Cell Structure and Function

The Cell Theory All living things are composed of cells.

Cells are the basic units of structure and function in living things.

All cells come from pre-existing cells.

Cell StructureMost cells have three basic structures.–cell membrane (outer boundary)

–cytoplasm (filling)–nucleus (control center)

All cells have a cell membrane and cytoplasm.

However some do not have a nucleus. These are called Prokaryotes. (bacteria)

Cells with a nucleus are called eukaryotes. (plant, animal, fungus and protists)

Nucleus

Separates and protects the cell from its surroundings.

Regulates what enters and leaves the cell.

Made of two lipid layers: (Phospholipid bilayer)

Cell Membrane

Hydro-phyllic

(Phos-phates)

Hydro-phobic

(Fatty acids)

Phospholipid Bilayer

The Cell Membrane

CytoplasmThe area between the cell membrane and nucleus.

Contains structures called organelles and each one performs a specific job.

Cytoplasm

Nucleus (Control center)

Contains DNA which are the instructions for making molecules the cell needs.

Nucleus (Control center)Directs the activities of the cell.

Surrounded by a membrane called the nuclear membrane or nuclear envelope.

Nucleus

Nucleolus

A small region of the nucleus made up of RNA and proteins.

The nucleolus makes ribosomes.

NucleolusN

ucl

eus

RibosomesFound in prokaryotic and eukaryotic cells

Protein factories.Some ribosomes are attached to the endoplasmic reticulum.

RibosomesOthers are free in the cytoplasm.

Smallest organelle.

Ribosomes

Rough ER

Endoplasmic ReticulumTwo forms

Rough ER

Smooth ER

Endoplasmic Reticulum

Smooth ER: no ribosomes are attached. Special enzymes and chemicals are stored here. Lipids (fats) are produced

Endoplasmic Reticulum

Smooth ER: also resp. for prod. of phospholipids for cell membrane.

Rough ER: has ribosomes

attached. After proteins are made in the ribosomes they are inserted in the rough ER where they can be modified.

Endoplasmic Reticulum

Rough ER: from the ER, proteins are sent to the Golgi Apparatus

Endoplasmic Reticulum

Golgi Apparatus (UPS)

modifies, collects, and packages molecules in the cell.

Also distributes the molecules to where they need to be in the cell.

Golgi Apparatus

LysosomesCleanup crews for the cell.

Lysosomes are formed in the Golgi apparatus.

Lysosomes

Contain chemicals and enzymes that digest and breakdown waste particles.

Lysosome in action:

Vacuoles (Warehouse)Storage tanks in the cell.

Store materials like water, salts, proteins, and carbohydrates.

Plants have only one big vacuole filled primarily with water.

Vacuoles (Warehouse)

CytoskeletonThe framework of the cell.

Made of microfilaments and microtubules

Provide support and are often involved in cell movement.

Mitochondria(Generator)Generator of the cell.Changes chemical energy stored in food (sugar) into compounds easier for the cell organelles to use (ATP).

Mitochondrion

Chloroplast (Solar Panel)Where photosynthesis takes place

Found only in plant cells and algae.

Chloroplast (Solar Panel)

Traps energy from sunlight and changes it into chemical energy (makes sugars).

Plant Cell

Chloroplast

Cell WallIn addition to the cell membrane, plant (& fungus) cells have a cell wall.

Provides extra support.Made up of cellulose and lignin

Cell Wall Found outside the cell membrane

Movement of materials through the cell membrane.Cells must take in materials, and release waste products.

Molecules must be able to move in and out of the cell.

Movement of materials through the cell membrane.

They do this by diffusion.

DiffusionThe process by which molecules move from areas of higher concentration to areas of lower concentration. (spread out)

Diffusion

Driven by the random movement of molecules.

Diffusion

Two factors determine if diffusion takes place equilibrium and permeability.

higher conc. lower conc.

membraneDiffusion

Equilibrium

Equilibrium is when the concentrations on both sides of the membrane are equal.

Equilibrium

Semi-permeablemembrane

Permeability

If a molecule can diffuse across a membrane, the membrane is permeable.

Permeability

If a molecule cannot diffuse across a membrane, the membrane is impermeable to that membrane.

Selective PermeabilityMembranes are

permeable to some molecules and impermeable to others.

These membranes are described as selectively permeable or semi- permeable.

OsmosisOsmosis is a special type of diffusion:

The diffusion of water molecules through a selectively permeable membrane.

There are three types of transports across a membrane.–passive transport (diffusion)

–facilitated diffusion–active transport

Passive Transport

Energy is not required for movement across the membrane to occur.

Diffusion and osmosis are examples

Facilitated DiffusionA carrier protein

“helps” the molecule to enter or leave the cell. (Passive)

Active TransportEnergy is required for movement across the membrane to occur.

Molecules move from low to high concentration.

Two types of active transport:

–Protein pumps: Pumps specific ions

–Endocytosis: cell engulfs (eats) material.

Active Transport

Pumps Proteins stuck in the membrane act as a doorway into the cell.

Allows only specific things through the doorway.

Energy is required to open the door

Pumps

Endocytosis

Endocytosis

Type of active transport when the membrane surrounds material and pulls it into the cell

Endocytosis Types

PhagocytosisPinocytosisReceptor Mediated Endocytosis

Phagocytosis“Cell Eating”Bringing large molecules across the membrane.

Membrane becomes a vacuole when entering the cell

Pinocytosis“Cell Drinking”Moving fluids and ions across a membrane.

Usually going against the concentration gradient

Ion concentration outside the membrane is

less than inside

Membrane surrounding ions and fluids

Vacuole

Receptor Mediated Endocytosis

Same process as pinocytosis.

Specific ions are moved across the membrane

Receptor Mediated Endocytosis

Receptor proteins trigger when endocytosis should begin

ExocytosisOpposite of endocytosis

Process when cell removes waste from cytoplasm

Vacuole or lysosome fuses with cell membrane and releases materials outside the cell