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Cell theory:
What are 3 core principles
Cell theory: the first unifying theory of biology
- Cells are the fundamental units of life
- All organisms are composed of cells
- All cells come from preexisting cells
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Why are cells so small? What do volume and surface area determine?
- Cells are small because a high surface area-to-volume ratio is essential.
- Volume determines the amount of chemical activity in the cell per unit time
- Surface area determines the amount of substances that can pass the cell boundary per unit time
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Define the plasma membrane
The outer surface of every cell made up of a phospholipid bilayer w/ proteins and other molecules embedded. It has more or less the same structure in all cells
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The phospholipid bilayer is not ____, but more like an ____ fluid in which the _____ & _____ are in constant motion
- rigid
- oily
- proteins & lipids
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4 characteristics of the plasma membrane
- is a selectively permeable barrier
- allows cells to maintain a constant internal environment
- is important in communicating & receiving signals
- often has proteins for binding and adhering to adjacent cells
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Two types of cells
- Prokaryotic cells
- Eukaryotic cells
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2 types of prokaryotic cells
bacteria & archaea
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In eukaryotic cells, the DNA is in a __________ compartment called the ______
- membrane-enclosed compartment
- nucleus
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Prokaryotes are enclosed by a ____ _____. Their DNA is contained in the _____.
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The cytoplasm of prokaryotes consists of _____ and ____
cytosol (water and dissolved material) & suspended particles
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Ribosomes
sites of protein synthesis found in prokaryotes and eukaryotes
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Eukaryotes haves other _____ _____ ____ (____) in which specific chemical reaction occur.
membrane enclosed compartments (organelles)
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State 4 characteristics of the nucleus
- usually the largest organelle
- contains the DNA
- site of DNA replication
- site where gene transcription is turned on or off
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Name an activity that begins in the nucleolus
assembly of ribosomes
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The nucleus is surrounded by a double membrane structure?
the nuclear envelope
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____ ____ in the envelope control movement of molecules between _____ and _____
- nuclear pores
- nucleus and cytoplasm
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some large molecules (like _____) must have a certain amino acid sequence known as a _____ ____ _____ to cross the nuclear envelope
- proteins
- nuclear localization signal
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The endomembrane system consists of (5)
- plasma membrane
- nuclear envelope
- endoplasmic reticulum
- golgi apparatus
- lysosomes
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Tiny ____ _____ _____ shuttle substances between various components of the endomembrane system
membrane surrounded vesicles
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Endoplasmic reticulum function:
- synthesis of new proteins (RER)
- synthesis of lipids, oils, phospholipids, & steroids (SER).
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____(SER/RER) does NOT have ribosomes
smooth endoplasmic reticulum (SER)
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endoplasmic reticulum
it is a network of interconnected membranes in the cytoplasm; has large surface area
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In ER, newly synthesized proteins are transported into the ____ ____. It then does what to the protien?
- RER lumen
- modifes, folds, and transorts protein
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Ribosomes consists of more than ___ ____ ____ molecules and are _____ bonded to ______ RNA
- 50 different protein molecules
- noncovalently
- ribosomal RNA
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______ are considered little factories for proteins. They also float freely in ______ cells
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3 characteristics of ribosomes in eukaryotes
- found in cytoplasm free or attached to the ER
- found inside mitochondria and chloroplasts
- in neurons can found over a meter from the cell body
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_____ are NOT considered an organelle
ribosomes
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The golgi apparatus is composed of?
- flattened sacs (cisternae)
- small membrane enclosed vesicles
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3 functions of golgi apparatus
- receives proteins from RER (can further modify them)
- concentrates, packages & sorts proteins
- adds and modifies carbohydrates to proteins
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The cis region receives _____ (a piece of the ER that buds off) from the ___
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In the golgi apparatus, what occurs at the trans region?
Vesicles bud off from the golgi apparatus and are moved to the plasma membrane or other organelles
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Primary lysosomes originate from the ___ ____. They contain ____ ____ (also state function)
- golgi apparatus
- digestive enzymes that hydrolyze macromolecules into monomers
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Food molecules enter the cell (lysosomes) via _____. What is formed?
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Phagosomes fuse with ____ _____ to form ____ _____. Enzymes in the ____ ____ hydrolyze the ____ ____
- primary lysosomes
- secondary lysosomes
- secondary lysosomes
- food molecules
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Lysosomes also digest cell materials (what is this process called?)
autophagy
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Cell components of lysosomes are frequently?
destroyed and replaced by new ones
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In the ______, energy in fuel molecules is transformed to the bonds of ____ ___ ___. This process is called ____ ____
- mitochondria
- energy rich ATP
- cellular respiration
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Cells that require of energy have a lot of _____
mitochondria
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Two membranes of mitochondria
- inner membrane: folds inward to form cristae
- outer layer
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The cristae creates?
a large surface area for proteins involved in cellular respiration reactions
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the mitochondrial matrix consists of: (3)
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Chloroplasts have a ___ ____ & are the site of ______. During this process, what occurs.
- double membrane
- photosynthesis
- energy is converted to the energy of chemical bonds
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Three major structures within chloroplasts
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_____ are stacks of thylakoids (what are thylakoids made of?)
- grana
- made of circular compartments of the inner membrane
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Thylakoids contain _____ and other ____ that harvest light energy for photosynthesis
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Define stroma and state 2 things it contains
- fluid within chloroplasts in which grana are suspended
- contains DNA and ribosomes
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Some organelles may have arose via ______ (living together)
symbiosis
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The endosymbiosis theory
proposes that mitochondria and plastids arose when one cell engulfed another cell
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2 factors that support the endosymbiosis theory
- The discovery of a single-celled eukaryote, hatena, that ingests a green alga (Nephroselmis)
- The green alga loses most of its structures and acts as a chloroplast
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4 functions of cytoskeleton
- holds organelles in position or moves them
- cytoplasmic streaming
- changes the shape of the cell
- interacts with extracellular structures to stabilize the cells
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The cytoskeleton's ability to change the shape of the cell is critical for?
Neurons (development, injury, learning and memory)
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3 components of the cytoskeleton
- microfilaments
- intermediate filaments
- microtubules
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4 characteristics of microfilaments
- help a cell or parts of a cell to move
- determine cell shape
- made from the protein actin
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Actin has _ & _ ends and polymerizes to form?
- + and - ends
- long helical chains (reversible)
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In some cells, microfilaments form a ______ just inside the ____ ____
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Purpose of the meshwork
provides structure, for example in the microvilli that line the human intestine
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4 characteristics of intermediate filaments
- tough, ropelike protein assemblages
- anchor cell structures in place
- resist tension
- axon growth
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4 characteristics of microtubules
- form rigid internal skeleton in some cells
- made from the protein tubulin (a dimer)
- have + and - ends
- can change length rapidly by adding and losing dimers
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