2.6 cell division, diversity, organisation Flashcards
name the phases of the cell cycle
interphase
mitosis
cytokinesis
name the phases and describe what happens in interphase
g0= resting phase, cells may die, differentiate
G1= first growth phase, cell increases in size, organelles duplicate, genes transcript, protein synthesis
S= synthesis, DNA replicates
G2= second growth phase, cell checks for errors
what happens at the checkpoints
cell cycle halted and checked
g1= DNA damage, cell size etc.
g2=prevents cell replicating if DNA error from replicating
why are there checkpoints in the cell cycle
prevent uncontrolled cell division
detect/repair DNA damage
ensure cell cycle cannot be reveresed
DNA is only duplicated once
why do cells undergo mitosis
asexual reproduction
tissue growth and repair
name the stages of mitosis
prophase
metaphase
anaphase
telephase
what happens in prophase
chromosomes condense and become visible
spindle fibres form by centriole splitting and moving to opposite poles
nuclear envelope breaks down
what happens in metaphase
pairs of chromatids line up in the middle
spindle fibres attach to centromeres
what happens in anaphase
centromere of each pair of chromatids split
spindle fibres pull apart (motor proteins)
what happens in telephase
new nuclear membrane forms
cell now contains two nuclei that are genetically identical
what happens in cytokinesis
cell splits in two
plasma membrane and cytoplasm spilt
2 daughter cells formed
what is the significance of meiosis
sexual reproduction
fertilisation
haploid cells/gametes
what are homologous chromosomes
Pair of chromosomes
One paternal and one maternal
containing the same genes (diff. alleles)
name the stages of meiosis
prophase 1
metaphase 1
anaphase 1
telephase 1
p2
m2
a2
t2
what happens at prophase 1
p1= chromatin condenses, chromosomes supercoil, nuclear envelope break down, spindle fibres form, chromosomes come together in homologous pairs, crossing over occurs
what happens at metaphase 1
bivalents attach along equator, spindle attaches to centromere, independant assortment occurs (random)
what happens at anaphase 1
pairs of h.c are pulled apart
what happens at telephase 1
spindle fibres break down
two new nuclear membranes form around each set of chromosomes
what happens during cytokinesis after stage 1 of meiosis
division of cytoplasm and plasma membrane
produces two haploid cells
what happens at prophase 2
the two new nuclear envelopes break down, chromosomes condense and spindle forms
what happens at metaphase 2
chromosomes line up at equator attached by centromere
what happens at anaphase 2
centromeres divide, chromatids pulled apart and randomly segregated
what happens at telophase 2
nuclear envelope form around each of 4 haploid nuclei
how does meiosis produces genetic variation
crossing over during prophase
independant assortment
what is independant assortment
production of different combinations of alleles in daughter cells due to random allignment of homologous pairs along the equator of the spindle during metaphase 1
Define chiasmata
point that the pair of homologous chromosomes are joined together
what are stem cells
unspecialised cells that are pluripotent
what are the sources of stem cells
adult stem cells
embryonic stem cells
induced pluripotent stem cells
umbilical cord blood
Pluripotent vs totipotent
Totipotent = any type of cell
Pluripotent = any cell apart from placenta cell
uses of stem cells
treatment of Alzheimers, paralysis, parkinsons
research into developmental biology
repair of damaged tissue
what is a bivalent
pair of homologous chromosomes
What is differentiation
Process of cells becoming specialised
How are embryonic cells differentiated
Certain genes are switched on or off/ expressed more so proportions organelles differ, shape of cell, and contents of cell changes
What is an erythrocyte
Red blood cell
What is the function of a erythrocyte
Carry oxygen to repairing cells
Structure of a erythrocyte and benefits of it
Large SA:V
Biconcave shape
Flexible - well developed cytoskeleton to change shape through capillaries
No organelles- more space for haemoglobin
What is a neutrophil
Type of white blood cell
What is the function of neutrophils
Attract to and travel towards infected sites by chemotaxis to ingest bacteria/fungi by phagocytosis
What is the structure of neutrophils
Multilobed nucleus
Flexible - squeeze through capillaries
Which are larger - erythrocytes and neutrophils
Neutrophils are larger
What is the spermatozoa
Sperm cell
Adaptations of spermatozoa
Many mitochondria- carry out aerobic respiration for ATP to tail to mobs
Small, long thin
Enzymes released from acrosome - digest outer layer of egg
Contains haploid male gametes in head
What are epithelial cells
Cells that make up lining tissue
What are squamous epithelium and how are they structured
Flattened cells that provide a surface covering/outer layer on organs
Think cross section - short diffusion path
Permeable
What are ciliated epithelium and what do they do
Cilia - moves substances across surfaces of tissues
Beat in coordinated movement to shift material
What do goblet cells secrete
Secret mucus to trap, dust , microorganisms
How do cilia and goblet cells work together
Goblet cells secret the mucus
Cilia waft the mucus out
What is a tissue
Group of similar cells working together to perform specific function
What are the 4 types of animal tissues
Nervous
Muscle
Epithelial
Connective
What do epithelial tissues do
Covers and lines free surfaces (skin, blood vessels, heart chambers, organ walls)
What are epithelial tissue specialised for to carry out
Projection
Absorbation
Filtration
Excretion
Secretion
How are epithelial tissue structured
Close together to form continuous sheets
Smooth surfaces with projections
What do connective tissues do
Holds structures together
Provides support
How is connective tissue structured
Has non living extracellular matrix containing proteins and polysaccharides and seperates living cells to withstan weight
What do cartilage do
Strong/ flexible -provides support
What are the three types of cartilage
Hyaline
Fibrous
Elastic
What do muscular tissue do
allow movement
What are types of muscle tissue
Skeletal
Cardiac
Smooth
How are muscle cells/fibres specialised
Elongated, contain mayofilaments
What is nervous tissue made of and what does it conduct
Neurones
Electrical impulses
Explain palisade cells
Within leaves for photosynthesis
Pack together closely
Large vacuole
Cytoskeleton threads/ motors proteins to move chloroplasts nearer to upper surface of leaf
explain guard cells
found in the lower epidermis
controls opening and closing of stomata so air can enter
explain root hair cells
found on outer layer of plant roots
hair like projections which increases SA for absorption of mineral ions and water
has special carrier proteins to actively transport ions
name tissues found in plants
epidermal
vascular
meristematic
what is epidermal tissue
consists of flattened cells
has waxy cuticle to reduce water loss
what is vascular tissue
transport tissue made up of phloem and xylem
what is meristematic tissue
tissue containing stem cells
found at the root/shoots and in cambium of vascular bundles
what is an organ system
a number of organs working together to carry out an overall life function
