Bio Unit 5: Cell Function and Homeostasis

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prokaryotic cell

unicellular organism that lacks a nucleus

eukaryotic cell

organism whose cells contain a nucleus

cytoplasm

fluid portion of the cell outside the nucleus

ribosome

cell organelle consisting of RNA and protein found throughout the cytoplasm in a cell; the site of protein synthesis

endoplasmic reticulum

internal membrane system found in eukaryotic cells; place where lipid components of the cell membrane are assembled

Golgi apparatus

organelle in cells that modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell

chloroplast

organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy

mitochondria

cell organelle that converts the chemical energy stored in food into compounds that are more convenient for the cell to use

cell wall

strong, supporting layer around the cell membrane in some cells

cell membrane

thin, flexible barrier that surrounds all cells; regulates what enters and leaves the cell

phospholipid bi-layer

the structure of the cell membrane consisting of a two-layered sheet

selectively permeable

property of cell membrane that allows some molecules to pass through it while others cannot

phospholipid

the building block of the cell membrane; makes up the phospholipid bi-layer

hydrophobic

hydrophilic

protein channel

channel that allows specific proteins to enter and exit the cell; located in the cell membrane

concentration gradient

osmosis

diffusion of water through a selectively permeable membrane

aquaporins

channel in the cell membrane for H2O molecules to pass

hypotonic

when comparing two solutions, the solution with the lesser concentration of solutes

isotonic

when the concentration of two solutions is the same

hypertonic

when comparing two solutions, the solution with the greater concentration of solutes

passive transport

diffusion

process by which particles tend to move from an area where they are more concentrated to an area where they are less concentrated

facilitated diffusion

process of diffusion in which molecules pass across the membrane through cell membrane channels

active transport

endocytosis

exocytosis

homeostasis

relatively constant internal physical and chemical conditions that organisms maintain

positive feedback loop

negative feedback loop

stimulus

signal to which an organism responds

effector

receptor

on or in a cell, a specific protein to whose shape fits that of a specific molecular messenger, such as a hormone