Chapter 4: Cell Structure

• plants: made out of cellulose (polysaccharide) • fungi: made out of chitin (polysaccharide) • bacteria: made of peptidoglycan (protein and sugar) • forms outer layer

• selectively permeable • composed of lipids and proteins • forms oily layer between the inside of the cell and the outside so hydrophilic substances cannot cross the hydrophobic barrier

• movement of a hydrophobic substance (like oxygen, carbon dioxide, and cholesterol) down a concentration gradient from an area of high concentration to low concentration until dynamic equilibrium is reached • only works when the substance is lipid soluble (hydrophobic) and can interact with the oily barrier • passive

• hydrophillic particles (like ions and glucose) diffuse across the membrane with the use of membrane proteins that form specialized channels • passive • some proteins act as carrier molecules that bind to a substance and “pull” it through a membrane

• can go against the concentration gradient • use energy to move something across the membrane • relies on membrane proteins to transport hydrophobic and hydrophillic particles

-movement of large, bulky items across the membrane through endocytosis or exocytosis

• cell takes in a particle by surrounding and engulfing it into a vesicle • phagocytosis: cell eating • pinocytosis: cell drinking

-particle in a vesicle is released to the outside by fusing the vesicle with the cell membrane

• diffusion of water across a membrane down the water concentration gradient • water’s concentration gradient is opposite of the solute’s concentration gradient • must cross through facilitated diffusion (with aquaporins)

• concentrated solution - causes cell to shrivel or become flaccid

• dilute solution - cell will lyse or become turgid for plants

• same concentration as cell - cell will be normal (plant will be shriveled)

• contains eukaryotic cell’s organelles - some prokaryotic cells do not have organelles

• no membrane - site of protein synthesis

• double membrane bound • contains genetic material (chromosomes and DNA) • control center of cell

• functions in cellular respiration (produces ATP for the cell) • bound by double membrane

-storage of wastes and other materials

• transports substances around the cell - creates lipids

-has ribosomes that synthesizes membrane (protein channels) and secreted proteins

-sorts and packages proteins made by ribosomes on the ER

-digest foreign substances and worn-out organelles

• small, dense structure in the nucleus - site of ribosome synthesis

• protein (organic molecule) that acts as a catalyst (a molecule that speeds up chemical reactions) in cells • reusable (not used up) • induced-fit or lock-and-key model (an enzyme has a specific shape catered to certain reactions bc active site is specific to certain reactants) • reactants are called substrates • determines which reactions occur inside a cell

• degradation of enzyme (often through heat or change in pH) - no longer useful because they lose their shape