Chapter 5 - Cellular Biology

Question 1

What is the fundamental unit of all living things?

Answer 1

TheDCell.

Question 2

Describe the 5 aspects of The Cell Theory:

Answer 2

1) All living things are composed of cells.
2) The cell is the basic functional unit of life.
3) The chemical reactions of life take place inside the cell.
4) Cells arise only from pre-existing cells.
5) Cells carry genetic info in the form of DNA - This genetic material is passed from parents cell to daughter cell.

Question 3

What organelles can be located within cells?

Answer 3

Nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, vesicles, vacuoles, lysosomes, mitochondria, chloroplasts, and centrioles.

Question 4

What are the 6 Kingdoms?

Answer 4

1) Bacteria
2) Archaea
3) Protista
4) Fungi
5) Plantae
6) Animalia

Question 5

Describe prokaryotes vs. eukaryotes:

Answer 5

1) Prokaryotes
- “Before nucleus”
- Lack membrane-bound nuclei and organelles
- Consist mostly of ribosomes and genetic material

Question 6

Describe the cell membrane in relation to its permeability, the fluid mosaic model, and carrier proteins:

Answer 6

The cell membrane encloses the cell and exhibits selective permeability which regulates passage of materials into and out of the cell.

The fluid mosaic model describes the cell membrane having a phospholipid membrane bilayer that has proteins embedded throughout.

• The phospholipid bilayer is arranged such that long, non-polar, hydrophobic fatty chains of carbon and hydrogen face each other (water-free region), with the phosphorous-containing, polar, hydrophilic heads facing outward (water region).
• This results in permeability to small, non-polar, hydrophobic molecules while larger and polar molecules cross the membrane via carrier proteins.

Question 7

Describe the nucleus in regard to histones, chromosomes, nucleolus, and ribosomal RNA:

Answer 7

The nucleus controls all activities of the cell and is surrounded by a nuclear membrane - it contains the DNA which is complexed with structural proteins called histones that form chromosomes.
- DNA winds around histones to be compact, and the histones are involved with regulation of gene transcription.

The nucleolus is a dense structure in the nucleus where ribosomal RNA synthesis occurs.

Question 8

Describe the ribosome in relation to production, synthesized, and free vs. bound ribosomes:

Answer 8

Ribosomes are the sites of protein production and synthesized by the nucleolus.

• Free ribosomes are found in the cytoplasm
• Bound ribosomes are found in he outer membrane of the endoplasmic reticulum

Question 9

Describe the endoplasmic reticulum in relation to smooth vs. rough ER:

Answer 9

The ER is a network of membrane-enclosed spaces involved in transport of materials throughout the cells, mostly destined to be secreted.

• Smooth ER does not contain ribosomes and is involved with metabolism and production of lipids
• Rough ER contains ribosomes and is involved with protein production

Question 10

Describe the Golgi apparatus:

Answer 10

The Golgi apparatus receives vesicles and their contents from smooth ER and packages them into vesicles to be distributed to the cell surface for exocytosis.

Question 11

Describe the mitochondria:

Answer 11

The mitochondria is the site of aerobic respiration within the cell and supplies energy in the form of ATP
- They have an outer and inner phospholipid bilayer

Question 12

Describe the cytoplasm:

Answer 12

Most of the cell’s metabolic activity occurs in the cytoplasm, which includes the cytosol and cellular organelles.
- Transport within the cytoplasm occurs via cyclosis

Question 13

Describe the vacuoles/vesicles:

Answer 13

They are membrane bound sacs involved in transport and storage of materials ingested, secreted, processed, or digested by the cell
- Vacuoles are larger than vesicles and are more likely to be found in plant rather than animal cells

Question 14

Describe centrioles:

Answer 14

Centrioles are composed of microtubules and are involved in spindle organization during cell division

• Not bound by a membrane
• Animals cells have a pair of centrioles organized at right angles to one another in a region called the centrosome
• Regulate progression of cell cycle
• Plant cells do not contain centrioles

Question 15

Describe lysosomes:

Answer 15

Lysosomes are membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion

• Break down ingested material
• Injured/dying cells will self-destruct by rupturing the lysosome membrane and releasing the hydrolytic enzymes (autolysis)

Question 16

Describe the cytoskeleton in relation tubulin, cilia, flagella, and actin:

Answer 16

The cytoskeleton supports the cell, maintains shape, and aids in motility - it is composed of microtubules, microfilaments, and intermediate filaments.

• Microtubules are hollow rods made up of polymerized tubulin that radiate throughout cell and provide support and organelle movement (ex. controls, cilia, flagella)
• Microfilaments are solid rods of actin which are important for cell movement and support, and move materials across the plasma membrane (ex. muscle contraction)

Question 17

What types of cellular transport is there?

Answer 17

1) Active

2) Passive

Question 18

What is simple diffusion? Energy required?

Answer 18

Net movement of dissolved particle down their concentration gradients from a region of higher concentration to a region of lower concentration.
- Passive process = requires no energy

Question 19

Describe osmosis in relation to hypertonic vs. hypotonic vs. isotonic:

Answer 19

Simple diffusion of water from region of lower solute concentration to region of higher solute concentration

• Hypertonic: Cytoplasm of cell has lower solute concentration than ECM (cell shrivels)
• Hypotonic: ECM is less concentrated than cytoplasm of the cell (lyse/swell)
• Isotonic: ECM has same concentration as cytoplasmic of cell

Question 20

What is facilitated diffusion?

Answer 20

The net movement of dissolved particles down their concentration gradient through special channels or carrier proteins in the cell membrane
- Does not require energy

Question 21

What is active transport? Symporters vs. antiporters vs. pumps?

Answer 21

The net movement of dissolved particles against their concentration gradients with the help of transport proteins

• Requires energy
• Carrier molecules aid in regulation of cell’s internal content of ions and large molecules
• Symporters: Move two or more ions or molecules in the same direction across membrane
• Antiporters: Exchange one or more ions for another ion or molecule across the membrane
• Pumps: Energy dependent carriers (ATP) - Ex. NA/K Pumps

Question 22

What is endocytosis? Pinocytosis vs phagocytosis?

Answer 22

It is a process in which the cell membrane invaginate, forming a vesicle that contains the ECM that allows the cell to bring in large volumes of ECM inside the cell

• Particles may first bind to receptors on the cell membrane before being engulfed
• Pinocytosis: Ingestion of fluids or small particles
• Phagocytosis: Engulfing of large particles

Question 23

What is exocytosis?

Answer 23

A vesicle within the cell fuses with the cell membrane and released a large volume of contents to the outside
- Fusion of the vesicle within the cell membrane can play an important role in cell growth and intercellular signalling

Question 24

Describe intracellular circulation in relation to Brownian vs. Cyclosis vs. Endoplasmic Reticulum:

Answer 24

Materials that move about within a cell in a number of ways:

• Brownian Movement: Kinestic energy spreads small suspended particles throughout the cytoplasm
• Cyclosis or Streaming: The circular motion of cytoplasm around the cell transports molecules
• Endoplasmic Reticulum: The ER forms a network of channels throughout the cytoplasm and provides a direct continuous passageway from the plasma membrane to the nuclear membrane

Question 25

Describe extracellular circulation in relation to diffusion vs. circulatory system:

Answer 25

A number of systems deal with the movement of materials on a larger scale throughout the body of an organism:

• Diffusion: Cells that are close or in direct contact, diffusion can serve as efficient way to transport food/oxygen
• Circulatory System: Complex organisms who’s cells are far apart require a circulatory system which includes vessels and a pump to drive circulation

Question 26

What is cell division? Unicellular vs. multi-cellular? What are the 2 different courses it may follow?

Answer 26

Cell division is the process by which a cell doubles its organelles and cytoplasm, replicates its DNA and then divides in two.

• Unicellular: Cell division is a means of reproduction
• Multicellular: Method of growth, development, and replacement of worn-out cells

1) Mitosis
2) Meiosis

Question 27

What is important to know about interphase?

Answer 27

Each course of cell division is preceded by interphase.

Question 28

What is interphase? What does it do? What happens after replication? Are chromosomes visible here?

Answer 28

Interphase is a period of growth and chromosome replication - a cell spends 90% of is life here.

• Cell performs normal cellular functions, and each chromosome is replicated so that during division a complete copy of the genome can be distributed to both daughter cells
• After replication, the chromosomes consist of two identical sister chromatids held together at a central region (centromere)
• During interphase the individual chromosome is not visible; the DNA is instead coiled (chromatin)

Question 29

What are the 3 phases of interphase?

Answer 29

1) G1 - Initiation of interphase; the active growth phase and varies in length. The cell increases in size and synthesizes proteins. Length of this phase determines length of the entire cell cycle.
2) S - Period of DNA synthesis.
3) G2 - Cell prepares to divide; it grows and synthesizes proteins.

Question 30

What is the last phase of the cell cycle? What does it typically result in?

Answer 30

The M-Phase

- Mitosis or meiosis may occur here which generally result in 2 identical or 4 non-identical daughter cells.

Question 31

What is mitosis? Where does it take place? What is nuclear vision followed by?

Answer 31

It is the division and distribution of cell’s DNA to its two daughter cells such that each cell receives a complete copy of the original genome.

• Takes place in somatic cells
• Nuclear division (karyokinesis) is followed by cell division (cytokinesis)

Question 32

What are the 5 phases of mitosis? Describe each.

Answer 32

1) Prophase
- Chromosomes condense and centriole pairs separate and move toward opposite poles of the cell
- Spindle apparatus forms btw them and the nuclear membrane dissolves allowing the spindle fibers to interact with the chromosomes

2) Metaphase
- Centriole pairs are now at opposite poles of the cells
- Fibers of spindle apparatus attach to each chromatid at its corresponding kinetochore, a protein location on the centromere
- The spindle fibers align the chromosomes at the centre of the cell forming the metaphase plate

3) Anaphase
- The centromeres split so each chromatid has its own distinct centromere, thus allowing sister chromatids to separate
- The sister chromatids are pulled toward the opposite poles of the cell by the shortening of the spindle fibers (composed of microtubules)

4) Telophase
- Spindle apparatus disappears
- Nuclear membrane reforms around each newly formed chromosome
- Each nucleus contains same number of chromosomes (2N - Diploid) as the original parent nucleus
- Chromosomes uncoil, resuming their interphase form

5) Cytokinesis
- End of telophase, cytoplasm divides into 2 daughter cells, each with a complete nucleus and its own set of organelles
- Animal cells = cleavage furrow forms and cell membrane indents, eventually pinching through the cell and separating the two nuclei
- Plant cells = cell plate forms between two nuclei, effectively splitting the plant cell in half and allowing the cell to divide

Question 33

What is meiosis? How is it similar and different from mitosis? What does it involve?

Answer 33

Sexual reproduction differs from asexual reproduction in that there are two parents involved. Sexual reproduction occurs via the fusion of 2 gametes - Meiosis is the process by which these sex cells are reproduced.

• Similar to mitosis in that the cell duplicates chromosomes before undergoing the process, however, mitosis preserves diploid number… meiosis provides haploid (1N) cells, halving the number of chromosomes
• Meiosis involves 2 divisions of primary sex cells, resulting in 4 haploid cells called gametes

Question 34

Describe interphase during meiosis:

Answer 34

As in mitosis, parent cell chromosomes replicated and result in 2N number of sister chromatids

Question 35

Describe the first meiotic division:

Answer 35

First division produces 2 intermediate daughter cells with N chromosomes and sister chromatids

1) Prophase 1
- Chromatin condenses into chromosomes, spindle apparatus forms, and the nucleoli and nucleus membrane disappear
- Homologous chromosomes come together and intertwine (synapsis)
- Each synaptic pair of homologous chromosomes contain 4 chromatids (tetrad)
- Sometimes homologous chromatids exchange DNA (crossing over)
- Recombination results in increased genetic diversity

2) Metaphase 1
- Homologous pairs (tetrads) align in the middle and each pair attaches to a separate spindle fiber at the kinetochore

3) Anaphase 1
- Homologous pairs separate and are pulled to opposite poles (disjunction) which accounts for Mendelian law - This is where each chromosome of paternal origin separates from its homage of maternal origin, and either chromsome can end up in either daughter cell… thus, the distribution of homologous chromosomes to the two intermediate daughter cells is random with respect to parental origin
- Each daughter cell will have a unique pool of genes from a random mixture of maternal and paternal origin

4) Telophase 1
- Nuclear membrane forms around each new nucleus
- Each chromosome still consists of sister chromatids jointed at the centromere

Question 36

Describe the second meiotic division:

- What occurs in women?

Answer 36

Very similar to mitosis, except the meiosis II is not preceded by chromosomal replication.

• Chromosomes align at middle, separate, and move to opposite poles, and are surrounded by a re-formed nuclear membrane
• New cells have haploid number of chromosomes
• In women = one of the daughter cells becomes functional gametes; other two are destroyed by the body

Question 37

What is non-disjunction?

Answer 37

Occurs when cells do not separate appropriately

- Each chromosome consists of sister chromatids joined at the centromere