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NOTES: Cell Structure & Function and Cellular Transport

Texas Expected Knowledge and Skills (TEKS)4A – Compare and contrast prokaryotic and eukaryotic cells, including their complexity, and compare and contrast scientific explanations for cellular complexity.

Cell Theory:Cells are the of life for ALL living things.

1. All living things are made of 2. CELLS are the basic units of and in

living things3. CELLS are produced from CELLS

Why do we call them cells?In 1665, Robert Hooke was the first to view cells from (dead material). He called them “cells” because they looked like cells in honeycomb.

All Cell share four key components:• (cell membrane): an outer covering that separates the

cell’s interior from its surrounding environment.• : jelly-like substance inside the cell, that holds cellular

structures suspended in it.• : the genetic material of the cell.• : molecular machines that synthesize (make) proteins.

There are two basic types of cells:Prokaryotic cells = Eukaryotic cells – protists, fungi, and

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Prokaryotic Cellspro means and kary means nucleusProkaryotic cells have ! organisms that membrane-bound organelles. are the only prokaryotes!

• Much than eukaryotic!• Simple• nucleus• Circular DNA in the cytoplasm• membrane-bound organelles • Cell membrane is surrounded by a

Eukaryotic Cells• Much • Much more • Contain a to hold the genetic material ( )• Linear DNA packaged into chromatin Eukaryotic Cells Continued…• Many : specialized structures in the

cytoplasm• Some have a cell wall (plants, fungi)

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Scientific Explanations for cellular complexity:Theory: cells evolved from prokaryotic cells into eukaryotes. But how???Endosymbiosis: a relationship in which one cell resides within a larger cell.

In other words, eukaryotic cells evolved from a symbiotic relationship between two prokaryotic cells.

Supported by studies of and .The mitochondrion and chloroplasts are believed to be that were by another cell, perhaps as a , and ended up staying. The host cell benefitted from the energy the mitochondrion produced, and the mitochondrion benefited from the protected, nutrient-rich environment surrounding it. Over time, they evolved into a .

What does cell size have to do with anything?• Prokaryotic cells are much smaller than eukaryotic cells. Why?

– surface area to volume allows nutrients to easily and quickly reach inner parts of the cell.

– Eukaryotic cells are larger and can not pass nutrients as quickly. They require specialized organelles to:• carry out • provides • chemicals throughout the cell

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Cell OrganellesOrganelle: “ ” or cell parts that perform functions for the cell.

Cytoplasm: • A that consists mostly of water and

all organelles within the cell.• Found within prokaryotic and eukaryotic cells.

Cell Membrane:• Semipermeable the cytoplasm of

cells.• Allows things in and out of the cell.• the cell. Maintains homeostasis (internal stability).

Nucleus:• Surrounded by a porous nuclear (a membrane that has tiny

pores/holes)• The of the cell• ONLY cells have a nucleus• Contains the wound up as chromatin• Chromatin – condensed DNA that is bound to protein.• Chromosomes – information• – makes (synthesizes) ribosomes

Ribosomes:• Site of • Found in the cytoplasm, and attached to the endoplasmic reticulum (ER).• Found in prokaryotic and eukaryotic cells (not a membrane-bound

organelle)

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Endoplasmic Reticulum (ER):• TransportER – The ER is mostly a system; moves things

through the cell.• Rough ER – has ribosomes attached• Smooth ER – no ribosomes• The site where lipid components of the cell membrane are assembled

Golgi Body /Golgi Apparatus:• Processing, , secretion• System of membranes made of flattened sack-like structures• “Golden Packer”

Lysosomes:• “Lysol” – the cell• Filled with • of macromolecules (carbs, lipids, proteins) into molecules that

can be used by the cell.• Involved in old cell parts

Vacuoles:• Temporary for materials, mainly water.

– Large in Plant Cells– Small in Animal Cells

Mitochondria:• “ ” of the cell – converts glucose (chemical energy) in food into

(usable energy) for the cell.• ATP is produced during the process of within the

mitochondria.Chloroplast:• Only in Cells• Capture energy from and convert it to (chemical

energy) during photosynthesis.Cytoskeleton• Helps maintain (protein); Helps some cells move• Made of microfilaments and microtubules.

Cilia & Flagella:• Extend from outside of cells (some

prokaryotic, some eukaryotic)• Both assist in • – short hair-like projections (not in plants)• – long whip-like projections

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Texas Expected Knowledge and Skills (TEKS)4B – Investigate and explain cellular processes, including homeostasis and transport of molecules.

Homeostasis:• The tendency to maintain a , relatively constant internal environment

– Ex. your body wants to be approximately 98.6∘F. • Homeostasis is maintained at levels.

– Ex. The stomach maintains a pH that's different from that of surrounding organs. Ex. Each individual cell maintains ion concentrations different from those of the surrounding fluid.

• Maintaining homeostasis at each level is key to an organism’s

• Review: cell membrane:• Semipermeable membrane surrounding the cytoplasm of all cells.• Allows some things in and out of the cell.• Protects the cell. Maintains homeostasis (internal stability).

cells have a cell

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Functions of cell membranes : a. Regulates what the cell to maintain an

internal balance ( ).b. Provides from the outside environment and

separates the inside of the cell from the environment.Structure of the cell membrane: -2 layers of phospholipids

a. Phosphate head is (water loving) b. Fatty acid tails (water fearing)c. Proteins are embedded in the lipid membraned. Cell membranes have pores (holes) in them:e. S : Allows some molecules in and keeps other

molecules outf. The helps it be selective!

Label the Cell Membrane:

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Cellular Processes and Transport of Molecules• A occurs when the concentration of particles

is higher in one area than another. • The areas are typically separated by a .

The difference between the concentration of a particular molecule in one area and the concentration in an adjacent area.

Molecules move with or down the concentration gradient when moving from high to low concentration.

Types of Cellular Transport:

Passive Transport Cell uses Molecules move the concentration gradient

– Diffusion– Facilitated Diffusion– Osmosis

Active TransportCell Particles move the concentration gradient

– Protein Pumps– Endocytosis– Exocytosis

Passive Transport• cell uses • molecules move • Molecules spread out from an area of concentration to an area of

concentration. (High concentration Low)3 types of passive transport:

1. D 2. F Diffusion – diffusion with the help of transport proteins 3. O – diffusion of water molecules

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Diffusion (passive transport)Diffusion: random movement of particles from an area of concentration to an area of concentration. (High to Low)• Diffusion continues until all molecules are spaced (

is reached)Note: molecules will still move around but stay spread out.

Facilitated Diffusion (passive transport)Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane

a. Transport Proteins are – they “allow” only certain molecules to cross the membrane

b. Transports or charged molecules

OsmosisOsmosis: diffusion of through a selectively permeable membrane• Water moves from to concentrations

Hypotonic Solutions: The has a concentration of solutes than inside the cell. (Low solute; high water)Result: Osmosis of water moves from the solution into the cell; cell Swells and bursts open (cytolysis)!Hypo like a hippo – water moves INTO the cell, it swells like a hippo and bursts.

Hypertonic Solutions: The solution has a concentration of and a lower concentration of water than inside the cell. (High solute; Low water)

Result: Water moves from inside the cell into the solution; Cell shrinks (Plasmolysis)!Hyper like a viper – cell shrinks like it’s being squeezed because water is moving out of it.

Isotonic Solutions: The concentration of in the solution is to the concentration of solutes inside the cell. (water concentration is equal in and out of the cell)

Result: Water in both directions and the cell remains same size! (Dynamic Equilibrium)

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Active Transport:Cell moves molecules to where they are neededMovement from an area of concentration to an area of concentration. (Low High) against concentration gradient

3 Types of Active Transport1. Protein Pumps2. Endocytosis3. Exocytosis

Protein Pumps (Active Transport)Protein -transport proteins that to do workExample: Sodium (Na+) / (K) Potassium Pumps are important in nerve responses; To help molecules pass, the protein changes shape…this requires energy!

Endocytosis (Active Transport)Endocytosis: taking bulky material a cell

• Uses energy: Cell membrane in-folds around particle

• “ ”

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• forms food vacuole & digests food• This is how white blood cells eat bacteria!• Endosymbiosis began here!

Endocytosis – process of cell taking materials in (entering)

Exocytosis (Active Transport)Exocytosis: Forces material of cell in bulk

• membrane surrounding the material fuses with cell membrane• Cell changes shape – requires energy• EX: Hormones or wastes from cell

Exocytosis – process of a cell releasing materials (exiting)

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