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Module 2.1 cell structure ocr a level bio
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Cards (46)
What is the cell cycle?
A regulated cycle of
division
with intermediate growth periods
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What are the stages of the cell cycle?
Interphase
Mitosis
or
meiosis
(
nuclear division
)
Cytokinesis
(
cytoplasmic division
)
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What happens during interphase?
Cell synthesizes proteins for
replication
, DNA replicates, and
organelles
divide
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What occurs during the G1 phase of interphase?
The cell synthesizes proteins for
replication
and doubles in size
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What occurs during the S phase of interphase?
DNA replicates
, resulting in
chromosomes
consisting of two sister
chromatids
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What happens during the G2 phase of interphase?
Organelles
divide
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What is the purpose of mitosis?
To produce two
genetically
identical
daughter cells
for growth, cell replacement, and
asexual reproduction
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What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
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What happens during prophase?
Chromosomes
condense,
centrioles
move to opposite poles, and the
nuclear envelope
breaks down
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What happens during metaphase?
Sister chromatids
line up at the cell equator, attached to the mitotic spindle by their
centromeres
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What happens during anaphase?
Spindle fibres
contract,
centromeres
divide, and
sister chromatids
are pulled to opposite poles
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What happens during telophase?
Chromosomes
decondense, and new
nuclear envelopes
form around each set of chromosomes
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What happens during cytokinesis?
A
cell membrane
cleavage furrow forms, leading to the contractile division of the
cytoplasm
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How is the cell cycle regulated?
Checkpoints
regulated by
cell-signalling
proteins ensure damaged cells do not progress
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What happens at each key checkpoint in the cell cycle?
Between
G1
&
S
: Checks for
DNA damage
Between
G2
&
M
: Checks
chromosome replication
Metaphase
checkpoint: Checks that
sister chromatids
are attached to the
spindle
correctly
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What is meiosis?
A form of cell division that produces four
genetically
different
haploid
cells known as
gametes
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What happens during meiosis I?
Homologous chromosomes
pair to form
bivalents
,
crossing over
occurs, and the cell divides
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What are homologous chromosomes?
A pair of chromosomes with genes at the same
locus
, one maternal and one paternal
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What happens during meiosis II?
Independent segregation of
sister chromatids
occurs, producing four
haploid cells
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How does meiosis produce genetic variation?
Through
crossing over
during
meiosis I
and independent assortment of
chromosomes
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How do cells become specialised?
Some
genes
are expressed while others are silenced due to cell differentiation mediated by
transcription factors
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What is a transcription factor?
A protein that controls the transcription of
genes
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How do transcription factors work?
They move into the
nucleus
, bind to the
promoter region
, and affect
RNA polymerase
binding
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What is a stem cell?
Undifferentiated
cells that can divide
indefinitely
and turn into other
specific
cell types
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What are the four types of stem cells?
Totipotent
: can develop into any cell type including the placenta and embryo
Pluripotent
: can develop into any cell type excluding the placenta and embryo
Multipotent
: can only develop into a few different types of cell
Unipotent
: can only develop into one type of cell
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What are some uses of stem cells?
Repair of damaged tissue, drug testing, treating neurological diseases, and researching
developmental biology
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What can stem cells do indefinitely?
Stem cells can divide indefinitely and turn into other specific
cell types
.
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What are the four types of stem cells and their definitions?
Totipotent
: can develop into any cell type including the placenta and embryo.
Pluripotent
: can develop into any cell type excluding the placenta and embryo.
Multipotent
: can only develop into a few different types of cell.
Unipotent
: can only develop into one type of cell.
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What are some uses of stem cells?
Repair of damaged tissue (e.g., cardiomyocytes after myocardial infarction).
Drug testing on artificially grown tissues.
Treating neurological diseases (e.g., Alzheimer’s & Parkinson’s).
Researching developmental biology (e.g., formation of organs, embryos).
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What are the two groups of specialised cells in blood?
Erythrocytes
(red blood cells): biconcave, no nucleus, lots of
haemoglobin
to carry oxygen.
Leucocytes
(white blood cells): include
lymphocytes
,
eosinophils
,
neutrophils
to engulf foreign material, and
monocytes
.
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How do specialised cells in blood form?
Specialised cells in blood form from multipotent stem cells in the
bone marrow
.
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What is the relationship between a system and specialised cells?
Specialised cells → tissues that perform
specific
functions → organs made of several tissue types →
organ systems
.
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Describe the structure of simple squamous epithelium.
Single smooth layer of squamous cells.
Thin and flat with a round
nucleus
.
Fixed in place by a
basement membrane
.
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Describe the structure of ciliated epithelium.
Made of
ciliated epithelial cells
.
Column-shaped with surface projections called cilia.
Cilia move in a
synchronised
pattern.
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What is the specialised structure of a spermatozoon?
A spermatozoon is specialised to fertilise an
ovum
during
sexual reproduction
in mammals.
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Describe the structure and function of palisade cells in plants.
Specialised to absorb light energy for
photosynthesis
.
Contain many
chloroplasts
.
Pack closely together.
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Describe the structure and function of guard cells in plants.
Form
stoma
.
When
turgid
, stoma opens; when
flaccid
, stoma closes.
Walls are thickened by spirals of
cellulose
.
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Describe the structure and function of root hair cells.
Specialised to absorb water and low-concentration minerals from soil.
Hair-like projections increase surface area for
osmosis
.
Carrier proteins
for active transport.
Many
mitochondria
produce ATP for active transport.
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What are meristems in plants?
Meristems are
totipotent
undifferentiated
plant cells that can develop into various types of plant cells.
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Describe the structure of a vascular bundle.
Phloem
tissue.
Xylem
tissue.
Cambium
(meristematic tissue).
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