DC BIO Exam 3

What are cells?

the basic structural and functional units of every organism

What do ALL cells have in common?

1. bound by a plasma membrane

2. contain cytosol

3. contain chromosomes (DNA)

4. contain ribosomes

What are the two types of cells?

prokaryotes and eukaryotes

Differences between prokaryotes and eukaryotes

Prokaryotes:

archaea and bacteria; DNA is in nucleoid region; smaller size

Eukaryotes:

protists, fungi, animals & plants; DNA in nucleus; contains membrane bound organelles; bigger size

What are organelles?

membrane bound structures within eukaryotes

The two classifications of organelles?

endomembrane organelles and energy organelles

What are the endomembrane organelles?

1. Nuclear envelope

2. Endoplasmic reticulum

3. Golgi complex

4. Lysosomes

5. Vesicles/vacuoles

6. Plasma membrane

What are the energy organelles?

1. Mitochondria

2. Chloroplasts

Compartmentalization

the separation of the cell interior into distinct compartments with specific local conditions that allow the simultaneous metabolic reactions and processes; increases surface area

What are the two main eukaryotic cells?

plant and animal

Unique components of plant cells

chloroplasts, central vacuole, cell wall, plasmodesmata (pores between cells)

Unique components of animal cells

lysosomes, centrosomes, flagella

Nucleus

contains chromosomes and a nucleolus;

enclosed by nuclear envelope (double membrane);

has pores (regulates entry/exit of materials)

Nucleolus

dense region in the nucleus where ribosomes are made

How are ribosomes made?

rRNA is synthesized in the nucleolus --> then combined with proteins to form large/small subunits of ribosomes --> subunits exit via nuclear pores and assemble into ribosomes

Ribosomes

comprised of rRNA (ribosomal RNA) and protein;

function: synthesizes proteins

Where can ribosomes be found?

1. cytosol (known as free ribosomes)

2. bound to ER or nuclear envelope

Proteins produced from ribosomes in the cytosol...

generally function only within the cytosol

Proteins produced from ribosomes bound to the ER/nuclear envelope...

can be secreted from the cell

Endoplasmic Reticulum

a network of membranous sacs & tubes;

function:

synthesize membranes; compartmentalize the cell to keep proteins formed in the rough ER separate from those of free ribosomes

What are the two types of endoplasmic reticulum?

rough and smooth

Rough Endoplasmic Reticulum

contains ribosomes that are bound to ER membrane

Smooth Endoplasmic Reticulum

contains no ribosomes;

synthesizes lipids;

metabolizes carbohydrates;

detoxifies the cell

Golgi Complex

contains flattened membranous sacs called cisternae (each cisternae are not connected);

has directionality (cis & trans face);

Functions of the Golgi Complex

1. receives transport vesicles with materials from the ER

2. modifies the materials (ensures proteins are folded/modified correctly)

3. sorts the materials

4. adds molecular tags

5. packages materials into new transport vesicles that exit the membrane via exocytosis

The Cis Face of the Golgi Complex...

RECEIVES vesicles from the ER (incoming)

The Trans Face of the Golgi Complex...

SENDS vesicles back out into cytosol to other locations or to the plasma membrane for secretion (away)

Lysosomes

membranous sac with hydrolytic enzymes (breaks things down);

function:

hydrolyzes macromolecules in animal cells for autophagy

What is autophagy?

recycling the cell's own organic material allowing it to renew itself

Peroxisomes

membrane-bound metabolic compartment (similar to lysosomes)

function:

catalyzes reactions that produce H2O2 (hydrogen peroxide);

enzymes in peroxisomes then break down H2O2 to water

Vacuoles

large vesicles that stem from the ER and Golgi; selective in transport;

types:

1. food vacuole

2. contractile vacuole

3. central vacuole

Food vacuole

forms from phagocytosis (cell eating) and then is digested by lysosomes

Contractile vacuole

maintains water levels in cells (pumps water out)

Central vacuole

found in plants, contains inorganic ions and water, important for turgor pressure

Endosymbiont Theory

explains the similarities mitochondria and chloroplast have to a prokaryote;

states that an early eukaryotic cell ate up a prokaryotic cell; prokaryotic cell lived in the eukaryotic cell and became one functional organism over time

Evidence of endosymbiont theory

double membrane

ribosomes

circular DNA

capable of functioning on their own

Mitochondria

site of cellular respiration; double membrane

of mitochondria in a cell correlates with metabolic activity (muscles will have more)

Structure of mitochondria's double membrane

1. smooth outer membrane

2. the inner membrane has folds called cristae; increases surface area; divided into two compartments

• intermembrane

• mitochondrial matrix

Intermembrane of mitochondria

space between inner and outer membrane

Mitochondrial matrix

enclosed by inner membrane; location for Krebs cycle

contains:

1. enzymes that catalyze cellular respiration and produce ATP

2. mitochondrial DNA

3. ribosomes

Chloroplasts

specialized organelles in photosynthetic organisms; the site for photosynthesis; contains green pigments called chlorophyll

Structure of chloroplast's double membrane

thylakoids:

membranous sacs that organize into stacks called grana where light-dependent reactions occur