AP Biology -

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

1. What is a “cell”?

• Smallest unit of structure AND function in all living things (each cell performs all the life processes (metabolism) to maintain homeostasis)

• Enclosed by membranes that maintains an internal environment separate from external environment

  • All membranes are made of phospholipids

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

2. Prokaryotic cells and Eukaryotic cells are the two major cell types: What do they have in common?

• Ribosomes (protein synthesis) → Archaea/Eukarya have larger ribosomes; Bacteria have smaller ribosomes

• Cytoplasm (most metabolism occurs here)

  • (aka cytosol)

• DNA (the genetic code; hereditary material) → Archaea/Bacteria have a single, circular piece of DNA; Eukarya have linear chromosomes

• Cell membrane (phospholipid bilayer barrier)

  • (plasma membrane)

• ALL CELLS have the same basic building blocks/macromolecules (carbs, lipids, amino acids, nucleic acids)

• Energy Molecule for all cells --> ATP

• All cells require & transform energy

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

2. Prokaryotic cells and Eukaryotic cells are the two major cell types: How are they different?

• Prokaryotes → 0.1-10 μm (very small), some have flagella (bacterial), *NO NUCLEUS or MEMBRANE BOUND ORGANELLES

•  Eukaryotes → 10-100 μm (larger, *HAVE NUCLEUS & MANY MBO [compartmentalization, mbos allowed eukaryotes to become larger ]

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

3. Explain how each are able to maintain high levels of energy efficiency.

• Both prokaryotes and eukaryotes are highly efficient:

  • Prokaryotes:

    • Due to size:

      • VERY HIGH Surface Area to Volume Ratio! (very fast metabolism/reproduction)

      • (They are 10-100 times smaller than eukaryotes!)

  • Eukaryotes:

    • Maintains efficiency by the use of membrane bound organelles (compartmentalization → mbos separated parts and said all the enzymes for cellular respiration are going to be here, and all the enzymes for digestion in lysosomes are going to be here, etc. )

    • *Ability to divide into 2 cells when it gets too large

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

3. Explain how each are able to maintain high levels of energy efficiency.

   1. More contact w/ the environment…

• higher SA : lower volume

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

4. Advantages to compartmentalization (membrane bound organelles)

• All materials/enzymes are together and "ready to use"; specialization and efficiency of each organelle!

• Allows for specialization of cells and more complex organisms without sacrificing efficiency

  • (Lots Mitochondria → muscle cells)

  • (Lots Golgi Bodies → endocrine cells, cells that secrete)

• Different reactions can occur simultaneously without disruption from other reactions

• Protects the cytoplasmic proteins and (DNA in the nucleus) to be protected and not degraded by enzymes (from peroxisomes and lysosomes)

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

4. Advantages to compartmentalization (membrane bound organelles)

   1. What are PEROXISOMES?

•  in ALL EUKARYOTES

• breaks down fats

• breaks down toxic H₂O₂ (hydrogen peroxide)

• contains an enzyme called catalase

• also helps in detoxification of drugs/alcohol (liver has a ton of peroxisomes)

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

4. Advantages to compartmentalization (membrane bound organelles)

   1. What are PEROXISOMES?

      1. What is HYDROGEN PEROXIDE?

•  a natural metabolite/waste product that accumulates in all cells

(Intro to UNIT 2: CELL STRUCTURE & FUNCTION (NOTES)) Let’s hear it for Cells! (A review of their form and function… another example of evolutionary design at its best!)

4. Advantages to compartmentalization (membrane bound organelles)

   1. What are LYSOSOMES?

• found mainly in animal cells

• contain enzymes that hydrolyze carbs, lipids, proteins, nucleic acids

• Hydrolytic Enzymes → Lysosome

(Organelle Worksheet) The Parts of a Cell: DEFINE “ORGANELLE.”

• small, specialized structures in cells that carry out specific tasks

(Organelle Worksheet) The Parts of a Cell: CELL MEMBRANE

• Found in prokaryotes and eukaryotes

• Found in animal and plant cells

• FUNCTION: controls the movement into and out of the cell; made of phospholipid

(Organelle Worksheet) The Parts of a Cell: CYTOPLASM

• Found in prokaryotes and eukaryotes

• Found in animal and plant cells

• FUNCTION: watery material/gel which contains many of the materials (nutrients & ions) involved in cell metabolism (AKA cytosol)

(Organelle Worksheet) The Parts of a Cell: ENDOPLASMIC RETICULUM

• Found in eukaryotes

• Found in animal and plant cells

• FUNCTION: a series of membrane “tubes” that allows materials to travel

  • One type with ribosomes (synthesizes proteins to be shipped out of the cell)

  • One type without ribosomes (synthesizes lipids)

(Organelle Worksheet) The Parts of a Cell: RIBOSOMES

• Found in prokaryotes and eukaryotes

• Found in animal and plant cells

• FUNCTION: smallest organelles (no membranes) which are the site of protein synthesis

(Organelle Worksheet) The Parts of a Cell: NUCLEUS

• Found in eukaryotes

• Found in animal and plant cells

• FUNCTION: serves as the “control center” for cell metabolism and reproduction; contains the genetic material (DNA)

(Organelle Worksheet) The Parts of a Cell: LYSOSOME

• Found in eukaryotes

• Found in animal cells

• FUNCTION: a membrane enclosed organelle that contains hydrolytic enzymes (digestive enzymes) that break down food, waste, and old cell parts that can be recycled to build new cell parts

(Organelle Worksheet) The Parts of a Cell: GOLGI BODIES

• Found in eukaryotes

• Found in animal and plant cells

• FUNCTION: packages, sorts, and secretes (“ships out”) the products of the cells

(Organelle Worksheet) The Parts of a Cell: MITOCHONDRIA

• Found in eukaryotes

• Found in animal and plant cells

• FUNCTION: performs respiration, releasing the energy (ATP) from food molecules

(Organelle Worksheet) The Parts of a Cell: VACUOLE

• Found in prokaryotes and eukaryotes

• Found in animal and plant cells

• FUNCTION: membrane enclosed organelle containing stored food, water, wastes; animals have many, small one, plants have one or two large, central ones

(Organelle Worksheet) The Parts of a Cell: NUCLEOLUS

• Found in eukaryotes

• Found in animal and plant cells

• FUNCTION: site of the production of ribosomes; found inside the nucleus

(Organelle Worksheet) The Parts of a Cell: CELL WALL

• Found in prokaryotes and eukaryotes

• Found in plant cells

• FUNCTION: gives cells its shape/structure and provides protection (outside the cell membrane); in plants it contains is made of cellulose

(Organelle Worksheet) The Parts of a Cell: DNA

• Found in prokaryotes and eukaryotes

• Found in animal and plant cells

• FUNCTION: the genetic material; in eukaryotes it’s linear, in prokaryotes it’s circular

(Organelle Worksheet) The Parts of a Cell: CHLOROPLAST

• Found in eukaryotes

• Found in plant cells

• FUNCTION: site of photosynthesis, produces sugars for plant cells

(Organelle Worksheet) The Parts of a Cell: NUCLEAR MEMBRANE

• Found in eukaryotes

• Found in animal and plant cells

• FUNCTION: controls movement into and out of the nucleus; contains “pores”

(Organelle Worksheet) The Parts of a Cell: CENTROSOME

• Found in eukaryotes

• Found in animal cells

• FUNCTION: small structures that aid in cell division by making microtubules (spindle fibers) that attach to chromosomes

(Organelle Worksheet) The Parts of a Cell: CYTOSKELETON

• Found in prokaryotes and eukaryotes

• Found in animal and plant cells

• FUNCTION: three proteins (microtubules, microfilaments, and intermediate fibers) that are found in the cytoplasm that help give structure to the cell and aid in cell movement

(Modern Cell Theory & Endosymbiotic Theory) Whether an organism is unicellular, or multicellular, every individual cell must be able to carry out all the life processes. Need a refresher? List the LIFE PROCESSES in this box.

1. Growth

2. Excretion

3. Nutrition

4. Transport

5. Synthesis

6. Regulation

7. Reproduction

8. Respiration

(Modern Cell Theory & Endosymbiotic Theory) To do this, each cell has ORGANELLES, which are…

• structures within cells that have specialized functions

(Modern Cell Theory & Endosymbiotic Theory) Recall the levels of organization in living things.

organelles → cells → tissue → organs → organ system → complex organism

(Modern Cell Theory & Endosymbiotic Theory) As cells become tissues, they become…

• specialized/differentiated = STEM CELLS

  • TOTIPOTENT → full potential to become any cell type

(Modern Cell Theory & Endosymbiotic Theory) What is SPONTANEOUS GENERATION?

• “Spontaneous generation” is the outdate theory that life can arise from non-living matter, which has been disproven by many scientific experiments.

• Believes living organisms can develop from non-living things like decaying matter.

• Examples:

  • Maggots appearing on rotting meat were once thought to arise spontaneously.

  • The “Van Helmont Experiment” (17th century) involved placing a dirty shirt in a container with wheat grains, believing that after a period of time (around 21 days), the combination of sweat from the shirt and the wheat would spontaneously generate mice.

(Modern Cell Theory & Endosymbiotic Theory) Francesco Redi’s Experiment to Disprove Spontaneous Generation (1668)

(Modern Cell Theory & Endosymbiotic Theory) Louis Pasteur’s Experiment to Disprove Spontaneous Generation

(Modern Cell Theory & Endosymbiotic Theory) What is BIOGENESIS?

• Biogenesis is the accepted scientific theory that all life comes from pre-existing life.

(Modern Cell Theory & Endosymbiotic Theory) The Modern Concept of Cell Theory (The original Cell Theory included the 3 highlighted in yellow.)

• Cellular basis of life: All living things are made up of one or more cells.

• Cell as the basic unit: The cell is the fundamental unit of structure and function in all living organisms.

• Cell division: New cells arise only from pre-existing cells through division.

• Genetic material: Cells contain DNA, which carries the genetic information passed on to new cells during division.

• Energy flow within cells: All metabolic activity and energy flow occurs within cells.

• Chemical similarity: Cells from similar organisms have a similar chemical composition (Carbs, Lipids, Proteins, Nucleic Acids!)

(Modern Cell Theory & Endosymbiotic Theory) What is the ENDOSYMBIOTIC THEORY?

• The Endosymbiotic Theory explains how eukaryotic cells evolved from prokaryotic cells through a symbiotic relationship.

(Modern Cell Theory & Endosymbiotic Theory) Here’s a step-by-step summary of the ENDOSYMBIOTIC THEORY.

1. Starting with a Prokaryotic Cell - A primitive ancestral prokaryotic cell existed, likely resembling a modern archaea or bacteria.

2. Infolding of Membranes - The cell’s plasma membrane folded inward over time, forming internal compartments like the nuclear envelope and endoplasmic reticulum, which led to early eukaryotic features.

3. Engulfing of Aerobic Bacteria - The early eukaryote engulfed an aerobic (oxygen-using) prokaryotic bacterium. Instead of digesting it, the bacterium survived inside the host cell and provided energy. This led to the formation of mitochondria, making the host cell more efficient at energy production.

   1. (larger cell recognized smaller cell provided energy while big cell protects small cell → mitochondria (engulfed 1st because not all eukaryotes have chloroplast but all have mitochondria)

4. Engulfing of Photosynthetic Bacteria (in Plants & Algae) - Some of these early eukaryotic cells also engulfed photosynthetic cyanobacteria, which eventually became chloroplasts. This allowed cells to harness sunlight for energy, giving rise to plant and algal cells.

   1. (big cell engulfs small cell that makes food for it → chloroplast)

5. Symbiotic Relationship Forms - Over time, these engulfed bacteria became permanent organelles, no longer able to survive independently. They transferred some of their DNA to the host nucleus and became dependent on the host cell for survival.

6. Evolution into Complex Eukaryotes - With mitochondria (in all eukaryotes) and chloroplasts (in photosynthetic eukaryotes), cells became more complex, leading to the diversity of eukaryotic life seen today.

(Modern Cell Theory & Endosymbiotic Theory) Label the steps of the ENDOSYMBIOTIC THEORY.

(Modern Cell Theory & Endosymbiotic Theory) Did MITOCHONDRIA or CHLOROPLASTS engulf first?

(Modern Cell Theory & Endosymbiotic Theory) EVIDENCE OF ENDOSYMBIOTIC THEORY?

• Mitochondria and chloroplasts are membrane-bound organelles that show strong evidence of prokaryotic origins.

• They:

  • are similar in size and shape to prokaryotic cells,

  • contain their own circular DNA and ribosomes (just like prokaryotes),

  • have a double membrane, suggesting they were once engulfed by another cell, and

  • divide independently of the rest of the cell.

(Modern Cell Theory & Endosymbiotic Theory) ENERGY TRANSFORMING ORGANELLES: The oxygen utilizing “bacteria” became…

• MITOCHONDRIA

  • performs CELLULAR RESPIRATION (releases energy from food)

    • All Eukaryotic cells have mitochondria: chemical energy → ATP (chemical energy)

(Modern Cell Theory & Endosymbiotic Theory) ENERGY TRANSFORMING ORGANELLES: Some of the prokaryotic cells engulfed were blue-green algal cells - which became…

• CHLOROPLASTS

  • performs PHOTOSYNTHESIS

    • All Eukaryotic PHOTOAUTOTROPHS (protists, plants) have CHLOROPLASTS

      • SUNLIGHT ENERGY → GLUCOSE (chemical energy)

        • *inoragnic carbon → organic forms

(Types of Cells) PLANT CELL VS ANIMAL CELL

• Explain the properties of PLANT CELLS.

• Cell wall (rigid shape)

• Large central vacuole

• Chloroplasts (autotroph)

• Lack centrosomes

• Some lysosomes

(Types of Cells) PLANT CELL VS ANIMAL CELL

• Explain the properties of ANIMAL CELLS.

• No cell wall (irregular shape)

• Numerous small vacuoles

• No chloroplasts (heterotroph)

• Centrioles / centrosomes

• Lysosomes → contain hydrolytic enzymes that break down stuff [heterotrophic]

(Types of Cells) Plant Structures & Organelles

• Cell Wall (Cellulose)

• PLASTIDS

  • chloroplast --> photosynthetic (makes glucose) pigments (chlorophyll)

  • leucoplast (amyloplast) - stores starch (amylose)

  • chromoplast ("chromo" --> color) - stores pigments for fruits and flowers (not photosynthetic)

(Types of Cells) The Different Types of Human Cells

• On average, there are over 30 trillion cells in a single person! It is estimated that there are >200 types of cells with different morphologies and functions.

• ___ _____ ____ is the most abundant cell type in the human body, accounting for >80% of all cells.

• The average lifespan of each type of cell varies greatly. For example:

  • White blood cells live for ~13 days

  • Red blood cells live for ~120 days

  • Neurons can live as long as the human

1. Red blood cell

(Types of Cells) Some types of cells, including some epithelial cells, have characteristics on the surface of the cell that help them perform certain functions, including:

• Microvilli

• Microvilli are non-motile (they don’t move) finger-like structures on the surface of epithelial cells that function to increase the cell’s surface area so that it can better absorb substances and have more contact w/ the environment. The epithelial cells that line your small intestine have thousands of microvilli that absorb nutrients from the food you eat and protect your body from intestinal bacteria.

• Microfilaments are proteins that don’t move but push the microvilli up.

  • Ex> small intestinal cells, reproductive tract

(Types of Cells) Some types of cells, including some epithelial cells, have characteristics on the surface of the cell that help them perform certain functions, including:

• Cilia

• Cilia are tiny, hair-like, motile (they can move) structures on the surface of the cell that help move entire cells or can move substances along the outer surface of the cell. Ciliated cells usually have hundreds of cilia on their surfaces. Epithelial cells lining your respiratory tract have cilia that trap dust and other substances you breathe in and move them toward your nostrils so that they don’t go into your lungs. Another example of cells with cilia are the epithelial cells that line the fallopian tubes that help move an egg from an ovary to the uterus.

  • wave around (“sweeping motion”), use a lot of energy (require a lot of ATP → lot of mitochondria present)

  • contain microtubules

(Types of Cells) Some types of cells, including some epithelial cells, have characteristics on the surface of the cell that help them perform certain functions, including:

• Stereocilia

• Stereocilia are specialized microvilli that resemble cilia and project from the surface of certain epithelial cells. Stereocilia are needed on the epithelial tissue in your inner ear for hearing and balance.

(Types of Cells) Explain the DIFFERENTIATION PROCESS.

(Types of Cells) NOT ALL CELLS WILL HAVE ALL CELL PARTS!

• Because certain cells are highly specialized, they lose the ability to perform certain functions

(Types of Cells) NOT ALL CELLS WILL HAVE ALL CELL PARTS!

• Red Blood Cells

• For example, red blood cells lose their nuclei and other cell parts during the specialization process to accommodate more hemoglobin to carry more oxygen!

  • (NO DNA)

(Types of Cells) NOT ALL CELLS WILL HAVE ALL CELL PARTS!

• Epidermal

• Other supportive cells, like epidermal, both in plants are not alive a serve a protective role.

(Types of Cells) NOT ALL CELLS WILL HAVE ALL CELL PARTS!

• Xylem and Phloem Cells

• In plants, xylem and phloem cells are support cells that allow materials to pass through them (capillary action for H₂O delivery)!

• Xylem is composed primarily of dead cells, but phloem cells are alive and transport sap.

(Types of Cells) Non-living cells can still have functions…

• last unused parts during specialization

• support!

• protection!

• transport!

(Cell Size (Maintaining Cellular Efficiency)) WHY CELLS ARE SMALL

• We use a _______ ____ (plasma membrane (contact w/ environment)) to ______ (cytoplasm) ratio as a measure of ______ _________ and ____ _________.

1. SURFACE AREA

2. VOLUME

3. ENERGY EFFICIENCY

4. CELL EFFICIENCY

(Cell Size (Maintaining Cellular Efficiency)) WHY CELLS ARE SMALL

• Specific cellular structures are used to maximize the exchange of materials with the environment. → these structures ________ _______ ____ _______ __________ ______!

1. INCREASE SURFACE AREA WITHOUT INCREASING VOLUME

   1. High SA : V = more efficient cells

(Cell Size (Maintaining Cellular Efficiency)) Some examples of these structures are: Root Hairs

• Root hairs are thin extensions of the root that increase the surface area for water/mineral absorption.

(Cell Size (Maintaining Cellular Efficiency)) Some examples of these structures are: Alveoli

• Alveoli are thin, small sacs in the lungs to increase surface area to maximize gas exchange.

  • O₂ into blood cells + O₂ out

(Cell Size (Maintaining Cellular Efficiency)) Some examples of these structures are: Villi and Microvilli

• Villi and microvilli (these are filled with microfilaments) are finger like projections of the small intestine to increase surface area to increase absorption of nutrients into the bloodstream.

(Cell Size (Maintaining Cellular Efficiency)) Are CENTRAL VACUOLES a part of the VOLUME MEASUREMENT?

(Cell Size (Maintaining Cellular Efficiency)) Surface area can even be increased inside organelles to increase organelle function efficiently!

• Cristae

• Cristae is the folded inner membrane of the mitochondria to increase surface area for maximum reactions to generate ATP through respiration.

(Cell Size (Maintaining Cellular Efficiency)) Surface area can even be increased inside organelles to increase organelle function efficiently!

• Thylakoids

• Thylakoids are the folded inner membranes of the chloroplast that increase surface area for maximum reactions to capture sunlight and create energy molecules for photosynthesis.

(Cell Size (Maintaining Cellular Efficiency)) Which increases faster as cells grow: Surface area or volume?

• Volume → it’s cubed!

(Cell Size (Maintaining Cellular Efficiency)) Which increases faster as cells grow: Surface area or volume?

• SA and Volume Formulas

(Cell Size (Maintaining Cellular Efficiency)) Determine the SA:V RATIO for a 1 μm cube.

(Cell Size (Maintaining Cellular Efficiency)) Determine the SA:V RATIO for a 2 μm cube.

(Cell Size (Maintaining Cellular Efficiency)) HOW SURFACE AREA TO VOLUME RATIO LIMITS CELL SIZE

• (AKA WHO DO CELLS HAVE TO STAY SMALL?)

  • All raw materials necessary for metabolism can enter the cell only through the membrane.

  • The number of reactions required to maintain cell efficiency increases as the volume within a cell increases.

  • As a cell grows, the SA:V ratio decreases (because volume (cubed) increases faster than surface area (squared))

  • At some point, the SA:V ratio becomes so small that the SA is too small (not enough contact with the environment) to supply the raw materials required to maintain the cell's metabolic needs.

(Cell Size (Maintaining Cellular Efficiency)) HOW SURFACE AREA TO VOLUME RATIO LIMITS CELL SIZE

• Cells at this point can…

(1) Undergo APOPTOSIS (cell death)

(2) Make more organelles

(3) Divide into 2 smaller cells

(Cell Size Practice) What is DIFFUSION RATE?

• Diffusion Rate = movement into cell (distance) / time

(Cell Size Practice) Does DIFFUSION RATE change with CELL SIZE?

• rate won’t change! the time it takes changes…

• Diffusion rate will be the same in all the cells, but the smallest cube will take the least amount of TOTAL TIME.