Bio 30S unit 1

Homeostasis - The ability of the body to maintain a constant internal balance

What conditions do cells need to work properly? - Proper temperature (37℃), water level, pH level, and glucose concentration 

Negative Feedback Loop - a mechanism that keeps the body in a consistent environment (Ex, blood sugar and temperature control)

Positive Feedback Loop - The body keeps amplifying the response and rapidly speeding up the process. (Ex: Child birth)

Components of the Negative feedback loop - Receptor -> Control Centre -> Effector -> 


What keeps the body warm/cool? - Vasoconstriction and piloerection keep the body warm. Vasodilation and sweating keep the body cool.

Vasodilation - capillaries under the skin fill with blood to let out heat into the air, making your skin red and warm

Sweating - When your body is hot, your sweat glands are stimulated to release sweat. The heat from your skin evaporates the sweat, cooling the body down.

Vasoconstriction - Capillaries under the skin shut off, trapping heat in the body

Piloerection/Goosebumps - Hairs trap a layer of air next to the skin, which is warmed by body heat. The air becomes an insulating layer.

What happens to excess glucose? - It is converted to glycogen in the liver.

What hormones regulate glucose levels? - Insulin and Glucagon

Function of Glucogen - When there is a lack of glucose in the blood, glycogen is converted back into glucose

Function of Insulin - Moves glucose from the bloodstream to cells to make energy, and prevents the buildup of glucose.

How do body systems coordinate to maintain homeostasis? - The nervous system instructs the body on how to act, controlling homeostasis.


Robert Hooke - Discovered Cells, coined the name cell, and only saw dead cells.

Anton van Leeuwenhoek - Discovered Living cells

Principles of Cell Theory - 

  1. All living organisms are composed of cells. 

  2. The cell is the basic unit of life. 

  3. All cells come from pre-existing cells.

Basic Features of all Cells - Plasma membrane, Cytosol, chromosomes, ribosomes

Plasma Membrane - Thin, flexible wall, controls what enters and leaves the cell, protects the cell from its surroundings. A selective barrier allows the passage of oxygen, nutrients, and waste.

Cytosol - Fluid that fills the cells in between organelles

Chromosomes - Carry genetic information

Ribosomes - Use information from the nucleus to make proteins

Types of cells - Prokaryotic and Eukaryotic

Prokaryotic Cell - No nucleus, DNA lies free in cytoplasm, no membrane-bound organelles, always single-celled organisms.

Eukaryotic Cell - DNA in nucleus, membrane-bound organelles, Cytoplasm between nucleus and plasma membrane, larger.

Nucleus - Organelle, the membrane of the cell, holds DNA.

Mitochondria - The powerhouse of the cell, break down glucose to create energy

Endoplasmic Reticulum (ER) - A network of membranes around the nuclear envelope. A transportation system within the cell.

Rough Endoplasmic Reticulum (RER) - ER studded with ribosomes for protein synthesis

Smooth Endoplasmic Reticulum (SER) - ER without ribosomes, involved in lipid synthesis and detoxification

Golgi Apparatus - made up of flat membranous sacs called cisternae. Packages proteins and other molecules for transport to the cell membrane and to other organelles. Produces vesicles with enzymes for digestion (lysosomes) 

Phospholipid Bilayer - a double layer of phospholipids that makes up the plasma membrane and organelle membranes.

Membrane Proteins - Proteins attached or embedded in the plasma membrane. Functions: Communication, Transport

Selective Permeability - Some molecules are allowed through the membrane while others are not

Effect of cholesterol on the cell membrane - Keeps the cell membrane fluid. It prevents it from becoming too fluid at high temperatures and too rigid at low temperatures.

Passive transport - The movement of substances across a cell membrane without the use of cellular energy. Moves from an area of higher concentration to an area of lower concentration.



Simple Diffusion - the passive movement of small, non-polar molecules across a cell membrane from an area of high concentration to an area of low concentration. No energy is used.



Facilitated Diffusion - cell transport where molecules move across a membrane down their concentration gradient with the help of specific transport proteins. (e.g. channel proteins, carrier proteins)



Osmosis - The passive movement of water across a semipermeable membrane from an area of high concentration to an area of low concentration.



Active Transport - Moves against a concentration gradient, requires ATP, and is performed by proteins in the membrane.



Concentration Gradient -  the difference in the concentration of a substance between two areas, which causes diffusion.



Cell Membrane - a semipermeable boundary that separates the cell from its external environment



Tonicity - A solution's ability to change a cell's volume by altering its water content with osmosis



Isotonic - a solution with the same solute concentration as another solution



Hypertonic - describes a solution with a higher solute concentration than another solution, like the cell's internal environment



Hypotonic - a solution with a lower solute concentration than the inside of a cell, causing water to move into the cell via osmosis



Sodium Potassium Pump - The sodium potassium pump rests open on the intracellular part of the cell, with room for 3 sodium ions. When the sodium ions bind to the pump, ATP will power it by transferring its phosphate to the pump, turning the pump around to the extracellular side. The sodium is released, and 2 potassium ions bind to the pump. The phosphate is released from the pump, flipping around and releasing the potassium into the cell. The cycle repeats.



What determines the rate of diffusion: temperature, concentration gradient, surface area, and distance