chapter 2: cell physiology

first basic cellular function

obtain nutrients and eliminate wastes

second basic cellular function

metabolism - use of O2 and nutrients to produce energy (ATP)

third basic cellular function

respiration - exchange of gases (O2 and CO2)

fourth basic cellular function

protein synthesis - transcription and translation

fifth basic cellular function

movement - internal and/or external movement

sixth basic cellular function

respond to stimuli

seventh basic cellular function

reproduction

plasma membrane

encloses the cell; composed of a phospholipid bilayer with embedded proteins; selectively permeable; separates the intracellular fluid from the extracellular fluid

phospholipid bilayer

forms basic structure of the membrane; hydrophilic interior serves as a barrier to passage of water soluble substances between ICF and ECF; responsible for fluidity of the membrane

phospholipid bilayer consists of

membrane proteins, cholesterol, and carbohydrates

membrane proteins

integral proteins and peripheral proteins

cholesterol

fluidity and stability; tucked between phospholipids

carbohydrates

outer surface of plasma membrane only

nucleus

the control center of the cell, protects its DNA. DNA directs the cell’s activities by providing the instructions for protein synthesis

components of the nucleus

nuclear envelope, nuclear pores, nucleoli, chromatin and chromosomes

nuclear envelope

composed of a double membrane; outer membrane continuous with the rough ER and has ribosomes on surface

nuclear pores

locations where the inner and outer nuclear membranes fuse together; allows RNA out of the nucleus and proteins into the nucleus

nucleoli

dark-staining bodies within nuclei; produces ribosomes; where rRNA is produced

chromatin and chromosomes

coiled DNA and proteins; extended chromatin is transcriptionally active and chromosomes are densely packed chromatin seen during mitosis and meiosis; suspended in nucleoplasm

cytoplasm

all cellular components between plasma membrane and nuclear envelope

components of cytoplasm

cytosol, organelles, cytoplasmic inclusions

cytosol

jelly-like fluid containing substance within the which other cytoplasmic elements are suspended

organelles

contain membranous and non-membranous

membranous

enclosed by plasma membrane like structure

non-membranous

not enclosed by lipid bilayer

cytoplasmic inclusions

diverse group of molecules

examples of cytoplasmic inclusions

melanin, glycogen, and triglycerides

endoplasmic reticulum

an extensive, continuous membranous network of flattened sacs and tubes, partially studded with ribosomes; protein and lipid producing system

rough endoplasmic reticulum

continuous with nuclear envelope; studded with ribosomes; stacks of relatively flattened interconnected sacs; makes lots of proteins

smooth endoplasmic reticulum

continuous with RER; lacks ribosomes; network of tiny interconnected tubes

how does the ER transport nutrients

proteins from RER are packaged into transport vesicles by the SER for transport to the golgi body

structure of ribosomes

non-membrane bound dense particles of RNA and protein composed of 2 distinct subunits (small and large)

function of ribosomes

site of protein synthesis or translation (RNA nucleotides → amino acid sequence)

two types of ribosomes

attached and free

attached ribosomes

proteins secreted from cell, incorporated into plasma membrane, or lysosomal enzymes; found outside nuclear envelope and outside of RER

free ribosomes

produce proteins that function within the cell; found within cytosol

golgi complex

consists of stacks of flattened, slightly curved membrane-enclosed sacks

function of golgi complex

receives transport vesicles from ER and processes the raw materials into finished products, then sorts and directs the finished products to their final destination

secretory vesicles

vesicles that contain secretory materials

first step in endomembrane system

the rough ER synthesizes proteins to be secreted to the exterior or to be incorporated into plasma membrane or other cell components

second step in endomembrane system

the smooth ER packages the secretory product into transport vesicles, which bud off and move to the golgi complex

third step in endomembrane system

the transport vesicles fuse with the golgi complex, open up, and empty their contents into the closest golgi sac

fourth step in endomembrane system

the newly synthesized proteins from the ER travel by vesicular transport through the layers of the golgi complex, which modifies the raw proteins into final form and sorts and directs the finished products to their final destination by varying their wrapper

fifth step in endomembrane system

secretory vesicles containing the finished protein products bud off the golgi complex and remain in the cytosol, storing the products until signaled to empty

sixth step in endomembrane system

on appropriate stimulation, the secretory vesicles fuse with the plasma membrane, open, and empty their contents to the cell’s exterior. secretion has occurred by exocytosis, with the secretory products never having come into contact with the cytosol

seventh step in endomembrane system

lysosomes also bud off from the golgi complex

lyosomes

small, membranous-enclosed organelles that contain approximately 40 hydrolytic enzymes that break down organic molecules

lysosomes function and description

vary in size and shape; formed by the golgi complex; carry out intracellular digestion by breaking down cellular debris, foreign bodies (bacteria), aged or damaged organelles through endocytosis

endocytosis

the internalization of extracellular material within a cell as a result of the plasma membrane forming a pouch that contains the extracellular material, then sealing at the surface of the pouch to form an endocytotic vesicle

hydrolytic

breakdown of larger molecules into smaller molecules using hydrolysis (water)

endocytosis forms

pinocytosis, receptor-mediated endocytosis, and phagocytosis

pinocytosis

1. solute molecules and water molecules are outside the plasma membrane

2. membrane pockets inward, enclosing solute molecules and water molecules

3. pocket pinches off as endocytic vesicle containing sample of ECF

receptor-mediated endocytosis

1. substances attach to membrane receptors

2. membrane pockets inward

3. pocket pinches off as endocytic vesicle containing target molecule

phagocytosis

1. pseudopods begin to surround prey

2. pseudopods close around prey

3. prey is enclosed in endocytic vesicle that sinks into cytoplasm

4. lysosome fuses with vesicle, releasing enzymes that attack material inside vesicle

mitochondria

oval, membrane-bound organelles that have an outer membrane and a highly folded inner membrane; site of aerobic respiration

cristae

infoldings of inner membrane that project into inner cavity (mitochondrial matrix)

mitochondria description

contains own piece of DNA; does not need to go through mitosis to replicate itself; produces ATP

peroxisomes

membranous organelles that produce and decompose hydrogen peroxide (H2O2) in the process of degrading toxic molecules

oxidative enzymes

use oxygen to strip H from organic molecules; major functions are detoxification and betaoxidation; alcohol, drugs, other toxic substances; abundant in liver

centrioles

short, cylindrical organelle that produces microtubules for the mitotic spindle

cytoskeleton

an elaborate, protein-scaffolding dispersed throughout the cytosol that functions in supporting, organizing, and moving cell components

3 distinct structural elements of the cytoskeleton

microtubules, microfilaments, intermediate filaments

microtubules

slender, hollows tubes of tubulin; largest

function of microtubules

position organelles, maintain cell shape, transport secretory vesicles, movement of cell projections (cilia and flagella), distribute chromosomes during cell division (form mitotic spindle)

microfilaments

intertwined helical chains of actin filaments; smallest

function of microfilaments

role in contractile systems; contractile ring of mitosis/meiosis; amoeboid movement; act as mechanical stiffeners for cell projections; microvilli

intermediate filaments

irregular thread-like proteins; intermediate in size

function of intermediate filaments

protein composition varies; form tough durable fibers; role in maintaining structural integrity of a cell; resists external mechanical stress

example of intermediate filaments

protein keratin forms intermediate filaments found in epidermal cells

endomembrane system

a network of organelles that exchange materials through small membrane-enclosed vesicles

components of endomembrane system

nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vesicles + vacuoles, plasma membrane