Biology cb2

INTERPHASE - The DNA in the cell is copied(making x-shapes, each containing a chromosome and its copy). Sub-cellular parts(such as mitochondria) are also copied. 

PROPHASE - The membrane around the nucleus breaks down. 

METAPHASE - The chromosomes line up in the middle of the cell. 

ANAPHASE - Each of the chromosomes x-shapes splits to form two single chromosomes. The single chromosomes move away from each other. 

TELOPHASE - The single chromosomes arrive at opposite ends of the cell. The membranes around each nucleus start to form again. 

CYTOKINESIS - The cytoplasm of the cell is seperated as a cell membrane divides the cell into two daughter cells. 

Growth is measured by reguarly weighing mass, length, head circumference, blood group, bone density. 

Percentile curves are used to measure the growth of babies. 

Problems that can occur in growth are putting on mass too quickly(childhood obesity)/slowly(feeding and digesting), not increasing in length(thyroxin), head circumference not increasing at right rate too slow(microcephaly) too fast (hydrocephalus. 

Chloroplasts contain chlorophyll 

Plant growth is measured using height and mass. 

Plants have specialised growing areas called meristems, they undergo cell division and cell elongation. As plants continue to grow the older meristems become specialised - they differentiate. 

Meristem is an area just behind the tip of the stem or root where cell division takes place. 

PLANT SPECIALISED CELLS:

root hair cell, reproductive cell, palisade cell, xylem cell, phloem cell

Xylem cell - carries water up from the stem and leaves through the stomata(small gap)

Phloem cell - carries glucose and nutrients by active transport

Stem cells can divide to produce lots of copies of themself and differentiate into highly specialised cells, with different functions. 

THREE TYPES OF STEM CELLS:

Embryonic cell - only found in the early ball of cells that forms from a fertilised egg

Foetal cell - not used in research

Adult cell - found in many tissues and organs like the gut, bone marrow and heart.

They normally act as an internal repair system, dividing to replace dead or damaged cells when needed. 

Stem cells are used to rebuild bones and cartiliage, repair damaged immune systems and replace heart valves.

SENSORY NEURONE/RELAY NEURONE/MOTOR NEURONE 

The CNS consists of the brain and spinal column. Sense organs detect changes in the environment called stimulus. Sense organs contain receptor cells that create electricaln signals called impulses. The impulses travel along cells called nerve cells or neurones. Dendrites recieve messages from receptor cells. The message is sent to other neurones, it only works in one direction. The myelin sheath insulates and protects the neurone. This makes the transmission faster. 

In a cell each chromosome replicates itself and the two copies remain attached to form x-shapes. 

Two sets of chromosome pair up making 23 pairs and then seperate into two new cells. 

In the two cells the two copies of a chromosome in each x-shape split and each cell divides.

Four haploid daughter cells are produced. 

KEYWORDS:                                                                                                                                        brain, effector, spinal cord, impulse, sensory neurone, receptor, stimulus, motor neurone, relay neurone, synapse, neurotransmitter, 

Synapes - a gap

Differentiation - process of unspecialised into specialised 

Diploid - a cell or nucleus with two sets of chromosomes

Haploid - a cell or nucleus with one set of chromosomes 

Daughter cell - a new cell produced from division of parents

Clone - offspring from asexual reproduction, geneticallt identical to parent's cell

Prokaryotic - cell with no nucleus

Eukaryotic - cell has a nucleus

EQUATION:percentage increase in mass= final value - starting value    x100%                                                                                                                 starting value