Unit 2: Cell Structure and Function

AP Bio (Chapter 6+7) LMK if I'm missing any terms that could be helpful by emailing me :)

Prokaryotic

• Always unicellular

• Smaller, simpler structure

• Lacks membrane bound organelles

• Lacks true nucleus

Eukaryotic

• Can be unicellular or multicellular

• Larger, more complex structure

• Has many organelles

• Has a nucleus

Nucleus

contains DNA and directs cellular functions

Nuclear Membrane

• Structure to allow the storing of information & allowing for it to flow from nucleus -> ribosomes in the cytoplasm

porous membrane separates cell’s DNA genome from rest of cellular environment

Ribosomes

• converts nucleic acid information (DNA) into polypeptide chains

site of protein synthesis

Free ribosomes

• make proteins that will stay inside the cell for use by the cell, like enzymes associated with metabolism or DNA replication

exists in the cytoplasm (in ALL types of cells)

Bound ribosomes

• make proteins that will leave the cell to be used elsewhere

• Most are for communication between cells, such as antibodies for fighting infection

bound to the ER

Cell Wall

Fibers of structural polysaccharides that provide structural support and protection for cell

Cell Membrane

controls passage of organic molecules, ions, water, & oxygen in and out of the cell (waste products leave by passing through)

Endoplasmic Reticulum (ER)

membranous channels that run through cell, producing membranes and transporting proteins

Smooth ER

• Helps with synthesis of lipids, phospholipids, steroids

• Helps carbohydrates (glycogen/stored sugar) breakdown into (glucose/useable sugar)

• Detoxify blood as liver cells have lots of SER (smooth ER)

• Store Ca++ needed for muscle contraction

• ER 3 and 4 (depicted above) make up the Endomembrane System, involved in production/transport of membrane & membrane proteins

ER not covered in ribosomes

Rough ER

• Provides safe folding area for proteins

• Ribosomes bound to outside, deposits proteins as they are made inside ER

• Proteins can fold into 3D structure needed to function

ER covered in ribosomes

Golgi Apparatus

flattened membranous compartments that receive material from ER, modify it before targeting it for delivery to other areas of cell

Mitochondria

site of aerobic cellular respiration

Endomembrane System

The flow of information from the nucleus to proteins. Nucleus → ER → Golgi → Final Destination

Chloroplasts

site of photosynthesis in plants and algae

Lysosomes

• plays a part in molecule digestion,

• recycling of cell’s damaged components

• programmed cell death

membrane enclosed sacs containing collections of digestive and hydrolytic enzymes

Vacuoles / Vesicles

• plant cells have large, central vacuole which store nutrients/material and support cell structure

• animal cells have smaller, individual

membrane bound sacs that store material w/ different structures for different products needed by the cell

Cytoskeleton

• Keeps inner organelles organized

  • Facilitates cell organelle movement

Supports and protects the cell

Microtubules

• supports movement and function of cell & organelles Important structures made of microtubules within a cell that you should know:

large, hollow tubes made of Tubulin protein

Centrosomes and Centrioles

Centrosomes contain a pair of centrioles and are the region where microtubules grow from.

Spindle Fibers

microtubules that grow out of the centrosome region (seen in mitosis and meiosis)

Cilia

microtubule extensions that project from cells (usually many) and are involved in movement of fluids/substances over the surface of the tissue

Flagella

Microtubule extensions that project from cells (usually just one or a few) involved in movement of a cell (like a tail)

Microfilaments

• provide pulling force

• abundant in muscle tissue cells in animals

solid rods made of actin or myosin protein

Intermediate filaments

• helps reinforce and brace large microtubules

permanent solid rods made of keratin protein

Fluid Mosaic Model

Connects membrane structure to function. 2 components: phospholipids and proteins

Selective Permeability

• Only small nonpolar molecules move through bilayer

• Gets oxygen and co2 in and out fast

  • Cell needs o2 & wants to get rid of co2 fast because it is waste

• Other materials move through protein pores

A property of biological membranes that allows them to regulate the passage of substances across them

Phospholipids

• Phospholipids are amphipathic.

• They spontaneously form a bi-layer in aqueous environments.

• The inside of the bi-layer is hydrophobic.

Cholesterol

• Reduces membrane fluidity at moderate temperatures by reducing phospholipid movement.

• At low temps, hinders solidification by disrupting regular packing of phospholipids.

Fluidity buffer

Passive Transport

• Doesn’t require energy

Diffusion, moves with the concentration gradient

Simple Diffusion

• Ex: oxygen, carbon dioxide

Small, nonpolar molecules are able to diffuse across the phospholipid bilayer

Facilitated Diffusion

• Protein pores

Large, polar/charged molecules must defuse through protein pores in cell membrane

Primary Active Transport

moves ions across a membrane against their gradient and creates a difference in charge across that membrane, which is directly dependent on ATP

Secondary Active Transport

describes the movement of material that is due to the electrochemical gradient established by primary active transport that does not directly require ATP

Co-Transport

Cells can transport multiple molecules simultaneously

Bulk Transport

Cells transport bulk molecules by surrounding them with membrane (“vesicles”)

Endocytosis

Internal vesicular transport

Exocytosis

External vesicular transport

Tonicity

A measurement of the relative concentrations of solute between two solutions (inside and outside of cell)

Hypertonic

Solution has more solute/less solvent

Hypotonic

• causes water to flow into the cell

  • Animal cell = shrivel

  • Plant cell = flaccid

Solution has less solute/more solvent

Isotonic

Equal concentrations or equal exchange rate of solute and solvent

Water Potential Ψ

• LOW water potential:

  • LESS water molecules are free to move around.

• HIGH water potential:

  • MORE water molecules are free to move around.

The potential energy of water per unit area compared to pure water. A measurement of how likely it is that water will move in/out of a solution. Water moves from an area of HIGH water potential to LOW (more negative) water potential.

Proteins (role in cell)

• act as channels that molecules can enter/exit the cell membrane through

integral and peripheral

Carbohydrates (role in cell)

signal to other cells

Cholesterol

• In cold temperatures, cholesterol acts a roadblock to prevent molecules from packing together too tightly (and stiffening too much)

• In warm temperatures, cholesterol acts a roadblock to hinder phospholipid movement, preventing excessive fluidity

acts as fluidity buffer to prevent cell membrane from being too fluid or too stiff

Phagocytosis

takes IN PARTICLES used for nutrients

Pinocytosis

takes IN FLUID droplets to use for nutrients

Receptor Mediated Endocytosis

Specific molecules bond to receptors (which can only accept specific molecules) and are brought into the cell

Aquaporins

Channels that allow water to diffuse

Osmosis

Diffusion of water in cell membrane

Sodium Potassium Pump

Cells move molecules against the concentration gradient by using energy. The energy is used to operate “pump proteins”.

Flaccid

when plants cells are isotonic

Turgid

when plants cells have excess water (hypotonic)

Plasmolysis

when plants cells have too little water (hypertonic)