UNIT 2: Cell Structure and Function

Cellular components universal to ALL cells

Genome(inside of mRNA, genetic code) and ribosomes

Ribosome structure

Two subunits made of ribosomal RNA and proteins; can be free in cytosol or bound to ER

Ribosome function

The 2 subunits come together to during translation to synthesize proteins from mRNA.

Endoplasmic Reticulum structure

Extensive network of membrane-bounded tubules and sacs; membrane separates lumen from cytosol; continuous with nuclear envelope

Smooth ER structure and function

Structure: Several lipid bilayers with space inside that allows it to be different

Function: detoxification of toxic wastes +lipid synthesis

Rough ER structure and function

Structure: Several lipid bilayers with space inside that allows it to be different w/ ribosomes

Function: Have ribosomes on it to transport membrane proteins made by the ribosomes.

Vacuole structure

Membrane bound storage sacs, generally one large in plant cells.

Vacuole function

Storage of water and biomolecules, release of cell waste through exocytosis=> fuses with cell membrane to expel waste products.

Golgi Complex/Apparatus structure

• consists of several disk-shaped cisternae (saccules) arranged in a stack

• organized functionally into cis, medial & trans faces

• has a distinct polarity across the stack

molecules flow from cis face and leave to trans-face.

Golgi Complex/Apparatus function

involved with the correct folding/chemical modification of proteins.

Packaging, modification, and transport.

Vesicles

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

Mitochondria structure

Consists of a double membrane, creating an inner membrane(folded), outer membrane, an intermembrane space, the matrix, and cristae

Mitochondria function

ATP(Adenosine Triphosphate) production

Lysosome structure

Membrane enclosed sacs containing hydrolytic enzymes

Lysosome function

Hydrolytic enzymes within the lysosome digest materials(damaged cell plants, macromolecules)

Metabolic reactions of the Mitochondria +Locations

1. Krebs cycle/citric acid cycle- matrix

2. ETC(Electron Transport Chain) +ATP synthesis- inner mitochondrial membrane

Mitochondria membrane folding of inner membrane effect

increases the surface area, allowing more absorption +ATP production

Chloroplast structure

Plant cells ONLY

1. Thylakoid

2.Membranes

3.Stroma

Thylakoid

highly folded membrane compartments organized into stacks(stacks=grana/granum)

Chloroplast Membranes

Contain Chlorophyll pigments for photosynthesis

Thylakoid membrane function

ETC proteins found within photosystems 1 and 2

Stroma structure + function

Fluid filled between the inner membrane and thylakoids-> carbon fixation occurs

Lysosomes 3 specific roles

1. Intracellular digestion

2. Recycling of organic materials

3. Programmed cell death=apoptosis

Turgor pressure

plant cells ONLY- the internal cellular force caused by water within the vacuole pushing on the plasma membrane + cell wall.

ex. Wilting plants- no turgor pressure

Typical cell size + why

SMALL CELLS- smaller the cells are, the more absorption of materials

SA/V ratio: needs to be high SA/V ratio

Purpose of Membrane folding

to increase surface area

ex. 1-Villi and microvilli on small intestine

ex.2-Root hairs on plant roots

Passive transport

The movement of solutes across the cell membrane from high to low concentration with NO USE of energy.

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Facilitated diffusion

The movement of molecules from an area of high concentration to low concentration with the help of a protein channel using NO energy.

Facilitated diffusion structures involved (2)

Protein channel- ; carrier protein- form pores along the membrane, allowing the membrane to move down

What molecules move across the cell membrane

SMALL, NON-POLAR molecules

Active transport

The movement of molecules from low to high concentration USING energy.

Co-transport

The transport of one substance coupled with the transport of another substance in the same direction through the same protein carrier.

Polarized membranes

Caused by an uneven distribution of charged molecules inside and outside the cell, with inside the cell being typically negative and the outside of the cell being typically positive.

electrochemical gradient

A difference in electrical charge inside and outside the cell, causing ions to move from an area to a high charge to a low charge.

Endocytosis

A process in which a cell engulfs extracellular material through an inward folding of its plasma membrane using a vesicle into the cell.

Exocytosis

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

Types of endocytosis(3)

Phagocytosis- large particles

Pinocytosis- extracellular fluid

Receptor-mediated- receptor proteins catch specific target molecules.

Osmosis

The passive movement of water across the cell membrane

Osmolarity

The total solute concentration(Moles)

Tonicity

The measurement of the relative concentrations of solute between inside and outside the cell.

hypertonic solution v.s cell environment

If the cell is in a hypertonic solution, water flows outside the cell into the solution.

hypotonic solution v.s cell environment

If the cell is in a hypotonic solution, water flows inside the cell from the solution

isotonic solution v.s cell environment

If the cell is in an isotonic solution, no water movement will occur.

Osmoregulation

regulation of solute concentrations and water balance by a cell or organism.

Plasmolysis

Contraction of a plant cell due to a loss of water; caused by a plant cell in a hypertonic environment

Flaccid

A limp plant cell with no turgor pressure; caused by a plant cell in an isotonic environment.

Turgid

A firm plant cell with turgor pressure; caused by a plant cell in an hypotonic environment(ideal)

Animal cell in an hypertonic solution

Cell shrivels

Animal cell in an isotonic solution

Normal, has equal solute and water and is the ideal solution animal cells want to be in.

Animal cell in a hypotonic solution

Lysed, more cellular solute and less cellular waste.

How vacuoles osmoregulate

Can take in water via osmosis, OR can pump out water using contractile vacuoles.

Cell compartmentalization

Cell membrane properties

- Fluid mosaic model

- allows cell growth

- selective permeability to small, nonpolar molecules

Aquaporin

A protein that facilitates the diffusion of water across a membrane.

water potential

Measure of potential energy in water that drives the movement of water across a membrane

Water flows to what water potential?

Water will flow to a LOWER WATER potential.

Hypotonic solution with water potential

Has HIGH water potential because MORE free water.

Hypertonic solution with water potential

Has LOW water potential because LESS free water.

Isotonic solution with water potential

Has 0 water potential because equal pressure potential.

Water potential equation + variables

Ψ = Ψs + Ψp

Ψ- Water potential

Ψs- Solute potential

Ψp- Pressure potential

solute potential equation

Ψs = -iCRT

-i- ionization constant(given)

C- Molar concentration(mol)

R- Pressure concentration(.0831 L/bars/mol/K)

T- Temperature in Kelvin(273+ Celsius)

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell. (animal cells)

Electrogenic pump

An active transport protein that generates voltage across a membrane while pumping ions.

Proton pump

An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient.