cell communication (signalling) and cell cycle

Question 1

What are the two types of communication?

describe them

Answer 1

Transport / trafficking (vesicular)
- physical movement of proteins and lipids within the cell

signalling
- transport of a specific signal received from outside to elicit a cellular response

Question 2

describe signalling

describe how the following play a part.
neurotransmitters
protein molecules
hormones

Answer 2

Signalling is linked to transport / trafficking; specific molecules secreted from the cells by exocytosis act as signalling molecules

neurotransmitters
- secreted from neuron act on downstream target - muscle cell or another neutron

protein molecules
- secreted from a signalling cell act locally on the target cell and ensures functioning of cell in very close proximity (within a tissues)

hormones
- secreted from endocrine cell and delivered t a target cell through circulation

Question 3

Further describe cell signalling

Answer 3

cell signalling is a process of covering extracellular signal (signalling molecules) into intracellular response (altered metabolism, gene expression or cell shape / motility) via transduction cascade initiated by
extracellular signal + receptor engagement.

Question 4

describe signalling - transduction cascade

Answer 4

• initiated by signal receptor engagement
• leads to amplification of signal
• done by firstly activating secondary messenger systems e.g G protein
• then activation of protein phosphorylation cascade (AKT)
• this activates specific target proteins

1 signal + receptor engagement can lead to activation of multiple responses

Question 5

Signalling - target protein & intracellular response.

what 3 target proteins are activated by phosphorylation cascade?

how do the cells respond?

Answer 5

transcription factors
enzymes
cytoskeletal proteins

gene expression regulation
metabolism alteration
cell motility and shape alteration

Question 6

overall response to signalling

Answer 6

survive
grow and divide
differentiation (progenitor cell differentiates into mature cell)
die (apoptosis - programmed cell death and necrosis)

Question 7

DNA - chromosomes. describe.

Answer 7

• long molecules of DNA coiled together with histones (proteins)
• present in non-dividing cell as chromatin (diffuse granular mass)
• in dividing cell, DNA replicates, loops condense forming pair of chromatids also known as chromosome
• somatic cell has 46 chromosomes (23 pairs)

Question 8

Cell cycle. definition and 2 major phases

Answer 8

orderly sequence of events in which somatic cell duplicates its contents and divides into two

interphase
- duplication of cell material

mitotic phase
- division of cell material

Question 9

Interphase stage of cell cycle

consists of 3 phases. what are they

Answer 9

G1 phase
- cell metabolic rate increases, organelles and cytosolic components duplicated

S phase
- DNA replication and chromosomes condensing

G2 phase
- cell growth continues, synthesis of proteins and enzymes

Question 10

Cell division definition.

describe the two types

Answer 10

cell division is the process by which cells reproduce themselves. it consists of nuclear division (mitosis and meiosis) and cytoplasmic division (cytokinesis)

• increased body cells is called somatic cell division
• production of sperm and eggs is called reproductive cell division

Question 11

Mitotic phase - definition and stages

Answer 11

formation of two identical somatic cells and consists of 2 divisions

• nuclear division (mitosis)
• cytoplasmic division (cytokinesis)

stages include (PMAT)

• prophase
• metaphase
• anaphase
• telophase

Question 12

Prophase. describe early and late

Answer 12

Early prophase

• chromatin condenses and shortens into visible chromosomes
• pair of identical chromatids held together by centromere

Late prophase

• nucleolus and nuclear envelope disappeared
• each centrosome starts to move towards opposite ends of cell via mitotic spindle

Question 13

Metaphase

Answer 13

• microtubules of mitotic spindle align centromeres of chromatid pair at centre of mitotic spindle
• midpoint region called metaphase plate

Question 14

Anaphase. early and late

Answer 14

Early

• centromeres split separating the 2 members of each chromatid pair
• each member now called a chromosome) moves towards opposite poles of cell

Late
- cleavage furrow forms

Question 15

Telophase

Answer 15

• begins after chromosomal movement stops
• chromosomes uncoil and revert to threadlike chromatin form
• nuclear envelope forms
• mitotic spindle breaks up

Question 16

Cytoplasmic division; cytokinesis.

definition and describe

Answer 16

division of a parent cell’s cytoplasm and organelles

• process begins in late anaphase or early telophase with the formation of a cleavage furrow
• when cytokinesis is complete, interphase begins

Question 17

reproductive cell division. who are the two major phases

Answer 17

Meiosis
- results in production of haploid (n) cells that contain only 23 chromosomes

interphase
followed by 2 successive cycles of cell divisions
- meiosis 1
- meiosis 2

Question 18

Meiosis 1. describe

Answer 18

• begins after interphase
• consists of 4 phases;
  prophase 1
  metaphase 1
  anaphase 1
  telophase 1

Question 19

Prophase 1

Answer 19

• chromosomes shorten and thicken
• nuclear envelope and nucleoli disappear
• mitotic spindle forms
• 2 sister chromatids of each pair of homologous chromosomes per off (synapsis) which forms a tetrad
• exchange of genetic material between homologous chromosomes (crossing over) which results in genetic recombination

Question 20

Meiosis 2 `

Answer 20

consists of 
prophase 2 
metaphase 2 
anaphase 2 
telophase 2 

these phases are similar to those in mitosis but result in 4 haploid cells