Unit 2 - AP Biology - Cell Function and Structure

Why are cells so small?

Because they are more efficient, cell size is limited by the ratio of cell surface area to volume

Prokaryotes have no…

internal membrane bound organelles

Eukaryotic Adaptations

Inner Membrane folds, membrane bound organelles, multicellular organisms with systems for exchanges/transport materials

Compartmentalization

Separation of microenvironments within a cell which boosts efficiency which also allows for the cell to establish concentration gradients and have more potential energy

Every Cell has:

Cytosol, Cell membrane, Ribosomes, and Genetic Material

Cytosol

Aqueous portion of the cell, composed of water, organic molecules and dissolved ions

Cell/Plasma membrane

Membrane that separates inside of a cell/structure with the outside of a cell/structure

Ribosomes

Creates proteins, can be free floating or bound

Genetic Material

DNA or RNA

Nucleus

stores genetic info. in Eukaryotes

Nucleolus

produces/assembles ribosomes (RNA)

Nuclear Envelope

Nucleus’ personal membrane

Endoplasmic Reticulum

the membrane system continuous with the nuclear membrane

Rough ER

makes proteins for export

Smooth ER

Makes lipids, breaks down carbs and stores calcium

Golgi Apparatus (bodies)

helps process and package proteins and lipid molecules, especially proteins destined to be exported from the cell

Lysosome

contains digestive enzymes, is the site of hydrolysis, breaks down excess/worn out cell parts, used to destroy invading viruses and bacteria, and commits self die/apoptosis

Vacoule

a space or vesicle within the cytosol of a cell, enclosed by a membrane and typically containing fluid/food

Mitochondria

double membrane-bound cell organelles, generates most of the ATP needed to power the cell’s biochemical reactions, and Cristae provide surface area for chemical reactions

Christae

the folds in the Mitochondria

Central Vacoule

Holds materials and waste (only plant cells)

Cell Wall

protects the cell (only plant cells)

Plastids

Inside Chloroplast, stacks of discs inside for increased surface area

Stem Cells

Grown and develop into specialized cells that have specific roles like signaling, immune system and structural

The cell membrane:

Defines borders of the cells, regulates what enters/leaves the cells, allows for cell-cell communication

Fluid Mosaic Model

The membrane is composed of a mosaic (mix) of phospholipids, proteins, and cholesterol that freely and fluidly slide past one another

Phospholipid Bilayer

Composed of polar heads that are hydrophilic and nonpolar tails that are hydrophobic

Integral Porteins

Goes fully through the phospholipid bilayer

Peripheral Proteins

Doesn’t go all the way through the phospholipid bilayer

Amphipathic

Both polar and non-polar

Glycolipid

attached to the phospholipid heads, helps with cellular recognition

Cellular Recognition

how cells recognize a you cell vs. an invasive cell

Glycoprotein

attached to peripheral proteins, and helps with cellular recognition

Cholestrol

Moderates fluidity, makes sure tails aren’t too close together or too far apart

Receptor Proteins

Receives transmissions and messages, usually integral proteins but sometimes peripheral

Selective Permeable Membrane

Depends on size, polarity and change of what tries to enter

Passive transport

Diffusion of a substance across a membrane with no energy investment, travels down concentration gradient until a dynamic equilibrium is reached

Facilitated Diffusion

passively transported through a transport protein (for large or charged molecules/ions)

Simple Diffusion

passively transported through the phospholipid bilayer (small and uncharged)

Active Transport

pumping a substance against its concentration gradient (low to high) thus disrupting equilibrium, requires energy input and carrier proteins

Primary Active Transport

active transport of ions creates voltage across the membrane, requires ATP

Secondary Active Transport

Uses and electrochemical gradient (created by primary transport) as an energy source, rather than ATP, when two substances get transported, one passively with the concentration gradient, and one actively against the concentration gradient

Uniporters

proteins that allow one substance

Contransporters

Two Substances at the same time

Symporter

Two substances int he same direction

Antiporter

Two substances in opposite directions

Osmosis

Diffusion of water across a membrane

More solute=

less free water concentration

water moves to establish…

an equally osmotic concentration (osmolarity)

Osmosis is what kind of transport?

It’s Passive Transport

Tonicity

the ability of a surrounding solution to cause a cell to gain or lose water

Hypotonic=

less concentrated

Isotonic=

Equal Concentration

Hypertonic=

More Concentrated

Animal Cell in Hypotonic Solution

Lysed

Animal Cell in Isotonic Solution

Normal

Animal Cell in Hypertonic Solution

Shriveled

Plant Cell in Hypotonic Solution

Turgid (normal)

Plant Cell in Isotonic Solution

Flacid

Plant Cell in Hypertonic Solution

Plasmalyzed

Water Potential

measured in bars, the potential energy of water or its tendency to move from one place to another

Aquaporin

passage for water into and out of the cell

Apoplast Pathway

fast pathway inbetween cells (only in plants)

Turgor Pressure

Force within the cell that pushes the plasma membrane against the cell wall (in plants)

Solvent follows…

Solute

Exocytosis

Vesicles released by the golgi fuse with the cell membrane, releasing their contents to the external environment (Vesicle becomes part of the membrane)

Endocytosis

a small area of the plasma membrance sinks inward, forming a pocket around a substance eventually it pinches off, forming a vesicle that carries substances into the cell

Phagocytosis

“cellular-eating”, large molecules (solid, won’t fit through protein)

Pinocytosis

“cellular-drinking”, small molecules suspended in fluid

Receptor-Mediated Endocytosis

Regulated entry of molecules (only triggers with specific amount needed)