Prokaryotic Cell Structures

• Eukaryotes and prokaryotes both contain ribosomes but prokaryotes contain smaller ribosomes (70s) than eukaryotes (80s), and they are free in the cytoplasm.
• Bacteria and archaea are examples of prokaryotes.

Cell Wall (Prokaryotic)

• Found outside the cell membrane, protects the cell against toxins, deep pressure, and maintains cell shape.

Plasma Membrane (Prokaryotic)

• Separates the cell's interior from its external environment and controls what enters and exits the cell.

Cytoplasm (Prokaryotic)

• Water-based jelly fluid that fills the cell, suspends DNA and ribosomes, and is the site of metabolic reactions.

Naked DNA (Prokaryotic)

• Stores information necessary for synthesizing proteins.
• DNA in prokaryotes lacks histone proteins.
• Located in a region called the nucleoid.

70S Ribosomes (Prokaryotic)

• Location of protein synthesis.

Plasmid (Prokaryotic)

• Small pieces of DNA that can be transferred between cells (horizontal gene transfer).

Additional Components of Prokaryotic Cells

• Capsule: Protects the organism and allows it to adhere to surfaces.
• Flagella: Responsible for locomotion.
• Pili: Protein filaments that aid in cell adhesion and DNA transfer between cells.

Eukaryotic Cells

• Contain a nucleus.
• Are more complex, and some are multicellular.
• Have membrane-bound cytoplasmic organelles like mitochondria or chloroplasts that can maintain different conditions than the cytoplasm.

Plasma Membrane (Eukaryotic)

• Separates the external environment from the cell's interior and controls the movement of substances in and out.

Cytoplasm (Eukaryotic)

• The site of metabolic reactions, fills the cell, and maintains the structure and organelles inside.

Mitochondria (Eukaryotic)

• Organelles that convert glucose into ATP.

80S Ribosomes (Eukaryotic)

• Location of protein synthesis, larger than prokaryotic ribosomes.

Nucleus (Eukaryotic)

• Contains DNA organized into chromosomes.
• Contains the nucleolus, involved in ribosome production.
• Has a double membrane with pores to regulate molecule entry and exit.

Rough Endoplasmic Reticulum (Eukaryotic)

• Has ribosomes attached to its surface and produces proteins, mainly for use outside the cell.

Smooth Endoplasmic Reticulum (Eukaryotic)

• Produces and stores lipids.

Golgi Apparatus (Eukaryotic)

• Processes, and packages proteins, then releases them in Golgi vesicles.

Vesicle (Eukaryotic)

• Small sac that transports and releases substances.

Vacuole (Eukaryotic)

• Helps maintain cell balance and stores substances.

Cytoskeleton (Eukaryotic)

• Helps hold organelles in place and maintains cell shape and structure.

Processes of Life in Unicellular Organisms

• A single cell is unicellular if it can carry out life processes. These processes consist of eight components.
• Metabolism: Chemical reactions within the cells.
• Response to stimuli: Reacting to external environment changes.
• Homeostasis: Maintenance of constant internal conditions.
• Movement: Controlling place and position.
• Growth: Increasing in size.
• Reproduction: Producing offspring (sexual and asexual).
• Excretion: Removing waste.
• Nutrition: Intake or production of nutrients.
• Paramecia live in aquatic environments and move with cilia.
• Chlamydomonas is autotrophic and produces its nutrition through photosynthesis using chloroplasts.

Animal Cells

• Animal cells have centrioles, cylindrical organelles that establish and organize microtubules, playing a role in cell division.
• Animal cells also have lysosomes, enzyme bags that break down and destroy biological molecules and old cellular organelles.
• Vacuoles are present but smaller than in plant cells, mainly storing water.
• Some animal cells have cilia, used for movement.

Plant Cells

• Have a cellulose cell wall (protects the cell) and chloroplasts, which convert light into energy via photosynthesis.

Fungal Cells

• The fungal cell wall contains polysaccharide.
• Contain large vacuoles, centrioles.
• Reproduce through budding, leaving a budding scar (crater-like ring of tissue) that indicates the number of divisions.

Endosymbiosis

• Eukaryotic organisms evolved when a common ancestor endocytosed a prokaryotic cell capable of generating energy from oxygen.
• Instead of being digested, these cells remained inside the host cell, carrying out aerobic respiration and providing energy, evolving into mitochondria.

Evidence for Endosymbiosis

• Mitochondria and chloroplasts:
• Are the same size as many prokaryotic organisms.
• Have double membranes.
• Contain circular naked DNA.
• Divide by binary fission like prokaryotic cells.
• Are susceptible to some antibiotics.

Organelles and Compartmentalization

• Organelles are structures that perform specific functions in both prokaryotic and eukaryotic cells.
• Compartmentalization refers to organizing different functions and processes within specific areas or structures in cell separated by plasma membranes.
• CMP allows the development of specialized structures, like membrane-bound organelles, so cells can separate chemical reactions and other processes.
• Breakdown of waste requires enzymes, but the enzymes could damage other parts of the cell; CMP stops this from happening.
• Lysosomes are small due to CMP so the concentration of enzymes is high, so they work quickly.

Cellular Components Not Considered Organelles

• Cytoskeleton: Network of proteins that provides shape but isn't membrane-bound or involved in metabolic processes.
• Cell wall: Protects the cell but isn't surrounded by a membrane and isn't involved in metabolic processes.
• Cytoplasm: Surrounds the organelles but doesn't have a real function.
• Lysosomes are organelles because they have are not membrane bound but have a specific function: make proteins.

CMP in Nucleus and Cytoplasm

• Nucleus: Double membrane, bound organelle, CMP of the nucleus & cytoplasm provides advantages.
• Nucleus Contains the cell's DNA, regulates genes via transcribing DNA into mRNA.
• Cytoplasm responsible for metabolic processes and translating mRNA into proteins on the ribosomes.
• After transcription, mRNA is modified by removing pieces allowing different protein production.
• CMP in nucleus & cytoplasm allows changes b4 translation, is impossible in prokaryotic cells because they lack a nucleus.
• CMP of nucleus & cytoplasm allows cytoplasm to send signals to nucleus.

Mitochondrial Membranes

• The main function is to produce ATP through the breakdown of molecules.
• Mitochondria contains two membranes: an inner and an outer membrane.
• The outer membrane is permeable to many small molecules and contains transport proteins that assist in moving larger molecules in mitochondria.
• The inner membrane is folded and forms structures called cristae, that increase surface area.
• The chemical reactions that occur on this membrane are vital for producing ATP in cell respiration.
• Crista allow enzymes to be present by increasing the surface area, which allows faster cell respiration, more enzymes=faster process.
• Cristae create a space between the inner membrane called MATRIX.
• The matrix space contains a lot of enzymes.
• The space between the outer membrane and the inner (inter membrane space), allows high concentration molecules, and creates a concentration gradient across the inner membrane that is used to generate ATP.

Chloroplast Membranes

• The chloroplast contains three distinct membranes: the outer membrane, the inner membrane, and thylakoid membranes.
• Creates three distinct areas: the intermembrane space, the stroma, and the thylakoid space.
• The thylakoid membranes form thylakoids (look like pancakes) and are where the light-dependent reactions of photosynthesis.
• Thylakoids absorb light energy and use it to generate ATP for photosynthesis.
• The disk-like structure of the thylakoid maximizes surface area & increases amount of chlorophyll & other enzymes allows faster rate of photosynthesis.
• The thylakoid space is another example for CMP being used to separate potentially damaging chemicals.
• The inner & thylakoid membranes create a compartment called stroma.
• The stroma contains all enzymes & substrates required for remainder steps.

Nuclear Membranes

• Nucleus contains most cells genetic information and regulates gene expression.
• Nucleus contains two membranes: "the inner" and "the outer".
• The outer has ribosomes attached to it and is continuous, and is joined with rough endoplasmic reticulum.

Functions of the Double Membranes

• Barrier between the genetic material inside & rest of the cell (prevent DNA damaging).
• Regulating gene expression (info in DNA is translated into proteins).
• The inner membrane controls entry & exit of signaling molecules & transcription factors.
• Molecules enter/exit through the inner membrane's nuclear pores are integral proteins that serve channel proteins that also regulate mRNA leaving the nucleus of the RER.
• CMP of molecules & regulation of entry & exit molecules is important in gene expression.
• During cell division the nuclear envelope breaks down to allow separating chromosomes.
• When division is complete the membranes must reassemble to form new nucleus.
• The process begins by forming small vesicles that contain proteins & lipids which are specific to the nuclear membrane then initially bind to the chromosome.
• These vesicles join the chromosomes then finally fuse together to form the double membrane.

Membranes and Protein Packaging

• Ribosomes (bound or free): Ribosomes translate the mRNA from the nucleus into proteins.
• Bound ribosomes the ribosome is bound to the cytosolic side of the RER & the proteins produced make it in the cell easier.
• Proteins produced by bound ribosomes will be later exported outside the cell.
• Pancreatic cells export many different types of digestive enzymes which means they will have of RER.
• Free ribosomes produce the proteins that will remain inside of the cytoplasm, and are instead used by the cell.

Processing and Transport of Proteins

• The RER is a system of interconnected membranes (flattened sacs & tubes) & is involved in protein synthesis.
• After proteins are synthesized on the ribosome they are quickly transported into lumen of RER for further processing & modification.
• RER has several enzymes that modify protein synthesis by adding carbohydrates.
• After proteins are modified they are transported by vesicles to the Golgi apparatus for further processing.
• This transport is done through a process like endocytosis.
• A fragment of the RER membrane breaks off to form vesicles that travels to the Golgi apparatus.

The Golgi Apparatus

• The Golgi apparatus is a flattened stack of sacs made of membrane which are organized into Cis, medial, and trans compartments.
• The cis receives new proteins from the RER, & vesicles fuse w/ the sis compartment and releases proteins to the Golgi apparatus.
• The Golgi apparatus sorts proteins by their specific destination.
• Proteins needed inside transported to the medial compartment for final processes.
• Proteins needed outside cell are transported to the trans compartment and packed into vesicles.

Vesicles and the Role of Clathrinid

• Vesicles are small membrane-bound structures play a key role in cellular processes of transport & storage; act as delivery trucks or store compartments.
• Vesicle examples:
  • Transport vesicles; Secretory vesicles; Lysosomes contain enzymes (used to break down macromolecules); Peroxisomes are involved in lipid metabolism.
• Clathrin is a protein that joins important role in forming vesicles by joining cytoskeleton & other proteins for the budding/scission from the plasma membrane & from the membranes of intracellular structures.
• Clathrin's cellular processes include: endocytosis, phagocytosis, transport from the Golgi apparatus to the plasma membrane, and formation of lysosomes
• Clathrin forms the structures of clathrin protein around a membrane (vesicle).

Stem Cells

• Stem cells are formed to start creating a whole organism.
• When a diploid single cell a zygote starts dividing to create a morula made of 16-32 cells.
• Cells continue to divide and after 6 days the morula begins to differentiate into blastocyst(ball of cells) a trophoblast which is the outer layer of cells and an inner cell mass.
• The trophoblast can develop into the placenta and the inner cell mass will become the embryo.

Morphogen Gradients

• Multicellular organisms have different cells.
• All cells will contain EXACTLY the same DNA sequence.
• Cells will NOT express the same genes because of the way a cell is made is changed.
• Unspecialized cells can be be changed so they can develop.
• In the embryo mass are made of are the same.
• In the form giving parts (cell) molecules are called morphogens are secreted which helps change shape.
• The diffuses determines the fate of the cells.

Stem Cell Potency

• All stem cells don't differentiate new types of cells, and have the same ability to do this.
  • Totipotent stem cells can differentiate any type of cell including placental cells; and give rise to a complete organism.
  • Pluripotent stem cells can differentiate all body cells to give rise to a whole organism
  • Multipotent stem cells can produce all types of blood cells (umbilical cord/bone marrow, and they cure of illnesses like leukemia) and can separate what kind of body cell they will be.
  • Unipotent stem cells can only differentiate between a certain cell type.

Stem Cell Niche

• Is microenvironment to have stem cells that can give their different directions.
• This environment have stems cells that makes the cells separate.
• Stem cells in humans studies are those of skin, brain, bones, and muscle cells.
• Blood stem cells are found in bones (spongy of the bone) which have combination that makes blood cells.
• The hair is an area called the bulge where follicle stem cells produce proliferation of the hair.

What Determines Cell Size?

• Variations determine the variation of human cells.
• The differences is shown that an egg is the biggest cells (example), sperm is the smallest.
• This shows the cells link in the function directly.
• The human cell can become bigger to nutrients will be bigger, but sperm does not need the content is very small.
• More human cells is spherical shapes, but not all.
• Some never cells is long like neurons have axons that can 1m long.
• Small red cells in human body don't have a nucleus, which packs in more hemoglobin.
• They also use a flexible cell to push air through them, and move the circulatory system.
• The white cells are bigger then the red cells.
• Nucleus have separate shapes, and move around inside an amoeba.

Keeping Cells Alive

• Before cells divide, they is more room for organelles.
• And need much growth to increase in room.