BIOL 130 Chapter 5 - CELL

Cell theory

The cell is the basic unit of life.
All living things are made up of cells. New cells arise from pre existing cells.

About how most cells are small

Small cells have a larger amount of surface area compared to the volume. An increase in surface area allows for more nutrients to pass into the cell and wastes to exit the cell more efficiently. There is a limit to how large a cell can be and be an efficient and metabolically active cell.

Diffusion times v volume in a cell

Time it takes the “average” molecule to diffuse a given distance.

Compound light microscope

• lower magnification

• uses light beams to view images

• can view live specimens

Transmission electron microscope, TEM

• 2-D image

• uses electrons to view internal structure

• high magnification, no live specimens

Scanning electron microscope, SEM

• 3-D image

• Uses electrons to view surface structures

• High magnification, no live specimens

Prokaryotic cells

• Thought to be the first cells to evolve

• Lack a nucleus

• Represented by bacteria and archaea

Eukaryotic cells

• Have a nucleus that houses DNA

• Many membrane-bound organelles

• Represented by most organisms larger than bacteria

What are the similarities between prokaryotic and eukaryotic cells?

Similarities:

• A plasma membrane that surrounds and delineates the cell (phospholipid bilayer)

• Cytoplasm: the semi fluid substance inside the cell that contains organelles

• DNA

Where did eukaryotic cells come from?

1. Cel gains a nucleus by the plasma membrane invaginating and surrounding the DNA with a double membrane. Nucleus allows specific functions to be assigned, freeing up cellular resources for other work.

2. Cell gains an endomembrane system by proliferation of membrane,

3. Cell gains mitochondria. Ability to metabolize sugars in the presence of oxygen enables greater function and success.

4. Cell gains chloroplasts. Ability to produce sugars from sunlight enables greater function and success.

Characteristics of the plasma membrane

• it is a phospholipid bilayer

• it is embedded with proteins that move in space

• it contains cholesterol for support

• it contains carbohydrates on proteins and lipids

• it is selectively permeable

Cytoskeleton

A series of proteins that maintain cell shapes as well as anchors and/or moves organelles in the cell.

Made of 3 types of fibers: large microtubules, thin actin filaments, and medium sized intermediate filaments.

Cell organelles

• Nucleus

• Mitochondria

• Endoplasmic reticulum (ER)

  • Rough ER - smooth ER

• Golgi apparatus

• Vesicles and vacuoles

• Centrioles

• Ribosomes

Nucleus

• largest organelle in the eukaryotic cell

• the cell’s control center

• contains most of the cell’s DNA as chromatin and chromosomes

• regulates gene expression - controlling which proteins the cell makes

• most eukaryotic cells contain just a single nucleus (some types of cells, such as red bod celll, contain no nucleus)

• a few other types of cells such as muscle cells contain multiple nuclei

Mitochondria

• organelle that makes energy

• sometimes referred to as the power plants of the cell

• use energy from organic compounds such as glucose to make molecules of ATP (adenosine triphosphate), an energy carrying molecule that is used almost universally inside cells for energy

• were likely once free living organisms because they contain their own DNA. were taken into other cells to form a symbiotic relationship

Endoplasmic reticulum (ER) rough - smooth

• network of phospholipid membranes that form hollow tubes, flattened sheets, and round sacs

• flattened hollow folds and sacs are called cisternae

• two major functions: transport and synthesis

transport (ER)

• molecules such as proteins can move from place to place inside the ER much like on an intracellular highway

synthesis (ER)

• ribosomes that are attached to the ER, similar to unattached ribosomes, make proteins. Lipids are also produced in the ER.

Golgi apparatus

• large organelle that processes proteins and prepares them for use both inside and outside the cell

• modifies, sorts, and packages different substances for secretion out of the cell, or for use within the cell

Vesicles and vacuoles

both vesicles and vacuoles are sac like organelle that store and transport materials in the cell. vesicles are much smaller than vacuoles.

Endomembrane system

• a series of membranes in which molecules are transported in the cell

• consists of the nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles, and vesicles.

• Endoplasmic reticulum, nucleus, and golgi apparatus work together:

  • nucleus produces RNA, moves it to the ER where proteins are made then moves the protein to the golgi where it is modified and used or released.

Parts of the endomembrane system

• rough endoplasmic reticulum - studded with ribosomes used to make proteins

• smooth endoplasmic reticulum - lacks ribosomes but aids in making carbohydrates and lipids

• golgi apparatus - flattened stacks that process package and deliver proteins and lipids from the ER

• lysosomes - membranous vesicles made by the golgi that contain digestive enzymes

• vesicles - small membranous sacs used for transport

centrioles

organelles involved in cell division. help organize the chromosomes before cell division occurs so that each daughter cell has the correct number of chromosomes after the cell divides.

ribosomes

small structures which build proteins from subunit AA’s. Red dots above left, dark dots above right

Why is a cell “selectively permeable”

the membrane allows some things in while keeping other substances out

cell membrane transport

five ways things move across the plasma membrane

1. diffusion

2. osmosis

3. facilitated diffusion

4. active transport

5. endocytosis and exocytosis

1. diffusion

random movement of molecules from a higher concentration to a lower solute concentration. in image, molecules move across the membrane until equilibrium is reached

2. osmosis

diffusion of water molecules from an area of higher water concentration to lower across a membrane

isotonic solutions (osmosis and tonicity)

• these solutions have equal amounts of solute inside and outside the cell thus do not affect the cell

hypotonic solutions (osmosis and tonicity)

• these types of solutions have less solute than the inside of the cell and lead to swelling and possible lysis (bursting)

hypertonic solutions (osmosis and tonicity)

• these types of solutions have more solute than the inside of the cell and lead to crenation (shriveling)

isotonic, hypotonic, and hypertonic solutions in human body

• all three conditions happen to a human body throughout itself

• isotonic conditions: most of the time, water intake matches water loss through sweat and urination

• hypertonic: go for a long run on a hot day and get dehydrated, water will leave cells to enter the blood

• hypotonic: less common, drink too much water quickly, water will leave the blood and enter cells until the kidneys can catch up

3. facilitated diffusion

• movement of molecules from a higher to a lower concentration using a protein channel or carrier but using no energy

4. active transport

• movement of molecules from a lower to a higher concentration using ATP as energy; it requires a protein carrier

5. endocytosis

transports molecules or cells into the cell via invagination of the plasma membrane to form a vesicle.

6. exocytosis

transports molecules outside the cell via the fusion of a vesicle with the plasma membrane

cellular respiration

• production of adenosine triphosphate (ATP)

includes:

1. glycolysis

2. citric acid cycle (krebs cycle)

3. electron transport chain

1. glycolysis

• occurs in the cytoplasm

• breaks one 6 c glucose into two 3 C pyruvate molecules

• NADH and 2 ATP molecules are made

• does not require oxygen

2. citric acid cycle (krebs cycle)

• a cyclical pathway that occurs in the mitochondria matrix

• produces NADH and 2 ATP

• releases carbon dioxide, CO2

3. Electron transport chain to do oxidative phosphorylation

• series of molecules embedded in the inner mitochondrial membrane

• NADH and FADH2 made in steps 1 and 2 carry electrons here

• 32-34 ATP are made depending on the cell

• requires oxygen as the final electron acceptor in the chain

ETC

• NADH and FADH₂ release high-energy electrons into the electron transport chain (ETC) in the inner mitochondrial membrane.

  • As electrons move through the ETC, their energy is used to pump H⁺ (hydrogen ions) from the matrix → intermembrane space.

  • This creates a H⁺ concentration gradient across the inner membrane.

  • At the end of the ETC, oxygen (O₂) accepts the electrons and is reduced to water (H₂O) in the mitochondrial matrix.

  Key flow:
  NADH/FADH₂ → electrons → ETC → H⁺ pumped to intermembrane space → O₂ accepts electrons → H₂O

ATP synthase

• Pumping H⁺ (hydrogen ion) into the intermembrane space creates an electrochemical (H⁺) gradient.

• H⁺ flows back into the matrix through ATP synthase — this is chemiosmosis.

• ATP synthase acts as a channel and uses the energy from H⁺ flow to make ATP from ADP + inorganic phosphate (Pi).

Key flow:
H⁺ gradient → H⁺ through ATP synthase → chemiosmosis → ATP production

other molecules in cellular respiration

• other carbohydrates - fructose, galactose

• proteins - remove n portion - enter in various parts of the citric acid cycle

• lipids- FA’s broken down into ketones - enter as acetyl-coA

how can cells make ATP without oxygen?

fermentation

• occurs in the cytoplasm

• does not require oxygen

• involves glycolysis only - no mitochondria

• makes 2 ATP and 2 pyruvates which convert into lactates in human cells (lactic acid)

• faster but less ATP

• can give humans a bust of energy for a short time - think sprinters, and lactic acid buildup

how much is ATP produced in all three stages combined?

glycolysis produces 2 atp molecules

krebs cycle produces 2 more

electron transport from the molecules of NADH and FADH made from glycolsis, the tranformation of pyruvate, and the krebs cycle creates as many as 32 more ATP molecules

therefore a total of up to 36 molecules of ATP can be made from just one molecule of glucose in the process of cellular respiration