Honors Biology - Cells

Honors Biology Severn School

Eukaryotic Cell

A cell with a nucleus and membrane-bound organelles (know all). Found in multicellular organisms and unicellular protists. 10-100 micrometers

Prokaryotic Cell

A cell without a nucleus or membrane-bound organelles, typically found in bacteria and archaea. 1-10 micrometers

Prokaryotic Cell Diagram

• Fimbriae → finger-like projections on bacteria that stick onto surfaces

• Ribosomes → in bacteria, same function as in eukaryotes (protein synthesis)

• Nucleoid → region where the circular DNA chromosome is

• Capsule → The sticky outermost layer of a bacterium that has fimbriae on it.

• Flagella → see cilia and flagella → aid in movement

• Cell wall

Light Microscope (Magnification, Resolution, Advantages and Disadvantages)

• beam of light passes through or reflects off the cells and passes through the glass lens

• Magnification → apparent increase in size compared the original size of the object

  • max is 1000x

• Resolution → ability to distinguish between two proximal (nearby) objects

  • max is 0.2 micrometers

• Advantages → can see living cells + objects in appropriate color

• Disadvantages → less magnification and resolution

• cell appears in og color

Electron Microscope

• beam of electrons passes through or reflects off the cells and passes through the electromagnets

• Magnification → can achieve up to 10 million times

• Resolution → provides extremely high detail, resolving power up to 0.1 nanometers

• Advantages → high magnification and detail

• Disadvantages → cannot view living cells and black and white images

• two different types

Scanning vs. Transmission Microscope

• Two types of electron microscopes are used for imaging.

• Scanning microscopes provide 3D images of surfaces and the external structure, while transmission microscopes allow for viewing of internal structure through cell sections (slices of cells).

Cell Theory

all living things are composed of cells, and all cells come from other cells.

Plasma Membrane

• Structure: made of two layers of phopholipids → phospholipid bilayer

• Function: controls the transport of substances into and out of the cell

  • ex. non polar molecules and gases can diffuse pn own, hydrophillic molecules require channel proteins to pass.

Surface Area to Volume Ratio

as cell size increases, surface area-to-volume ratio decreases

organelles

• “little organ”

• “each have a unique funtion

• surronded by membranes

Endomembrane System

• a network of internal membranes in eukaryotic cells that are either directly or indirectly connected in which organelles work together to sythesize, modify, and transport macromolecules (proteins + lipids)

• Materials can easily move between them, allowing for:

  • efficient transport of molecules within the cell → membrane of nuclear envelope continuous with lumen of RER

  • compartmentalization of reactions → protects RXNS specific to each organelle (occur simultaneously)

  • consistent membrane composition and enzyme environments → phospholipid bilayer (organelles, vesicles), environment is ideal for each organelle’s enzymes

Nucleus

• Structure

  • surrounded by a double-layer membrane called the nuclear envelope (each layer is a phospholipid bilayer)

  • holes in the nucleus called nuclear pores → allow material in and out of the nucleus

  • Nucleolus → region of rRNA (ribosomal) and proteins that produce it, its function is to synthesize ribosomes

  • Connected directly to the RER

• Function: to store and protect DNA

DNA/Genes/Chromosomes

• DNA is a nucleic acid = a polymer of nucleotides

• A gene is a specific nucleotide sequence.

• Function: gene is compiled into RNA which then delivers the instructions to a protein.

• Chromosomes (a structure composed of DNA and attached proteins) - long strand of genes

• Eukaryotic cells have one or more linear chromosomes while Prokaryotic cells have only one circular chromosome.

• Condensed Chromosome → DNA is "threaded" around a "spool" of proteins (good for transportation)

• Uncondensed Chromosome (Chromatin) → good for copying (for RNA

• The proteins bound to DNA allow for the Chromosome to change its structure

Features that all Cells Share

• Cell/plasma membrane

• Cytosol - liquid part of cytoplasm (cytosol+organelles)

• DNA → Prokaryotic (1 circular chromosome), Eukaryotic (many linear chromosomes)

  • Ribosome → cell structures that make proteins

Smooth ER (SER)

• Structure

  • interconnected network of tubules

  • smooth in appearance because the SER membrane lacks ribosomes

  • SER is directly connected to the RER (lumens connected)

• Functions

  • detoxification of harmful chemicals (liver)

  • store calcium ion (Ca+2) (required for muscle contractions)

  • In all cells → produce lipids (phospholipids → used for membranes)

Rough ER (RER)

• Structure

  • network of flattened sacs (cisternae)

  • rough in appearance due to the presence of ribosomes on its surface (bound)

  • RER is directly connected to the SER, directly connected to the nuclear envelope, and indirectly connected to the Golgi

• Functions

  • makes proteins destined for secretion (outside of the cell) or insertion into membranes

  • make membranes for vesicles, cell membrane, organelle membranes

  • know the production of proteins (attached)

Production of a Protein in the RER

1. A ribosome (4 degree enzyme) uses mRNA to make a polypeptide (1 degree)

2. Polypeptide, once inside the RER, is folded and attached with sugars, making it a glycoprotein

3. A transport vesicle buds off the RER with the glycoprotein inside

4. A transport vesicle takes a glycoprotein to the Golgi apparatus

Ribosome (NOT AN ORGANELLE)

• Structure

  • rRNA + proteins

  • large and small subunits (burger) → 4^o enzyme

• Functions → differ depending on the location of the ribosome

  • creates polypeptides from amino acids

  • translates mRNA into polypeptide chains

  • Bound ribosomes→ synthesize proteins for secretion or interact with a membrane (cross or embed), ex., in RER

  • free-floating ribosomes → found in cytosol (liquid part of cytoplasm), synthesize proteins with a function in the cytosol

SER and RER connection

SER → makes phospholipids → delivered to RER to make membranes

RER and Nuclear Envelope Connection

• instructions (mRNA) → building ribosomes

  • fast for reading RNA

• RER makes membranes NE needs

• The nucleolus produces ribosomes, which need to be embedded in the RER

Golgi Apparatus

• Structure

  • flattened sacks (made of membrane) in a network (vesicles allow for movement between)

  • sacks not connected, unlike RER

  • Has directionality: Cis face (“Receiving”) (close to RER) and trans face (“Shipping”) (close to plasma membrane; other side)

• Function

  • modifies proteins (by adding parts, removing parts, or changing parts through chemical reactions)

  • Tags proteins for destination

After Golgi (3 Fates)

1. Plasma Membrane - functions as membrane proteins (glycoprotein, channel protein, enzyme)

2. Jobs outside the cell - ex. gastrin

3. Lysosome - recycled/hydrolysis

Lysosome 

• Structure → A ball of membrane that contains hydrolytic (hydrolysis) enzymes

• Function → digests macromolecules and worn-out organelles and helps recycle cellular components.

• Directly connect themselves with a food (storage) vacuole

Contracticle Vacuole

• Organism: unicellular, freshwater eukaryote (protists)

• Structure: a ball of membrane with channels that extend from the center

• Function: to pump out excess water, preventing the cell from bursting

Central Vacuole

• Organism: plants

• Structure: a ball of membrane that contains H2O, ions, enzymes, nutrients (food)

• Function: Store water to maintain the pressure of the cell

Food (Storage) Vacuole

• Organism: plants and animals

• Structure: ball of membrane

• Function: holds food for temporary storage

Peroxisomes

• Structure: ball of membrane that contains enzymes

• Function

  • break down fatty acids → releases energy

  • detoxification of harmful substances (produced by some chem RXNS) into less harmful byproducts like H₂O₂ → (catalase) H₂O + O₂

Mitochondria/Mitochondrion

• Structure

  • outer membrane

  • inner membrane (highly folded, increases SA as enzymes that make ATP line the inner membrane)

  • intermembrane space

  • cristae (folds)

  • matrix (inside fluid)

• Function → perform cellular respiration

  • purpose to convert the chemical energy of glucose to chemical energy of ATP

  • Equation + be able to explain in words: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP; In the presence of oxygen, glucose is broken down into CO2, H2O and ATP

  • Organisms: all eukaryotes (plants, animal, unicellular)

Chloroplast

• Structure

  • Outer membrane

  • Inner membrane

  • Intermembrane space

  • Stroma (fluid)

  • Thylakoids (disks)

  • Granum (stack of disks, increases SA as chlorophyll lines membranes of disks)

  • Chlorophyll (pigment, light absorption

• Function → photosynthesis

  • Convert solar energy into chemical energy of glucose know chemical formula (sunlight + H2O + CO2 = Glucose + O2)

  • Plants must make their own glucose since they don't consume it

  • Organisms: plants, unicellular organisms (algae)

Endosymbiosis

• Reason why mitochondria and chloroplasts aren't apart of endomembrane system

• Eukaryotic cell engulfed prokaryotic cell for symbiotic relationship

• Evidence of endosymbiosis:

  • double layer membrane (outer is plasma membrane added when engulfed)

  • Have own DNA (circular not linear chromosomes) and ribosomes sim to prokaryotic ribosomes

  • Divide by binary fission (bacterial cell division)

Cytoskeleton

• a dynamic network of protein fiber that give a cell its shape, provide internal organization, and enables movement → scaffolding system inside the cytoplasm

• made of 3 types of proteins that each contribute to cell structure and shape, and also have specialized functions, including microtubules, intermediate filaments, and microfilaments

Microtubles

• provide shape and support for the cell

• provide tracks along which organelles and chromosomes move

• main component of cilia and flagella

• constantly break and rebuild (can do this for cell division)

Intermediate filaments

• cell shape

• anchor some organelles

• permanent → don’t break and rebuild

microfilaments

• cell shape

• cell movement (muscle contractions and amoeboid movement)

• attach to the extracellular matrix to keep cells of the same type together in an organ

Cilia and Flagella

• Structure

  • both made of microtubules

  • cilia → short projections, often numerous

  • flagella → long projections, most often singular

• Function

  • cilia → movement of materials or movement of a cell

  • flagella → whips around to move cells

Extracellular matrix (ECM)

• complex network of molecules outside the cell that provide structural and biochemical support to the cells within a tissue → scaffolding that holds cells together and helps them communicate with their environment.

• Structure

  • The main components are glycoproteins and collagen fiber

  • Proteins in the ECM connect to the intergin protein in the cell membrane, which tethers the cytoskeleton (microtubules) to the ECM.

• Function

  • to communicate information from the outside of the cell to the inside

Cell Junctions (Types and Functions)

• Specialized connections where the plasma membranes of neighboring cells (animal) come into close contact

• Function → allow cells to...

  • Adhere to one another for tissue stability

  • Communicate through signals or materials

  • Seal off spaces between cells to control the movement of substances

• Structure

  • Tight junction → Holds cells close together, keeps liquids in

  • Anchoring junction → Flexible connection

  • Gap junction → Channels that allow the movement of materials

Cell Wall

• Structure → Rigid outer layer that surrounds the plasma membrane of plant cells, fungi, bacteria, and some protists

• Made of cellulose

• Function:

  • Provides shape and structural support for plant cells

  • Protects from mechanical stress or bursting when water enters

  • plasmodesmata → pores/passageways that allow for the movement of materials through the cell wall