biology Flashcards
what is the endocrine system made up of
endocrine glands
what do the endocrine glands secrete
hormones into the blood
what does the endocrine system regulate
maintenance of internal homeostasis, growth and development, use of energy, salt and sugar levels in the blood, amount of fluids, stress, appetite
what is the master gland and why
the pituitary gland controls the functions of many of the other endocrine glands
example of an endocrine disorder and cause
diabetes, pancreas doesn’t produce enough insulin/insulin isn’t used properly by the body
what are target cells
cells with a matching shaped receptor to the signalling hormone
what is a hormone
a signalling molecule
what do hormones do
send signals internally, long acting and slower to be received
what do nerve signals do
send signals internally, short acting but send a message quickly
how does a hormone travel
through the bloodstream
what controls the release of hormones
external and internal stimuli
how is external stimuli received
through the nerves from the sensory organs in the nervous system
examples of external stimuli
temperature change, hearing a loud noise, something scary
how is internal stimuli received
through the nerves and other hormones in the body
examples of internal stimuli
hunger, thirst, being sick
what is homeostasis
the bodies ability to maintain a constant internal environment, despite changes to the external environment
what conditions need to be constant
temperature and blood glucose level
how is homeostasis maintained
through a negative feedback loop
what does SRBERN stand for
stimulus, receptor, brain, effector, response, negative feedback
what happens in the stimulus stage
the change that triggers the negative feedback
what happens in the receptor stage
signal is received/detected (chemo or thermo receptors
what happens in the brain stage
receives message and sends message to effectors
what happens in the effector stage
the responding organ receives the message and respond
what happens in the response stage
the organ responds and the stimulus reverses
what happens in the negative feedback stage
original stimulus is reversed and brain tells effectors to stop
what is a positive feedback loop
brain tells effectors to keep going, response keeps occurring e.g giving birth, hormones keep coming
what are chromosomes
structures made of a tightly wound DNA, found in nucleus
what are genes
segments of DNA that code for a specific protein which determines traits
what is a genome
complete instructions for making an organism
what is the function of DNA
contains instructions for making proteins which code for traits
what is the structure of DNA
double helix shape, made of nucleotides and held together by hydrogen bonds
what makes up a nucleotide
phosphate, deoxyribose sugar and a nitrogenous base (A, T, C, G)
what is the base pairing rule
adenine with thymine and cytosine with guanine
what is the main function of RNA
create proteins by translation
structure of RNA
phosphate, ribose sugar and nitrogenous base (A, U(uracil), G, C)
similarities between DNA and RNA
both have nucleotides with same structure, follow same phosphate sugar backbone, G and C pairing is the same
differences between DNA and RNA
RNA is single stranded, sugar is different, RNA can leave the nucleus
what are proteins and what are they made of
made up of amino acids and code for particular traits
how is a protein produced (from DNA)
transcription - DNA is copied into a RNA molecule by polymerase enzyme, translation - RNA travels to a ribosome and decodes RNA into amino acids that form proteins
what are the stages of the cell cycle
G1, S, G2, mitosis (PMAT) and cytokinesis
what occurs in the G1 phase
The cell grows in mass and size by creating more proteins
what occurs in the S phase
DNA is replicated (synthesised), chromosomes are doubled
what occurs in the G2 phase
the cell continues to grow by making more organelles
what occurs in the mitotic phase
in 4 stages, the cell divides chromosomes evenly and gets the cell ready to split into 2
what occurs in the cytokinesis phase
the cytoplasm is divided and creates 2 new cells, in animal cells the cell membrane pinches (cleavage furrow) and in plant cells a cell plate is produced dividing the 2 daughter cells and then thickens into a cell wall
what percent/time of the cell cycle is mitosis
10%, 1 to 2 hours
what are the 4 stages of mitosis
prophase, metaphase, anaphase and telophase
when does mitosis occur
after G2 (interphase)
what occurs in prophase
DNA coils and chromosomes become visible, nucleus disappears and centrioles begin forming the spindle fibres
what occurs in metaphase
chromosomes attach to the spindle by the centromere and line up in the middle of the cell (equator)
what occurs in anaphase
centromere splits and sister chromatids seperate and are pulled to opposite ends of the cell by spindle fibres
what occurs in telophase
chromosomes begin to uncoil, spindle fibres disappear and nuclear membrane re-forms
what do cell checkpoints do
check the cell (DNA) for any damage, ensures it has enough nutrients and ensures the DNA has been properly replicated
what do mutations cause
uncontrollable cell division and may lead to cancer
when is DNA replicated and why
in the S phase to ensure new daughter cells will have the same, matching DNA to the parent cell
what does the helicase do in DNA replication
it unzips and unwinds DNA
what does the DNA polymerase do in DNA replication
creates a new DNA strand by joining nucleotides, turns one strand of DNA into 2
what is produced at the end of DNA replication
2 new daughter strands (with 2 parent strands)
why do cells need to divide/reproduce
to grow the organism and repair and replace the damaged cells
what are the cells called after division
daughter cells
what does not enough mitosis cause
it doesn’t allow for cells to grow or repair/replace damaged cells
what does too much mitosis cause
can lead to cancer due to uncontrolled cell division, cells may mutate in uncontrolled division
