Anatomy Exam Chap. 3

Describe Cell Theory

• a cell is the structural and functional unit of life

• how well the entire organism functions depends on individual combined activities of its cells

• structure and function are complementary

Describe the structure, function, and composition of the plasma membrane

structure

• flexible outer boundary

Composition

• consist of membrane lipids that form a flexible lipid bilayer

• Specialized membrane proteins float through this fluid membrane, resulting in

  constantly changing patterns

Function

• functions as barrier for ICF and ECF

Describe the functions of the three lipids found in the plasma membrane

1. phospholipids

• Phosphate heads: are polar (charged), so are hydrophilic (water-loving)

• Fatty acid tails are nonpolar (no charge), so are hydrophobic (water-hating)

2. glycolipids

• Lipids with sugar groups on outer membrane surface

3. cholesterol

• Increases membrane stability

Describe the structure and function of integral and peripheral membrane proteins

• allow cell communication with environment

• make up about half the mass of plasma membrane

Integral

• in membrane

• transmembrane proteins

• have hydrophobic and hydrophilic regions

• function as transport proteins

Peripheral

• face 1 direction

• loosely attached to integral proteins

• in membrane but don’t go completely across

• a lot function like enzymes or motor proteins

Describe the six functions of membrane proteins

1. transport

   1. form hydrophillic channels or use atp to pump substances across the membrane

2. receptors

   1. bind chemical messengers like hormones to trigger internal cellular reactions

3. Enzymatic activity

   1. Catalyze sequential steps of metabolic pathways at the membrane surface

4. Cell recognition

   1. some glycoproteins serve as identification tags that are specifically recognized by other cells

5. attachment to cytoskeleton

   1. Anchor internal fibers and external matrix to maintain shape, fix locations, and aid movement

6. cell to cell joining

   1. Hook adjacent cells together for structural support or guided migration

Describe the three factors that influence rate of diffusion

• difference of concentration gradient causes diffusion across plasma membrane

  • 1. concentration

    • the higher the concentration, the faster diffusion

  • 2. Molecular size

    • smaller molecules diffuse faster

  • 3. Temperature

    • high temps increase kinetic energy which results in faster diffusion

Describe how simple diffusion works in a cell

molecules that are able to passively diffuse in membrane include lipid-soluble, non-polar substances, and very small molecules that can pass through membrane

Describe how carrier-mediated facilitative diffusion works in a cell

transports lipid-insoluble, polar, or hydrophilic molecules that cannot pass directly through theplasma membrane on their own

• Carrier-mediated facilitated diffusion

  • Substances bind to protein carriers

Describe how channel mediated facilitative diffusion works in a cell

Certain hydrophobic molecules are transported passively down their concentration gradient by:

Channel-mediated facilitated diffusion

– Substances move through water-filled channels

substances move in and out of cell

Describe how osmosis works in a cell

• goes through specific channels called aquaporins

• movement of water

• based on concentration gradience difference

• where water is going to go based on the higher soluble concentration

Describe osmolarity and explain how solutes move when the membrane is permeable to do both or water only

• total # of solutes in solutions

• when solute concentration goes up, water concentration goes down- vice versa

• water moves by osmosis from areas of low solute concentration to high areas of solute concentration

Describe how hydrostatic and osmotic pressure influence the movement of water

Hydrostatic pressure

• outward pressure exerted on cell side of membrane caused by increases in volume of cell due to osmosis

Osmotic pressure

• inward pressure due to tendency of water to be “pulled” into a

cell with higher osmolarities

Describe how water moves when an animal when placed in hypotonic, hypertonic, and isotonic solution

Hypertonic

• cell will shrivel, water goes out

Hypotonic

• cell will burst, water goes in

Isotonic

• they will be at equilibrium, water moves in and out but cell retains shape

Describe the function of uniporters, antiporters, and symporters

Uniporters

• transport 1 substance in or out of cell

Antiporters

• move 1 substance in while moving 1 substance out

Symporters

• transports 2 different substances out or in at the same time

Describe how primary active transport works in a cell, using the NA+, K+ pump as an example

required energy comes directly from ATP

Na+K+ pump

• moving both sodium and potassium against concentration gradient using an antiporter

Describe how secondary active transport works in a cell

• requires use of ATP first to set up a gradient, moves ions across membrane

• Energy stored in gradients is used indirectly to drive transport of other solutes

Describe phagocytosis, pinocytosis, receptor-mediated endocytosis, and exocytosis: include examples

phagocytosis

type of endocytosis that is referred

to as “cell eating”

– Membrane projections called pseudopods

form and flow around solid particles that are

being engulfed, forming a vesicle which is

pulled into cell

ex. white blood cells

Pinocytosis

type of endocytosis that is

referred to as “cell drinking” or fluid-phase

endocytosis

– Plasma membrane infolds, bringing

extracellular fluid and dissolved

solutes inside cell

ex. small intestine

Receptor-mediated endocytosis

• involves endocytosis and transcytosis of specific

molecules

ex. iron uptake

exocytosis

• Process where material is ejected

from cell

• Usually activated by cell-

surface signals or changes in

membrane voltag

ex. hormones

Describe resting membrane potential and explain its importance for biological systems

• RMP- electrical potential energy produced by seperation of oppositely charged particles across plasma membrane in all cells

• difference in electrical charge between 2 points called a voltage

• its neutral inside + outside cell

• cells that have charge is polar

Describe the five functions of cell adhesion molecules

• anchor cell to extracellular matrix or to each other

• assist in movement of cells past one another

• attract WBC’s to injured/infected area

• stimulate synthesis or degradation of adhesive membrane junctions

• Transmit intracellular signals to direct cell migration, proliferation, and specialization

Describe contact and chemical signaling of plasma membrane receptors

contact

• where the cells touch

• recognize each other by their surface proteins

chemical

• ligands bind to receptors on surface of cell

• ligands tell cell what to do

Describe G-protein signaling using second messengers

indirectly cause cellular changes by activation g protein, ligand binds to receptor, receptor acts on g protein, acts on effector, second message is sent based on effector protein

Describe the four phases of the cell cycle

interphase

• cells grow+carries on usual activity

• Period from cell formation to cell division, when cell carries out its routine activities and

  prepares for cell division

  • During interphase, nuclear material is in uncondensed chromatin state

  • Interphase consists of subphases, which include the process of DNA replication

g1

• vigorous growth and metabolism

S phase

• DNA replication occurs

G2

• preparation for division

*Describe DNA replication, include the function of all nine of the enzymes involved

During DNA replication, helicase unwinds the DNA while topoisomerase relieves tension. SSB proteins stabilize single strands, and double-stranded binding proteins maintain double-stranded regions. Primase lays down primers so DNA polymerase III can synthesize new strands—continuously on the leading strand and discontinuously on the lagging strand as Okazaki fragments. Sliding clamps and clamp loaders boost polymerase efficiency, while DNA polymerase II repairs DNA and restarts stalled forks. DNA polymerase I (or RNase H) removes RNA primers and replaces them with DNA nucleotides, and ligase seals the fragments to complete high-fidelity replication.

Describe the five phases of mitosis

• Prophase

  • dna packages in, makes spindle fibers, sister chromatids, and they are held by centromere

• Prometaphase

  • nuclear envelope is gone, microtubules attach to specific area on centromeres called kinetochore and serve to pull chromosomes to center

  • Remaining nonkinetochore microtubules push against each other, causing poles of cell to move farther apart

• Metaphase

  • sister chomatids line up in middle of cell

• Anaphase

  • Centromeres of chromosomes split simultaneously—each sister chromatid now

    becomes a separate chromosome

    – Chromosomes are pulled toward their respective poles by motor proteins of

    kinetochores

     One chromosome of each original pair goes to opposite poles

    – Nonkinetochore microtubules continue forcing poles apart

• Telophase

  • Begins when chromosome movement stops

    – Each set of chromosomes uncoils to form chromatin

    – New nuclear membranes form around each chromatin mass

    – Nucleoli reappear

    – Spindle disappears

  • Cytokinesis

    – Begins during late anaphase and continues through mitosis

    – Ring of actin microfilaments contracts to form cleavage furrow

Describe what is required for the cell to proceed through the three cell cycle checkpoints and explain how the cell deals with any issues

g1- restriction point, looking for the signal that the cell is big enough

• if does not pass it goes to g0, no longer divide

g2- looking for errors w DNA replication, it will either fix errors or go through apoptosis

Metaphase

• quality control in mitosis that ensures every chromosome is correctly attached to spindle microtubules before the cell proceeds to anaphase

• prevent premature separation of sister chromatids and to maintain genetic stability by avoiding aneuploidy

• Blocks anaphase onset, Prevents premature separation, fix errors

• if cant be fixed enters apoptosis

Describe G0 and explain its importance

• Cells in G0 remain metabolically active and continue performing their specialized functions, but they do not actively prepare for or undergo cell division.

• can be temporary or permanent

• A cell typically enters G0 from the G1 phase when it encounters a lack of growth factors

• Stops uncontrolled cell division

• Allows cells to dedicate their energy to specialized tasks rather than giving resources to continuous division.

• Prevents damaged or nutrient-deprived cells from duplicating, giving them time to recover or protecting the organism from multiplying genetic errors.

Describe exons and introns and explain the functions of mRNA, tRNA, and rRNA

• Exons are part of gene that actually codes for amino acids

• Introns are noncoding segments interspersed amongst exons

Describe transcription factors and explain their role in a cell

• how we make protein

• proteins that regulate gene expression by controlling whether specific genes are transcribed into RNA, thereby directing cell function, development, and response to signals.

• they activate transcription

Describe the 3 stages of transcription

Initiation

• Binds to promoter

• RNA polymerase separates DNA strands

Elongation

• reads template strands and RNA polymerase adds complimentary nucleotides

Termination

• Transcription stops when RNA polymerase reaches special termination signal code

Describe the 3 ways mRNA is processed prior to translation

1. add poly a tail for protection

2. add 5 prime cap to put the ribosome in position

3. splicing, get rid of introns

Describe genetic code and explain its importance

Each three-base sequence on DNA is represented by a complementary three-base

sequence on mRNA called codon

– There are 64 possible codons

• 4 bases (A, U, C, G)

• 64 total options

– There are 3 “stop” codons but rest are codons

for amino acids

• There are only 20 possible amino acids, so this

means that some amino acids are repeated

• Redundancy helps protect against

transcription errors

Describe the function of aminocyl-tRNA synthase and explain its role in accurate translation

• essential enzymes that attach the correct amino acid to its corresponding tRNA molecule

• correct pairing between amino acids and tRNAs:

Role: Cognate recognition, Proofreading, High fidelity

Describe the three stages of translation

1. Initiation- ribosome coming together for translation, binding to the mRNA and the first tRNA

2. codon recognition- tRNA binds complementary codon in A site of ribosome

   1. peptide bond formation- ribosomal enzyme transfer + attach

3. termination- termination factor comes+ sits in a site, prompting release of the completed polypeptide chain from the ribosome

Describe the function of signal recognition particles

• directs mRNA–ribosome complex where to

  dock

• recognize a short hydrophobic signal peptide that appears at polypeptide as soon as it emerges from the ribosome

• it spots the signal peptide, pauses translation, and directs the ribosome to the correct membrane destination

Describe the functions of miRNA, siRNA, and riboswitches

miRNA

• small RNAs that can bind to +silence mRNAs by certain exons

siRNA

• similar to MiRNA, can also be made to silence mRNA from pathogenic

Riboswitches

• folded RNAs that act as switches that can turn protein synthesis on or off in response to certain environmental conditions

Describe autophagy and explain its importance

• cells that have become obsolete/ damaged need to be taken out of system

• autophagy (self eating) is the process of disposing of nonfunctional organelles and sweeping up cytoplasmic bits by forming autophagosomes, which can then be degraded by lysosomes

describe the ubiquitin-proteasome pathway

• unneeded, misfolded, or damaged proteins can be marked for distruction by protein called ubiquitin

• proteasomes disassembled ubiquitin-tagged proteins, recycling the amino acids…

Describe apoptosis and explain its importance

• programmed cell death, causes certain cells to neatly distruct

  • process begans with mitochondrial membrane leaking chemicals that activate enzymes called caspases

  • caspases cause degradation of DNA and cytoskeleton, which leads to cell death

Describe the developmental aspects of cells

All cells of body contain the same DNA, but not all cells are identical or carry out same function

chemical signals in embryo channels into specific developmental pathways by turning some genes on and others off

• Development of specific and distinctive features in cells is called cell differentiation

Describe the four hypothesis of cellular aging

wear + tear theory: a lifetime of chemical insults+ free radicals have cumulative effects

mitochondrial theory: free radicals in mitochondria diminish energy production

immune system disorders: autoimmune responses as well as progressive weakening of immmune system

genetic theory: cessation of mitosis+ cell aging are programmed into genes

Describe progeria and explain the consequences of having it

• rare disease that mimics aging

• caused by defective progerin protein in the nuclear lamina that results in unstable, abdominal nucleus

• Children with disease display slow growth, thinning hair, brittle bones, arthritis, and severe cardiovascular disease, with death usually by age 20

smooth er

breaks down toxins and produces lipids, storage of calcium

nucleus

DNA containing control center

rough er

makes proteins that work in membrane or part of other organelles

nuclear pore

allows substances to pass into and out of nucleus

golgi apparatus

modifying and disrupting proteins

lysosomes

recycling centermere break down things that aren’t working and cell resuses

mitochondrion

regenerates ATP

peroxisome

oxidize fats, get rid of toxins

cytoskeleton

provides structure, attachment points, and ways to move

cilia

move material away from avoli

flagella

movement of cell

centriole

cell division, seprates chromosomes

nuclear envelope

protects DNA

nucleolus

provides ribosomal RNA and ribosomal proteins

cytoplasm

free ribosomes

make proteins that work inside the cell

centrosomes

make microtubules

microfilaments

intermediate filaments

attachment and strongest of fillaments, keeps organelles in their postion

plasma membrane

chromatin

microtubules

movement of materials in cell, highway system

glococalyx

specific biological markers for cell to cell recongnition

tight junctions

Integral proteins on adjacent

cells fuse to form an

impermeable junction that

encircles whole cell

gap junctions

communication junctions between animal cells

desmosomes

motor proteins

can help with movement of materials and organelles, requires ATP but much more efficient movement

microvilli

increase surface area of small intestine in order to absorb more nutrients

chromosome

condensed chromatin helps protect fragile chromatin threads