Chapter 3 Flashcards
What is the the outer boundary of the cell?
plasma membrane
what does the nucleus do?
directs cell activities
Where is the cytoplasm?
between nucleus and the plasma membrane
-where most cell activities take place
Cells perform what functions..?
-Cells metabolize and release energy
-cells synthesize molecules
-cells provide a mean of communication
-cells reproduce and provide for inheritance
Light microscopes
allow us to visualize the general feature of cells
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electron microscopes
allow us to visualize the fine structure of cells
Plasma Membrane
-passively or actively regulates what enters or leaves the cell
-composed of phospholipid bilayer, where proteins are suspended (fluid-mosaic model)
What gives plasma membrane most of its structure/function?
lipids
What do membrane proteins function as?
-Marker molecules
-attachment proteins
-transport proteins
-receptor proteins
-enzymes
Transport proteins
-channel proteins
-carrier proteins
-ATP powered pumps
Receptor Proteins
-linked to and control channel proteins
-linked to G protein complexes which control numerous cellular activities
What passes through plasma membrane readily?
-Lipid-soluble molecules pass through by dissolving in the lipid bilayer.
-small molecules diffuse b/w phospholipid molecules of the plasma membrane
How are large non-lipid soluble molecules (glucose/amino acids) pass through membrane?
glucose/amino acids via transport proteins
How do large non-lipid soluble molecules, as well as whole cells, pass through membrane?
vesicles
diffusion
movement of a substance from a higher solute concentration to one of lower solute concentration (down concentration gradient)
Concentration Gradient
difference in solute concentration b/w two points divided by distance separating points
How does rate of diffusion increase?
increases with increase in concentration gradient, an increase in temp and decrease in molecular size, decrease in viscosity
What is end result of diffusion?
uniform distribution of molecules
Does diffusion require energy?
No, no expenditure of energy
Osmosis
diffusion of water (solvent) across a selectively permeable membrane
Osmotic pressure
force required to prevent movement of water across a selectively permeable membrane
Isosmotic solutions
have same concentration of solute particles
hyperosmotic solutions
have greater concentration of solute particles
hyposmotic solutions
have lower concentration of solute particles
what happens to cells in isotonic solution?
neither shrink or swell
what happens to cells in hypertonic solution?
they shrink (crenate)
what happens to cells in hypotonic solution?
they swell and may burst (lyse)
mediated transport
movement of substance across membrane by means of transport protein
- large, water soluble molecules
facilitated diffusion
moves substances down their concentration gradient and does not require energy (ATP)
active transport
moves substances against their concentration gradient and req ATP
- exchange pump
exchange pump
active transport
moves substances in opposite directs across plasma membrane
secondary active transport
ion is moved across plasma membrane by active transport
-energy produced by ion diffusing back down its concentration gradient transports another molecule (glucose) against its concentration gradient
vesicular transport
movement of large volumes of substances across plasma membrane through formation or release of vesicles
endocytosis
Req energy. bulk movement of materials into cells
- phagocytosis
-pinocytosis
phagocytosis
bulk movement of solid material into cells by formation of vesicle
pinocytosis
similar to phagocytosis except ingested material is much smaller and is in solution
receptor-mediated endocytosis
allows for endocytosis of specific materials
exocytosis
secretion of materials from cells by vesicle formation
- req energy
cytoplasm
material outside the nucleus and inside plasma membrane
cytosol
fluid part (site of chem reactions), cytoskeleton, and cytoplasmic inclusions
cytoskeleton
supports cell and responsible for cell movements.
consists of protein fibers
microtubules
hollow tubes composed of protein tubulin
-form spindle fibers and are components of centrioles, cilia and flagella
actin filaments
small protein fibrils that provide structure to cytoplasm and cause no cell movements
intermediate filaments
protein fibers that provide structural strength to cells
cytoplasmic inclusions
(lipochromes) are not surrounded by membranes
nuclear envelope consists of what
double membrane with nuclear pores
organelles
sub cellular structures specialized for specific functions
Chromatin
DNA and assoc proteins found inside nucleus
DNA
hereditary material of the cell
controls cell activities by producing proteins through RNA
Gene
portion of DNA molecule
determine proteins in a cell
Nucleoli
consist of RNA and proteins and are sites of ribosomal subunit assembly
ribosomes
consist of small/large subunits manufactured in nucleolus and assembled in cytoplasm
- sites of protein synthesis
-can be free or associated with endoplasmic reticulum
endoplasmic reticulum
extension of outer membrane of nuclear envelope
-forms tubules or sacs (cisternae) through cell
rough endoplasmic reticulum
has ribosomes and is a site of protein synthesis and modification
smooth endoplasmic reticulum
lacks ribosomes and is involved in lipid production, detoxification and calcium storage
Golgi apparatus
series of closely packed, modified cisternae that modify, package and distribute lipids/proteins produced by endo reticulum
secretory vesicles
membrane bound sacs that carry substances from golgi apparatus to plasma membrane, where contents of vesicles are released by exocytosis
lysosomes
membrane bound sacs containing hydrolytic enzymes. Within cell, enzymes break down phagocytize material and nonfunctional organelles (autophagy)
what digests extracellular material
enzymes released from cell by lysis or enzymes secreted from cell
peroxisomes
membrane-bound sacs containing enzymes that digest fatty acids and amino acids / enzymes that catalyze breakdown of hydrogen peroxide
proteasomes
large, multi enzyme complexes, not bound by membranes that digest selected proteins within the cell
mitochondria
major sties of production of ATP (cells use this as energy source)
-smooth outer membrane and folded inner membrane with cristae.
-contain own DNA, produce some own proteins, and replicate independently of cell
centrioles
cylindrical organelles located in the centrosome. specialized zone of cytoplasm that serves as site of microtubule formation
spindle fibers
involved in separation of chromosomes during cell division
cilia
facilitate movement of materials over surface of cell
flagella
much longer than cilia, propel sperm cells
microvilli
increase surface area of plasma membrane for absorption or secretion
transcription
info in DNA is copied to form mRNA
-DNA unwinds- nucleotide pairing, produces pre-MRNA
-introns (non-coding seq) removed, exons (coding seq) spliced together during postranscriptional processing.
-modifications to end of mRNA occur
translation
mRNA goes to ribosomes, to direct synthesis of proteins
What does genetic code do?
specifies amino acids and consists of codons
codons
sequences of 3 nucleotides in mRNA
Translation
mRNA moves through nuclear pores to ribosomes
tRNA (carries amino acids) interacts with ribosome mRNA.
anticodons of tRNA bind to codons of mRNA and amino acids join to form protein.
Posttranslational processing
pro proteins (some proenzymes) are modified into proteins, some are enzymes.
Cells becoming specialized
b/c certain parts of DNA molecule are activated and some parts are not
level of DNA activity is controlled by
(protein production) controlled internally or affected by regulatory substances secreted by other cells
Life cycle’s stages
interphase and cell division
Interphase
period b/w cell divisions. Time of DNA replication.
-DNA unwinds, each strand produces new DNA molecule
cell division
-nuclear division and cytoplasmic division
mitosis
replication of cells nucleus
- 4 phases
prophase, metaphase, anaphase, telophase
cytokinesis
division of the cells cytoplasm
-begins with formation of cleavage furrow during anaphase.
-complete when plasma membrane comes together at equator- producing two new daughter cells
Prophase
Stage 1 Mitosis
-chromatin condenses to become visible chromosomes.
-each chromosome contains two chromatin joined at centromere.
-centrioles move to opposite ends, astral fibers/spindle fibers form.
-nucleoli disappear, and nuclear envelope degenerates
Metaphase
Stage 2 Mitosis
- chromosomes align at center of cell
Anaphase
Stage 3 of Mitosis
Chromatids of each chromosome separate at centromere. Each chromatid is called chromosome. Chromosomes migrate to opposite poles.
Telophase
Stage 4 Mitosis
- chromosomes unravel to become chromatin. The nuclear envelope and nucleoli reappear
apoptosis
programmed cell death.
cell # within various tissues is adjusted and controlled
Aging is hypothesized from what
cellular clocks, death genes, DNA damage, free radicals, mitochondrial damage.
