biology - unit 3

Homeostasis

Relative stability of the internal environment and the mechanisms that maintain the stability of it

Feedback loops

Evolved to help maintain homeostasis in organisms. The output of a system is used as a signal so that the input is changed. Can be positive or negative.

Effector

An organ that does the response in a feedback loop

Receptor

Sensory organ that receives the stimulus in a feedback loop

Stimulus

An action that evokes a response

Response

Effect caused by a stimulus

Cell theory

1- cells are the basic unit of all living things 2- all living things are made up of one or more cells 3 - cells come from preexisting cells

Positive feedback loop

Occurs in nature when the product of a reaction leads to an increase in that reaction. Response ENHANCES the initial stimulus. Ex: child birth

Eukaryotic cells

Contains a nucleus, contains organelle, DNA found in nucleus. Ex: animal cells, plant cells, fungi, protists

Prokaryotic Cells

Single-celled, no nucleus, no organelles, DNA found in the central part of cell. Ex: Bacteria, archaea

Phosoplipid

Main component of cell membranes - made up of two fatty acids, a phosphate group, and a glycerol molecule. Hydrophilic head and hydrophobic tails

Negative Feedback Loop

balancing feedback, response reverses the original stimulus. Ex: Thyroid hormone

Nucleus

Directs the cells activities, houses DNA

Cytoplasm

Liquid that fills the inside of cells, contains organelles,

Rough ER

protein synthesis (production, folding, quality, control, dispatch of proteins)

Smooth ER

lipid synthesis, detox

Ribosomes

makes proteins

Golgi Apparatus

Protein modification, sorting and packaging of protiens

Vesicles

Used to ship materials to other parts of the cell.

Lysosomes

Breaks down things in the cell (ex: sugar, protein, etc.)

Mitochondria

Powerhouse of the cell - produces energy for the cell

Cell Membrane

Regulates transport of materials entering and exiting the cell

Vacuole

Storage - in plants it is larger and mainly stores water.

Cytoskeletons

helps maintain cell shape and internal organization

Passive Transport

requires NO EXTRA energy by the cell because molecules move from high concentration to low concentration areas DOWN the concentration gradient

Active Transport

Requires EXTRA energy (in the form of ATP) to be spent to bring materials into the cell or expel materials out of the cell moving from low concentration to high concentration AGAINST the concentration gradient. Pumps molecules across membrane through a protein channel.

Concentration

number of molecules of a substance in a given volume

Concentration gradient

Difference in concentration of a substance from one location to another.

Diffusion

The spreading out of molecules across a membrane until they are equally concentrated on both sides of the membrane. High concentration to low concentration.

Facilitated diffusion

A transport protein acts as a protein channel to help facilitate the diffusion of the molecules that normally couldn't pass through the membrane

Osmosis

Diffusion of water across the cell membrane. Moves down the concentration gradient - from high to low concentration. Evens out solute concentration until an isotonic solution is achieved

Hypertonic solution

Water concentration is less outside of the cell, so this means solute concentration is greater outside of the cell. Less solute in the cell (higher water concentration). Water moves out of cell and cell shrivels

Hypotonic solutions

Water concentration is greater outside of the cell, so this means there is less solute outside the cell. More solute inside of the cell (lower water concentration in cell). Water moves into the cell and the cell swells

Isotonic solution

Identical water concentrations to what is found in a cell's cytoplasm. Cell stays the same.

Endocytosis

A cell uses energy to import large amounts of materials INTO the cell using a vesicle

Exocytosis

A cell uses energy to export large amounts of materials OUT OF the cell using a vesicle.

Transport protein

Moves materials within an organism. Allows for selective passage of specific molecules from the external environment

Integral protien

Resides within the bilayer membranes that surround cells and organelles, playing critical roles in movement of molecules across the membrane and the transduction of energy and signals. Locks itself into the membrane.

Peripheral protien

Forms temporary bonds with the cell membrane, allowing them to detach and reattach at specific times, with specific signals. Acts on the lipid-water interface, in contrast to transmembrane proteins, which are fully embedded in the cell membrane.

Cholesterol

Increases the order of the lipid packing, lowers the membrane permeability (provides stability), and maintains membrane fluidity by forming liquid-ordered–phase lipid rafts.

Glycoprotien

Enables cells to recognize another cell as familiar or foreign, which is called cell-cell recognition. Also helps cells attach to and bind other cells.

Receptor Protein

Transmit information to the cell by sensing the presence or absence of a stimulus. Facilitate communication between the cell and the external environment

Protien pump

Moves ions and/or solutes across biological membranes against a concentration or electrochemical gradient.

Sodium potassium pump

Transports sodium and potassium ions across the cell membrane in a ratio of 3 sodium ions out for every 2 potassium ions brought in. Pumps against concentration gradient.