BIO 181 Cell Structure

The 3 ideas of cell theory

1. The cell is the basic unit of life

2. All organisms are made from cells

3. Cells arise from preexisting cells

Cell

the basic unit of structure and function in organisms

Cell structure

the smallest building blocks that make up every organism

cell function

obtaining energy, growing, responding to the environment, reproducing

organisms

an individual living system or being

unicellular vs multicellular organisms

1. Unicellular: 1 cell performs all life functions

2. Multicellular: Many specialized cells work together, leads to the levels of biological organization

Cell arise from preexisting cells

they can divide to make new cells

Cell size

Cell size varies, but it is limited by the relationship between surface area and volume(SA:V ratio)

three domains of life

bacteria prokaryotes, archaea prokaryotes, eukaryotes

what do prokaryotes not contain that eukaryotes do?

prokaryotes do not contain a nucleus or any other membrane-bound organelles, generally single-celled

3 parts of prokaryotic cells

1. cell envelope

2. cytoplasmic region

3. flagella or pili that can project from cell surface

cell envelope

this is generally a plasma membrane covered by a cell wall (peptidoglycan in bacteria). In some cases, there can be a third layer called a capsule.

cytoplasmic region

contains the DNA, ribosomes, and proteins.

eukaryotic cell examples

plants, animals, fungi, slime molds, algae

compartmentalization

the division of the cell interior into distinct, membrane-bound regions that isolate specific biochemical processes and optimize cellular efficiency achieved through presence of membrane-bound organelles, most important of these: the nucleus

what are viruses made of

acellular

1. genetic material(DNA,RNA)

2. protein coat

3. some primes a lipid envelope

what can viruses not do

1. carry out metabolism by themselves

2. grow

3. maintain homeostasis

4. reproduce independently

cell/plasma membrane

surrounds cytoplasm

A phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment

Controls the passage of organic molecules, ions, water, and oxygen into and out of the cell.

cytoplpasm

the gel-like inner region b/w plasma membrane and nuclear envelope. 70-80% water, but semi-solid due to internal proteins

nucleus

houses the cell DNA and directs protein synthesis.

The nuclear envelope/membrane: a double-membrane outermost structure that allows material to move in and out 

1. The nucleoplasm: the semi-solid fluid inside the nucleus 

2. Nucleolus: condensed region where ribosomes form  

3. Chromatin: When a cell is not dividing, DNA is usually packed into a loose chromatin form. 

4. Chromosomes: structures within the nucleus that are made up of DNA, the hereditary material.

ribosomes

 the cellular structures responsible for protein synthesis. 

1. Consists of two subunits 

2. In eukaryotes, the size of a ribosome is 80S 

3. Ribosomes may be attached to the cytoplasmic surface of the rough endoplasmic reticulum (ER), the outer membrane of the nuclear envelope, or they may be free in the cytosol.

endoplasmic reticulum(ER)

A network of interconnected membrane sacs and tubes that extends from the nuclear envelope throughout the cytoplasm. Two types of ER: Rough ER and Smooth ER

rough ER (RER)

Ribosomes attached; makes proteins. e.g., pancreatic cells have lots of RER because they produce digestive enzymes and insulin.

smooth ER(SER)

No ribosomes; makes lipids. e.g., Liver cells have lots of SER as they detoxify alcohol and drugs.

golgi apparatus

Made up of flattened, stacked pouches.

1. It modifies, transports, and packages newly made proteins and lipids in eukaryotic cells.

2. Proteins produced by ribosomes on the RER are packaged into transport vesicles, which bud off from the RER and carry the proteins to the Golgi apparatus.

mitochondria

Mitochondria provide energy to the eukaryotic cell by converting sugars into ATP. They have two surrounding membranes: 

1. The outer membrane 

2. The inner membrane: folded into invaginations called cristae (where aerobic respiration takes place).

3. They have their own DNA (circular) and 70s ribosomes, like in prokaryotes.

vesicle

small membrane-bound sac that transports materials (Proteins, Lipids, Waste, Enzymes) between organelles within the cell or to the cell membrane.

vacuole

larger membrane-bound organelle used primarily for storage of water, nutrients, pigments, waste, and toxins. (Can be found in animal and plant cells, but the central vacuole is larger in plants.)

peroxisomes

• Small, round organelles enclosed by a single membrane 

• Detoxification and breakdown of fatty acids 

• For example, peroxisomes tend to be abundant in liver cells for detoxification purposes

lysosomes

• Small, round organelles enclosed by a single membrane 

• Digestion and recycling of proteins, lipids, polysaccharides, nucleic acids, and even worn-out organelles (the cell’s ‘garbage disposal’)

• The interior is more acidic than the cytoplasm.

cytoskeleton

The cytoskeleton is a network of protein fibers that extends throughout the cytoplasm. 

It helps the cell: Maintain its shape, Organize organelles, Move materials inside the cell, Move the cell itself, Separate chromosomes during cell division

The eukaryotic cytoskeleton has three types of fibers

Microfilaments, intermediate filaments, microtubules

microfilaments

smallest in size, formed of actin protein

function is cytokinesis and suppost just beneath plasma membrane

intermediate filaments

medium in size, made of several proteins(keratin, vimentin, etc.)

function resist stretching, hold organelles in place strengthen cells

microtubules

largest in size, composed of tubulinprotein

function transport, form cilia and flagella, seperate chromosomes during mitosis

components of a eukaryotic(animal) cell

1. Plasma Membrane: phospholipid bilayer 

2. Cytoplasm: jelly-like substance that contains organelles 

3. Nucleus: houses the cell’s DNA and directs the synthesis of ribosomes and proteins 

4. Endoplasmic Reticulum: 

   1. Rough: makes secretory and membrane proteins 

   2. Smooth: makes lipids 

5. Ribosomes: site of protein synthesis 

6. Golgi apparatus: modifies proteins 

7. Mitochondria: produces energy ATP 

8. Vacuole: stores and transports materials 

9. Lysosome: digests contents 

10. Peroxisomes: metabolize waste 

11. Cytoskeleton 

chloroplasts

carry out photosynthesis

1. Double-membranes 

2. Contain chlorophyll, a green pigment that absorbs light energy. 

3. Have their own DNA (circular) and 70s ribosomes, like in prokaryotes.

cell walls

rigid covering that protects the cell, provides structural support, and gives shape to the cell(often made of cellulose)

plasmodesmata

channells that connect two plant cells

plastids

store pigments