topic 1 Flashcards
cell structure and organisation
cells
building blocks of living organisms
arise only by division of existing cells
contains inherited information which controls their activities
metabolism takes place in cells
capable of independent existence
what are prokaryotic cells
genetic material not enclosed by nuclear envelope (lies free in cytoplasm)
what are eukaryotic cells
has a distinct nucleus surrounded by a nuclear envelope
features of prokaryotic cells
small (0.5 - 10 um)
peptidoglycan cell wall
no distinct nucleus
no membrane-bound organelles
few organelles
smaller ribosomes
binary fission (for cell division)
features of eukaryotic cells
larger (10 - 100 um)
cellulose cell wall (fungi: chitin)
distinct membrane-bound nucleus
linear DNA molecule
many (membrane-bound) organelles
larger ribosomes
mitosis and meiosis (for cell division)
what does eukaryotic cells have
plasma membrane
cytoplasm
organelles
non membranous: ribosome, cytoskeleton, cilia, flagella
membranous organelles: nucleus, mitochondrion, chloroplast, vacuole, endoplasmic reticulum, golgi apparatus, lysosome
cytoplasm
jelly like substance, contains 90% water, ions and small molecules as well as large molecules that form colloidal mixtures
site of most cell activities and stores vital chemicals
nucleus
membranous
all eukaryotic cells (except mature phloem sieve tube and mammalian red blood cells)
enclosed by a nuclear membrane (a double membrane separated by narrow space)
outer membrane is continuous with rough endoplasmic reticulum
contains genetic information in form of chromosome
contains nucleolus (structure where ribosomes are made)
controls cell activities such as growth and repair
required for cell division
stores hereditary material (dna) protects it from cytoplasm
regulate exchange of substances between nucleus and cytoplasm
endomembrane system
create, modify and transport proteins and lipids throughout the cell
outer nuclear envelope
endoplasmic reticulum
golgi apparatus
lysosomes
plasma membrane
various kidns of vacuoles and vesicles
all are related through direct physical continuity or transfer of membrane segments as tiny vesicles
RER
particularly abundant in cell active in protein secretion
network of flattened spaces lined with a membrane
continuous with the nuclear membrane
surface appears rough (ribosomes on outer surface)
functions of RER
site for synthesis of proteins destined for secretion or incorporation into membranes
ribosomes attached to rer make proteins that are transported to other compartments in cell via transport vesicles
FACILITATES FOLDING OF POLYPEPTIDE CHAIN INTO THREE DIMENSIONAL SHAPE (protein)
ser
connected to rer and abundant in liver cells and other cells active in hormone secretion
consist of a network of tubules
no ribosomes
synthesises lipids
converts harmful substances into harmless substances through DETOXIFICATION
golgi apparatus
stack of flattened membrane-bound sacs (cisternae)
cis face (nearest to er)
trans face (closest to plasma membrane)
further modifies products of er
store and package processed products in vesicles and transport them to other parts of the cell or out of cell
vacuoles
fluid-filled sacs bound by a single membrane
surrounded by tonoplast (plant cell)
fluid called cell sap (plant cell)
animal cell:
- contain food reserve
- contract to pump excess water out of a protist cell, to maintain a suitable concentration of ions and minerals
plant cell:
- maintain cell turgidity
- depository site for metabolic waste
- storage of pigments
- storage of food reserves
- protect against predators
mitochondria
smooth outer membrane
highly convoluted inner membrane (cristae)
interior: organic, semi-fluid mitochondrial matrix with ribosomes, circular dna and various enzymes
main site of atp production
release heat
