AP Test Cell Review

Basic Definitions A cell is the basic unit of life.

All living things are made of cells.

Inside cells are organelles, which are small, membrane bound structures that have specific jobs.

Cells are small because nutrients and water must be able to get to all parts of the cell (higher surface area to volume ratio with smaller cells)

Eukaryotic vs. ProkaryoticA prokaryotic cell does NOT have

a nucleus or membrane bound organelles. It is small and simple, having only cytoplasm (fluid) and ribosomes (organelles that make protein). Bacteria are prokaryotic.

A eukaryotic cell DOES have a nucleus and organelles. They are larger and more complex, and include plants and animals.

Animal vs Plant Cell

Review of the Endomembrane System

AP Biology

Phospholipids

Fatty acid

Phosphate

Phosphate head Hydrophilic and polar

Fatty acid tails Hydrophobic and non

polar

Arranged as a bilayer

Aaaah, one of those

structure–functionexamples

“repelled by water”

“attracted to water”

AP Biology

Permeability to polar molecules? Membrane becomes semi-permeable via

protein channels specific channels allow polar substances

like water, ions, and sugars across cell membrane

inside cell

outside cell

sugaraaH2O

saltNH3

AP Biology

Getting through cell membrane Passive Transport

Simple diffusion diffusion of nonpolar, hydrophobic molecules

lipids HIGH LOW concentration gradient

Facilitated transport diffusion of polar, hydrophilic molecules through a protein channel

HIGH LOW concentration gradient

Active transport diffusion against concentration gradient

LOW HIGH uses a protein pump requires ATP

ATP

AP Biology

Osmosis is just diffusion of water Water is very important to life,

so we talk about water separately Diffusion of water from

HIGH concentration of water to LOW concentration of water across a

semi-permeable membrane

AP Biology

Concentration of water Direction of osmosis is determined by

comparing total solute concentrations Hypertonic - more solute, less water

Hypotonic - less solute, more water

Isotonic - equal solute, equal water

hypotonic hypertonic

water

net movement of water