Cell Division, Diversity And Differentiation Flashcards Preview

Biology A Level > Cell Division, Diversity And Differentiation > Flashcards

Flashcards in Cell Division, Diversity And Differentiation Deck (58):

In the cell cycle,
M is the ________
G, S are part of the ______

division phase (mitosis/meiosis)


What are checkpoints in the cell cycle for?

prevent uncontrolled division (lead to tumors), repair damage to DNA


What happens in the M phase of the cell cycle?

chromatin condenses
the checkpoint ensures that the cell is ready for mitosis
cell growth stops and mitosis occurs


What happens in the G₀ (gap 0) phase of the cell cycle?

apoptosis (programmed cell death)


What happens in the G₁ phase of the cell cycle?

growth phase, cell grows
checkpoint ensures ready to enter S phase
transcription of genes to RNA
organelles duplicate


What happens in the S (synthesis) phase of the cell cycle?

rapid phase (reduces mutation)
chromosomes unwind
DNA replicates
genes that are active in all cells replicate first


What happens in the G₂ phase of the cell cycle?

chemicals ensure the cell is ready for mitosis
stimulate proteins which make chromosomes condense to spindle
cells grow


Mitosis prophase is when...

2 sister chromatids shorten, thicken as DNA coils, nuclear envelope breaks down,
centrioles move to poles,
cytoskeleton protein threads form spindle between centrioles


Mitosis metaphase is when..

pairs of chromatids attach to spindle threads in middle and are attached by their centromeres.


Mitosis anaphase is when...

pairs of chromatids are pulled apart, the centromere splits,
motor proteins pull chromatids in opposite directions to poles
they are now chromosomes


Mitosis telophase is when...
cytokinesis is when...

chromosomes reach the poles
nuclear envelope forms around the chromosomes
now there are 2 identical nuclei

the cytoplasm splits leading to 2 new daughter cells.


Meiosis is...

a type of nuclear division that results in the formation of gametes.



one set of chromosomes (23)


2 gamete nuclei fuse = ...

diploid zygote


Homologous chromosomes

containing same genes, same place
same genes but different alleles (variants)


What happens in the S phase of interphase, in Meiosis?

chromosomes are duplicated as the DNA is replicated
now, each chromosome consists of 2 sister chromatids
in meiosis, chromosomes pair with homologous pair.


Meiosis prophase 1

chromatin condenses, supercoils
nuclear envelope breaks down
microtubules form from centrioles
chromosomes come together in homologous pairs, each member consists of 2 chromatids

crossing over occurs (non-sister chromatids wrap, swap sections, alleles shuffled)


Meiosis metaphase 1

line in middle, attach to spindle thread by centromere
independent assortment occurs (homologous pairs arranged randomly) = determines how pulled apart


Meiosis anaphase 1

pair of homologous chromosomes pulled apart by motor proteins
each chromosome has 2 chromatids


Meiosis telophase 1
and after?

nuclear envelope forms
cell divides by cytokinesis

then there's a short interphase when chromosomes uncoil (each chromosomes = 2 chromatids)


Meiosis prophase 2

nuclear envelope breaks down
chromosomes coil and condense
chromatids of each chromosomes are no longer identical
spindles form


Meiosis metaphase 2

chromosomes attach by centromere to middle of the spindle
chromatids randomly arrange


Meiosis anaphase 2

centromeres divide
chromatids pulled apart by motor proteins towards poles
chromatids randomly segregated


Meiosis telophase 2

nuclear envelope forms around each 4 haploid nuclei
2 cells now divide to give 4 haploid cells


How does Meiosis produce variation?

crossing over (prophase 1)
independent assortment (anaphase 1 and 2) or metaphase
random haploid gametes fuse


Why do organisms need specialised cells for particular functions?

Multicellular organisms are large so have a small SA to V ratio. This means that not all cells are in direct contact with the external environment.



undifferentiated cell, stem cell



stem cells become specialised into different types
genes switch on or off so that proportions of organelles differ, the shape of the cell changes, the contents of the cell changes.


How are erythrocytes (RBC) adapted to their function?

large SA:V because they are small (O₂ can diffuse and reach all regions of the cell)
biconcave shape (large SA:V)
flexible (change shape, easily travel through capillaries
organelles lost at differentiation (no nucleus, more space for haemoglobin molecules)


How are neutrophils adapted to their function?
(ingest invading pathogens)

twice the size of RBS
multi-lobed nucleus
attracted to infection sites by chemotaxis
ingest by phagocytosis


How are spermatozoa adapted to their function?

many mitochondria (aerobic respiration, ATP for undulipodium to move)
small, long, thin (move easily)
enzymes released from acrosome (head) = lysosome (digest covering of ovum and allow entry)
head contains haploid male gamete nucleus and little cytoplasm


How are epithelial cells adapted to their function? (lining tissue in alveoli, capillaries)

squamous epithelial cells (flattened)
many have cilia


How are palisade cells adapted?

long, cylindrical (pack closely)
small spaces between (air circulate)
large vacuole (chloroplasts near top so reduce diffusion distance for CO₂)
many chloroplasts (for photosynthesis)
cytoskeleton threads, motor proteins (move chloroplasts to upper surface


How are guard cells adapted? (in lower epidermis [outer layer of cells covering organism])

light energy used to produce ATP
ATP transports potassium ions to guard cells (lowers water potential so water enters from other cells by osmosis)
cells swell and stoma enlarges
stomata opens to let air enter spaces within layer of cells below palisade
gaseous exchange occurs, CO₂ into palisade (photosynthesis)
O₂ out palisade, out stomata


How are root hair cells adapted? (epidermal cells)

hair-like projections (increases SA to absorb from soil)
mineral ions actively transported into cells (lower water P so water follows)
carrier proteins in plasma membrane (actively transports mineral ions
produce ATP (for active transport)


What are the 4 main animal tissue types?



What are epithelial tissues, their function and structure?

covers and lines surfaces

cells close, continuous sheets
no blood vessels
receive nutrients from diffusion from tissue fluid
short cell cycles

protection, absorption, filtration, excretion, secretion

e.g. skin


What are connective tissues for, and structure?

hold structures
provide support

has non-living extra cellular matrix containing proteins and polysaccharides
matrix separates living cells within tissue and enables it to withstand forces like weight

e.g. blood bone, cartilage


________ _____ in cartilage are called _____________

immature cells


What happens when chondroblasts divide by mitosis?

secrete extracellular matrix
matrix synthesised and chondroblasts becomes mature, less active chondrocytes which maintain the matrix


What are the 3 types of cartilage?



What is Hyaline cartilage?

it forms embryonic skeletons
covers ends of long bones in adults
joins ribs to sternum
in nose
trachea (c-shaped rings)
larynx (voice box)


What is Fibrous cartilage?

occurs in discs between vertebrae in the backbone
and knee joint


What is Elastic cartilage?

makes up outer ear (pinna) and epiglottis (flap that closes over larynx when swallow)


Tell me about muscle tissues, Anna.

cells specialised to contract and cause movement
well vascularised (blood vessels)
fibres are elongated
contain myofilaments that allow muscle tissue to contract


3 muscle tissues?

skeletal muscle - packaged by connective tissue sheets, joined to bones by tendons, cause movement

cardiac muscle - walls of heart, allow to beat and pump blood

smooth muscle - walls of intestine, blood vessels, uterus, urinary tracts, propels substances along these tracts


Epidermal plant tissues (equivalent to epithelial in animals)

flattened cells
lack chloroplasts (apart from guard cells)
protective covering
some contain waxy substance that forms cuticle (in dry environments)


Vascular plant tissues

transport (xylem, phloem)
xylem transports water and minerals from roots to plant
phloem sieve tubes transfer products of photosynthesis from leaves to plant


Meristematic plant tissues

contain stem cells (meristem)
from this tissue, all plant tissues are derived
at root, shoot tips, cambium of vascular bundle (these areas called meristems)
cells in meristems have thin walls, little cellulose, no chloroplasts, not large vacuole, divide by mitosis so differentiate.


What happens when most plant cells mature?

develop large vacuole, rigid cell wall so can't divide
new cells arise at meristems by mitosis


How do cambium cells differentiate into xylem vessels?

lignin (woody substance) deposits in cell wall to reinforce it and make waterproof, but also kills cells
end of cells break down so xylem forms in columns with wide lumen.


How do cambium cells differentiate into phloem sieve tubes?

lose most organelles, sieve plates develop between them


How do cambium cells differentiate into companion cells?

retain organelles, continue metabolic functions, provide ATP for active loading of sugars into sieve tubes


Digestive system
Circulatory system
Respiratory system
Urinary system
Immune system
Nervous system + Endocrine system
Reproductive system

nutrition to provide ATP and materials for growth and repair

transport to and from cells

breathing, gaseous exchange

excretion and osmoregulation

protect against pathogens

communication, control and coordination



Integumentary system
Musculo-skeletal system
Lymph system

(skin, hair, nails) waterproof, protection, temp regulating
(skeleton, skeletal muscles) support, protection, move
(lymph nodes and vessels)transports fluids back to circulatory system, resists infection



undifferentiated cell capable of becoming any type


What are 4 sources of stem cells?

embryonic stem cells (formed when zygote begins to divide)

umbilical-cord blood

adult stem cells (developed in tissues) (blood, brain, bone) like repair system

induced pluripotent stem cells (iPS cells) (in labs by reprogramming differentiated cells to switch on key genes so become undifferentiated)


What are 4 stem cell uses?

bone-marrow transplants: to treat diseases of the blood, immune system and restore blood after cancer treatment

drug research: test on differentiated cells derived from stem

developmental biology: study how cells develop, function, what's wrong when diseased. Find out if can extend capacity that embryos have for growth and repair, into later life

repair damaged tissues/replace: treat mice with type 1 diabetes, research to develop in humans, bone-marrow can treat liver disease, could grow organ so no need for immunosuppressants.