Cell Structure and Functions Flashcards
Prokaryotes is
- single-celled (unicellular)
- the smallest and the simplest cells
Cytoplasm/ Protoplasm of prokaryotes enclosed by
plasma membrane
Prokaryotes has no
- cytoskeleton (filamentous network of protein)
- membranous organelles
Cell wall of prokaryotes made of
peptidoglycan (maintain cell shape)
Gram negative bacteria has
- thinner cell wall
- does not retain the gram stain
Gram positive bacteria has
- thicker cell wall
- retain the gram stain (purple)
Prokaryotes has
- mesosomes (infolding of plasma membrane, site of cellular production)
- ribosomes (synthesis protein)
- genetic material (‘naked’ circular DNA-nucleoid)
- pili (attach to surface)
- high metabolic and growth rate
- short life time
Only some prokaryotes has
- capsule (limit phagocytosis)
- plasmid (small circular DNA - store important genes)
- flagella (movement in liquid environment)
Prokaryotes grow and reproduce by
binary fission
Main groups of eukaryotes
animal and plant cells
Eukaryotes is bounded by
plasma membrane
Eukaryotes contain
- cytoskeleton (supporting matrix of protein)
- membrane-bound organelles
Cell wall enclose
the plasma membrane of plants, bacteria, fungi, algae and some archae (not in animals and protozoa)
Cell wall made of
- cellulose (plant)
- peptidoglycan (bacteria)
Cell wall is
tough, usually flexible but sometimes rigid
Cell wall functioned as
protection and supports against mechanical stress
Plasma membrane enclosed the
cytoplasm/ protoplasm
Plasma membrane made of
phospholipid bilayer with embedded proteins
Plasma membrane is
semi-permeable (selectively permeable)
Functions of plasma membrane
- separating the interior from the environment
- provide shape
- as cell adhesion
- ion channel conductance
- cell signaling (cell interact with their environment and other cells around them)
- attachment point for the cytoskeleton
Cilia is
- the projections from the cell
- motile and non-motile (primary)
Primary cilia are found on
every cell in human body (sensory)
Functions of cilia
- movement
- sweep substances across cell surface
Cilia is made up of
microtubules covered by plasma membrane
Microtubules is
hollow cylinders made up of repeating protein structures
Arrangement of microtubules (in a ring)
- Primary cilia (nine triplets 9+0)
- Motile cilia (nine pairs surround two central microtubules 9+2)
- Basal body/ centriole (anchor cilium to the cell)
Flagella is
projections from the cell
Flagella is made up of
microtubules covered by plasma membrane
Arrangement of flagella (in a ring)
nine pairs surround two central microtubules (9+2)
Function of flagellum
movement
Cytoplasm is
viscous gel, enclosed within the cell membrane
Cytoplasm consist of
- Cytosol (liquid component of the cytoplasm - mixture of cytoskeleton filaments, dissolved molecules and water)
- Organelles
Cytoplasm functions as
medium for most cellular activities
Cytoskeleton is
- skeleton of cytoplasm
- a dynamic structure
Cytoskeleton made of
filamentous protein network
Cytoskeleton present in
plant and animal cells
Functions of cytoskeleton
- maintains cell shape, enables cellular motion
- play important roles in intercellular transport and cell division.
Cytoskeleton included three types of fibres which is
- microfilament
- microtubules
- intermediate filaments
Functions of microfilaments
- muscle contraction and movements of certain cells
- provide support (more in muscle cells and amoeboid)
Microfilaments is
- major portion of cytoskeleton, two chains twisted around one another
- thinnest filaments, flexible and strong
Each subunit of microfilaments is made of
actin (protein)
Microtubules involved in many cellular processes such as
- transport vesicle
- provide cell shape and support
- separate chromosomes during cell division.
Microtubules is
- part of the cilia and flagella of eukaryotic cells
- form spontaneously around centrosomes (microtubule organizing centre)
- unstable, easily assembled and disassembled
Microtubules are made of
beta and alpha tubulin (protein)
Functions of intermediate filaments
- preventing excessive stretch of cells shape
- fix organelles position
intermediate filaments is
the most durable and stable
Intermediate filaments are made of
vimentin (protein)
Endomembrane system is
a group of membrane and organelles in eukaryotic cells that work together to modify, package and transport lipids and protein
Endomembrane system include
endoplasmic reticulum, golgi apparatus, lysosomes, vesicles, endosomes, vacuoles (plant cell) and the cell membrane
Endoplasmic reticulum (ER) is a
network of membranous tubules, vesicles and flattened sacs called cisternae
ER separate cisternal space from
cytosol
Function of ER
varies depending on the type of ER and the type of cell
Type of ER
- Smooth ER
- Rough ER
Quantity of SER and RER in a cell
quickly interchange depending on metabolic needs
Membrane of RER continuous with
the outer layer of the nuclear envelope
Cisternae are
flat and rough (studded with ribosomes that synthesis protein)
Ribosomes are part of the RER that are
not stable
Function of RER
- protein enter the cisternal space (lumen), altered/changed by enzyme (carbohydrate molecules normally added to glycoprotein)
- keep secretory proteins temporarily before being packed in vesicles and exported to the Golgi apparatus
- Proteins normally for export or membrane insertion
Smooth ER found in
a variety of cell types (both animal and plant) and it serves different functions
Cisternae of SER are
tubes-like, connected with RER, smooth surface
Function of SER
- synthesis lipids
- enzymes within SER catalyze various processes
Golgi apparatus made of a
stack of flattened membranous sacs (cisternae)
Cisternal space separated from cytosol by
membrane
Number of Golgi apparatus in an active cell
abundant
Function of Golgi apparatus
- modify, sort and package the macromolecules that are synthesized by the cells for secretion purposes or for use within the cell
Processes occur in Golgi apparatus
- Vesicles from RER fuse with cis face (receiving side)
and release the contents - contents are modified during the transit from cis to
trans face by various enzymes, marked and sorted
into batches, distribute to different destination in
transport vesicles which bud from trans face
(shipping side facing plasma membrane) - Vesicles move to plasma membrane, fused with it,
released the contents out. - Vesicle remain as a permanent addition to plasma
membrane
Lysosomes can be found in
all animal cells and some plant cells
Lysosomes is
- dark spherical bodies, smaller than mitochondria
- membrane-bound sac of digestive enzymes: digest macromolecules
Lysosome functions optimally in
acidic condition (pH 5)
Function of lysosome
- Enzymes found in lysosomes such as lipases,
carbohydrases and proteases - intracellular
digestion. - Recycling centre for the organelles - old organelles
are digested (autophagy), product reuse to form
new organelle. - Digest the remains of dead cell (autolysis)
- The process - RER put the enzymes and membranes
together, then Golgi apparatus chemically refine
the enzymes and releases mature lysosomes
Vacuoles is
a membrane-enclosed fluid filled sac found in the cells of plants including fungi
Main functions of vacuoles
- Contributes to the rigidity of the plants using water to develop hydrostatic pressure (contractile vacuole)
- store nutrient and non-nutrient chemicals (food vacuoles, central vacuoles)
- break down complex molecules (function lysosomes in animal cells)
A selective membrane enclosing the central vacuole
Tonoplast
Function of tonoplast
Controls passage of chemicals thought it in both directions, water can pass in and out freely but other small molecules are retained within the vacuole
Mitochondria and chloroplast
- Function in energy production.
- Contain own DNA and ribosome.
- Believe to be endosymbiotic bacteria.
Ribosomes and nucleus
Involved in protein synthesis (gene expression)
Mitochondria is a
rod-like structure
Amount of mitochondria
- large number (more in animal cells compared to plant cells)
Double-membrane of mitochondria
Outer membrane is smoot, define the shape
Cristae of mitochondria
infolded inner membrane partially divide the matrix
Mitochondria has
inter-membrane space between outer and inner membrane
Function of mitochondria
Use glucose and fatty acids to produce
ATP (energy) during cellular respiration (Krebs
cycle and electron transport chain - ETC)
Plant cristae of mitochondria are
tubular or villus-like but sheet-like plates in animal
Cristae of mitochondria facing
the matrix covered with stalked particles (carrier proteins in electron transport chain)
Matrix contain
enzymes, DNA and ribosome
Chloroplast contains
starch granules and oil droplets
Function of chloroplast
- Convert light energy of the sun into sugars that can
be used by cells. - Process is called photosynthesis by chlorophyll
molecules in each chloroplast.
Chloroplast has
- Double membrane separated by intermembrane space
- 50 grana - each granum
(singular) has about 50 thylakoids. - Photosynthetic pigments (chlorophyll a, b, carotenoid),
electron transport chain (ETC) are embedded within the
thylakoid membrane.
Stroma (dark reaction site) of chloroplast contain
ribosomes, DNA and photosynthetic
enzymes
Internal membrane of chloroplast is called
lamella which consist of
thylakoids that stacks up to form grana.
Light reaction site occur at
thylakoid membrane (surface)
Nucleus enclosed by
a nuclear envelope - double
membrane perforated by nuclear pores (100nm).
nuclear membrane is
impermeable to large
molecules
Function of nuclear pores
channel that allows free
movement of small molecules and ions
Outer membrane of the nucleus continuous with
membrane of RER
Nucleoplasm is the
semi-fluid substance in the
nucleus.
Nucleus contains
- Genetic material in
the form of chromatin or chromosomes - nucleolus (synthesis ribosomes)
Functions of nucleus
Control centre of the cell by:
- Maintain the genetic material
- Control gene expression (protein synthesis)
- Mediate the replication of DNA during cell cycle
- Provides a site for genetic transcription (synthesis
of mRNA)
- Allowing gene regulation (e.g.: lac operon system)
- Synthesis ribosomes (nucleolus)
Ribosomes made up of
RNA and proteins
Each subunit is released through
nuclear pores
Functions of Ribosomes
Synthesis protein:
- Based on genetic information carried by mRNA
from nucleus.
- Ribosomes joined amino acids to form polypeptide
/ protein
- Proteins synthesized by cytoplasmic ribosomes
(free) are used within the cell.
- Protein from RER (synthesized by attached
ribosomes) are exported out or inclusion of
membrane (digestive enzymes in lysosome)
