Allied Health 02 Pt A: Cells

Criteria of living organisms

made of cells, rspd to stimuli, able to grow & reproduce, use energy (have metabolism), contain DNA/RNA

Cells are

• basic structural & functional unit of life

• diverse

• has organelles

Cytoplasm

• jelly like fluid, mainly water

• holds everything in place

Cell Membrane

• selectively permeable barrier/phospholipid bilayer

  • hydrophilic heads, hydrophobic tails

  • carbohydrates for structure

  • proteins for transport nutrient signals

• pass easily: small, nonpolar, hydrophobic, neutral molecules & water

• can not pass easily: polar & large molecules

• maintain homeostasis

Membrane transport (active vs. passive)

Active:

• move up concentration gradient (low conc. → high conc.)

• takes ATP

• for homeostasis

Passive:

• move down concentration gradient (high conc. → low conc.)

• zero ATP

• molecules naturally spread to reach equilibrium

• simple diffusion: for small, non polar molecules

• facilitated diffusion: for larger/changed molecules

• osmosis: diffusion of water

Cytoskeleton

• threadlike fibers made of proteins

• 3 types: microtubules, intermediate filaments, microfilaments

• support, maintain shape, mobility, regulate biochemical activities

Centrioles (2=centrosome)

• where microtubules grow out of

• cell division (pull apart chromosomes in anaphase)

Cilia vs. flagella

Cilia: shorter, numerous tiny oars

• move fluid across cell’s surface

• located in respiratory tract/female reproductive sys

Flagella: longer, fewer

• move entire cell through extracellular fluid

• ex. on sperm in humans

Nucleus

• contain genetic material (DNA)

• Surrounded by a nuclear envelope/membrane with pores that control what goes in and out

• Protects DNA (which controls cell activity)

Chromosomes vs. chromatin

chromatin: threadlike form

chromosomes: chromatin condensed into 46 chromosomes in body cells (sex cells have 23)

Genes

sections of chromosomes that code for proteins (which then do most of the work in the cell)

nucleolus

• inside nucleus

• ribosomes formed here

Ribosomes

• made of proteins & rRNA

• makes proteins

• located on rough ER & floating in cytoplasm

  • on rough ER = proteins export out of cell

  • in cytoplasm = proteins to use within cell

Rough ER

• Ribosomes on surface

• hugs nucleus

• network of membranes & sacs

• makes proteins!

• package them for secretion

• send transport vesicles for Golgi apparatus

Vesicles

“mini-carts” that transport proteins around/ out of the cell

Smooth ER

• no ribosomes on surface

• attached to rough ER

• netwrok of membranes & sacs

• makes lipids (membrane)

• chemically modifies small molecules

• site of glycogen degradation

• stores Ca2+

Golgi Apparatus

• folded/flattened membrane sacs

• receive vesicles from rough ER & processes, modifies, packages & sorts them for transport

• ships these proteins where needed

Lysosomes

• Contain hydrolytic enzymes for breaking stuff down (food, bacteria, old parts, etc.)

• Can do apoptosis (programmed cell death)

Vacuoles

• smaller & can be more numerous in animal cells

• storage (water, food, nutrients, waste, etc.)

Mitochondria

• 2 parts: cristae (folded inner membrane) & matrix (enzyme-packed fluid)

• Cellular respiration here (breaks down chemical energy in food [nutrients] to release it as a usable form of energy (ATP))