Chapter 4 Flashcards
What do cells contain?
Water and other small and large molecules
How many different types of molecules do cells have?
Over 10,000
What do cells use their molecules for?
~transforming matter and energy
~responding to their environments
~reproducing
cell theory
~cells are the fundamental units of life
~all living organisms are composed of cells
~all cells come from preexisting cells
What is the diameter range for most cells?
1 to 100 micrometers
surface area-to-volume ratio
decreases as the size increases
as an object increases in volume, its surface area also increases, but not as quickly
What does the volume of a cell determine?
the amount of metabolic activity it carries out per unit time
What does the surface area of a cell determine?
the amount of substances that can enter it from the outside environment, and the amount of waste products that can exit to the environment
What happens as a living cell grows larger?
metabolic activity, and thus its need for resources and its rate of waste production, increases faster than its surface area
Substance motion is more easily accomplished in what size cell?
smaller cells
How does a multicellular organism make use of the surface area-to-volume ratio?
large surface area-to-volume ratio represented by the many small cells of a multicellular organism enables it to carry out the many different functions required for survival
What is another way for cells to attain an adequate exchange of materials with the environment?
increase surface area through folds in the cell membrane or increase the rate of exchange of materials across the cell
light microscope
~uses glass lenses and visible light to form images
~size limit is 0.2 micrometers
~visualise living cells and general cell structure
electron microscope
~uses an electron beam focused by magnets to illuminate a specimen and produce an image on a TV-like screen
~size limit is 0.1 nanometers
~specimens must be preserved and stained using toxic heavy metals
cell membrane
~selectively permeable barrier
~allows cell to maintain a stable internal environment distinct from the surrounding environment
~important in communicating with adjacent cells and receiving signals from the environment
~has proteins responsible for binding and adhering to adjacent cells or surfaces
~important structural role, contributes to shapes
What are the three domains?
Archaea, Bacteria, and Eukarya
prokaryotes
~Archaea and Bacteria kingdoms
~typically no membrane-enclosed internal compartments
~no nucleus
eukaryotes
~contains membrane-enclosed compartments called organelles
~contains a nucleus, where DNA is located and gene expression begins
advantages of compartmentalization
provides possibilities for regulation and efficiency that were important in the evolution of complex organisms
cell membrane (prokaryotes)
encloses the cell, separating its interior from the external environment, and regulates the traffic of materials into and out of the cell
nucleoid
region in the cell where the DNA is located
DNA
the hereditary material that controls cell growth, maintenance, and reproduction
cytoplasm (prokaryotes)
the rest of the material inside the cell (liquid and other insoluble filaments/particles)
cytosol (prokaryotes)
consists mostly of water containing dissolved ions, small molecules, and soluble macromolecules such as proteins
ribosomes (prokaryotes)
complexes of RNA and proteins that are the sites of protein synthesis
protein synthesis
where the information encoded by nucleic acids directs the sequential linking of amino acids to form proteins
cell wall (prokaryotes)
~supports cell and determines shape
~mostly containing peptidoglycan
~some bacteria have cell walls with phospholipid membranes or layers of polysaccharides
capsule (prokaryotes)
the polysaccharide layer enclosing the cell in bacteria, which protects the bacteria from attack, keeps the cell from drying out, and sometimes helps them attach to other cells
internal membrane
~in some groups of bacteria
~contains molecules needed for photosynthesis
flagella (prokaryotes)
~appendages that help cells swim and move around
~made of protein called flagellin
cytoskeleton (prokaryotes)
filaments made up of polymers of monomer subunits that play roles in cell division or in maintaining the shapes of cells
Why is compartmentalisation the key to eukaryotic cell function?
each type of organelle has a specific role in the cell
ribosomes (eukaryotes)
~translate the nucleotide sequence of a messenger RNA molecule into a polypeptide chain
~consist of one larger and one smaller subunit, each containing one to three ribosomal RNA molecules and smaller protein molecules
~not membrane-enclosed compartments
nucleus (eukaryotes)
~contains most of the DNA ~usually the largest organelle ~location of the DNA and the site of DNA replication ~where DNA is transcribed into RNA ~contains a region called the nucleolus
nucleolus
a region inside the nucleus where ribosomes begin to assemble from RNA and proteins
What is the nucleus enclosed by?
two lipid bilayer membranes that together form the nuclear envelope
chromosomes
extremely long, thin threads of DNA molecules and proteins
chromatin
DNA-protein complexes
What is the outer membrane of the nucleus continuous with?
the membrane of the endoplasmic reticulum
endomembrane system
~interconnected system of membrane-enclosed compartments
~includes: nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes
vesicles
tiny membrane-surrounded droplets which shuttle substances between the various components of the endomembrane system
endoplasmic reticulum
networks of interconnected membranes branching through the cytoplasm, forming tubes and flattened sacs
rough endoplasmic reticulum
~has ribosomes attached to the outer surface of the membrane
~protein enters if it contains a specific sequence of amino acids that signals the ribosome to attach to the RER
~inside, proteins are chemically modified to induce 3D functional shape
~transports proteins to other locations in the cell
glycoproteins
proteins covalently linked to carbohydrate groups
smooth endoplasmic reticulum
~connects to portions of the RER but lacks ribosomes and is more tubular
~chemical modification of small molecules
~glycogen degradation in animal cells
~where lipids and steroids are synthesised
~stores calcium ions, which when released trigger a number of cell responses, including muscle contraction
Golgi apparatus
~cisternae and small vesicles
~concentrates, packages, and sorts proteins before they are sent to their cellular or extracellular destinations
~adds some carbohydrates to proteins
~where some polysaccharides for the plant cell wall are synthesised
cisternae
~cis region - lies closest to the nucleus or a patch of RER, protein-containing vesicles fuse here
~trans region - lies closest to the cell membrane, vesicles carry their component away from the Golgi apparatus
~medial region - lies in between
primary lysosomes
~originate from the Golgi apparatus
~contain hydrolases (digestive enzymes)
~macromolecules (proteins, polysaccharides, nucleic acids, and lipids) are hydrolysed into their monomers
phagocytosis
pocket forms in the cell membrane and then deepens and encloses material from outside the cell, becoming a phagosome which breaks free of the cell membrane to move into the cytoplasm
phagosome
a small vesicle containing macromolecules, formed by phagocytosis, which can fuse with a primary lysosome to form a secondary lysosome
secondary lysosome
where hydrolysis occurs, later fuses with the cell membrane to release undigested contents to the environment
phagocytes
specialised cells whose major role is to take in and break down materials
autophagy
the programmed destruction of cell components
mitochondria
~primary function is to harvest the chemical energy of energy-rich molecules in a form the cell can use, namely ATP
~contains some DNA
~can divide independently of the central nucleus
~outer membrane - large pores which most substances can pass through
~inner membrane - extensively folded into cristae
~contains enzymes for energy metabolism, as well as DNA and ribosomes for the synthesis of some mitochondrial proteins
mitochondrial matrix
fluid-filled region inside the inner membrane
ATP
adenosine triphosphate, an energy rich nucleotide
plastids
present in the cells of plants and algae and can divide autonomously
chloroplast
~contains chlorophyll
~site of photosynthesis
thylakoids
~internal membranes of the chloroplast that look like stacks of flat, hollow disks
~here, light is converted into chemical energy
grana
stacks of thylakoids
peroxisomes
accumulate toxic peroxides and break them down safely without mixing with other components of the cell
glyoxysomes
~found only in plants
~converts stored lipids into carbohydrates for transport to growing cells
vacuoles
~storage for toxic by-products and waste products
~structure, dictates turgor pressure based on osmosis
~contains some pigments which help in attracting animals for pollination and seed dispersal
~contain enzymes for catabolism that hydrolyse stored seed proteins into monomers
roles of the cytoskeleton
~supports the cell and maintains its shape
~holds cell organelles in position
~moves organelles and other particles around within the cell
~involved with cytoplasmic streaming
~interacts with extracellular structures
cytoplasmic streaming
movements of the cytoplasm
What are the components of the eukaryotic cytoskeleton?
~microfilaments (smallest diameter)
~intermediate filaments
~microtubules (largest diameter)
microfilaments
~help entire cell or cell parts to move
~determine and stabilise cell shape
~made from actin monomers
~dynamic instability
actin
monomers that attach to the filament at one end (plus end) and detach at the other (minus end) to assemble microfilaments
motor protein
any protein that causes movement within a cell
pseudopodia
cellular extensions formed by microfilaments that enable some cells to move
intermediate filaments
~more permanent and do not show dynamic instability
~anchor cell structures in place
~resist tension
microtubules
~form a rigid internal skeleton for some cells or cell regions
~act as a framework along which motor proteins can move structures within the cell
~dynamic instability
tubulin
the protein which microtubules are assembled from
cilia
move stiffly either to propel a cell or to move fluid over a stationary cell
flagella
occur either singly or in pairs, and can push or pull the cell through its aqueous environment
“9+2” array of microtubules
9 fused pairs of microtubules (doublets) form an outer cylinder, and one pair of unfused microtubules runs up the centre
dynein molecules
a motor protein, which can change its three dimensional shape, that binds between two neighbouring microtubule doublets
kinesin
carry protein-laden vesicles or other organelles from one part of the cell to another by “walking” it along a microtubule
Dynein moves attached organelles towards which end of the microtubules?
minus end
Kinesin moves attached organelles towards which end of the microtubules?
plus end
What are the “extracellular” molecules made from?
~fibrous macromolecule
~gel-like medium in which the fibres are embedded
What are the roles of the cell wall?
~provides support for the cell and limits the volume of a mature cell by remaining rigid
~acts as a barrier to infection by fungi and other organisms that can cause plant diseases
~contributes to plant form by controlling the direction of cell expansion during growth and development
plasmodesmata
cell membrane-lined channels connecting the cytoplasms of adjacent plant cells
extracellular matrix
~hold cells together in tissues
~contribute to physical properties of tissues
~filter materials passing between different tissues
~orient cell movements during embryonic development and tissue repair
What connects the cell membrane to the extracellular matrix?
proteins (ex: integrin) that bind to the interior of the cell and to collagen in the extracellular matrix
cell junction
specialised structures protruding from adjacent cells to “glue” them together
tight junctions
prevent substances from moving through spaces between cells
desmoosmes
hold adjacent cells together with stable protein connections, but materials can still move around in the extracellular matrix
gap junctions
channels that run between membrane pores in adjacent cells, allowing substances to pass between cells
