Question 1

Purposes of cell replication

Accepted Answer

Growth and
development , Maintenance
and repair, Reproduction

Question 2

binary fission

Accepted Answer

the method of cell
replication used by prokaryotes

Question 3

Exponential growth

Accepted Answer

Cells replicate exponentially, meaning that after each round of replication the number
of cells present doubles.

Question 4

Exponential growth example

Accepted Answer

the rapid nature of binary fission allows a single
bacterium to replicate into a few million bacteria in a very short span of time. A colony
of Escherichia coli (E.coli) bacteria doubles in size every 20 minutes

Question 5

Prokaryotes reproduction

Accepted Answer

reproduce rapidly via binary fission, which produces two
genetically identical copies of a cell. (asexual reproduction)

Question 6

different stages of binary fission

Accepted Answer

D – DNA replication
E – Elongation
S – Septum formation
C – Cell division

Question 7

The process of binary fission pt 1

Accepted Answer

The circular chromosome is uncoiled and the DNA is
replicated. Plasmids also replicate,  , the cell elongates as it prepares to
separate into two new cells and the duplicated circular
chromosomes migrate to opposite ends.

Question 8

The process of binary fission pt 2

Accepted Answer

The cell then begins to undergo cytokinesis – the
process of separating into two new cells – by pinching
inwards and creating a septum,  A new cell wall and membrane are formed down the
centre of the cell

Question 9

eukaryotic cell cycle

Accepted Answer

composed of three stages including interphase, mitosis,
and cytokinesis.

Question 10

interphase

Accepted Answer

the first stage of the
eukaryotic cell cycle which involves
cellular growth and duplication of
chromosomes. Composed of three
phases: G1, S, and G2

Question 11

Interphase processes

Accepted Answer

the cell
synthesises the necessary DNA, proteins, and organelles required for growth and
replication

Question 12

Gap 1 (G1) phase

Accepted Answer

• increasing the volume of its cytosol
• synthesising proteins for DNA replication
• replicating its organelles.
At the end of the G1 phase, the cell either proceeds to the S phase or exits the cell cycle and
enters the G0 phase.

Question 13

Gap 0 (G0) phase

Accepted Answer

Cells that are not required to replicate rest in the G0 phase either
quiescent or terminally differentiated. While quiescent cells are dormant and have the
ability to re-enter the cell cycle, terminally differentiated cells remain in G0 indefinitely.

Question 14

Synthesis (S) phase

Accepted Answer

the cell replicates its DNA turning one chromosome into two
genetically identical sister chromatids, While sister chromatids are held
together by a centromere, the pair is regarded as a single chromosome.

Question 15

Gap 2 (G2) Phase

Accepted Answer

The G2 phase is the final stage of interphase where the cell continues to grow and prepare
itself for mitosis. 
• increasing the volume of the cytosol
• synthesising proteins in preparation for mitosis.

Question 16

Mitosis

Accepted Answer

second stage of the eukaryotic cell cycle and involves the separation of the
newly replicated chromosomes into two new nuclei. (4 substages)

Question 17

Prophase

Accepted Answer

begins with the condensation chromosomes so that they are visible
Simultaneously, the centrioles migrate towards
opposite ends (or poles) of the cell, and spindle fibres
begin to form. The nuclear membrane breaks down
and the nucleolus disappears.

Question 18

Metaphase

Accepted Answer

, the spindle fibres fully form and attach
to the centromere of each chromosome. This allows
the spindle fibres to guide the chromosomes towards
the equator of the cell where they line up.

Question 19

Anaphase

Accepted Answer

The spindle fibres contract, splitting the centromere and
pulling sister chromatids to opposite ends of the cell.

Question 20

Telophase

Accepted Answer

new nuclear membranes form,
producing two genetically identical nuclei. The spindle
fibres disintegrate and the chromosomes decondense.

Question 21

Cytokinesis

Accepted Answer

the third and final
stage of the eukaryotic cell cycle, where the cell divides into two daughter cells.

Question 22

cytokinesis process

Accepted Answer

the cytoplasm divides and the
organelles evenly distribute themselves before separating into two daughter cells.

Question 23

cytokinesis process in animals

Accepted Answer

occurs when a cleavage furrow develops and pinches the plasma
membrane into two cells

Question 24

cytokinesis process in plants

Accepted Answer

because they have a cell wall, a cell plate first forms at the equator before
separating into two cells (vesicles accumalte in the centre of the cell and the cell plate froms along the equator)

Question 25

Regulation of the cell cycle

Accepted Answer

The cell cycle has three checkpoints where the cell inspects itself for errors before
proceeding to the next stage.

Question 26

3 checkpoints

Accepted Answer

occur at the end of the G1 and G2 phases,
and during metaphase

Question 27

G1 checkpoint

Accepted Answer

verifies that the cell has grown to the correct size, has synthesised
enough protein for DNA replication, checks if the DNA has been damaged during
mitosis and cell growth, and checks if there are enough nutrients and oxygen

Question 28

G2 checkpoint

Accepted Answer

ensures that DNA has replicated properly in the S phase, and that the
cell has enough resources for mitosis

Question 29

metaphase checkpoint

Accepted Answer

the cell checks the formation of the spindle fibres. If the
chromosomes are lined up in the correct location, the cell proceeds to anaphase.

Question 30

apoptosis

Accepted Answer

the controlled death of
cells in the body. Also known as
programmed cell death

Question 31

two pathways of apoptosis

Accepted Answer

the mitochondrial and the death receptor
pathways

Question 32

Mitochondrial pathway (intrinsic pathway)

Accepted Answer

the
pathway of apoptosis which
is initiated by the detection of
internal cellular damage. Also
known as the intrinsic pathway

Question 33

Mitochondrial pathway (intrinsic pathway) process

Accepted Answer

When internal components of the cell  are damaged
mitochondria detect this damage and release cytochrome c into
the cytosol. Cytochrome c binds with cytosolic proteins to form an
apoptosome, which activates caspase enzymes, initiating apoptosis.

Question 34

death receptor pathway

Accepted Answer

the
pathway of apoptosis which
is initiated by the reception of
extracellular death signalling
molecules. Also known as the
extrinsic pathway

Question 35

Death receptor pathway (extrinsic pathway) process

Accepted Answer

Death signalling molecules can be recognised by death receptor proteins
on the surface of cells, and are often released by immune cells. When
these molecules bind to a death receptor surface protein, caspase
enzymes are activated, initiating apoptosis.

Question 36

what do teh two processes have in common

Accepted Answer

Following
caspase activation, the two pathways become nearly identical.

Question 37

further 4 stage process of apoptosis

Accepted Answer

1. Activation of caspases
2. Digestion of cell contents
3. Cell shrinks
4. Membrane blebbing and breakage

Question 38

1. Activation of caspases

Accepted Answer

activated by the intrinsic or extrinsic pathway

Question 39

2. Digestion of cell contents

Accepted Answer

caspases cleave intracellular proteins, which leads to the
breakdown of organelles.

Question 40

3. Cell shrinks

Accepted Answer

the cell and nucleus shrink as intracellular material is broken down.

Question 41

4. Membrane blebbing and breakage

Accepted Answer

as the cytoskeleton is digested, the cell is weakened. The membrane warps and detaches from the cell in
membrane-enclosed vesicles known as apoptotic bodies which contain the broken
down intracellular material.

Question 42

what happens after apoptosis

Accepted Answer

phagocytes engulf and digest the free-floating apoptotic bodies
by phagocytosis.

Question 43

phagocytosis

Accepted Answer

endocytosis of solid
material or food particles

Question 44

phagocytes

Accepted Answer

a cell of the
immune system responsible
for engulfing and destroying
harmful microorganisms and
foreign materia

Question 45

when the rate of apoptosis decreases

Accepted Answer

cell growth can increase
exponentially, resulting in the formation of tumours. Tumours can be classified into two
categories:
• benign tumours and malignant tumours (considered to be cancerous due to their ability to
migrate)

Question 46

stem cell

Accepted Answer

undifferentiated
cells with the capability of
differentiating into specialised cells

Question 47

process of cells in our body

Accepted Answer

each cell begins as a stem cell
and through the process of differentiation, they develop into specialised cells with a
particular function

Question 48

The two properties of stem cells

Accepted Answer

Self-renewal and potency

Question 49

Self-renewal

Accepted Answer

Stem cells have the capacity to replicate without disrupting their ability to differentiate
by producing both a differentiated cell and a copy of themselves when they replicate

Question 50

potency

Accepted Answer

Stem cells are undifferentiated cells which can give rise to differentiated cells with a
specialised function

Question 51

stem cells equality

Accepted Answer

not stem cell are equal with some able to differentiate into any cell type, and others capable of differentiating into
only a handful of cell types. Based on these relative capabilities, we can categorise stem
cells according to their relative potency.

Question 52

Totipotent

Accepted Answer

Stem cells that can differentiate
into any cell type. eg The zygote ( replicates into any cells required to build a foetus)

Question 53

Pluripotent

Accepted Answer

Stem cells that can differentiate
into multiple cell types. eg empryonic stem cells (differentiates into 3 germ layers mesoderm, ectoderm, endoderm)

Question 54

Multipotent

Accepted Answer

Stem cells that can differentiate
into a limited number of
specialised cell types belonging to
a specific tissue or organ eg bone marrow stem cell which can diffenrtiate into red and white blood cells

Question 55

diagram of potency

Accepted Answer

zygote (totipotent) differntaites into an embryonic stem cell (pluripotent) which can differntaite into an ectoderm, mesoderm and endoderm (multipotent) an endoderm differentiates into specialised cells like stomach, pancreatic and liver cells.

Question 56

multipotnet cells

Accepted Answer

ectoderm= neuron, skin cells and pigment cells
mesoderm=skeletal muscle,smooth muscle,cardiac muscle, red blood cells and bone cells
endoderm=stomach, liver and pancreatic cells

Question 57

NECROSIS

Accepted Answer

Another way cells die,  unregulated death of cells initiated by
significant damage which causes the cell to swell, burst, and release cell contents into the surrounding
environment. This may lead to inflammation and damage in nearby cells and tissues.

Question 58

when does apoptosis rates decrease

Accepted Answer

failure to initiate apoptosis not always due to checkpoints,cells may no longer express functional death
receptor proteins, leads to death signalling molecules not initiating apoptosis
By failing to initiate, cells have a reduced rate of apoptosis.

Question 59

cancer

Accepted Answer

a disease caused by the
uncontrolled replication of cells
with the ability to migrate to other
parts of the body (only malignant tumours are cancerous  as they can migrate)

Question 60

characteristics of cancer cells

Accepted Answer

Tissue invasion and metastasis

Question 61

what is Tissue invasion and metastasis

Accepted Answer

When benign tumour cells become malignant/cancerous they are
capable of invading nearby layers of tissue and migrating to other
parts of the body away from the primary tumour site, typically via the
bloodstream or lymphatic system (metastasis).

Question 62

tissue types for animals

Accepted Answer

Animal bodies are composed of four primary tissue types: Epithelial (covers and protects), Connective (supports and binds), Muscle (enables movement), and Nervous (controls and communicates)

Biology Chapter 4

4A, 4B, 4C, 4D

Question	Answer
Purposes of cell replication	Growth and development , Maintenance and repair, Reproduction
binary fission	the method of cell replication used by prokaryotes
Exponential growth	Cells replicate exponentially, meaning that after each round of replication the number of cells present doubles.
Exponential growth example	the rapid nature of binary fission allows a single bacterium to replicate into a few million bacteria in a very short span of time. A colony of Escherichia coli (E.coli) bacteria doubles in size every 20 minutes
Prokaryotes reproduction	reproduce rapidly via binary fission, which produces two genetically identical copies of a cell. (asexual reproduction)
different stages of binary fission	D – DNA replication E – Elongation S – Septum formation C – Cell division
The process of binary fission pt 1	The circular chromosome is uncoiled and the DNA is replicated. Plasmids also replicate, , the cell elongates as it prepares to separate into two new cells and the duplicated circular chromosomes migrate to opposite ends.
The process of binary fission pt 2	The cell then begins to undergo cytokinesis – the process of separating into two new cells – by pinching inwards and creating a septum, A new cell wall and membrane are formed down the centre of the cell
eukaryotic cell cycle	composed of three stages including interphase, mitosis, and cytokinesis.
interphase	the first stage of the eukaryotic cell cycle which involves cellular growth and duplication of chromosomes. Composed of three phases: G1, S, and G2
Interphase processes	the cell synthesises the necessary DNA, proteins, and organelles required for growth and replication
Gap 1 (G1) phase	• increasing the volume of its cytosol • synthesising proteins for DNA replication • replicating its organelles. At the end of the G1 phase, the cell either proceeds to the S phase or exits the cell cycle and enters the G0 phase.
Gap 0 (G0) phase	Cells that are not required to replicate rest in the G0 phase either quiescent or terminally differentiated. While quiescent cells are dormant and have the ability to re-enter the cell cycle, terminally differentiated cells remain in G0 indefinitely.
Synthesis (S) phase	the cell replicates its DNA turning one chromosome into two genetically identical sister chromatids, While sister chromatids are held together by a centromere, the pair is regarded as a single chromosome.
Gap 2 (G2) Phase	The G2 phase is the final stage of interphase where the cell continues to grow and prepare itself for mitosis. • increasing the volume of the cytosol • synthesising proteins in preparation for mitosis.
Mitosis	second stage of the eukaryotic cell cycle and involves the separation of the newly replicated chromosomes into two new nuclei. (4 substages)
Prophase	begins with the condensation chromosomes so that they are visible Simultaneously, the centrioles migrate towards opposite ends (or poles) of the cell, and spindle fibres begin to form. The nuclear membrane breaks down and the nucleolus disappears.
Metaphase	, the spindle fibres fully form and attach to the centromere of each chromosome. This allows the spindle fibres to guide the chromosomes towards the equator of the cell where they line up.
Anaphase	The spindle fibres contract, splitting the centromere and pulling sister chromatids to opposite ends of the cell.
Telophase	new nuclear membranes form, producing two genetically identical nuclei. The spindle fibres disintegrate and the chromosomes decondense.
Cytokinesis	the third and final stage of the eukaryotic cell cycle, where the cell divides into two daughter cells.
cytokinesis process	the cytoplasm divides and the organelles evenly distribute themselves before separating into two daughter cells.
cytokinesis process in animals	occurs when a cleavage furrow develops and pinches the plasma membrane into two cells
cytokinesis process in plants	because they have a cell wall, a cell plate first forms at the equator before separating into two cells (vesicles accumalte in the centre of the cell and the cell plate froms along the equator)
Regulation of the cell cycle	The cell cycle has three checkpoints where the cell inspects itself for errors before proceeding to the next stage.
3 checkpoints	occur at the end of the G1 and G2 phases, and during metaphase
G1 checkpoint	verifies that the cell has grown to the correct size, has synthesised enough protein for DNA replication, checks if the DNA has been damaged during mitosis and cell growth, and checks if there are enough nutrients and oxygen
G2 checkpoint	ensures that DNA has replicated properly in the S phase, and that the cell has enough resources for mitosis
metaphase checkpoint	the cell checks the formation of the spindle fibres. If the chromosomes are lined up in the correct location, the cell proceeds to anaphase.
apoptosis	the controlled death of cells in the body. Also known as programmed cell death
two pathways of apoptosis	the mitochondrial and the death receptor pathways
Mitochondrial pathway (intrinsic pathway)	the pathway of apoptosis which is initiated by the detection of internal cellular damage. Also known as the intrinsic pathway
Mitochondrial pathway (intrinsic pathway) process	When internal components of the cell are damaged mitochondria detect this damage and release cytochrome c into the cytosol. Cytochrome c binds with cytosolic proteins to form an apoptosome, which activates caspase enzymes, initiating apoptosis.
death receptor pathway	the pathway of apoptosis which is initiated by the reception of extracellular death signalling molecules. Also known as the extrinsic pathway
Death receptor pathway (extrinsic pathway) process	Death signalling molecules can be recognised by death receptor proteins on the surface of cells, and are often released by immune cells. When these molecules bind to a death receptor surface protein, caspase enzymes are activated, initiating apoptosis.
what do teh two processes have in common	Following caspase activation, the two pathways become nearly identical.
further 4 stage process of apoptosis	1. Activation of caspases 2. Digestion of cell contents 3. Cell shrinks 4. Membrane blebbing and breakage
1. Activation of caspases	activated by the intrinsic or extrinsic pathway
2. Digestion of cell contents	caspases cleave intracellular proteins, which leads to the breakdown of organelles.
3. Cell shrinks	the cell and nucleus shrink as intracellular material is broken down.
4. Membrane blebbing and breakage	as the cytoskeleton is digested, the cell is weakened. The membrane warps and detaches from the cell in membrane-enclosed vesicles known as apoptotic bodies which contain the broken down intracellular material.
what happens after apoptosis	phagocytes engulf and digest the free-floating apoptotic bodies by phagocytosis.
phagocytosis	endocytosis of solid material or food particles
phagocytes	a cell of the immune system responsible for engulfing and destroying harmful microorganisms and foreign materia
when the rate of apoptosis decreases	cell growth can increase exponentially, resulting in the formation of tumours. Tumours can be classified into two categories: • benign tumours and malignant tumours (considered to be cancerous due to their ability to migrate)
stem cell	undifferentiated cells with the capability of differentiating into specialised cells
process of cells in our body	each cell begins as a stem cell and through the process of differentiation, they develop into specialised cells with a particular function
The two properties of stem cells	Self-renewal and potency
Self-renewal	Stem cells have the capacity to replicate without disrupting their ability to differentiate by producing both a differentiated cell and a copy of themselves when they replicate
potency	Stem cells are undifferentiated cells which can give rise to differentiated cells with a specialised function
stem cells equality	not stem cell are equal with some able to differentiate into any cell type, and others capable of differentiating into only a handful of cell types. Based on these relative capabilities, we can categorise stem cells according to their relative potency.
Totipotent	Stem cells that can differentiate into any cell type. eg The zygote ( replicates into any cells required to build a foetus)
Pluripotent	Stem cells that can differentiate into multiple cell types. eg empryonic stem cells (differentiates into 3 germ layers mesoderm, ectoderm, endoderm)
Multipotent	Stem cells that can differentiate into a limited number of specialised cell types belonging to a specific tissue or organ eg bone marrow stem cell which can diffenrtiate into red and white blood cells
diagram of potency	zygote (totipotent) differntaites into an embryonic stem cell (pluripotent) which can differntaite into an ectoderm, mesoderm and endoderm (multipotent) an endoderm differentiates into specialised cells like stomach, pancreatic and liver cells.
multipotnet cells	ectoderm= neuron, skin cells and pigment cells mesoderm=skeletal muscle,smooth muscle,cardiac muscle, red blood cells and bone cells endoderm=stomach, liver and pancreatic cells
NECROSIS	Another way cells die, unregulated death of cells initiated by significant damage which causes the cell to swell, burst, and release cell contents into the surrounding environment. This may lead to inflammation and damage in nearby cells and tissues.
when does apoptosis rates decrease	failure to initiate apoptosis not always due to checkpoints,cells may no longer express functional death receptor proteins, leads to death signalling molecules not initiating apoptosis By failing to initiate, cells have a reduced rate of apoptosis.
cancer	a disease caused by the uncontrolled replication of cells with the ability to migrate to other parts of the body (only malignant tumours are cancerous as they can migrate)
characteristics of cancer cells	Tissue invasion and metastasis
what is Tissue invasion and metastasis	When benign tumour cells become malignant/cancerous they are capable of invading nearby layers of tissue and migrating to other parts of the body away from the primary tumour site, typically via the bloodstream or lymphatic system (metastasis).
tissue types for animals	Animal bodies are composed of four primary tissue types: Epithelial (covers and protects), Connective (supports and binds), Muscle (enables movement), and Nervous (controls and communicates)

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