CHAPTER 5 Flashcards
cell theory is an important unifying theory of biology:
-cells are the fundamental units of life
-all organisms are composed of cells
-all cells come from preexisting cells
-modern cells evolved from a common ancestor
surface area-to-volume ratio of a cell
as a cells volume increases chemical activity increases, along with the need for resources and waste removal which means they need more energy, more organelles, etc but volume increasing limits the surface area which is why cells stay small
magnification
increases apparent size
resolution
clarity of magnified object–minimum distance two objects can be apart and still be seen as two objects
two basic types of microscopes:
-light microscopes: glass lenses and light; resolution = 0.2 μm
-electron microscopes: electromagnets focus an electron beam; resolution = 0.2μm
cell membrane
outer boundary of evert cell; similar structure in all cells– a phospholipid bilayer with embedded proteins
cytoplasm
everything in the cell except the nucleus
cytosol
fluid cytoplasm not contained inside another compartment
the cell membrane
-is a selectively permeable barrier
-allows cells to maintain a constant internal environment
-is important in communication and receiving signals
-often has proteins for binding and adhering to adjacent cells
two types of cells?
-prokaryotic (bacteria and archaea): have no membrane-enclosed internal compartments
-eukaryotic (eukarya): have membrane-enclosed organelles in which different functions occur
features of prokaryotic cells?
-enclosed by a cell membrane
-DNA located in a region called the nucleoid
-cytoplasm:the rest of the cell contents
ribosome: sites of protein synthes
cytoplasm
the rest of the cell contents
ribosomes
sites of protein synthesis
prokaryotes cell wall
the cell wall is rigid on the outside of the cell membrane which helped withstand environment and gave it stronger structural support
what do bacterial cell walls contain?
-they contain peptidoglycan and some have an additional outer membrane
-some bacteria have slimy capsule of polysaccharides
bacteria that carry out photosynthesis have?
they have internal membrane system that contains the molecules needed for photosynthesis
cytoskeleton
system of protein filaments that maintain cell shape and play roles in cell movement and cell division.
-protein fibers support the shape and movement
how do some prokaryotes swim?
they use flagella (long) made of the protein flagellin; which helps with movement as well swimming, moving back and forth from propelling
pili
pili (short)are hairlike structures projecting from the cell surface. they help bacteria adhere to other cells (sticky)
fimbriae
they are shorter and they also help cells adhere to surfaces such as animal cells
eukaryotic cells
-about 10 times larger than those of prokaryotes
-membrane-enclosed organelles carry our specific functions
-most eukaryotic cells have similar organelles
organelles
-organelles were first studied using light microscopy and then electron microscopy
ribosomes
-sites of protein synthesis
-similar structure in prokaryotes and eukaryotes
-consist of two subunits: ribosomal RNA (rRNA) and more Thant 50 different protein molecules
nucleus
-usualyl the largest organelle
-contains most of the DNA
-site of DNA replicaiton
-site where gene transcription is turned on or off
-assembly of ribosomes begins in a region called the nucleolus
nucleolus
a small, generally spherical body found within the nucleus of eukaryotic cells. the site of synthesis of ribosomal RNA
nuclear envelope
-A double membrane that encloses the cell nucleus.
-surrounds the nucleus
-nuclear pores in the envelope control movement of molecules across the envelope
-the outer membrane is continuous with the endoplasmic reticulum
chromatin
-The nucleic acid–protein complex that makes up eukaryotic chromosomes.
-DNA combined with proteins form chromatin
chromosomes
DNA and protein that contain genetic information
endomembrane system
-interconnected system of membrane-enclosed compartments
-tiny membrane surrounded vesicles shuttle substances between the various components
-in the living cell, the membranes and the materials they contain are in constant motion
endoplasmic reticulum (ER)
-network of membranes in the cytoplasm; large surface area
rough endoplasmic reticulum (RER)
-ribosomes are attached
-newly made proteins enter the RER lumen and are modified, folded, and transported to other regions in vesicles that pinch off from the RER
smooth endoplasmic reticulum (SER)
-no ribosomes
-chemically modifies small molecules such as drugs and pesticides
-site of glycogen degradation in animal cells
-synthesis of lipids and steroids
-stores calcium ions
Golgi apparatus
-flattened sacs (cistern) and small vesicles
-receives proteins from the RER
-modifies, concentrates, packages, and sorts proteins
-in plant cells, polysaccharides for cell walls are synthesized here
lysosomes
-contain digestive enzymes that hydrolyze macromolecules into monomers
-primary lysosomes originate from the golgi apparatus
-breakdown
how do food molecules enter the cell?
-by phagocytosis- a phagosome is formed
-the cell is eating something that comes inside
secondary lysosomes
-phagosomes fuse with primary lysosomes to form secondary lysosomes
-enzymes hydrolyze the food molecules
how is waste ejected?
by the exocytosis
mitochondria
-energy in fuel molecules such as glucose is transformed to the bonds of energy-rich ATP (cellular respiration)
-if a cell requires more energy it will have many mitochondria
-power house of the cell
-they can reproduce and divide independently of the central nucleus
what does the mitochondria have?
-it has two membranes
-inner membrane folds inward to form cristae: creates large surface area for the embedded proteins involved in cellular respiration
what does the mitochondrial matrix contain?
-contains DNA and ribosomes to make the proteins needed for cellular respiration
plastids
-only in plants and some protists
chloroplasts
-site of photosynthesis; have a double membrane. can divide independently of the nucleus
what does the inner membrane form in the chloroplasts?
-forms thylakoids(stack of discs) which contain chlorophyll and other pigments that harvest light energy
other plastids?
-chromoplasts contain red, orange, and yellow pigments– give color to flowers
-leucoplasts store starches and fats
peroxisomes
collect and break down toxic byproducts of metabolism such as H2O2, using specialized enzymes
glyoxysomes
only in plants– lipids re converted to carbohydrates for growth
plant and protist cells have vacuoles?
-provide structure for plant cells– water enters the vacuole by osmosis, creating tumor pressure
-store anthocyanin (pink and blue pigments) in flowers and fruits; the colors attract pollinators
cytoskeleton
-supports and maintains cell shape
-holds organelles in postion
-moves organelles
-involved in cytoplasmic streaming
-interacts with extracellular strictures to hold cell in place
-composed of three types of filaments
microfilaments
-help a cell or plants of a cell to move
-determine cell shape
-made from the protein actin
-actin polymerizes to form long helical chains (reversible)
-have distinct ends: plus and minus
intermediate filaments
-50 different kinds in 6 molecular classes
-tough, roselike protein structures
-anchor cell structs in place
-resist tension
microtubules
-big and tubelike
-long hallow cylinders
-form a rigid internal skeleton
-act as a framework for motor tubulin
-can change length rapidly by adding or losing dimers at plus or minus ends
cilia and flagella
-cilia and eukaryotic flagella are made of microtubules in “9 + 2” array
-cilia: short, hundreds on one cell, move stiffly to propel the cell or move fluid over a cell
-flagella: longer, usually one or two present, movement is snakelike
motor proteins
-moving stuff around
-microtubules serve as tracks for motor proteins, which moves vesicles or organelles from one part of a cell to another
experiments to determine the function of cellular components fall into two categories:
-inhibition: use a drug that inhibits a structure of process (slow/stop something from happening)
-mutation: examine a cell that lacks the gene for the structure or process
what happens to extracellular structures?
-they get secreted to the outside of the cell membrane
-they consist of fibrous macromolecules embedded in a gel-like medium
plant cell walls
-cellulose fibers are embedded in other complex polysaccharides and proteins
-provide rigid yet flexible support for the plant
-are a barrier to diseases organisms
-contribute to plant form as growing cells expand
plasmodesmata
-adjacent plant cells are connected by cell membrane-lined channels called plasmodesmata that permit movement of water, ions, small molecules, RNA, and proteins
extracellular matrix
-many animal cells are surrounded by an extracellular matrix composed of fibrous proteins such as collagen, gel-like proteoglycans, and other proteins
-holds cells together in tissues
-contributes to properties of bone, cartilage, skin, etc
-filters materials passing between different tissues
-orients cell movements in development and tissue repair
-plays a role in chemical signaling
when did the first eukaryote cells appear? what led to the evolution of eukaryotic cells?
-evidence of the first eukaryote cells appears in the fossil record 2.7 billion years ago
-the advent of compartmentalization and evolution of eukaryotic cells
how may the nucleus and endomembrane system originated?
-from the inward folds of the cell membrane in prokaryotes
enclosed compartments would be advantageous?
-chemicals could be concentrated and chemical reactions would processed more efficiently
symbiosis
-cells came about through symbiosis
-some organelles too
the theory of endosymbiosis
-proposes that mitochondria and plastids arose when one cell engulfed another cell
-many of the ingest cell’s genes were transferred to the host’s DNA but the symbionts retained specialized functions
