Cell Biology

ATP is composed of…

nucleotides and phosphate groups

monosaccharides are…

• simple sugars

• individual building blocks

examples of monosaccharides:

glucose, fructose, galactose

how are monosaccharides obtained in the body?

through digestion of more complex carbs that are consumed

examples of disaccharides:

sucrose, lactose, maltose

examples of polysaccharides:

starch, glycogen, cellulos

what is glycogen?

the primary storage form of carbs in animal cells

where is glycogen typically found?

glycogen is typically stored in skeletal muscle and in the liver

what is the primary storage form of carbs in plant cells?

cellulose and starch

how many doubles bonds do saturated fatty acids have?

0

how many doubles bonds do unsaturated fatty acids have?

1

how many doubles bonds do polsaturated fatty acids have?

>1

what is the primary storage form of lipid in animals?

triglycerides

how are triglycerides composed?

3 fatty acids esterified to a glycerol back bone

how are phospholipids composed?

2 fatty acids esterified to a glycerold and phosphate head

where are phospholipids used?

in the cell membrane

what type of organic molecule is cholesterol?

lipid

why is cholesterol imporant?

it is a precursor to steroid hormones like testosterone, estrogen, and cortisol

what are proteins composed of?

proteins are composed of folded polypeptide chains

polypeptides = peptides = chains of amino acids linked by peptide bonds

how are primary structure of proteins determined?

• type, number, and order of amino acids in the polypeptide chain

• dictated by genetic code and gene expression

how are secondary structure of proteins determined?

hydrogen bondings

common structures include alpha helices or beta sheets

how are tertiary structures formed?

coiling and folding of polypeptide to form a 3D globular protein

how are quaternary structures formed?

multiple separate polypeptide subunits interact to form a larger functional molecular

examples include hemoglobin or structural collagen

what is cell theory?

• cells are the smallest basic unit of life of which all organisms are composed

• cells are autonomous and self replicating

what are the 3 basic components of a cell?

• nucleus

• cell membrane/plasma membrane

• cytoplasm

what is the cytoplasm?

the space between the nucleus and cell membrane

what is the cytoplasm composed of?

cytosol (actual name of the fluid) & organelles

what is the extracellular space and what does it contain?

extracellular space is everything outside the cell membrane

it contains interstitial fluid or blood plasma

what is the intracellular space and what does it contain?

intracellular space is inside the cell membrane

contains intracellular fluid, cytosol

what is the function of the smooth endoplasmic reticulum?

it synthesizes lipids and carbs

what is the function of the rough endoplasmic reticulum?

it modifies and packages proteins that are synthesized by the attached ribosomes

what is the function of the golgi apparatus?

it stores, modifies, and packges the secretory products from the ER

what is the function of peroxisomes

metabolism of fatty acids

what is the function of lysomes?

removal of damaged organelles

“garbage can”

what is the function of mitochrondria?

produces 95% of ATP required by the cell

list the membranous organelles:

• smooth ER

• rough ER

• golgi apparatus

• peroxisomes

• lysosomes

• mitochondria

list the non-membranous organelles:

• ribosomes

• cytoskeleton

• microvilli

• centrioles

• proteosomes

what is the function of ribosomes?

• site of protein synthesis

• can be free in cytoplasm of bound to the ER

why is the rough ER “rough”?

b/c of the ribosomes that are attach to it

what is the function of the cytoskeleton?

cellular shape, support, and strength

what is the function of microvilli?

increase cell surface area to aid with absorption of extracellular material

unlike cilia, microvilli are…

passive

where else can microvilli be found?

in the small intestines

what is the function of centrioles?

to arrange chromosomes during cell division (mitosis)

what is the function of proteasomes?

site of protein degradation

what is the function of the cell nucleus?

• control center of the cell

• site of gene expression

  • transcription specifically, DNA → mRNA

what is inside the cell nucleus?

• nucleoplasm

• chromatin

• nucleolus

what is the function of the nuclear envelope?

barrier of the nucleus

what is the function of nuclear pores?

allow passage mRNA and proteins out of the nucleus

what is the function of the nucleolus?

site of ribosomal RNA (rRNA) production

what is the function of the cell membrane?

physically separates the intracellular and extracellular space

what is the cell membrane composed of?

phospholipid bilayer

• hydrophobic fatty acid tails of phospholipids face the core of bilayer

• hydrophilic phospholipid heads face outward towards the extracellular and intracellular spaces

what does “selectively-permeable” mean for the phospholipid bilayer?

• lipid-soluble molecules pass freely via passive diffusion from region of high-to-low concentration

  • ex: O₂, CO₂, steroid hormones

• H₂O diffuses freely through protein channels via osmosis (a special form of passive transport)

what is osmosis?

the passive transport of water through a selectively permeable membrane where H₂O moves from a region of less solute concentration toward a region of higher solute concentration

“water follows salt”

☆ does not require energy

osmosis results in…

equilization of solute concentration via movement of H₂O molecules

what is an isotonic solution?

no osmotic flow occurs

solute concentration is equal inside and outside cell

what is a hypotonic solution?

lower solute concentration outside the cell than inside

water flows into the cell

☆ swelling may continue until the plasma membrane reputes, or lyses

what is a hypertonic solution?

higher solute concentration outside the cell than inside

water flows from the cell, outside

☆ the cell shrivels and becomes crenated

what is facilitated diffusion?

the molecule doesn’t need energy to permeate the cell membrane, but needs a channel

the molecule finds the receptor site and is transported into the cell via a carrier protein

occurs from a region of high-to-low concentration

facilitated diffusion - glucose:

• glucose is too large to permeate the cell membrane

• glucose → receptor site

• a protein called GLU4 transports glucose into muscle and fat cells (adipocytes) in response to the hormone insulin

what is active transport?

movement of molecules from a region of low-to-high concentration

↪ against the concentration gradient

requires energy

ATP + H₂O → ADP + Pi

☆ maintains resting cell membrane

example of active transport

the sodium (Na⁺) - potassium(K⁺) ATPase pump

moves 3x Na⁺ ions out of the cells and 2x K⁺ ions in for each single molecule of ATP broken down

what are the factors that affect rate of diffusion?

• steepness of concentration gradient

• molecular size

• electric charge

• lipid solubility

• temperature

• presence of channel proteins

factors affecting rate of osmosis?

• concentration gradient

• opposing osmotic or hydrostatic pressure

substance involved in diffusion?

• small inorganic ions

• most gases and lipid-soluble materials (all cells)

substances involved in osmosis?

water only (all cells)

factors affecting rate of facilitated diffusions?

• steepness of gradient

• temperature

• availability of carrier proteins

factors affecting rate of active transport?

availability of:

• carrier proteins

• substrate

• ATP

subtances involved in facilitated diffusion?

• glucose

• amino acids

(all cells)

substances involved in active transport?

Na⁺, K⁺, Ca²⁺, Mg²⁺ (all cells)

other solutes by specialized cells

what is the function of DNA?

encodes instructions for all cell processes

where is DNA found>

in the cell nucleus

what is DNA composed of?

2 polynucleotide chains in the form of a double helix

DNA backbone is made of sugar (deoxyribose) and phosphate groups

what is chromatin?

DNA wrapped around histone proteins

list the nitrogenous bases (DNA & RNA):

• adenine

• thymine

• guanine

• cytosine

• uracil

list the complimentary pairs (for both DNA & RNA)

DNA:

• adenine & thiamine

• guanine & cytosine

RNA:

• adenine & uracil

• guanine & cytosine

what is RNA’s backbone

ribose backbone instead of deoxyribose

what is transcription?

the initial step in protein synthesis that begins in the nucleus of the cell

creates a single stranded molecule of messenger RNA (mRNA)

↪ carries the genetic code of proteins to produce

the mRNA sequence is __ to the encoding DNA sequence

complimentary with replacement of thiamine with uracil

how does mRNA leave the nucleus?

via pores in the nuclear envelope → moves to cytosol

what is the process of translation?

1. mRNA binds to a ribosome in the cytoplasm

↪ either free in cytosol or attached to the RER

2. tRNA reads the mRNA sequence and now has the complimentary anticodon nucleotide sequence

3. tRNA transfer the appropriate amino acid to the ribosome

↪ mRNA start codon = AUG, tRNA anticodon = UAC

4. the ribosome moves along the mRNA with additional tRNAs adding further amino acids until a stop codon is read

5. the completed polypeptide is released

mRNA is complimentary to

DNA

tRNA is complimentary to

mRNA