Cells

Question 1

What are the 3 main parts of the cell?

Answer 1

1. Cell Membrane (Plasma Membrane)
2. Nucleus
3. Cytoplasm

Question 2

Cell Membrane (Plasma Membrane)

Answer 2

– made up of 2 layers of
phospholipids and cholesterol molecules. Cholesterol helps
stabilize the phospholipid molecules to prevent breakage of the
membrane
-The cell membrane is the gateway of the cell that controls the passage of materials in and out of the cell.

Question 3

Proteins in the cell membrane act as…

Answer 3

receptors that “communicate” chemical messages from hormones
that influence the function of the cell.

Question 4

Carbohydrate chains on the membrane play a part in the…

Answer 4

identification of the cell as specifically belonging to an individual. This is used during tissue typing prior to
organ transplant.

Question 5

Nucleus

Answer 5

– a small spherical structure in the central portion of the cell that is surrounded by the nuclear envelope.
It is the cell’s command center that controls every organelle in the cytoplasm.
- It contains the genetic material, the DNA (deoxyribonucleic acid)
- In the nucleus are chromatin granules which are made up of proteins (histones) around which the DNA is tightly bound.

Question 6

Nucleolus

Answer 6

• dense region of the nucleus that produces subunits that form ribosomes.

Question 7

Ribosome

Answer 7

Ribosome subunits migrate through the nuclear envelope into the cytoplasm to form ribosomes which produce proteins.

Question 8

Cytoplasm

Answer 8

– the internal living material in cells
The cytoplasm contains the following organelles:

1. Ribosomes
2. Endoplasmic Reticulum (ER)

Question 9

Endoplasmic Reticulum (ER)

Answer 9

– The ER is the transport system of the cell. It consists of a membranous
network of interconnected canals and channels that carry proteins and other substances through the cytoplasm of the cell.

• The rough ER has ribosomes attached to it. Fats, carbohydrates and proteins that make up the cell membrane are manufactured in the smooth ER.

Question 10

Golgi Apparatus

Answer 10

– consists of tiny sacs stacked
on one another near the nucleus.
It chemically processes and ‘packages’ substances from the ER, exports them in vesicles outward to the plasma membrane
Example: mucus ‘packaged’ into the plasma membrane

Question 11

Mitochondria

Answer 11

• “power plant” of the cell containing
  enzymes and substances whose reactions release energy to recharge the cell’s “battery” – the Adenosine
  Triphosphate (ATP)

Question 12

Lysosomes

Answer 12

• the “digestive bags” of the cell
  containing enzymes that break apart large food molecules through hydrolysis. Lysosomes digest and destroy microbes that invade
  the cell.

Question 13

Centrioles

Answer 13

are paired rod-shaped structures that
play an important role for moving the chromosomes during cell division

Question 14

Microvilli

Answer 14

are small finger-like projections of the plasma membrane that increases the absorptive capacity of the cell Example: intestinal microvilli

Question 15

Cilia

Answer 15

are extremely fine hair-like extensions on the exposed surface of the cell serving as “antennae” for the cell to sense its surroundings
Example: cilia in taste buds
- Some cilia are capable of moving as a group in one direction to propel mucus.
Example: cilia in respiratory tubes involved in mucociliary escalator

Question 16

flagellum

Answer 16

is a single, long projection of the cell used for movement
(Example: flagellum of the sperm cell)

Question 17

Passive Transport

Answer 17

involves the movement of substances from a high concentration to a low concentration.
- No cellular energy is required
Examples: diffusion, osmosis, filtration – movement “down a concentration gradient” until equal proportion of the substance is achieved on both sides of the membrane

Question 18

Diffusion

Answer 18

• requires big pores for the particles to pass through the cell membrane. Solute as well as water both move from high to low concentration to achieve equilibrium.
  Examples: movement of carbon dioxide from cells into blood

Question 19

Osmosis

Answer 19

is the diffusion of water (only)through selectively permeable membrane that does not allow solutes to pass through.
Example: movement of water in and out of red blood cells

Question 20

Filtration

Answer 20

• requires the force of hydrostatic pressure gradient that allows water and diffusible solutes to filter out from the solution with higher hydrostatic pressure to the solution with lower hydrostatic pressure.

Example: movement of water from plasma into renal tubules to begin formation of urine

Question 21

Active transport

Answer 21

• involves the movement of substances from a low concentration to a high concentration therefore, cellular energy from ATP is required
• Active transport occurs only through living membranes.

Examples: ion pump, phagocytosis, pinocytosis – movement of substances against a concentration gradient

Question 22

Principles in Active Transport Processes:

Answer 22

1. Ion pumps are carriers that move ions against concentration gradients. Pumps may be particular to one ion or may be “coupled” to pump two ions simultaneously
   Example: Na+/K+ pump
2. Large particles are engulfed during phagocytosis, whereas fluid and dissolved substances are brought into the cell in pinocytosis.
   Example: phagocytosis by white blood cells pinocytosis by microvilli of intestinal cells to take up nutrients

Question 23

Chromosomes

Answer 23

• housed in the cell nucleus, are
  composed of lengthy and tightly bound DNA (deoxyribonucleic acid) strands

Question 24

DNA

Answer 24

• made up of smaller sub-units called nucleotides each consisting of a sugar, phosphate and a nitrogen base. Complimentary base pairing(nitrogen-containing bases) include: adenine-thymine, cytosine – guanine – form the “rungs of the ladder”

Question 25

DNA Structure:

Answer 25

Each strand has a backbone made up of (deoxy-ribose) sugar molecules linked together by phosphate groups. Each sugar molecule is linked to one of 4 possible bases (adenine,guanine,cytosine andthymine)

Question 26

The Genes

Answer 26

DNA segments that contain hereditary information is the genetic code.

Question 27

genetic code dictates?

Answer 27

• directions for protein synthesis – structural and functional proteins.

Question 28

Proteins determine?

Answer 28

• cell structure and function and therefore the traits passed on by heredity.

Question 29

The main differences between RNA and DNA are:

Answer 29

1. RNA molecules are single-stranded
2. The sugar in RNA is a ribose sugar (as opposed to deoxyribose
   in DNA)
3. Thymine in DNA is replaced byuracil in RNA.

Question 30

Transcription in Protein Synthesis

Answer 30

In the nucleus, the DNA unwinds and messenger RNA (mRNA) copies (transcribes) the gene sequence in the DNA. The mRNA moves out of the nucleus to the cytoplasm to direct protein synthesis in the ribosomes and the ER.

Question 31

Translation in Protein Synthesis

Answer 31

• is the synthesis of proteins in the cytoplasm by ribosomes based on the information from mRNA.
  In the cytoplasm, mRNA directs the assembly of amino acids as dictated by the genetic code. The amino acid strands fold and combine with other strands to complete the protein structure.
  The shape and function of each protein in the cell is thus dictated by the DNA.

Question 32

Stages of Cell Division in Mitosis

Answer 32

1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase

Question 33

Interphase

Answer 33

The cell prepares for cell division; DNA makes a copy of itself in the process called DNA replication which ensures that genetic material would be the same for both daughter cells.

Question 34

Prophase

Answer 34

The replicated DNA strands form pairs
of chromatids (tightly coiled, “visible” chromosomes) that are held together by the centromere. In the cytoplasm,
centrioles separate and form spindle fibers.

Question 35

Metaphase

Answer 35

The chromosomes align at the center of the cell and centrioles migrate to the opposite poles of the cell. Spindle fibers attach themselves to the centromeres. The nucleolus and nuclear envelope disappear.

Question 36

Anaphase

Answer 36

The centromeres break apart and the chromosomes move away from the center of the cell. The cleavage furrow forms to divide the cell into 2 daughter cells.

Question 37

Telophase

Answer 37

The nuclear envelope and nuclei reappear; the cytoplasm and organelles divide equally resulting in two identical daughter cells each with identical genetic characteristics.