Topic 3- Cellular Level of Organization

Prokaryotic cells

Simple cells tat are Pro (before) karyon(nucleus)- they have no nucleus

Are red blood cells prokarytes?

Yes, because they come from stem cells

Eukaryotic cells

Complex cells with a nucleus and subcellular structures (organelles)

What are eukaryotes?

All fungi, plants, and animals

The plasma membrane

Outer boundary and separates the cell's internal environment from the outside environment

The cytoplasm

Cellular contents between the plasma membrane and the nucleus. Broken down into cytosol, and organelles

The nucleus

A large organelle which contains DNA in the molecules called chromosomes

How many pairs of DNA is in the nucleus

23 pairs. 46 DNA molecules in total

Fluid Mosaic Model

A representation for the arrangement of molecules within the membrane

-The lipids act as a barrier to certain substances

-The proteins act as 'gatekeepers', allowing passage of specific molecules and ions

Phospholipids

Form a lipid bilayer

Integral proteins

Extend into or through the bilayer

Transmembrane proteins

Most integral proteins. Span the entire lipid bilayer. Amphipathic just like the phospholipids

Peripheral proteins

Attach to the inner or outer surface but do not extend through the membrane

Glycoproteins

Membrane proteins with a carbohydrate group attached that protrude into the extracellular fluid

The Glycocalyx

The entire 'sugar coating' surrounding the membrane

-enables white blood cells to detect foreign organisms

-allows cells to adhere to one another and protect cells from enzymes in the extracellular fluid

Why do cells need to recognize each other?

So the immune system can distinguish if a cell is harmful or not

Ion channels

Allows specific ion into or out of the cell

Carrier

selectively move substances through the membrane by changing shape

Receptors

Bind to specific molecules (ligand) and then alter the cells function

Enzymes

Catalyze chemical reactions inside or outside cell

Selective permeability

The membrane allows some substances across (small and non-polar molecules) but not other (large and polar molecules)

Passive processes

Substances moving across the cell membranes without the input of any energy- They are said to move 'with' or 'down' their concentration or electrical gradient

-Simple diffusion of a solute (in a solution)

---high to low concentration

-Diffusion of water (osmosis- movement of water)

-Facilitated diffusion (requires a specific channel or a carrier molecule, but no energy is used)

Active processes

Involves the use of energy, primarily from the breakdown of ATP, to move a substance against its [gradient]

-primary and secondary transport

-Vesicular transport

Membrane potential

The charge different (electrical gradient) across the membrane

Diffusion

The passive spread of particles through randoms motion, from areas of high concentration to areas of low concentration

-tuna example

Simple diffusion

Occurs when substances move through the lipid bilayer without transport proteins

Channel-mediated facilitated diffusion

A process where a solute moves down the concentration gradient through a membrane channel

Osmosis

The net movement of a solvent through a selectively permeable membrane from an area of high solvent (water) concentration to one of lower solvent (water) concentration

-Only occurs when membrane is permeable to solvent and not solute

Water can pass through plasma membrane in 2 ways

Through lipid bilayer by simple diffusion

-Through aquaporins

Antiporters

Carry two substances across the membrane in opposite directions

Symporters

Carry two substances across the membrane in the same direction

Vesicle

A small spherical sac formed by budding off from a membrane

Endocytosis

Material move into a cell in a vesicle formed from the plasma membrane

Three types of endocytosis

-Receptor- mediated endocytosis

-Phagocytosis

-Bulk-phase endocytosis (pinocytosis)

Exovytosis

Vesicle fuse with the plasma membrane, releasing their contents into the extracellular fluid

Transcytosis

A combination of endocytosis and exocytosis used to move substance from one side of a cell, across it, and out the other side

Cytosol

Intracellular fluid in the cytoplasm

-Surrounding the organelles 75-90% water

-The site of many chemical reactions

-Reactions provide the building blocks for cell maintenance, structure, function and growth

Organelles

In the cytoplasm

-specialized structures within the cell

-each organelle has specific enzymes

Cytoskeleton

-Network of protein filaments throughout the cytosol

-Provides structural support for the cell

Centrosome

Located near the nucleus, consists of two centrioles (right angles) and pericentriolar material

-organizing center which plays an important role in cell division

Cilia

Short, hair-like projections from the cell surface; move fluids along a cell surface

-intestines- move stuff along

Flagella

Longer than cilia, move an entire cell; sperm cell's tail

Ribosomes

site of protein synthesis

Endoplasmic reticulum

Network of membrane in the shape of flattened sacs or tubules

Rough ER

connect to the nuclear envelope, a series of flattened sacs, surface is studded with ribosomes, produces various proteins

Smooth ER

A network of membrane tubules, does not have ribosomes but contain enzymes that play a key tole in syntheses of fatty acids and steroids, detoxification of certain drugs

Golgi- complex

Stack of pancakes

-consists of 3-20 flattened, membranous sacs (cisternae)

Function of golgi-complex

face receives and modified proteins from the rough ER enzymes adds carbs and lipids to form glyoproteins and lipoproteins, sort, and package proteins for transport to different destinations

Lysosomes

Vesicles that form from the Golgi-complex and contain powerful digestive enzyes that break down molecules within vesicles formed during enzymes for use in the cytosol

Function of lysosomes

engulf other organelles, digest them and return components to cytosol or destroy the cell that contains them

Perozisomes

Smaller than lysosomes

-Detoxify several toxic substances

-Abundant in liver

Proteasomes

Continuously destroy unneeded, damages, or faulty proteins

-Found in the cytosol and the nucleus

-Contain proteases

Mitochondria

Powerhouse of the cell

-Generate ATP through aerobic respiration

-More in active cells

-Cristae- more location for ATP synthesis to happen

-Matrix

-Self-replicate

-Contain own DNA

Cristae

The series of folds of the inner membrane to increase surface area

Matrix

The large central fluid-filled cavity

Nuclear envelope

A double membrane that separates the nucleus from the cytoplasm

Nuclear pores

Numerous opening in the nuclear envelope, control movement of substance between nucleus and cytoplasm

Nucleoli

Spherical body the produce ribosomes. Cluster of DNA, RNA, and protein

Genes

The cells hereditary units, control activities and structure of the cell. Arranged along chromosomes

Chromosomes

Long molecules of DNA combined with protein molecules

Chromatin

Genetic material when it is freely disperses around the cell

Transcription

occurs in the nucleus

-it is the process by which genetic information encoded in DNA is copied onto a strand of RNA to direct protein synthesis

-DNA is copied- RNA is the receipt to how to create a protein

Translation

Occurs in the cytoplasm and is the process of reading the mRNA nucleotide sequence to determine the amino acid sequence of the newly formed protein

Diploid cells

Somatic cells contain two sets of chromosomes

Homologous chromosomes (homologs)

the two chromosomes that make up each pair

Somatic cell division- Mitosis

the cell cycle is a sequence of events in which a body cell duplicates it contents and divides in two

-Two daughter cells identical to each other and the parent cell

Interphase

the cell is no dividing

-consists of three cells

G1- Interphase

Metabolic activity and duplicates organelles

S- Interphase

Replication of DNA occurs

G2- Interphase

Cell growth, protein and enzyme synthesis

Mitotic phase

Consists of a nuclear divison (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells

1st Phase of Mitosis 1/4

Prophase

Prophase

The chromatin fibers condense into chromosomes

2nd phase of mitosis 2/4

Metaphase

Metaphase

Microtubules align the centromeres of the chromatid pairs at the metaphase plate

3rd phase of mitosis

Anaphase

Anaphase

The chromatid pairs split at the centromere and move to opposite poles of the cell

Last phase of mitosis 4/4

Telophase

Telophase

Two identical nuclei are formed around the identical sets of chromosomes now in their chromatin form

Cytokinesis

Division of a cell's cytoplasm to form two identical cells

Telomeres

DNA sequences found at the tips of each chromosome

-Protect the chromosomes from sticking to one another and from erosion

-Normal cell division shortens telomeres and after many years