Cell Structure & Function

Objectives

Discoveries important to the cell theory

State the parts of the cell theory

Identify the limiting factor on cell size

Describe the relationship to cell shape and function

Differentiate between prokaryotic and eukaryotic cells

Cell Theory

All living things are composed of cells

Cells are the basic units of structure and function of an organism

Cells come only from other cells

Diversity

Size: limited by the ratio of volume to surface area

Shape: depends on the function of the cell

Internal Organization: organelles

Limits to Cell SizeMore demands on the cells DNA

• increase in volume means more materials are needed• nucleus must keep up with cell’s needs• volume increase places strain on the nucleus

Trouble moving materials across the cell membrane• materials have a long way to travel• takes more time to travel farther• cell needs more food and oxygen greater volume

Surface area to volume ratio• volume increases more rapidly than surface area• surface area must allow needed materials to enter• greater volume requires more materials

Prokaryotic vs. Eukaryotic

Prokaryotic cells are unicellular and lack organelles and a nucleus

Eukaryotic cells have membrane bound organelles and nucleus

Eukaryotic Cells

Objectives

Describe the structure and function of the cell membrane

Name and describe cell organelles by function

Describe the function of the nucleus

Differentiate between plant and animal cells

Cell Membrane

Selectively Permeable – allows only substances to cross

Made of phospholipids • Polar heads

• Non-polar tails

• Form a bilayer (2 layers)

Membrane Proteins

Cell recognition

Cell transportation

Sites of attachment

May be peripheral or integral

Fluid Mosaic Model

Membrane behaves like a fluid

Proteins are free to move

Like beach balls on the surface of water

Organelles

Cytoplasm – gelatin-like substance between the cell membrane and nucleus (cytosol)

Mitochondria – site of energy production (ATP); two layers• Outer layer – barrier

• Inner layer – called christae

• Has its own DNA

Ribosomes – smallest organelle; important in protein synthesis; small bits of RNA

Endoplasmic Reticulum – shipping• RER – has ribosomes attached; makes proteins

for export from the cell

• SER – makes new parts for cell membrane

Golgi Apparatus – modifies proteins; exports from cells

Lysosomes – digestion and protection

Cytoskeleton – shape and movement• Mitrotubules – spindle fibers for cell division

• Microfilaments - movement

Cilia and Flagella – movement• Cilia – short hair-like; many

• Flagella – long whip-like; 1 or 2

Nucleus – cell activities and inheritance• Nuclear envelope – surrounds (membrane)

• Chromatin – thread-like strands of DNA

• Chromosomes – condensed chromatin for cell division

• Nucleolus – site of ribosome production

Plant CellsCell wall – • Outside the cell membrane

• Supports and protects

• Made of cellulose

Vacuole – storage for enzymes and wastes

Plastids – similar to mitochondria• Capture light for photosynthesis (chloroplasts)

• Flattened sacs called thylakoids (photosynthesis)

Multicellular Organization

Tissues – cells working together

Organ – tissues working together

Organ System – organs working together

Colonial Organization – genetically identical cells living together

Cell Transportation

PASSIVE

• Osmosis

• Diffusion

• Filtration

Active

• Exocytosis

• EndocytosisPhagocytosisPinocytosisIon Pumps

DNA

Deoxyribose

Double Helix

Nitrogenous Bases• Adenine

• Cytosine

• Guanine

• Thymine

Protein Synthesis

Replication -

Transcription -

Translation -

DNA makes a copy of itself

DNA template used to make RNA

RNA moves to cytoplasm to make protein

Cell Division: Mitosis

Interphase

Prophase

Metaphase

Anaphase

Telophase

Parts of a CellStructure

Plasma MembraneRibosomesEndoplasmic ReticulumSmooth ERRough ERMitochondriaLysosomesCentriolesGolgi ApparatusNucleusCilia / Flagella

FunctionProtectionMake protein

Makes lipids / carbohydratesTransports proteins Energy (ATP)Digestive enzymesCell divisionPackages from ERHeredity / MetabolismMovement