The Cell

Question 1

Four basic tenets of The Cell Theory (Which ones were the first 3?)

Answer 1

1. All living things are composed of cells.
2. The cell is the basic functional unit of life.
3. Cells arise only form preexisting cells.
4. Cells carry genetic info in the form of DNA. Passed down from parent to daughter cell.

Question 2

The Cell Membrane is made up of…?

what are the functions of each.

Answer 2

1. Phospholipids (their heads are hydrophilic and their tails are hydrophobic) they for a phospholipid bilayer.
2. Cholesterol (makes the cell more fluid and durable, no matter the weather.
3. Embedded proteins.
4. Carbohydrates (bound to proteins form glycoproteins, bound to lipids from glycolipids) they are unique to each cell and help cells recognize one another.

Question 3

Why the cell membrane is sometimes referred as Fluid Mosaic Model?

Answer 3

The cholesterol and proteins in the membrane are not static, they float horizontally along the phospholipid bilayer.

Question 4

What organelles are membrane bound?

What does membrane help to do on organelles?

Answer 4

1. Nucleus
2. Mitochondria
3. Lysosomes
4. RER & SER
5. Golgi Apparatus
6. Peroxisomes
   Membrane allows for compartmentalization of functions.

Question 5

Nucleus (Room where the blueprints are kept)

Answer 5

Short version –> DNA Storage

1. Control center of the cell.
2. Contains all the genetic material necessary for replication of the cell.
3. Surrounded by the envelope which has nuclear pores: allows for the selective 2-way exchange of material btw cytoplasm and nucleus.
4. It has a subsection called the Nucleolus where the rRNA is synthesized.

Question 6

Mitochondria (Powerplant)

Answer 6

Short version –> Energy production

1. Is the power plant of the cell, in reference to their important metabolic functions
2. Outer membrane serves as a barrier between the cytosol and the inner environment of the mitochondrion .
3. Inner membrane, has numerous foldings called Cristae, contains molecules and enzymes necessary for the ETC.
   - The cristae is a highly convoluted structure that increases the surface area available for ECT enzymes.
4. Keeps cell alive by providing energy
5. Capable of killing the cell by releasing enzymes from ECT. Kick-starts apoptosis

Question 7

The serial Endosymbiosis theory

Answer 7

Attempts to explain the formation of some of the membrane-bound organelles; it assumes (posits) that these organelles formed by the engulfing of one prokaryote by another and the establishment of a symbiotic relationship between the two.

• Mitochondria is semi-autonomous: contains some of their own genes and replicates independently of the nucleus via binary fission.
  
  • Thought to have evolved from an anaerobic prokaryote engulfing an aerobic prokaryote. (extracellular inheritance)

Question 8

Lysosomes (Recycling and security)

Answer 8

Short version –> Protein destruction

1. Cell’s recycling center
2. Spheres full of enzymes ready to hydrolyze (chop up the chemical bonds of) whatever substance crosses the membrane, so the cell can reuse the raw material.
3. Enzymes only function on a pH of 5 - acts as safety mechanism for the rest of the cell; if the lysosome were to somehow leak or burst, the degradative enzymes would inactivate before they chopped up proteins the cell still needed.

Question 9

RER (Primary production line - makes the toys)

Answer 9

Short version –> Protein production; in particular for export out of the cell.

1. its surface is studded with ribosomes, the molecules in charge of protein production (translation)
2. ribosome finds a specific RNA segment, segment may tell the ribosome to travel to the RER and embed itself.
3. The protein created from this segment will find itself inside the lumen of the RER, where it folds and is tagged with a molecule (usually carbohydrate) in a process known as glycosylation that marks the protein for transport to the Golgi apparatus.
4. Proteins made in the rough endoplasmic reticulum are destined to either be a part of a membrane, or to be secreted from the cell membrane out of the cell. Thus, the rough endoplasmic reticulum helps cells specialize

Question 10

SER (Accessory production - makes decorations for the toy, etc.)

Answer 10

Short version –> Lipid production; Detoxification

1. Makes lipids and steroids: fat-based molecules that are important in energy storage, membrane structure, and communication (steroids can act as hormones).
2. Also responsible for detoxifying the cell.
3. Metabolizes carbohydrates.
4. Every cell has a SER, but the amount will vary with cell function. For example, the liver, which is responsible for most of the body’s detoxification.
5. Not necessarily continuous with the nuclear envelope

Question 11

Golgi apparatus (Shipping department, sends our product to customers)

Answer 11

Short version –> Protein modification and export

1. It is responsible for packing proteins from the rough endoplasmic reticulum into membrane-bound vesicles
2. Which then translocate to the cell membrane.
3. At the cell membrane, the vesicles can fuse with the larger lipid bilayer, causing the vesicle contents to either become part of the cell membrane or be released to the outside.

Question 12

The different molecules packed in the Golgi apparatus go to different places, which ones.

Answer 12

1. Cytosol: the proteins that enter the Golgi by mistake are sent back into the cytosol
2. Cell membrane: proteins destined for the cell membrane are processed continuously. Once the vesicle is made, it moves to the cell membrane and fuses with it.
   - Molecules in this pathway are often protein channels which allow molecules into or out of the cell, or cell identifiers which project into the extracellular space and act like a name tag for the cell.
3. Secretion: some proteins are meant to be secreted from the cell to act on other parts of the body. Before these vesicles can fuse with the cell membrane, they must accumulate in number, and require a special chemical signal to be released
4. Lysosome:Vesicles sent to this acidic organelle contain enzymes that will hydrolyze the lysosome’s content.

Question 13

Peroxisomes (Security and waste removal)

Answer 13

Short version –>Lipid Destruction; contains oxidative enzymes

Contains catalase which is able to break down Hydrogen Peroxide H2O2 turning it into water and oxygen.

1. Like the lysosome, the peroxisome is a spherical organelle responsible for destroying its contents.
2. Unlike the lysosome, which mostly degrades proteins, the peroxisome is the site of fatty acid breakdown.
3. It also protects the cell from reactive oxygen species (ROS) molecules which could seriously damage the cell. EX: H2O2

Question 14

What are reactive oxygen species (ROS) molecules which could seriously damage the cell

Answer 14

1. ROSs are molecules like oxygen ions or peroxides that are created as a byproduct of normal cellular metabolism, but also by radiation, tobacco, and drugs.
2. They cause what is known as oxidative stress in the cell by reacting with and damaging DNA and lipid-based molecules like cell membranes.
3. These ROSs are the reason we need antioxidants in our diet.

Question 15

Transcription

Translation

Answer 15

1. Transcription: making a complementary strand of RNA from DNA, is completed within the nucleus
2. Translation: making protein from RNA instructions, takes place in the cytoplasm.

Question 16

Nucleolus

Answer 16

1. It is not bound by a membrane, so it is not an organelle.
2. This space forms near the part of DNA with instructions for making ribosomes, the molecules responsible for making proteins.
3. Ribosomes are assembled in the nucleolus, and exit the nucleus with nuclear pores.

Question 17

Cytoskeleton

Answer 17

1. Within the cytoplasm there is network of protein fibers known as the cytoskeleton.
2. This structure is responsible for both cell movement and stability. Helps maintain the shape.
3. The major components of the cytoskeleton are microtubules, intermediate filaments, and microfilaments.

Question 18

Microtubules

Answer 18

1. Microtubules are small tubes made from the protein tubulin (alpha and beta).
2. These tubules are found in cilia and flagella, with a 9+2 arrangement. C-> movement of materials / F-> movement of the cell itself.
3. They also help provide pathways for secretory vesicles to move within the cell. (important internal transport in neurons)
4. Involved in cell division as they are a part of the mitotic spindle (9+3 arrangement)

Question 19

Intermediate filaments

Answer 19

1. Provides structural support to the cell. Helps resist mechanical stress (como el resorte del colchón)
2. Smaller than the microtubules, but larger than the microfilaments, the intermediate filaments are made of a variety of proteins such as keratin, Desmin, Vimentin, Lamins and/or neurofilament
3. Cell-to-cell adhesion
4. Helps anchor other organelles
5. Help provide structure to the nuclear envelope

Question 20

Microfilaments

Answer 20

1. Microfilaments are the thinnest part of the cytoskeleton, found in the cytoplasm and are made of actin
2. Movement of the cell (from within, not like cilia or flagella, moves like an amoeba). by polymerization and depolymerization of actin.
   - polymerization lengthens the microfilament and depolymerization shortens the microfilament. That is why microfilaments are dynamic.
3. Can cause muscle contraction through the interactions with myosin.
4. Help form the cleavage furrows during cytokinesis in mitosis.

Question 21

Actin

Answer 21

1. a highly-conserved protein that is actually the most abundant protein in most eukaryotic cells
2. Actin is both flexible and strong, making it a useful protein in cell movement
3. In the heart, contraction is mediated through an actin-myosin system.

Question 22

Chloroplasts

Answer 22

1. Chloroplasts, organelles that resemble mitochondria and are responsible for turning sunlight into useful energy for the cell (this is like factories that are powered by energy they collect via solar panels).

Question 23

Epithelial tissue

Answer 23

1. Consists of tightly packed sheets of cells that cover surfaces—including the outside of the body—and line body cavities.
2. Because they are tightly packed, this lets them act as barriers to the movement of fluids and potentially harmful microbes
3. in some organs they are involved in absorption, secretion and sensation.
4. Diverse, and serve numerous of functions depending on the organ.
   - They mostly constitute the functional part of the organ (parenchyma).
5. They are polarized meaning that they have a top and a bottom side. The apical, top, side of an epithelial cell faces the inside of a cavity or the outside of a structure and is usually exposed to fluid or air. The basal, bottom, side faces the underlying cells.

Question 24

Type and shape of epithelial cells

Answer 24

1. Simple epith.
2. Stratified epith.
3. Pseudostratified Epith.
   - Cuboidal
   - Columnar
   - Squamous