Cell

Question 1

What is a cell?

Answer 1

The smallest unit that can live on its own and that makes up all living organisms and tissues of the body

Question 2

What are the types of cell division?

Answer 2

Mitosis and meiosis

Question 3

What is mitosis?

Answer 3

Mitosis is a process of cell division in which one cell divides into two genetically identical daughter cells.

Question 4

What are the stages of mitosis?

Answer 4

Prophase: chromosomes condense, the nuclear envelope breaks down, chromosomes attach to spindle fibers by centromeres

Metaphase: spindle fibers line the chromosomes along the middle of the cell

Anaphase: sister chromatids are pulled to the opposite sides of the cell

Telophase: nuclear envelope reforms, chromosomes decondense into chromatin, two new nuclei form and cytokinesis can begin.

Cytokinesis: division of the cytoplasm to form two new cells

Question 5

What is meiosis?

Answer 5

Meiosis is a process of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell.

Question 6

What are the stages of meiosis?

Answer 6

Meiosis I:

• prophase I: nuclear envelope breaks down. homologous chromosomes condense and pair up and exchange genetic material (crossing over)
• metaphase I: homologous pairs line up at the middle of the cell
• anaphase I: homologues separate to opposite ends of the cell but sister chromatids stay together
• telophase I and cytokinesis: two new haploid cells are formed and each chromosome has a duplicated copy of each homologous chromosome pair. Cytoplasm is divided by a cleavage furrow.

Meiosis II:
-prophase II: chromosomes condense and nuclear envelope breaks down. Centrosomes move apart and spindle forms between them
-metaphase II: chromosomes line up at the middle of the cell
-anaphase II: sister chromatids separate and are pulled to opposite ends of the cell
-telophase II: nuclear membrane forms around each set of chromosomes and the chromosomes decondense.
Cytokinesis spilts chromosomes sets into new cells forming four haploid cells with each chromosome having one chromatid.

Question 7

What are stem cells?

Answer 7

Stem cells are cells that are derived from the inner cell mass or embryo proper from which all other cells with specialized functions are generated

Question 8

What are some specialized cells and their functions?

Answer 8

• The muscles and other contractile cells are specialised for movement.
• The epithelial cells are specialised to form adhesive and tight junctions between cells.
• The fibroblasts, cells of bone and cartilage are specialised to synthesize and secrete components of the ECM.
• The neurons and sensory cells are specialised to convert physical and chemical stimuli into action potentials.
• The cells of digestive glands are specialized to synthesize and secrete degradative enzymes.
• The cells of mucous glands are specialized to synthesize and secrete glycoproteins.
• Certain cells of the adrenal gland, testis and ovary are specialized to synthesize and secrete steroids.
• The cells of the kidney and salivary gland ducts are specialised for ion transport.
• The macrophages and neutrophils are specialized for intracellular digestion.
• The fat cells are specialised for lipid storage.
• The cells lining the intestine are specialized for metabolite absorption.

Question 9

What is the plasma membrane and its function?

Answer 9

The plasma membrane is a lipid bilayer that forms the cell boundary as well as the boundaries of many other organelles. It acts as a physical barrier where it protects the cellular contents and supports the cell structure and it is selectively permeable which means it controls which ions, nutrients and other molecules are allowed to enter and exit the cell. It also contains receptors that recognize and respond to chemical signals, as well as establishing and maintaining an electrical charge differential across the plasma membrane.

Question 10

What is the endoplasmic reticulum and its function?

Answer 10

The endoplasmic reticulum is a network of inter communicating channels formed by a continuous membrane.

There are two types: Rough endoplasmic reticulum is associated with ribosomes and is the site of protein synthesis, while smooth endoplasmic reticulum is involved in lipid and steroid production but is not related with ribosomes. The endoplasmic reticulum also transports molecules from one region of the cell to another and it stores newly synthesized molecules. The smooth ER detoxifies both drugs and alcohol.

Question 11

What is the Golgi apparatus and its function?

Answer 11

The Golgi apparatus is a membrane organelle that modifies proteins and sorts and packages materials for secretion or transport to other organelles.

Question 12

What are lysosomes and their function?

Answer 12

Lysosomes are small organelles that contain digestive enzymes which break down macromolecules

Question 13

What are the mitochondria and their function?

Answer 13

The mitochondria are organelles that provide majority of the aerobic energy of the cell by producing ATP and initiate apoptosis

Question 14

What are peroxisomes and their function?

Answer 14

Peroxisomes are spherical organelles which contain enzymes that immediately break down hydrogen peroxide so that it does not damage the cell.

Question 15

What is the nucleus and its function?

Answer 15

The nucleus contains the cell’s genetic material, which controls cellular structure and guides all cellular processes. It also manufactures ribosomal subunits in the nucleolus and exports them to the cytoplasm for ribosome assembly.

Question 16

What is the cytoskeleton and its function?

Answer 16

The cytoskeleton is a complex network of microtubules (tubulin), microfilaments (actin), and intermediate filaments (protofilament) that determines cell shape and aids in the movement of organelles and cytoplasmic vesicles

Question 17

What is the centrosome and its function?

Answer 17

The centrosome arranges microtubules and assists in the creation of mitotic spindles during cell division. It also distributes chromosomes evenly among daughter cells.

Question 18

What are inclusions and their function?

Answer 18

Inclusions are temporary storage sites for lipid droplets, glycogen granules, pigment granules or residual bodies.

Question 19

What is a chromosome?

Answer 19

A chromosome is a DNA molecule with part or all of the genetic material of an organism.

Question 20

What is a chromatid?

Answer 20

A chromatid is a chromosome that has been newly copied.

Question 21

What is chromatin?

Answer 21

Chromatin is the material of which the chromosomes of organisms other than bacteria are composed. It consists of protein, RNA and DNA

Question 22

What is a Barr body or Gender Chromatin?

Answer 22

A Barr body is an inactive X chromosome in a female somatic cell. Barr bodies allow for gender determination in persons whose exterior sex organs do not allow it (hermaphroditism and pseudo hermaphroditism).

Question 23

What is apoptosis?

Answer 23

Apoptosis is a form of programmed cell death that occurs in multicellular organisms. It is initiated by the mitochondria.

Question 24

What is necrosis?

Answer 24

Necrosis is a type of cell damage that causes autolysis, which causes cells in live tissue to die prematurely. It is triggered by external factors such as infection, toxins, or trauma to the cell or tissue, which result in uncontrolled digestion of cell components. Necrosis can be reversed with the right treatment.

Question 25

What is gangrene?

Answer 25

Gangrene is a condition in which body tissue dies as a result of a lack of blood supply caused by an underlying sickness, injury, or infection. The fingers, toes, and limbs are frequently affected, but gangrene can also affect organs and muscles inside the body.

Question 26

Where is there a high concentration of rough endoplasmic reticulum?

Answer 26

In pancreatic cells because the pancreas functions in the digestive system by producing many digestive enzymes. Therefore, it requires a lot of rough endoplasmic reticulum to meet the demand.

Question 27

Where is there a high concentration of smooth endoplasmic reticulum?

Answer 27

In the liver because it is responsible for detoxification

Question 28

Where are lysosomes most abundant and why?

Answer 28

In macrophages and neutrophils (white blood cells) because they help facilitate the processes of phagocytosis, endocytosis and pinocytosis. In the liver because of phagocytosis of bacteria and dead/foreign material.

Question 29

Why are peroxisomes important in the body?

Answer 29

All metabolic processes end with hydrogen peroxide as a product and an accumulation of hydrogen peroxide in the cells and body is extremely toxic. Therefore, peroxisomes are needed to break down the hydrogen peroxide into water or oxygen.

Question 30

Why are peroxisomes most abundant in the liver and kidney cells?

Answer 30

Peroxisomes contain various oxidative enzymes which detoxify the toxic material. Since the blood carries various toxic substances to kidney and liver, a large number of peroxisomes are present in them to oxidise the toxic material.