Biology Exam

Cells

The basic structural and functional units of every organism.

All cells consist of the following:

1. Bound by a plasma membrane

2. Contain cytosol

3. Contain chromosomes

4. Contain ribosomes

What are the two types of cells?

Prokaryote and Eukaryotes

Prokaryotes:

1. Domains bacteria and archaea

2. DNA is in the nucleoid region

3. Generally smaller in size than eukaryotes

Eukaryotes:

1. Protists, fungi, animals, and plants

2. DNA is in the nucleus

3. Contain membrane bound organelles

Organelles:

Membrane bound structures in eukaryotes.

Endomembrane organelles:

1. Nuclear envelope

2. Endoplasmic reticulum

3. Golgi complex

4. Lysosomes

5. Vesicles/Vacuoles

6. Plasma membrane

Energy organelles:

Chloroplasts and Mitochondria.

Compartmentalization:

Allows for different metabolic reactions to occur in different locations.

Increases surface area for reactions to occur.

Prevents interfering reactions from occurring in the same location.

Unique cell components for plants:

1. Chloroplasts

2. Central vacuole

3. Cell wall

4. Plasmodesmata

Unique cell components for animals:

1. Lysosomes

2. Centrosomes

3. Flagella

Nucleus:

1. Contrains chromosomes

2. Enclosed by the nuclear envelope

3. Double membrane

4. Has pores that regulate entry and exit of materials from the cell

What is within the nucleus?

Contains a nucleolus.

What is a nucleolus?

A dense region where ribosomal rRNA is synthesized.

How is rRNA synthesized?

rRNA is combined with proteins to form large and small subunits of ribosomes which exit view nuclear pores.

What do ribosomes do?

They translate messages found on mRNA into the primary structure of polypeptides.

Transcription and Translation:

How DNA leaves the nucleus

Ribosomes:

Comprised of ribosomal RNA and protein
Function: Synthesiszes protiens.

Not membrane bound.

Which two places can you find ribosomes?

Cytosol - free ribosomes and ER bound ribosomes.

Endoplasmic Reticulum:

A network of membranous sacs and tubes

Synthesize membranes

Compartmentalize the cell to keep proteins formed in the rough ER from those of free ribosomes

Two types or ER:

Smooth ER and Rough ER

Smooth ER:

Had no ribosomes

Synthesizes lipids, metabolizes carbohydrates, and detoxifies the cell

Rough ER:

Contains ribosomes bound to the ER membrane

Golgi Complex:

Contains flattened membranous sacs called cisternae,

Separates the sacs from the cytosol,

Each cisternae is not connected,

Had directionality - Cis face receives vesicles from the ER and Trans face sends vesicles back out into cytosol to other locations or to the plasma membrane for secretion.

Functions of Golgi Complex:

Functions:
1. Revieves the transport vesicles with materials from the ER

2. Modifies the materials

3. Sorts the materials

4. Adds molecular tags

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

Lysosomes:

Membranous sac with hydrolytic enzymes

Function of Lysosomes:

Hydrolyzes macromolecules in animal cells,

Autophagy - Allows the cell to renew itself.

Autophagy:

Lysosomes can recycle their own cell’s organic materials

Peroxisomes:

Similar to lysosomes, membrane bound metabolic compartment,

Catalyze reactions that produce H202 which is then broken down into water by enzymes.

Vacuoles:

Large vesicles that stem from the ER and the Golgi

Types of vacuoles:

Food vacuole - formed from phagocytosis,

Contractile vacuole - maintain water levels in cell,

Central vacuole - found in plants, contains inorganic water and ions important for turgor pressure.

Endosymbiote Theory

The theory that explains the similarities mitochondria and chloroplasts have to a prokaryote.

What does the endosymbiote theory say?

It states that an early eukaryotic cell engulfed a prokaryotic cell and then became a functional orgamism.

What is the evidence for the endosymbiote theory?

1. Double membrane

2. Ribosomes

3. Circular DNA

4. Capable of functioning on their own

Mitochondira:

The site of cellular respiration

Structure of double membrane

Outer membrane is smooth

Inner membrane has folds called cristae that increase surface area and divides the inside into two compartments.

Mitochondira intermembrane:

Space between inner and outer membrane.

Mitochondrial matrix:

Enclosed by inner membrane,

Location for the Krebs Cycle,

Contains:
Enzymes that catalyze cellular respiration and produce ATP,

Mitochondrial DNA,

Ribosomes

What does the number of mitochondria in a cell correlate to?

It correlates with metabolic activity.
Therefore, cells with high metabolic activity have a large amount of mitochondria.

Chloroplasts:

Specialized organelles in photosynthetic organisms,

Site of photosynthesis,

Contains the green pigment chlorophyll.

what is inside of the chloroplast’s double membrane?

Thylakoids.

What are Thylakoids/Grana?

Thylakoids are membranous sacs that can organize into stacks called grana,

These grana are responsible for light dependent reactions.

Stroma:

Fluid around thylakoids,

Location for the Calvin cycle,

Contains:

1. Chloroplast DNA

2. Ribosomes

3. Enzymes

Cytoskeleton:

A network of fibers throughout the cytoplasm that gives structural and mechanical support,

They anchor organelles,

They allow for movement of the cell or vesicles by interacting with motor proteins.

What are the 3 types of fibers in the cytoskeleton?

1. Microtubules

2. Microfilaments

3. Intermediate filaments

Microtubules:

Hollow rod-like structures made of the protein tubulin,

Grow from the centrosome,

Assist in microtubule assembly.

What are the functions of microtubules?

They serve as structural support for the movement of organelles that are interacting with motor proteins,

They assist in the separation of chromosomes during cell division,

Cell motility (i.e. cilia and flagella)

Microfilaments:

Thin solid rods made of the protein actin.

Functions of microfilaments:

They maintain cell shape,

Bear tension,

Assist in muscle contraction and cell motility,

Actin works with another protein called myosin to cause a contraction,

Division of animal cells,

Contractile ring of the cleavage furrow.

Intermediate filaments:

Fibrous proteins made up of varying subunits,

Permanent structural elements of cells

Functions of intermediate filaments:

Maintain cell shape,

Anchor nucleus and organelles,

Form the nuclear lamina,

Lines the nuclear envelope.

Plasma membrane:

Separates the internal cell environment from the external environment,

It is comprised primarily of phospholipids which are amphipathic which means hydrophilic heads and hydrophobic tails.

Selective permeability:

The ability of membranes to regulate the substances that enter and exit.