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Biology in Focus | Campbell
What is life’s basic unit of structure and function?
the cell
What occurs as a cell increases in volume?
its surface area-to-volume ratio decreases, causing the exchange of materials to become less efficient
How can the concept of surface-area-to-volume ratio be applied to organisms?
as organisms increase in size, their surface-area-to-volume ratio will decrease, affecting the organism’s properties
What is an example of how surface-area-to-volume ratio affects the properties of organisms?
small organisms lose heat at much higher rates than larger organisms as a result of their efficient exchange of heat
What are light microscopes used to study?
stained or living cells
What are electron microscopes used to study?
detailed structures of a cell that cannot be easily seen or observed by light microscopy
What summarizes how prokaryotic and eukaryotic cells differ?
prokaryotic cells are smaller and simpler while eukaryotic cells are bigger and more complex
What are the two distinct types of cells?
prokaryotic and eukaryotic
What are examples of prokaryotes?
bacteria and archaea
What is cytoplasm?
the substance the fills the inside of a cell
What are the characteristics of the genetic material in a prokaryote?
it is one continuous circular DNA molecule that is found free in the in the nucleoid
What structures are found in both prokaryotic and eukaryotic cells?
plasma membrane, cytoplasm, ribosomes, and DNA
What structures are only found in eukaryotic cells?
the nucleus, endoplasmic reticulum, Golgi apparatus, vacuoles, lysosomes, mitochondria, and chloroplasts
What structures are only found in prokaryotic cells?
nucleoids, plasmids, and capsules
What are flagella?
structures found in some bacteria that are used for motility and might have a thick capsule outside their cell wall for extra protection
True or false: Prokaryotes have membrane-bound organelles
false
What are examples of eukaryotes?
fungi, protists, plants, and animals
What are organelles?
smaller structures within cells
What is the plasma membrane?
the outer envelope of the cell
What is the plasma membrane made up of?
mostly phospholipids and proteins
Why is the plasma membrane important?
it regulates the movement of substances into and out of the cell
What does it mean for the plasma membrane to be semipermeable?
it allows certain substances to pass through it and blocks others
What are peripheral proteins?
proteins loosely associated with the lipid bilayer of the plasma membrane
What are amphipathic/integral proteins?
proteins firmly bound to the plasma membrane
What is the fluid-mosaic model?
the currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids
What type of proteins form junctions between adjacent cells?
adhesion
What is the function of receptor proteins?
to serve as docking sites for arrivals at the cell
What do transport proteins form?
pumps that use ATP to actively transport solutes across the membrane
What do channel proteins form?
channels that selectively allow the passage of certain ions of molecules
What are cell surface markers?
proteins or carbohydrates exposed on the extracellular surface that play a role in cell recognition and adhesion
Where are carbohydrate side chains found?
only on the outer surface of the plasma membrane
What is usually the largest organelle in the cell?
the nucleus
What is the function of the nucleus?
to direct what goes in on the cell and be responsible for the cell’s ability to reproduce
What is the nucleus the home of?
the cell’s hereditary information (DNA)
What are chromosomes?
large structures that a cell’s DNA is organized into
What is the most visible structure within the nucleus?
the nucleolus
What is the function of the nucleolus?
to serve as the location where rRNA is made and ribosomes are assembled
What are ribosomes the site for?
protein synthesis
What is the function of ribosomes?
to manufacture all the proteins required or secreted by the cell
What are the physical characteristics of ribosomes?
round structures composed of two subunits, the large subunit and the small subunit, both of which are composed of rRNA and proteins
can either be free floating in the cell or attached to the endoplasmic reticulum (ER)
What is the endoplasmic reticulum (ER)?
a continuous channel that extends into many regions of the cytoplasm
What is the function of the endoplasmic reticulum (ER)?
to provide mechanical support and transportation and compartmentalize the cell
How do the smooth and rough ER differ in terms of structure?
the rough ER has ribosomes on its surface while the smooth ER doesn’t
How do the smooth and rough ER differ in terms of function?
the smooth ER makes lipids, carbs and enzymes and detoxifies drugs and poisons, while the rough ER makes proteins and membranes
What is the post office of the cell?
the Golgi apparatus
What is the function of the Golgi apparatus?
to modify, process, and sort the products after the rough ER synthesizes proteins
What are vesicles?
the little sacs that materials sent out of the cell through the plasma membrane are packaged into
What are the power stations of the cell?
mitochondria
What is the function of mitochondria?
to convert energy from organic molecules into useful energy for the cell
What is the most common energy molecule in the cell?
adenosine triphosphate (ATP)
What do mitochondria consist of?
an inner portion and an outer portion
What does the inner mitochondrial membrane do?
form folds known as cristae and separate the innermost area from the intermembrane space
What does the outer mitochondrial membrane do?
separate the intermembrane space from the cytoplasm
What are the garbage collectors of the cell?
lysosomes
What are lysosomes?
sacs of digestive enzymes that break down old, worn-out organelles, debris, or large ingested particles
When are lysosomes made?
when vesicles containing specific enzymes form the trans Golgi fuse with vesicles made during endocytosis
What process are lysosomes essential to?
apoptosis
What are vacuoles?
fluid-filled sacs that store water, food, wastes, salts or pigments
What are peroxisomes?
organelles that detoxify various substances, producing hydrogen peroxide (H2O2) as a product and have enzymes that break down hydrogen peroxide into oxygen and water
What is the cytoskeleton?
the network of protein fibers that determine the shape of a cell
What are the most important fibers in the cytoskeleton?
microtubules and microfilaments
What are microtubules made up of?
a protein called tubulin
What is the function of microtubules?
cellular division and movement
What are microfilaments made up of?
a protein called actin
What are microfilaments important for?
movement
How do microfilaments grow and shrink?
actin monomers are joined together and broken apart as needed
What properties do cilia and flagella have in single-celled organisms?
locomotive
What allows the cilia and flagella structure to move?
their beating motion
What structures do plant cells have that animal cells don’t?
cell walls, chloroplasts, and central vacuoles
What structures do animals cells that plant cells don’t?
centrioles
What is a cell wall?
a rigid layer just outside the plasma membrane that provides support for plant cells
What gives plants their characteristic green color?
chlorophyll
What is the function of chloroplasts?
to convert light energy to chemical energy (ATP)
What is the central vacuole?
the large vacuoles that take up the cytoplasm within a plant cell
What is the function of centrioles?
to help move chromosomes
What 2 factors does the ability of molecules to move across the cell membrane depend on?
the semipermeability of the plasma membrane
the size and charge of particles that want to get through
How do small substances cross the membrane without any resistance?
like dissolves like
Why can only hydrophobic materials pass the central zone of the membrane?
the lipid bilayer is hydrophilic on the outside and hydrophobic on the inside
What occurs if a hydrophilic material attempts to pass through the membrane?
the bilayer won’t let it pass without assistance
What are aquaporins?
water-specific channels
How are glucose and ions transported across the membrane?
via membrane proteins
What can happen to membranes as ions move across them?
they may become polarized
What is diffusion?
the movement of particles from an area of high concentration to an area of low concentration; moving down the concentration gradient
When does simple diffusion occur?
when the molecule that is diffusing is hydrophobic
Why is it called simple diffusion?
because the small nonpolar molecule can just drift right through the membrane without trouble
When does facilitated diffusion occur?
when diffusion requires the help of a channel-type protein
When does passive transport occur?
anytime that a substance is moving by diffusion
Why is it called passive transport?
because there is no outside energy required to power the movement
What is the difference between osmosis and diffusion?
the membrane is usually permeable to solute in diffusion, while in osmosis, it is not
How is the cell wall important to protect it against osmotic changes in plants?
the cell membrane can shrink away from the wall if it loses water and can expand and squeeze tightly against the cell wall if it takes in water
What is tonicity used to describe?
osmotic gradients
What does it mean for an environment to be isotonic to the cell?
the solute concentration is the same inside and outside
When is a solution hypertonic?
when it has more total dissolved solutes than the cell
When is a solution hypotonic?
when it has less total dissolved solutes than the cell
What is water potential?
the measure of potential energy in water
What does water potential describe?
the eagerness of water to flow from an area of high water potential to an area of low water potential
What is water potential affected by?
pressure potential and solute potential
What does adding a solute do to the water potential of a solution?
it lowers the water potential, causing water to be less likely to leave this solution and more likely to flow into it
What is active transport?
the movement of particles from an area of low concentration to an area of high concentration; moving against the concentration gradient
When does primary active transport occur?
when ATP is directly utilized to transport something
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