homeostasis, cell organisation and the function of specific organelles Flashcards
definition of homeostasis
condition of equilibrium or balance in the body’s internal environment produces by the interplay of all the body’s regulatory processes
dynamic process
able to maintain the internal environment with specific physiological limits by responding to the changing conditions
homeostasis
is able to respond to both internal and external environment disruptions
control of homeostasis
homeostasis = regulated by the nervous system and endocrine system.
act together or indeed gently using feedback systems
feedback systems - nervous
nervous system detects changes and sends nerve impulses to counteract the disruption; rapid change
feedback systems - endocrine
regulates homeostasis by secreting hormones; slow change
how may cell types are there
200
smallest cell type
sperm (5-6 micrometres)
largest cell type
ovum 120-150 Micrometres
what are the two shapes in cellular diversity
round - red blood cell
elongated - smooth muscle cell
Cytoplasm
what is it?
what are the two components
cellular contact between plasma membrane & nucleus
2 components
- cytosol
- organelles
cytosol
what is it?
structure?
function?
fluid portion of cytoplasm that surrounds organelles
55% total cell volume - water, ions, glucose, amino acids, fatty acids, proteins, lipids, AP and waste products
(WIG AF PL AP W)
CONTAINS CYTOSKELETON (network of protein filaments that extend through the cytosol
it is the sit of chemical reactions (glycolysis)
cytoskeleton
what are the three protein filament systems
microfilaments
intermediate filaments
microtubules
microfilaments
- structure
- function
S - thinnest filaments
actin and myosin
edge of cell
F - generate movement
mechanical support
intermediate filaments
- Structure
- function
S - intermediate size
several different types of proteins
F- stabilise position of organelles
attach cells to one another
microtubules
- structure
- function
S - largest in size
protein tubular
long hollow tubes
F - determine cell shape
movement of organelles
- also make up cylindrical centrioles in centrosome*
- also make up cilia and flagella*
Organelles (in cytoplasm)
- definition
specialised structures with characteristic shape and specific functions
Organelles cont.
- organelles have own set of enzymes. carry out specific reactions
numbers and types vary
cooperate to maintain homeostasis
Endoplasmic reticulum (ER)
- structure
- function
TWO TYPES
smooth & rough
ROUGH
s - continuous with nuclear membrane
network of membrane enclosed sacs
studded with RIBOSOMES
f -
protein synthesis
phospholipid synthesis
SMOOTH
S - extends from rough ER
network of membrane tubules
f -
synthesises fatty acids and steroids
inactivates / detoxifies drugs
stores / releases calcium ions (muscle cell)
Ribosomes
structure & function
S - 2 subunits (leg / sml) synthesised in nucleolus constructed in cytoplasm attached to nuclear membrane, rough ER, within mitochondria or free in cytosol
f - site of protein synthesis
Golgi complex
structure & function
S - 3-20 small stacked, flattened membranous sacs (cisternae)
f - modify, sort, package proteins into vesicles for transport
(to different destinations)
destinations inc - membrane vesicle, transport vesicle and secretory vesicle.
processing and packaging proteins in golgi complex
how many steps are there?
summarise steps
9 steps STECEM SMO
1 - protein synthesised by ribosome
2 - transport vesicle to GC
3 - contents released in GC (entry face)
4 - proteins move from entry face to cisterna. proteins modified. transfer ves move enzymes to entry/exit face
5 - move to exit face
6 - proteins further modified, sorted and packaged
7 - some proteins sorted into secretory and exported from cell
8 - some proteins sorted into membrane vesicle and incorporated into plasma membrane
9 - some proteins sorted in transport vesicles and carried out to other organelles
Mitochondria
structure & funciton
S - double membrane bound organelle.
outer membrane is smooth
inner arranged into folds and called cristae
F - site of cellular ATP production (cellular respiration)
powerhouse of cell
proteasome
structure & function
s - barrel shaped structure consisting of four stacked rings of proteins around a central core
controls proteases
f - destruction of unneeded, damaged or faulty proteins
Lysosome
structure & funciton
s - membrane enclosed vesicle
formed from GC
container digestive and hydrolytic enzymes
f - digestion of endocytic vesicles
recycle worn out cell structure (autophagy)
Peroxisomes
structure and function
s - small membrane enclosed organelles
similarly in structure to lysosome but smaller
contain multiple enzymes
f - oxidise amino and fatty acids
detoxifies hydrogen peroxide and free radicals
centrosome
structure and function
s - specialised structure composed of 2 cylindrical centrioles
centrioles composed of microtubules
f - growth of mitotic spindle in cell division
microtubule formation
Cilia and flagella
structure and functions
S - motile projections of cell surface that are composed of microtubules
f - CILIA
move materials across surface of cell
FLAGELLA
move entire cell (sperm)
Nucleus
general structure & function
GS - spherical or oval shaped prominent structure
may be present singularity or in multiples
f - controls cellular structure directs cellular activity produces ribosomes (nucleolus)
nucleus - associated structures (3)
Nuclear envelope
- double membrane separates nucleus from cytoplasm
nuclear pores
- openings that extend through nuclear envelope
- control movement of substances between nucleus and cytoplasm
Nucleolus
- spherical body containing DNA, RNA and protein
DNA - deoxy-ribonucleic acid
molecules composed of 2 strands twisted around each other to form double helix
each strand composed of nucleotides - nitrogen-containing nucelobasis
what paired nucleotides make up each strand of DNA
AT & CG organised into chromosomes
adenine & thymine
Cytosine & guanine
genetic information carried by DNA is contained on genes
Chromosomes
- long molecule of DNA coiled together with HISTONES (proteins)
- present in non-dividing cell as chromatin (diffuse, granular mass)
- dividing cell. Dan replicated loops condense forming pair of chromatids
somatic cell has how many chromosomes?
46.
23 pairs
