A&P 8/29 The Cell

Cells

The basic unit of life

surface-to-volume ratio → allows for diffusion due to small side

size 2-120mcm → Avg. 10-12mcm

Cell size

only a human egg is visible to the human eye → abt size of a period at end of sentence

Cell components

• cell membrane

• cytoplasm

• organelles

Cell membrane

Phospholipid bilayer

• phosphate head → Attract H2O (Hydrophilic)

• lipid is the tails → no like H20 (Hydrophobic)

Not static → proteins can move in the membrane

Membrane Components

• proteins allow things to pass through or anchor things

• Cholesterol molecule controls the fluidity of the cell membrane

  • more = less fluidity

  • less = more fluidity

Membrane Protein Functions

• transport

• enzymatic activity

• signal transduction

• intercellular joining

• cell-cell recognition

• attachment to the cytoskeleton & extracellular matrix (ECM)

Types of cellular transportation

• diffusion

• facilitated diffusion

• active transport → using ATP

Diffusion

goes high concentrations in 1 area to low & hotter it is the faster rate of diffusion (stops @ abs zero [0 degree K])

ex: Kool Aid into water later the whole glass would turn red

What particles can move freely (slide 10)

• Water

• Oxygen

• Carbon dioxide

• lipids

Facilitated diffusion

involves a “bridge” (PROTEIN) to help transport larger objects/particles through cell membrane

2 diff. kinds → channel & revolving door

Active Transportation

Can pump move in 2 directions

Normally goes from areas of LOW concentrations to HIGH

ex: Sodium Potassium pump

Sodium Potassium Pump

Na → 3 out

K → 2 in

Water Molecule

Universal Solvent

• bc is slightly positive charge on H side & slight negative charge on O side

High Heat capacity

Osmosis

Movement of water across a selective semipermeable membrane

• more solute = less H2O

• less solute = more H2O

Types of Osmosis

1. Hypotonic

2. Isotonic

3. Hypertonic

What is Hypotonic

less solute so water goes into cell → cell expands (can lyst/burst)

What is Isotonic

when the solute is the same, so water moves equally throughout → cell stays the same

What is the Percentage for an Isotonic solution?

0.9%

What is Hypertonic

when there is more solute outside so water leaves → cell shrinks (becomes crenated/spikey)

Osmotic Pressure

the pressure of the flow of water against the membrane due to the osmotic difference on either side of the membrane

ex: capillaries, blood plasma

What is Endocytosis

Transfer of substance intact going into the cell

THINK: ENDO → INside

What are the types of Endocytosis

1. pinocytosis

2. receptor-mediated

3. phagocytosis

What is Pinocytosis (slide 18)

when extracellular fluid gets trapped in a vesicle

What is Receptor-mediated Endocytosis (slide 18)

when there are receptors inside the vesicle

What is Phagocytosis (slide 18)

when the cell goes around the substance or bacteria to bring it inward to digest or destroy

What is Exocytosis

it’s used when the cell wants to get rid of waste/something via the use of a vesicle that releases to into the extracellular fluid

THINK: EXO → EXIT → OUT

Resting Membrane potential

A cells membrane is charged (pos outside & neg inside)

REMINDER: this is due to Na being high outside the cell & K being high inside the cell

Cell Junctions

is the anchoring & communication nessies between cells

What are the types of Cell Junctions

1. tight

2. desmosome

3. channel/gap junction

Cell Junction - Tight (slide 21)

Proteins pass through cell membrane & fuse with other protein so nothing can bypass the cell

THINK: of a tight seal

Cell Junction - Desmosome

many different types but main job is to hold cell membranes together

More structural

Cell Junctions - Channel

channel proteins line up so both cells are in communication w/out having to put it through the extracellular fluid

Quick Communication

Nucleus

• largest organelle

• stores DNA

• site of RNA generation

• double membraned

  • outer membrane is similar to rER

• has nuclear pores

  • helps with movement of substances from cytoplasm directly to the nucleoplasm

DNA

• double helix structure

• made up of phosphate & sugar (deoxyribose)

What are the Nitrogen bases

• A & T

• G & C

Central Dogma

is that the genes code for RNA & that allows for us to process into proteins

What are the parts of Central Dogma

• Transcribe

• Translate

RNA Synthesis (Transcription)

Begins w/ the unwinding of DNA molecule to expose ½ of DNA sequence, then enzymes come in and start building RNA molecule (Transcript) of the DNA molecule

What is the Start Codon

AUG

What are the Stop Codon(s)

UAA, UAG, UGA

What is Post-transcriptional Modification

Is when the translated entire sequence has spacers (introns) that need to be rid of so there is just exons (code for proteins)

is when the pre-mRNA gets the introns cut out for the mRNA → left w/ just 5’ cap & exons & Poly(A) tail

What is tRNA

Transfer RNA

is responsible for attaching codon @ anticodon point

Ribosome

is the factory in which proteins are made

has 2 parts, Large ribosome subunit & Small ribosome subunit

What is Initation

How a protein stats being formed

mRNA binds to smaller subunit & then large subunit binds together w/ all

What is Elongation

is then the tRNA comes in and binds to its codon (codon recognition)& peptide bond forms, reads the codon then ejects & repeats (translocation)

What is Termination

when the Stop Codon tells the ribosome to release the protein since it’s done being made

What are Polysomes

when multiple ribosomes are reading 1 strand of mRNA

Docking Ribosome to rER

when a protein function is to be outside cell membrane, then needs to go through before it’s too big

so a signal peptide pauses reading then goes to Rough ER & continues protein synthesis

Endoplasmic Reticulum (ER)

• membrane channels functioning in protein (rER) and fat metabolism (sER)

• Smooth (sER) or Rough (rER)

• rER has ribosomes on surface

Golgi Apparatus

is the “shipping department” of cells

transports substances through creating its own vesicle