DAT Cells and Organelles

7 components of Cell Theory

1. All organisms are composed of 1 or more cells.

2. The cell is the basic unit of structure and organization in organisms.

3. All cells come from pre-existing cells.

4. The activity of an organism depends on the combined activity of independent cells.

5. Cells have functional metabolisms (energy flow occurs within cells).

6. Cells contain hereditary genetic information, which is passed on when a cell divides or an organism has offspring.

7. All cells of similar species have the same basic chemical composition.

3 Things all cells contain

1. Plasma membrane: selective barrier that separates and protects cell contents from the outer environment.

2. DNA: the source of genetic information.

3. Ribosomes: synthesize functional proteins from DNA.

Permeability of small, uncharged, polar molecules

• Can cross membrane on its own

• Ex: H2O, Glycerol, Urea, Ethanol

Permeability of small, nonpolar (hydrophobic) molecules

• Can cross membrane on its own

• Ex: Steroids, CO2, O2, N2

Permeability of large, uncharged, polar molecules

• Unable to cross on its own

• Ex: Glucose, sucrose

Permeability of Ions

• Unable to cross on its own

• Ex: Na+, H+, Ca2+

What are the 3 types of membrane proteins?

1. peripheral

2. integral

3. transmembrane

Fluid Mosaic Model

• Mosaic- Composed of multiple different parts (phospholipids and proteins)

• Fluid- Cell membrane components are constantly shifting arounds

Which of the following is the phospholipid bilayer most permeable to?

• Small and nonpolar molecules

Besides phospholipids, the major components of the phospholipid bilayer are ________.

• proteins and cholesterol (animal cells)/ sterol (plant cells)

What is the main function of cholesterol in the cell membrane?

Membrane fluidity

Which component of a phospholipid is hydrophilic?

The phosphate head

Since the cell membrane is semi-permeable, all of the following can passively diffuse across EXCEPT for one. Which one is the EXCEPTION?

Glucose

All of the following characteristics would allow a substance to freely cross the cell membrane EXCEPT one. Which one is the EXCEPTION?

Charged

Nucleus

Contains the cell’s DNA. Controls gene expression. The structure of the nucleus includes:

Most cells have one nucleus, but some can have…

multiple (osteoclasts and skeletal muscle cells), or none (red blood cells and platelets).

Components of Nucleus

1. Nuclear Envelope

2. Nuclear Lamina

3. Nucleolus

Nuclear envelope

double membrane (two phospholipid bilayers) with pores allowing molecules to enter and exit.

Nuclear lamina

protein network that maintains the shape of the nucleus.

Nucleolus

• region inside the nucleus where ribosomal RNA (rRNA) is made.

• Ribosomal proteins are imported from the

  cytoplasm to the nucleolus and combined with

  rRNA to form ribosomal subunits. The subunits

  are exported to the cytoplasm for final

  assembly into complete ribosome.

Nucleosome

a bundle of 8 histones with DNA coiled around them.

Chromosome

tightly condensed chromatin which is visible when the cell is ready to divide.

DNA Inside the Nucleus

1. Chromosome- Organized, compact form of DNA

2. Chromatins- General Packaging of DNA and proteins

3. Histones- Allows for structures to be bundled into nucleosomes

Cytosol vs Cytoplasm

• Cytosol

  • Only the gel-like fluid inside the cell; does not include the components suspended within the gel substance

• Cytoplasm

  • Area in which the cell’s metabolic processes occur. Includes cytosol and organelles suspended in the cytosol

Ribosomes

• non-membrane-bound organelles found in both prokaryotes and eukaryotes.

• Responsible for protein synthesis (translation).

• composed of 2 subunits containing rRNA and proteins (euk subunits bigger than prokaryotic subunits)

• Can be found free floating (make proteins that function that inside the cell) or bound to the rough ER (make proteins exported outside of the cell)

Rough ER (RER)

• synthesizes and modifies proteins before they are exported. Close to the nucleus and studded with ribosomes.

• Capable of post-translational modifications of protein (e.g. attaching carbohydrates to make glycoproteins).

Smooth ER (SER)

• synthesizes lipids and steroid hormones for export. Has no ribosomes.

• In liver cells, it functions in breakdown of toxins, drugs, and toxic by-products.

• Muscle cells have a specialized SER called the sarcoplasmic reticulum that stores and releases Ca2+ ions.

Golgi Apparatus:

• series of flattened membrane sacs (cisternae) that sort, modify, and transport proteins after synthesis.

• Also produces lysosomes and transports lipids.

• Directionality: the golgi has a cis end (accepts incoming vesicles) and a trans end (exports vesicles).

Route of Golgi Apparatus

1. Proteins made by rough ER

2. Lipids and steroid hormones made by smooth ER

3. Cis face of golgi receives transport vesicles from ER

4. Golgi modifies and packages the substances

5. Trans face of golgi secretes vesicles for substances to exit

Lysosomes and its functions

• Made by golgi, Contains digestive enzymes with a low pH

• Apoptosis

• Autophagy

• Break down nutrients, pathogens, and cell debris

Peroxisomes

• Commonly found in liver

• Breakdown substances, fatty acids, and amino acids

• Generate hydrogen peroxides (H2O2) to oxidize substrates

Vacuoles

• Vesicles inside cells that store and move materials and are membrane bound

4 types of vacuoles

1. Transport- move materials between organelles

2. Food- transport food and fuses with lysosomes

3. Central- Tonoplasts in plant cells

4. Contractile- Collect and pump excess water out of the cell (in protists)

Cytoskeleton

• Maintain cell shape and provide mechanical support

• Move components within the cell

• Cell motility

• Anchors membrane proteins

3 Components of the Cytoskeleton and their functions

• Microfilaments- Made of actin involved in cell motility

• Intermediate Filaments- Support for maintaining cell shape

• Microtubules- Made of tubulin for support and motility

Bundles of microtubules form the following…

1. Cilia- Short hair like extensions from cell for movement

2. Flagella- Thread-like extensions for cell movement

3. Centrioles- Development of spindle fibers for cell division

Microtubules organizing centers (MTOCs)

• arrange microtubule structures within the cell (e.g. centrioles and basal bodies).

• Form the spindle apparatus during cell division

• Are structures that include centrosomes and basal bodies

• Are found at the base of flagellum and cilium

• Structure- 9×3 array

Mitochondria

• Creates ATP and breaks down fatty acids (beta-oxidation)

• inner membrane highly folded (cristae) to increase SA, contained within the inner membrane in mitochondrial matrix

Chloroplasts

• Double membrane bound organelle that is the site of photosynthesis in plants and algae

• Uses light energy to produce sugar

• Absorbs red and blue and reflects green light

• Evolved from photosynthetic cyanobacteria

Endosymbiotic Theory

certain organelles (mitochondria and chloroplasts) in eukaryotic cells were once independent prokaryotic organisms that later formed a symbiotic relationship with a larger cell, leading to their presence as organelles in eukaryotic cells today. Mitochondria and chloroplasts:

1. Have their own circular DNA genome.

2. Are similar in size to prokaryotic cells.

3. Replicate similarly to prokaryotic cells (binary fission).

4. Contain small, prokaryotic-like ribosomes.

Components of Plant cells

• Contains cell walls

• Spindle pole bodies

• Unique organelle- Plastids, storage vacuoles

Plastids

Chloroplasts (site of photosynthesis), leucoplasts (store nutrients) and chromoplasts

(store pigments).

Peripheral Membrane

• Attached to membrane surface

• Hydrophilic and bound to the membrane by H-bonds and electrostatic interactions. Removable with high salt concentration or extreme pH

Integral Proteins

• Extend into the membrane and have hydrophobic regions. Removable with a detergent which destroys the membrane

Transmembrane Proteins

• Integral Proteins that pass completely through the membrane, connecting the interior and exterior of the cell

Transport Proteins

• Transport Materials across the membrane

Channel Proteins

• Hollow tubes substances can move through ( e.g aquaporins allowinf for quick movement of water across the membrane)

Ion Channels

Allow the passage of ions across the membrane of water across the membrane

Voltage gated ions

• Opens or closes in response to a difference in membrane potential

Mechanically-gated ions

• opens in response to pressure, vibration, temperature, etc.

Ligand-gated ions

• Open or closes in response to molecule binding

Carrier Proteins

• Pass molecules across the membrane by changing shape

Receptor Proteins

• Binding site for hormones and other signaling molecules that triggers changes inside of the cell when activated

Glycoproteins

• Proteins with carbohydrates attached

• Important for cell to cell recognition, signaling, and adhesion

  • Immune cells check membrane glycoproteins to determine if a cell is foreign

  • Can function as receptor proteins

Adhesion/ Anchor Proteins

• Attach cells to adjust cells and other extracellular/ intracellular proteins for stability and communication

Tight Junctions

form a seal between adjacent cells, preventing the passage or leakage of material between them (e.g. in the digestive tract and blood brain barrier).

Adherens Junctions:

• firmly attaches adjacent cells together, allowing organization into tissues (e.g. cells lining blood vessels).

  • Stabilized by attachment to intracellular actin filaments.

Desmosomes

• Similar to adherens junctions, but stronger. Found in tissues prone to mechanical stress (e.g. cardiac muscle, epidermis).

  • Stabilized by attachment to intracellular intermediate filaments (keratin).

Hemidesmosomes

• attach cells to the extracellular matrix (at the basement membrane) to hold them in place to underlying tissues.

• Found in epidermis of skin.

Gap Junctions

• narrow tunnels between cells which allow for cell-to-cell communication.

• Allow ions and small molecules to flow directly from one cell to another.

  • Can conduct electrical signals smoothly between cells (e.g. cardiac muscle cells).

Basement Membrane:

• part of the extracellular matrix that anchors and supports cells attached to it.

Cell orientation

• the apical (top) surface points outward

• lateral surfaces are on the side, and the basal surface forms the bottom of the cell.

Hypotonic

• More solutes inside the cell than outside

• Causes H20 to rush into cell and causes cell to swell

Isotonic

• Balanced H2O entry and exit at equal rate

Hypertonic

• H2O rushes out of cell because more solutes outside than inside

Bacterial Cell wall contains…

Peptidoglycan

Plant cell wall contains…

Cellulose

Fungal cell wall contains

Fungi

Which membrane proteins provide a passageway through the membrane for hydrophilic, polar, and charged substances?

channel proteins

Which membrane proteins are a type of glycoprotein that distinguish between self and foreign substances?

recognition proteins

(Note: MHC on macrophage)

Which membrane proteins are used to pass ions across the membrane and referred to as gated channels in nerve and muscle cells?

ion channels

What are the types of ion channels?

1. voltage-gated

2. ligand-gated

3. mechanically gated

Which membrane proteins allow the passage of certain ions and small polar molecules, are less specific, and create relatively large openings?

porins

Which membrane proteins are specific to movement across the membrane via integral membrane proteins?

carrier proteins

How do carrier proteins allow specific molecules to pass across the membrane?

changes shape after

binding to specific molecule

Which membrane proteins can use ATP to transport materials across the membrane?

transport proteins

(Note: includes active

transport and facilitated

transport)

What is the difference between active transport and facilitated diffusion?

active transport requires energy and facilitated diffusion does not

Which membrane proteins attach cells to neighboring cells and provide anchors for stability via internal filaments and tubules?

adhesion proteins

Which membrane proteins serve as binding sites for hormones and other trigger molecules?

receptor proteins

Which membrane property allows small uncharged molecules to cross the cell membrane?

phospholipid membrane

semi permeability

(Note: all other substances

require a transporter)

Which membrane component maintains membrane integrity over a range of temperatures?

cholesterol

(Note: sterols perform

similar functions in plants)

What do prokaryotic cells use instead of cholesterol in their membrane?

hopanoids

Which membrane component makes a carbohydrate coat that covers the cell wall of some bacteria and the plasma membrane of some animal cells?

glycocalyx

What are the components of the glycocalyx?

1. glycolipids attached

to the plasma membrane

2. glycoproteins serving

as recognition proteins

What are the functions of the glycocalyx?

1. adhesion

2. barrier to infection

3. markers for

cell-cell recognition

Which organelle contains chromatin, which is the general packaging structure of DNA around proteins in eukaryotes?

nucleus

(Note: tightness in

packaging depends

on cell stage)

What are tightly condensed chromatin when the cell is ready to divide?

chromosomes

What structures serve to organize DNA which coil around it into bundles called nucleosomes?

histones

Nucleosomes are wrapped around what number of histone proteins?

8

Which structure is located inside the nucleus and serves as the site of ribosome synthesis?

nucleolus

What organelles are synthesized using rRNA and proteins which are imported from the cytoplasm?

ribosomes

(Note: Once ribosomal

subunits form, they are

exported to the

cytoplasm for final

assembly into a

complete ribosome)

What is the double-layered boundary that binds the nucleus?

nuclear envelope

What structures allow transport across the nuclear envelope?

nuclear pores

What is the cytoplasm-like substance within the nucleus?

nucleoplasm

What is a dense fibrillar network inside of the nucleus of eukaryotic cells?

nuclear lamina

What are the components of the nuclear lamina?

1. intermediate filaments

2. membrane-associated proteins

What are the functions of the nuclear lamina?

1. mechanical support

2. regulation of DNA replication, cell division, and chromatin organization

Which organelle is the irregular shaped region within prokaryote cells that contains all or most of the cell’s genetic material?

nucleoid

What is the area that contains the cell’s metabolic activity and transportation (cytosol and organelles)?

cytoplasm