into bacteria

Bacteriophages

Bacteriophages are _____.

1 2 3 4

6%0%

93%

1%

1. bacteria that infect viruses

2. bacteria that infect humans

3. viruses that infect bacteria

4. viruses that infect humans

Hershey and Chase’s Experiments

• Created labeled bacteriophages– Radioactive sulfur – Radioactive phosphorus

• Allowed labeled viruses to infect bacteria

• Where were the radioactive labels after infection?

virus particlelabeled with 35S

DNA (blue)being injected into bacterium

35S remainsoutside cells

virus particlelabeled with 32P

DNA (blue)being injected into bacterium

35P remainsinside cells

Fig. 9-2, p.139

Hershey and Chase Results

35S remains outside cells

32P remains inside cells

Structure of DNA

2nm diameter overall

0.34 nm between each pair of bases

3.4 nm length of each full twist of helix

In 1953, Watson and Crick showed that DNA is a double helix

Watson and Crick

Watson-Crick Model

• DNA molecule is a double helix

• Consists of two nucleotide strands that run

in opposite directions

• Strands are held together by hydrogen

bonds between bases

• A binds with T, C binds with G

Structure of Nucleotides in DNA

• Each nucleotide consists of– Deoxyribose (5-carbon sugar)

– Phosphate group

– A nitrogen-containing base

• There are four bases:– Adenine, Guanine, Thymine, Cytosine

Nucleotide Bases

phosphate group

deoxyribose

ADENINE (A)

THYMINE (T)

CYTOSINE (C)

GUANINE (G)

Composition of DNA

• Amount of adenine relative to guanine

differs among species

• Amount of adenine always equals amount of thymine, and amount of guanine always equals amount of cytosine

A=T and G=C

Rosalind Franklin’s Work

• Expert in x-ray crystallography

• Used technique to examine DNA fibers

Concluded that DNA was some sort of helix

The double-helix structure of the DNA molecule was discovered by _____.

1 2 3 4

58%

34%

7%

0%

1. Watson and Crick

2. Wilkins

3. Franklin

4. all of the choices

DNA Structure Allows It to Duplicate

• Two nucleotide strands held together by hydrogen

bonds

• Hydrogen bonds between two strands are easily

broken

• Each single strand serves as template for new

strand

2-nanometer diameter overall

0.34-nanometer distance between each pair of bases

3.4-nanometer length of each full twist of the double helix

In all respects shown here, the Watson–Crick model for DNA structure is consistent with the known biochemical and x-ray diffraction data.

The pattern of base pairing (A only with T, and G only with C) is consistent with the known composition of DNA (A = T, and G = C).

Fig. 9-6, p.141

DNA Models

In 1952, Franklin reported that the DNA molecule was a double helix with a

backbone formed of _____.

1 2 3 4

62%

16%12%10%

1. phosphate groups

2. purines

3. pyrimidines

4. nitrogen-containing bases

Patterns of Base Pairing

• A to T

• G to Cone base pair

or or

DNA Replication

newnew old old

• Each parent

strand remains

intact

• Every DNA

molecule is half

“old” and half

“new”

Base Pairing during

Replication

Each old strand is template for new complementary strand

Which of the following is a correct pairing of nitrogen-containing bases in DNA?

1 2 3 4

90%

3%3%4%

1. A = T

2. T = G

3. C = A

4. G = A

Enzymes in Replication

• Enzymes unwind the two strands and

complementary base pairs unzip

• DNA polymerase attaches new

complementary nucleotides

• DNA ligase fills in gaps

• Enzymes wind two strands together

DNA Repair

• Mistakes can occur during replication

• DNA polymerase reads correct

sequence from complementary strand

and, together with DNA ligase, repairs

mistakes in incorrect strand

In DNA replication, a permanent alteration in the DNA sequence is called a _____.

1 2 3 4

9%2%5%

84%1. genetic code

2. mutation

3. proofreading error

4. semiconservative replication

Which of the following statements about DNA is true?

1 2 3 4

0%

97%

2%2%

1. changes in DNA can be inherited by future generations

2. the term DNA stands for deoxyribonucleic acid

3. DNA codes all information needed to produce a human being

4. all of the choices

DNA Sequencing

• Order of fluorescent bands indicates DNA sequence

DNA Fingerprints

• Unique array of DNA fragments

• Inherited from parents in Mendelian

fashion

• Even full siblings can be distinguished

from one another by this technique

Analyzing DNA Fingerprints

• DNA is separated by gel electrophoresis

• Pattern of bands is used to

– Identify or rule out criminal suspects

– Identify bodies

– Determine paternity

A DNA Fingerprint

Clones

Cloning

• Making a genetically identical copy of

an individual

• Researchers have been creating clones

for decades

• Clones can be created by embryo

splitting (artificial twinning)

• In nucleus of differentiated cells, most DNA is

turned off

• Some DNA is turned on when nucleus is

transferred to egg cell

• New organism is genetically identical to donor of

nucleus

Clones from Adult Cells

Nuclear Transfer

• Nucleus of egg replaced with nucleus of adult cell

More Clones

• Numerous species been clonedMice, pigs, cattle, cats, etc.

• Most cloning attempts are still unsuccessful

• Many clones have defects

• Clones may vary in their phenotype

More Clones

Stem Cells

• Embryonic

• Adult

Embryonic Cells

I’m familiar with the arguments about stem cell research.

True

False

50%50%

1. True

2. False

Stem cell research is morally/ethically objectionable

I agre

e

I disa

gree

50%50%1. I agree

2. I disagree