AP BIO - Unit 2

Light Microscope

An optical instrument with lenses that refract (bend) visible light to magnify images of specimens.

Electron Microscope

Microscope that forms an image by focusing beams of electrons onto a specimen

Scanning Electron Microscope (SEM)

An electron microscope used to study the fine details of cell surfaces. Electron beams bounce off the surface

Transmission Electron Microscope (TEM)

An electron microscope used to study the internal structure of thin sections of cells. Electron beams pass through the cell

Cells

The basic unit of structure and function in all living things

Subcellular

Existing or occurring within a cell

Organelle

A tiny cell structure that carries out a specific function within the cell

Cell Fractionation

Technique in which cells are broken into pieces and the different cell parts are separated. Think mitochondria, nuclei, pieces of membrane, and ribsome

Prokaryotic Cell

A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.

Eukaryotic Cells

Contain a nucleus and other organelles that are bound by membranes.

Endomembrane System

A network of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

Nucleolus

Found within the nucleus, area of tightly packed chromosomes where ribosomes and rRNA production occurs

Nuclear Envelope

Double membrane perforated with pores that control the flow of materials in and out of the nucleus.

*Ribosome

A non-membraned enclosed organelle, it is made up of RNA and proteins which form one large and one small subunit. Makes proteins

Free ribosomes

Ribosomes suspended in the cytosol that mostly synthesize proteins which dissolve in the cytosol and function there

Bound ribosomes

Attached to outside of ER or nuclear envelope - proteins that are destined for insertion into membranes or packaging certain organelles (ex: lysosome)

*Endoplasmic Reticulum (ER)

A network of membranous tubules (think of it as a continuous membrane) within the cytoplasm of a eukaryotic cell, continuous with the nuclear membrane. It usually has ribosomes attached and is involved in protein and lipid synthesis.

*Rough ER

A network of interconnected membranous sacs in a eukaryotic cell's cytoplasm; covered with ribosomes that make membrane proteins and secretory proteins. Proteins are packaged in vesicles and are transported to Golgi apparatus. Also, it helps serve as a membrane factory

*Vesicles

Small membrane sacs that specialize in moving products into, out of, and within a cell

*Smooth ER

That portion of the endoplasmic reticulum that is free of ribosomes. Helps in the production of lipids, helps detoxify drugs and poisons, and stores calcium ions

*Golgi Apparatus

A system of membranes that modifies, sorts, and packages proteins from the endoplasmic reticulum. They package the proteins into vesicles where they can be transported out of the cell or somewhere else in the cell

Cytoskeleton

Network of protein filaments within cells that help hold the cell together, keep its shape, and aid in movement

*Lysosomes

A membrane-enclosed sac of hydrolytic enzymes. Its pH range is acidic. One of its main function is intracellular digestion (phagocytosis) where it engulfs smaller organisms, food particles, harmful substances.

Hydrolytic Enzymes

Enzymes that speed up/aid in the breakdown of chemical bonds through the addition of water (hydrolysis)

*Vacuole

Cell organelle that stores materials such as water, salts, proteins, and carbohydrates

Central Vacuole

A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development. Known most for its role in holding water

Contractile Vacuole

The cell structure that collects extra water from the cytoplasm and then expels it from the cell. Found in prokaryotic cells

*Mitochondria

Double-membrane organelle with a folded inner membrane. Powerhouse of the cell, organelle that is the site of ATP (energy) production

*Chloroplast

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

Why are so many of the membranes in the cell folded?

Highly folded membranes increase the surface area without increasing the volume. Thus they increase the surface area to volume ratio. This is utilized in the mitochondria and the chloroplast, which have folded inner membranes

*Flagella

A long, whip-like filament that helps in cell motility. Many bacteria are flagellated, and sperm are flagellated.

Centrioles

Located near the nucleus and help to organize cell division

Intercellular Junctions

Intercellular junctions are structures between cells that allow neighboring cells to form strong connections with each other, prevent passage of materials, or establish rapid communication between adjacent cells. The three types of intercellular contact in animal cells are: desmosomes, gap junctions, and tight junctions.

Tight Junctions

Membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

Desmosomes

Anchoring junctions that prevent cells from being pulled apart

Gap Junctions

(communicating junctions) provide cytoplasmic channels between adjacent cells

Plasmodesmata

An open channel in the cell wall of plants through which strands of cytosol connect from adjacent cells

Endosymbiont

A cell living within another cell

Endosymbiotic Theory

A theory that states the mitochondria and chloroplasts were aerobic prokaryotes that were swallowed by larger anaerobic prokaryotes. They formed a mutualistic relationship and eventually evolved into the organelles of modern-day eukaryotes

Endosymbiotic Theory Evidence

1.) Double membranes

2.) Organelles with own DNA and its similar to bacterial DNA - circular molecules

3.) Reproduce similarly to prokaryotes and independently (binary fission)

4.) Same cell size as bacteria

Mutualism

A relationship between two species in which both species benefit

Cell Size

• Limited by surface area-to-volume ratio.

• As cell grows its volume increases much faster than its surface area

• Cells need a large surface area in order to allow materials to leave and enter the cell quickly enough for its needs.

Why are cells limited in size?

• Cells wouldn't be respire effectively if it were too large, it would be difficult for it to move nutrients and waste products in and out of the cell.

• If they were too small, they cannot keep enough material inside to be able to keep the cell alive

As the length of a cube-shaped cell increases, the surface area to volume _________?

Decreases

As cells increase in volume, the relative surface area ________ but the demand for internal resources __________

Decreases, increases

Surface Area

The sum of all the areas of all the faces or surfaces that enclose a solid.

Cell Size Solution #1

Multicellular organisms - maintains large volumes by having multiple cells to increase their surface areas

Cell Size Solution #2

Cell Shape/Specialized Structures - Large cells that interact with environment will change shape, like stretch out or fold.

• EX. organelles with mitochondria*, chloroplasts, ER, and golgi body.

• EX. Small intestine with cilia and microvilli. These folded projections help increase surface area and absorption of nutrients and allow for materials to pass on quicker by

• EX. Root hairs on roots allow for increased absorption of water and nutrients by extending membrane

Phospholipids

A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a non-polar, hydrophobic tail.

In an aqueous solution, phospholipids form

A bilayer, heads are exposed to aqueous parts while the tails are tucked inside

Hydrophobic

Water fearing

Hydrophilic

Water loving

Amphiphatic

A molecule that has both hydrophobic and hydrophilic regions.

Cell Membrane

The semipermeable phospholipid bilayer surrounding the cytoplasm of a cell. Controls which substances can enter or leave the cell.

Fluid Mosaic Model

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.

Membrane Fluidity

The property by which most of the plasma membrane lipids and proteins easily rotate and move side ways in their own half of the lipid bilayer. This property allows the membrane to self seal if torn; proteins seldom flip-flop from one half of the bilayer to to the other.

What affects membrane fluidity?

• Temperatures (lower temps = membrane packed together, solidifies)

• Lipid concentration (unsaturated fatty tails = more fluid)

• Length of hydrocarbon tails (shorter= more fluid)

• Cholesterol = more fluid at low temps, restrains phospholipid movement at high temps

Integral proteins

Penetrate the hydrophobic interior of the lipid bilayer

Peripheral proteins

The proteins of a membrane that are not embedded in the lipid bilayer; they are appendages loosely bound to the surface of the membrane.

Transmembrane Proteins

Integral proteins that span the membrane.

Cholesterol

A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.

Glycolipids

Membrane carbohydrates that are covalently bonded to lipids. Important for cell signaling

Glycoproteins

Membrane carbohydrates that are covalently bonded to proteins.

What do proteins do in the cell membrane?

Regulate what goes in and out of cell membrane

Membrane Permeability

Degree to which a membrane allows a substance to pass through it

What easily passes through the cell membrane?

Small, nonpolar/hydrophobic molecules

• O2, CO2

What cannot easily pass through the cell membrane?

Large polar/hydrophilic molecules

• H2O, glucose

• Needs channel/carrier proteins

Channel Proteins

Have a hydrophilic channel that certain molecules or ions can use as a tunnel

Carrier Proteins

Bind to molecules and change shape to shuttle them across the membrane

Cotransporter

A protein in a cell membrane that allows movement of one molecule when linked to the movement of another molecule in the same direction by active transport.

Aquaporins

A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration (technically random)

Concentration Gradient

A difference in the concentration of a substance across a distance.

Osmosis

Diffusion of water through a selectively permeable membrane

Osmolarity

Total concentration of all solute particles in a solution

Hypertonic Solution

A solution in which the concentration of solutes is greater than that of the cell that resides in the solution; water potential is lower and cell loses water

Flaccid

Limp due to lack of turgor pressure

Turgor Pressure

The pressure that water molecules exert against the cell wall

Plasmolysis

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

Hypotonic Solution

A solution in which the concentration of solutes is less than that of the cell that resides in the solution; water potential is greater and cell gains water

Lyse

Cell bursting

Turgid

Very firm, healthy state for most plant cells

Isotonic Solution

A solution in which the concentration of solutes is essentially equal to that of the cell which resides in the solution; cell and solution are in equillibrium

Solute

A substance that is dissolved in a solution.

Solvent

A liquid substance capable of dissolving other substances

Water Potential

The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.

Water will always move from an area of ________ water potential to an area of ________ water potential

greater, lesser

Solute Potential relationship with Water Potential

They have an inverse relationship; the greater the concentration of a solute, the lower the water potential will be

Pressure Potential relationship with Water Potential

A direct relationship; physical pressure increases water pressure

solute potential

This measurement has a maximum value of 0; it decreases as the concentration of a solute increases.

Passive Transport

The movement of substances across a cell membrane without the use of energy by the cell

Simple Diffusion

Movement of a solute from an area of high concentration to an area of low concentration

Facilitated Diffusion

Movement of specific molecules across cell membranes through protein channels, requires no energy and moves from high to low concentration

Facilitated diffusion with a carrier protein

Glucose

Simple Diffusion, what substances

O2, CO2, N2

Facilitated diffusion with a channel protein

H+, H2O (aquaporins)

Active Transport with a carrier protein

Sodium Potassium Pump (Na/K)

Active Transport

Energy-requiring (ATP) process that moves material across a cell membrane against a concentration difference

Sodium-Potassium Pump

A carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell