HSCI Chapter 3

What are basic cellular functions?

Cell metabolism (Catabolic and Anabolic), maintaining shape and integrity, dispose of waste, and cell reproduction.

What are key features of a general cell structure?

Plasma membrane, cytoplasm (Cytosol, organelles, and cytoskeleton), and nucleus

Plasma Membrane Structure

Phospholipid bilayer with membrane proteins, cholesterol, and glycolipids/proteins. 2 layers of phospholipid molecules. Hydrophilic head - Pointed both inside and outside of cell. Hydrophobic tail - Keeps water from getting in or out.

Plasma Membrane Functions

Physical barrier, selective permeability, communication, and cell recognition

Integral Proteins

Hydrophobic areas interact with lipid tails and hydrophilic areas interact with water. Function as transport proteins

Peripheral Proteins

Enzymes, cell to cell communication, structural support. Only on one side of the membrane. Inside or out.

Leaky Channel Proteins

Integral protein. Facilitated diffusion. A tunnel that allows substances to enter or exit the cell. Always open. Anything with a charge (ion) can enter.

Gated Channel Protein

Integral protein. Facilitated diffusion.Tunnel that allows substances to enter or exit the cell. Closed by a gate. Opened by a chemical binding to the channel or a voltage change. Anything with a charge (ion) can enter.

Carrier Protein

Integral protein. Closed until the substance binds to the protein. Changes the protein’s shape to allow the substance to pass through. Only open one direction at a time. Small polar molecules (amino acids and glucose) can pass through.

Glycocalyx

Glycolipid/protein. Carbohydrate attached to a lipid or a protein. Important for cell recognition and the immune system. Extracellular, attached to the plasma membrane.

Cholesterol

Stabilized plasma membrane fluidity. Makes sure it isn’t too tight or loose. Resists temperature changes. Embedded in plasma membrane with slight extracellular portion.

Passive Transport

Movement of solutes from areas of high concentration to areas of low concentrations (Between extracellular and intracellular fluids). Diffusion (simple and facilitated) and osmosis.

Diffusion rate is dependent on…

Steepness of gradient, temperature (High temp = faster), distance molecules must move (Closer = faster), surface area (larger = faster), molecule size (smaller = faster)

Simple Diffusion

Diffusion dependent on concentration gradient only. Used by nonpolar solutes (Ex. O2, CO2, lipids)

Facilitated Diffusion

Diffusion dependent on transport proteins and concentration gradients. Used by charged or polar solutes (Ex. Ions - Cl- and Ca2+, Glucose). Carrier and channel proteins used.

Osmosis

Movement of water across plasma membrane. Through lipid bilayer on its own or through an aquaporin. Needs a water molecule concentration gradient (High water to low water). High water concentration = Low solute concentration

Tonicity

Ability of an extracellular solution to make water move in or out of a cell via osmosis. Iso, hypo, and hyper tonic concentrations.

Isotonic

Same concentration of solution in the extracellular and intracellular fluid

Hypotonic

More solute/less water molecules in the intracellular fluid. Water flows into the cell. (ECF < ICF). Swollen red blood cell.

Hypertonic

Less solute/more water molecules in the intracellular fluid. Water moves out of the cell. (ECF > ICF). Crenated red blood cell (Shriveled up)

What are the three types of active transport and what are the universal processes of all three?

Primary, secondary, and vesicular. They all require energy to function.

Primary Active Transport

Transport where solutes are pumped from low to high concentration using ATP directly. Ex. Calcium, hydrogen, Na+/K+ pumps

How does ATP give energy?

Hydrolysis of phosphate bonds in the ATP molecule release energy that change the shape of the transport protein pump.

Na+/K+ Pump

Type of primary active transport. Pushes against the concentration gradient. 3 Na+ pumped out for every 2 K+ ions pumped in. Uses 40% of the body’s ATP. Essential for electrochemical gradients.

Na+ is primarily where in the cell?

Outside

K+ is primarily where in the cell?

Inside the cell

Cl- is primarily where in the cell?

Outside

Ca2+ is primarily where in the cell?

Outside

Proteins are primarily where in the cell?

Inside

Secondary Active Transport

Required energy comes indirectly from ATP made during primary. Can’t happen without primary because glucose hitches a ride on the Na+ gradient.

Uniport Transport Protein

One substance is moved one way (in or out of the cell)

Symport Transport Protein

2+ substances moved in the same direction (in or out of the cell)

Antiport Transport Protein

2+ substances moved in opposite directions (in and out of the cell)

Vesicular Transport

Used for large polar macromolecules. Moved in and out of the cell in a vesicle.

Vesicle

Membranous enclosed sacs that envelop large polar macromolecules. Require ATP. Don’t require concentration gradients

Endocytosis

Bring into cell

Exocytosis

Bring out of the cell

Resting Membrane Potential (RMP)

Difference in electrical charge across the plasma membrane when the cell is at rest. Determined by the ion/molecule charges. Inside of the cell is negatively charged compared to the outside.

What are the conditions for establishing RMP?

Unequal distribution of ions/molecules (positive/negative charges) across the plasma membrane

What are the conditions to maintain RMP?

Selective permeability (Keeping negatively charged proteins trapped) and Na+/K+ pumps to keep the concentration gradient maintained

Cytosol

Gel like substance in a cell that supports organelles

Non Membranous Organelles

Organelles that are freeballing in the cytosol.

Non Membranous Organelles Examples

Cytoskeleton, Ribosomes, and Centrosomes

Endoplasmic Reticulum

System of tubes and cisterns that accounts for half of the cells membranes. 2 kinds, smooth and rough.

Rough ER

Contains ribosomes, interconnected cisterns, and is continuous with the nuclear envelope. The ribosomes manufacture all proteins secreted from cells (Ex. Immune and liver cells). Form the integral proteins and phospholipids used in the cell membrane.

Smooth ER

Continuous with the rough ER and is made up of looping tubules. No ribosomes. Metabolizes lipids, synthesizes steroid based hormones, detoxifies drugs, breaks down glycogen, and stores calcium ions.

Golgi Apparatus

Stacked, flattened cisterns. Not connected to the nucleus. Modifies, concentrates, and packages proteins and lipids made in the ER. Forms vesicles for the exocytosis of proteins and lipids.

Lysosomes

Spherical membranous bags that contain digestive enzymes. Digest foreign substances, non functional organelles, and injured/damaged cells. Also aids in metabolism. 

Peroxisomes

Membranous sacs that are slightly larger than ribosomes. Contain detoxifying substances. They oxidize toxins into hydrogen peroxide and help breakdown fatty acids.

Mitochondria

Contains a double layer membrane. Outer layer contains large channels with openings that allow substances in and out of the cell. Inner layer has multiple folds (cristae) that’s embedded with membrane proteins. Inner layer executes the cells main function, the creation of ATP through cellular respiration. 

Nucleus

Made up of the nuclear envelope (With the nuclear pores which allow substances in and out), the nucleolus (makes ribosomes), and the chromatin (condensed chromosomes). It directs the activities of other cellular components and participates in ribosome and genetic synthesis. Has it’s own DNA. Not every cell will have a nucleus.

Ribosomes

Tiny granular organelles with large and small subunits. Composed of ribosomal proteins and RNA. Bound to the rough ER or free in the cytoplasm. Synthesizes proteins.

Microvilli

Short and thick finger like extensions on the outside of a cell. Increase surface area allowing for greater absorption.

Cilia

Thin and long hair like projections on the outside of a cell. Move substance across and away from a cell.

Flagella

Single long extension that propels a whole cell. Ex. Sperm

Name the intracellular junctions

Tight junctions, desmosomes, and gap junctions.

Tight Junctions

Hold cells tightly together to stop molecules from moving between cells.

Desmosomes

Zips cells together (Looks like a zipper). Resists mechanical stress and keeps cells together.

Gap Junctions

Look like butterfly stitches. Small pores within protein channels that aid electrical signal cell to cell communication.