2.6 cell division

what are the features of erythrocytes?

• no nucleus, mitochondria, Golgi Apparatus, RER

• biconcave discs for large surface area

• flexible so can fit through small gaps

• contains haemoglobin (protein)

what are the features of neutrophils?

• lobed nucleus which allows them to fit through small gaps e.g between capillary cells

• flexible shapes which allows them to engulf pathogens/ foreign particles

• lysosomes which contains enzymes

what are features of squamous epithelial cells?

• flat and thin which allows for rapid diffusion e.g. in the lungs

what are features of ciliated epithelial cells?

• cilia (hair like structures)

• line the trachea and waft mucus away from the lungs

what are features of sperm cells?

• flagellum

• acrosome which contains digestive enzymes to penetrate the egg

• lots of mitochondria to provide energy

• less cytoplasm to reduce mass

what are features of palisade cells?

• chloroplasts to absorb light from photosynthesis

• tall and thin so further to travel before going through a second cell wall (light absorbed/ reflected)

what are features of root hair cells?

• long projection increases surface area to absorb water and mineral ions from soil

• thin permeable cell wall

• lots of mitochondria to provide energy for active transport

what are features of guard cells in light?

• guard cells take up water into their vacuole and becomes turgid (stoma opens)

• inner wall becomes thicker and outer wall thinner so they bend

what are features of squamous epithelial tissue?

• single layer of flat cells

• thin surface allows easy exchange of substances

what are features of ciliated epithelial tissue?

• found on surface where things need to be moved

• e.g. trachea and oviduct

what are features of cartilage?

• protects and strengthens 

• found in connective tissue in joints, ears, nose, trachea

• chondrocytes produce an extracellular matrix of collagen fibres (strength) and elastin fibres (flexibility)

what are 3 types of muscles?

• skeletal (used for movement)

• smooth (involuntary e.g. stomach lining)

• cardiac (heart only)

what are the features of muscles?

• made up of bundles of elongated cells called muscle fibres

• bundle of muscle fibres is called a fascicle

• contains contractile protein myofilaments called actin and myosin which form structures called myofibrils

what are features of xylem?

• transports water and minerals up the stem

• supports the plant

what is the structure of the xylem?

• xylem cells are dead and have no cytoplasm

• parenchyma cells fill gaps between other cells

• vessel elements - water transporting cells with wide lumen

• fibres for support made of lignin

• tracheids - transport of water and support in angiosperms (flowering plants)

what is the feature of phloem?

• transports organic nutrients up and down in plants

• sieve tube elements - reduced cytoplasm , few organelles, and walls from sieve plates

• companion cells - help sieve cells with functions using ‘plasmodesmata’ (these allow molecules to pass between cells)

what are two things that stem cells can either do?

• self-renew

• differentiate

what does it mean when a stem cell self-renews?

• makes copies of themselves

• this maintains the stem cell pool

what does it mean when stem cells differentiate?

• make other types of cells so specialised cells

• its replaces dead or damaged cells throughout your life

what does a totipotent cell mean?

• cell that has potential to form any and every type of cell

• e.g. fertilised egg

what is a pluripotent cell mean?

• cell that has ability to differentiate into almost any type of ells but not placenta

• e.g. embryonic stem cells

what is multipotent cell mean?

• cell has ability to differentiate into limited number of specialised cell types

what is a multipoint cell mean?

• cell has ability to differentiate into limited number of specialised cells types

• e.g. bone marrow stem cells can produce any type of blood cell

how do you produce erythrocytes and neutrophils?

• bones are living organs containing blood and nerve tissue

• larger bones contain bone marrow

• adult stem cells divide and differentiate to replace worn out erythrocytes and neutrophils

how is xylem vessels and phloem sieve tubes produced from meristems

• meristematic tissue contains plant stem cells where plant is growing

• tips of roots and shoots

• between phloem and xylem tissue

where are two types of stem cells?

• embryonic stem cells

• tissue stem cells (adult stem cells)

what is a blastocyst?

• very early embryo

• 50-100 cells

what are parts of embryonic stem cell?

• inner mass of cells become the embryo

• outer circle becomes placenta and umbilical cord

where are tissue stem cells found?

• fetus, baby and throughout life

what are the uses of stem cells in medicine?

• can be transplanted into any area of body that needs new healthy growth and they’ll adapt

• adaption of Stem cells and following growth stimulates more new, healthy growth which replaces or repairs damage or illness in the area

what are examples of diseases treated with stem cells?

• Neuro degenerative diseases (Parkinson’s, Alzheimers)

• spinal injury

• heart disease

• Type 1 diabetes

• macular degeneration

• burns

• drug trials

what are uses of stem cells in research?

• can be grown into different tissues to test how effectivity, toxicity, side effects of new medical drugs

• study how they develop into different cell types

• cell functions can be studied to find out what can make it fail to work properly in certain diseases e.g. cancer

what are the ethics behind stem cells in research and medicine?

• objection to using stem cells

• destruction to embryos

• religious reasons (life begins at conception therefore is a destruction of life)

what are the three main phrases of the cell cycle?

• interphrase

• nuclear division (mitosis)

• cytoplasmic division (cytokenisis)

what happens in G1 intephrase?

• proteins which organelles are synthesised are made

• organelles replicate

• transcription and translation takes place

• size of the cell also increases

what happens in S interphase?

• replication of DNA (synthesis)

what happens in G2 interphase?

• size of cell increases

• energy stores are increased

• duplicated DNA is checked for errors

what are two stages of the mitotic phrase?

• mitosis

• cytokinesis

what is mitosis?

• the nucleus divides

what is cytokinesis?

• cytoplasm divides into two and two cells are produced

what are point of checkpoints?

• to verify that the previous part of the cell cycle has been completed

what are the 3 checkpoints called?

• G1 checkpoint

• G2 checkpoint

• Spindle Assembly / Metaphrase checkpoint

what does G1 checkpoint check?

• correct size of cell

• nutrients

• growth factors

• DNA damage

what does G2 checkpoint check?

• cell size

• DNA replication (right number of chromosomes)

• DNA damage

what does Spindle assembly / Metaphrase checkpoint check?

• chromosomes aligned

• attached to spindle

what are the 4 phrases of nuclear division (mitosis) in order?

• prophase

• metaphase

• anaphase

• telophase

what is the G0 stage?

when cell exits cell cycle

what are the 3 reasons for cells going into G0 stage?E.g?

• fully differentiated cells e.g. adults neurones

• senescent cells e.g. Damaged DNA

• temporarily cells e.g. B memory cells

what is P53 protein associated with?

• DNA damage

what two things can P53 protein do once activated?

• if there is DNA damage

• can halt cell cycle at various checkpoints to allow DNA repair

• if damage is extensive to be repaired it can tigger apoptosis (programmed death) preventing prolongation of cells with damaged DNA

what type of factor is P53?

• transcription factor

what happens in the body to cause cancer?

mutation of genes that regulate the cell cycle

How can treat cancer?

• prevent DNA replication using cisplastin

• inhibit metaphrase - interfere with spindle fibres using vinca alkaloids

what is the problem with treating cancer?

treatment also affects healthy cells

what happens in interphase?

• chromosomes are uncoiled and therefore can’t be seen

• DNA replication, protein and ATP synthesis takes place

what happens in prophase?

• chromosomes condense and become visible

• nuclear envelope and nucleolus disappear

• centrioles move to opposite sides of cell

• spindle fibres attaches to centromeres and start to move chromosomes to the equator

what happens in the metaphase?

• chromosomes align themselves along the equator of the cell (line is called metaphrase plate)

what happens in anaphase?

• chromatids pairs are divided into individual chromosomes

• this is achieved by contraction of spindle fibres

• separate pairs then travel to opposite poles

what happens in telophase?

• nuclear envelope reforms

• nucleolus reforms

• chromosomes uncoil and become long and thin again

what happens in cytokinesis?

• cell divides into two daughter cells identical to the parent cell

what happens in cytokinesis in animal cell?

• cleavage furrow forms in the middle of the cell

• the cell surface membrane is pulled inwards by the cytoskeleton

what happens in cytokinesis in plant cell?

• cells all prevents cleavage

• cell plate forms in middle of the cell

• vesicles from the Golgi apparatus line up along the metaphase plate

• vesicles fuse with each other and the cell surface membrane

• new cell wall then forms

what are homologous chromosomes?

• one from each parent

• same genes in the same positions (these could be different alleles)

• same length and size

what is centrosome?

• point where two sister chromatids join 

what is an allele?

• form of a gene

what is a haploid cell?

• have 1 set of chromosomes

• half number of normal chromosomes in cell

what is a diploid cell?

• have 2 set of chromosomes

• full number of normal chromosomes in cell

what is locus?

• where on chromosomes the alleles are

what are the ways in we can create genetic variation in meiosis?

• crossing over

• independent segregation of chromosomes

• random fertilisation

what is crossing over?

• chromatids from homologous chromosomes (bivalent) twist around each other and swap sections of DNA
  the sections contain the same genes but potentially different alleles

what is independent segregation of chromosomes?

• chromosomes align on the metaphrase plate randomly during metaphase

• one from each pair passes into a daughter cell

what is random fertilisation?

• any sperm cell can fertilise any egg

• each individual is unlike any to have existed before or any that will exist again