Cell theory & Structure

Modern Cell Theory

1)all living things are composed of 1 or more cells

2) Cells are organisms basic units of structure and function

3) Cells come only from existing cells

Prokaryotic Cells

-Includes domain, bacteria & archaea

-No nucleus

-usually single cellular & smaller

-anaerobic, no membrane bound organelles

Eukaryotic

-Includes domain Eukarya

-no nucleus, larger

-often multi - cellular

-aerobic, membrane bound organelles

Parts of the Cell

Each living cells carriers out the task of taking food, transforming food into energy, getting rid of waste, and reproducing

Organelles

organized specialized structures within a cell

Cells Main Components

1) Plasma membrane 2)Cytoplasm 3)Region of DNA 4)Ribosomes

Plasma Membrane (Eukaryotic)

Is the outer boundary of the cell

-Function: to protect the cell and allow materials in & out

Prokaryotic cells also have one

Nucleus (eukaryotic)

-is a membrane- lined compartment that serves as the cells information center (contains DNA)

Function: storage center of the cell’s DNA & manages cell activities

-The site of DNA replication & transcription

Cytoplasm (eukaryotic)

Includes the cytosol and all of the organelles in a cell except the nucleus

-It’s a protein rich, jelly like fluid in which the organelles are immersed

-Function:to maintain water and other chemicals within the cell and to surround the other organelles

Ribosomes (eukaryotic)

-The site of transcription where the mRNA transcript is used to make proteins

-Can be found as independent structures within a cell or attached to the ER.

Endoplasmic Reticulum (ER)

Can be smooth ER or rough ER with both having separate functions

Rough ER

has ribosomes on it and folds the proteins that are formed in the ribosomes (from translation)

Smooth ER

doesn't have ribosomes and functions in the lipid synthesis, storage and detoxification of the cell

Golgi Body (Eukaryotic)

-functions in receiving proteins from the rough ER and distributing them to the other organelles or out of the cell

Mitochondria (Eukaryotic)

Converts energy stored in food (sugars) into usable energy for the body (ATP) during respiration

-called the “powerhouse” it provides the energy to the rest of the organelles

Lysosomes (eukaryotic)

-contain digestive enzymes

Function in recycling dead organelles, breaking down invading bacteria or virus within the cells

Vacuoles (eukaryotic)

fluid sacs that function in temporary storage of waste, nutrients or water needed by the cell

cell wall

thick outer membrane (outside of the plasma membrane) that gives plants structural strength and retains water

Central vacuole

contains water and waste. Can compromise 90% of the cell volume

Chloroplasts

site of photosynthesis

Cellular Transport

All materials that go in and out of the cell & must go through the plasma membrane

Plasma membrane importance

-selectively isolates the cell’s contents from the external environment

-controls the passage of substances moving out and in

-communication with other cells

-Creates attachments with and between cells

Phospholipid bilayer

a double layer of molecules with hydrophobic fatty acid tails on the inside

Proteins (plasma membrane)

provide structural support to the membrane, can trigger responses in cell, prevent harmful substances from entering cell, allow certain molecules to pass through

Carbohydrates

attached to the outermost side of the cell and helps communication, adherence, and recognition

Cholesterol

makes the bilayer stronger and more flexible

Fluid Mosaic

describes the plasma membrane as a mosaic of proteins moving within the fluid of phospholipid bilayer

Composition is dynamic

selectively preamble

it can choose what passes through it & what doesn’t depending on needs of the cell

Passive transport

“no energy”

Ex: diffusion, osmosis, facilitated diffusion

Diffusion (passive)

movement of very small molecules/ions down a concentration (high to low)

Osmosis (passive)

movement of water across a semi- permeable membrane from an area of (high to low concentration)

Depends on the concentration of solute (solids) to solvent (water)

Facilitated Diffusion (passive)

passage of materials aided by both the concentration gradient and transport protein

Used for water soluble substances

Active transport

“needs energy”

many substances are needed a higher concentration in the cell

ATP is required to power transport protein pumps (low to high)

means for exocytosis (large moved out) & endocytosis(large moving in)