Feeback Loop components
Stimulus=>receptor=>control center=>effector=>response=>controlled condition
Negative loop: stimulus reversed (body temp)
Positive loop: stimulus amplified (childbirth)
Membrane Structure
Lipid and Protein (and carbohydrate)
Principle membrane lipid: phospholipid (includes polar head and non polar tail)
Membrane made from a phospholipid bilayer
Hydrophobic solutes can cross membrane but hydrophilic cannot
Integral proteins vs peripheral proteins
Integral- extends into or across cell membrane and are amphipathic with hydrophobic portions hiding among phospholipid tails of membrane
Peripheral-attached to their inner or outer surface of cell membrane and are easily removed
Osmosis
- Diffusion is movement of solute due to concentration gradient.
- Osmosis is net flow of water (across semipermeable membrane) in response to a gradient in the chemical activity of water
- Water moves in order to make both sides of semipermeable membrane the same chemical concentration
- Tonicity is a measure of the effective osmotic pressure gradient
Carrier-Mediated Transport
- Diagnostic characteristics: saturability (finite number of transporters and each transporter has limited turnover) and selectivity (each protein can accept a limited range of chemical structures as substrates)
- Categories of Carriers: Facilitated diffusion (cannot catalyze flux against electrochemical gradient) and active transport (Develop and maintains solute gradients and requires and energy source)
Primary Active Transport vs. Secondary Active Transport
Primary Active Transport: immediate energy source => ATP
Secondary Active Transport: immediate energy source => trans-membrane ion gradients (uses antiporters and symporters)
Facilitated Diffusion
Happens across the semipermeable membrane without a protein
Vesicular Transport
Endocytosis: bringing something into cell (Na+)
Exocytosis: release something from cell (waste)
Cytoskeleton
- Microfilaments: strands of protein (actin). Connect organelles to membranes and influence cell motility and shape
- Intermediate filaments: keratins. Structural stability
- Microtubules: strands of tubulin. influence cell structure and shape and motility through cilia/flagella
Mitochondria
Major site of cell energy metabolism
Oxidative ATP production
ATP ADP + Pi Oxidative phosphorylation enzymatically-controlled breaking of bonds 1. consumes O2 2. Produces CO2 3. Efficient production of ATP
Endoplasmic Reticulum
4 functions: Lipid and protein synthesis, storage (protein; Ca2+), transport within cell, and detoxification
- Smooth ER: lipid synth; Ca2+ storage
- Rough ER: protein synth and storage
- Golgi Apparatus: site of packaging and processing of protein products for secretion (location on the outside of ER)
Lysosomes and Peroxisomes
Contains digestive enzymes for turning over old cellular material; detoxification
Nucleus
- Contains genetic material: Nucleic Acid
- 3 constituents of nucleotide: sugar, phosphate group, and one of four nitrogenous bases (Adenine, Thymine (Uracil in RNA), Guanine, Cytosine) AT and CG
- phosphate at the 5’ end and OH group on 3’ end. runs 5’=>3’
Define Homeostatis
Relative constancy of the internal environment with regards too heat, moisture, pressure, chemical composition. Employs negative feedback loops. Equilibrium is a steady-state achieved w/o energy expenditure. Maintaining Homeostasis is energy consuming.
