Cellular Biology

Question 1

Cell Membrane

Answer 1

Selective permeability
Readily permeable to small, nonpolar hydrophobic molecules and small polar molecules
Small charged particles are able to cross through protein channels
Charged ions and larger charged molecules cross by carrier proteins
Fluid Mosaic Model: Phospholipid bi-layer with proteins embedded

Question 2

Endoplasmic Reticulum

Answer 2

Transport of materials throughout cell, especially materials destined to be secreted by cell.
Smooth ER is involved in metabolism and production of lipids.
Rough ER is involved in protein production.

Question 3

Nucleus

Answer 3

Controls the activities of the cell, including cell division.
Contains DNA which is complexed with histone (protein) to from chromosomes.
The nucleolus is a dense structure in the nucleus where rRNA is synthesized.

Question 4

6 Kingdoms

Answer 4

Bacteria
Archaea
Protista
Fungi
Plantae 
Animalia

Question 5

Cell Theory

Answer 5

All living things are composed of cells.
Cell is basic functional unit of life.
Cells can only arise from pre-existing cells.
Cells carry genetic info in the form of DNA.

Question 6

Ribosomes

Answer 6

Site of protein production.

Synthesized by nucleolus.

Question 7

Golgi Apparatus

Answer 7

Receives vesicles and their contents from the smooth ER and then modifies them, repackaging them into vesicles and distributes them to the cell surface by exocytosis.

Question 8

Mitochondria

Answer 8

Sites of aerobic respiration.
Supply ATP.
Composed of outer and inner phospholipid bilayer.

Question 9

Cytoplasm

Answer 9

Where most of the cell’s metabolic activity occurs.
Includes cytosol (cellular fluid) and organelles.
Cyclosis: streaming movement within cell (transport).

Question 10

Vacuoles / Vesicles

Answer 10

Membrane-bound sacs involved in the transport and storage of materials that are ingested, secreted, processed or digested by the cell.
Vacuoles are larger and more likely to be found in plant cells.

Question 11

Centrioles

Answer 11

Involved in spindle organization during cell division.

Plant cells do not have centrioles.

Question 12

Lysosomes

Answer 12

Membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion.
Break down material ingested by the cell.
Autolysis: injured or dying tissue may “commit suicide” by rupturing its lysosomes membrane and releasing the hydrolytic enzymes.

Question 13

Cytoskeleton

Answer 13

Supports cell, maintains shape, and aids in cell motility.
Composed of microtubules, microfilaments, and intermediate filaments.
1. Microtubules: hallow tubes made of polymerized tubulin and provide cell with support.
Provide framework for organelle movement within cell.
2. Microfilaments: solid rods of actin, important for cell movement and support.
Move materials across plasma membrane , i.e., in contraction phase of cell division and in amoeboid movement.

Question 14

Cellular Transport: Simple Diffusion

Answer 14

Net movement of dissolved particles down their concentration gradients- from a region of higher concentration to a region of lower concentration.
Passive - does not require external source of energy.

Question 15

Cellular Transport: Osmosis

Answer 15

Simple diffusion of water from a region of lower solute concentration to a region of higher solute concentration.
Hypertonic: cytoplasm of cell has a lower solute concentration than the extracellular medium, the medium is hypertonic to cell and water will flow out of cell (plasmolysis –>cell will shrivel).
Hypotonic: extracellular environment is less concentrated than the cytoplasm of the cell, the extracellular medium is hypotonic to cell and water will flow into cell, causing it to swell and lyse.
Isotonic: extracellular environment has the same concentration of solutes as the cell cytoplasm, the cell is isotonic to the environment and water will move back and forth equally.

Question 16

Cellular Transport: Facilitated Diffusion

Answer 16

Net movement of dissolved particles down their concentration gradient through special channels or carrier proteins in the membrane.
Passive transport.

Question 17

Cellular Transport: Active Transport

Answer 17

Net movement of dissolved particles against their concentration gradients with the help of transport proteins.
Requires energy.
Aid in regulation of cell’s internal content of ions and large molecules.
Carrier molecules:
1. Energy-independent Carriers: facilitate movement of compounds along a concentration gradient.
2. Symporters: move 2+ ions or molecules in the same direction across the membrane.
3. Antiporters: exchange one or more ions/molecules for another across the membrane.
4. Pumps: energy dependent carriers (require ATP).

Question 18

Endocytosis

Answer 18

Process in which the cell membrane invaginates, forming a vesicle that contains extracellular medium.
Allows cell to bring large volumes of extracellular material inside cell.
Pinocytosis: ingestion of fluids or small particles.
Phagocytosis: engulfing of large particles.

Question 19

Exocytosis

Answer 19

Vesicle within cell fuses with cell membrane and releases a large volume of contents to the outside.
Can play a role in cell growth and intercellular signaling (synapse).

Question 20

Intracellular Circulation

Answer 20

Material move about within cell in a number of ways:

1. Brownian Movement: kinetic energy spreads small suspended particles throughout the cytoplasm of the cell.
2. Cyclosis/Streaming: circular motion of cytoplasm around the cell transports molecules.
3. ER: 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 21

Extracellular Circulation

Answer 21

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

1. Diffusion: if cells are in direct or close contact with external environment, transports food and oxygen. In larger, more complex animals, transports materials between cells and interstitial fluid.
2. Circulatory System: complex animals require a circulatory system, the cells are too far from external environment. Includes vessels and a pump.

Question 22

Interphase

Answer 22

Period of growth and chromosome replications.

90% of cell life.

Question 23

Sister Chromatids

Answer 23

After replication, 2 identical chromosomes held together at centromere.

Question 24

Chromatin

Answer 24

Uncoils DNA that is not visible during Interphase.

Question 25

Phases of Interphase

Answer 25

G1: initiates interphase, active growth phase, increases in size and synthesizes proteins.
S: period of DNA synthesis.
G2: cell prepares to divide, grows and synthesizes proteins.
M: mitosis or meiosis occurs

Question 26

Mitosis

Answer 26

The division and distribution of the cell’s DNA to its 2 daughter cells.
Occurs in somatic cells
Nuclear division (karyokinesis) is followed by cell division (cytokinesis).
Prophase, Metaphase, Anaphase, Telophase (PMAT)

Question 27

Prophase

Answer 27

Chromosomes condense.
Centriole pairs (animals) separate and move toward opposite poles of cell.
Spindle apparatus forms between them, and nuclear membrane dissolves.

Question 28

Metaphase

Answer 28

Centriole pairs are now at opposite poles of cell.
Fibers of spindle apparatus attach to each chromatid at its corresponding kinetochore (protein located on centromere).
Spindle fibers align chromosomes at the equator forming the metaphase plate.

Question 29

Anaphase

Answer 29

Centromeres split, allowing sister chromatids to separate.

Sister chromatids are pulled toward the opposite poles of the cell by shortening spindle fibers.

Question 30

Telophase

Answer 30

Spindle apparatus disappears.
Nuclear membrane forms around each set of newly formed chromosomes.
Diploid (2N)
Chromosomes uncoil.

Question 31

Cytokinesis

Answer 31

Near the end of telophase the cytoplasm divides into 2 daughter cells, each with a complete nucleus and its own set of organelles
Animals: a cleavage furrow forms and the cell membrane indents along the equator of the cell, pinching through the cell and separating the 2 nuclei.
Plants: a cell plate forms between the 2 nuclei, splitting the plant cell in half and allowing the cell to divide.

Question 32

Meiosis

Answer 32

Process by which sex cells are produced.
Like mitosis, the cell duplicated its chromosomes before undergoing the process.
Unlike mitosis, meiosis results in haploid cells (1N).

Question 33

First Meiotic Division

Answer 33

Produces 2 intermediate daughter cells with N chromosomes and sister chromatids.

Question 34

Prophase I

Answer 34

Homologous chromosomes come together and intertwine in a process called synapsis.
Each synaptic pair of homologous chromosomes contains 4 chromatids and is called a tetrad.

Question 35

Crossing Over

Answer 35

Sometimes chromatids of homologous chromosomes break at corresponding points and exchange equivalent pieces of DNA.
Chiasmata: points of contact between homologous chromosomes where crossing over can occur.
Does not occur between sister chromatids of the same chromosomes (bc they are identical, no genetic variation).
Occurs in Prophase I.

Question 36

Metaphase I

Answer 36

Homologous pairs (tetrads) align at the equatorial plane, and each pair attaches to a separate spindle fiber at the kinetochore.

Question 37

Anaphase I

Answer 37

Homologous pairs separate and are pulled to opposite poles of cell (disjunction).
Each chromosome of paternal origin separates from its homologous of maternal origin, and either chromosome can end up in either daughter cell.
Each daughter cell will have a unique pool of genes from a random mixture of maternal and paternal origin.

Question 38

Nondisjunction

Answer 38

Occurs when cells do not separate appropriately during meiosis.
Occurs during anaphase

Question 39

Telophase I

Answer 39

Nuclear membrane forms around each new nucleus.

Each chromosome still consists of sister chromatids joined at the centromere.

Question 40

Second Meiotic Division

Answer 40

Meiosis II is not preceded by chromosomal replication.
The chromosomes align at the equator, separate and move to opposite poles, and are surrounded by a reformed nuclear membrane.
The new cells have a haploid number of chromosomes.
In women, only one of these daughter cells becomes a functional gamete, the others are destroyed by the body.