Chapter 3a: Cell Theory, Cell Membranes, Cell Transport Learning Goals

What is the fundamental unit of life?

The cell

What are the components of cell membranes?

Lipids, proteins, carbohydrates

What is the role of the cell membrane?

Selective barrier

How does the cell membrane maintain homeostasis?

Controls substance movement

What are cell membranes composed of?

Lipids, proteins, carbohydrates

What role does the cell membrane play?

Selective barrier for homeostasis

What is the endomembrane system?

Interconnected membranes in eukaryotes

What organelles harness energy?

Mitochondria and chloroplasts

Who built a microscope in 1665?

Robert Hooke

What did Robert Hooke observe in cork?

Cells

Who improved microscope lenses in the 17th century?

Anton van Leeuwenhoek

What types of organisms were observed with improved microscopes?

Unicellular organisms

What are the three tenets of Cell Theory?

Organisms made of cells, basic units, preexisting cells

What is the basic unit of structure and function in living things?

Cells

From where do cells originate?

Preexisting cells

What is the relationship highlighted in Cell Theory?

Form and function

What are all organisms made up of?

Cells

Where do cells come from?

Preexisting cells

Why do larger organisms have more cells?

Limited cell size

What do cells rely on for nutrient and waste passage?

Plasma membrane

How does volume increase compared to surface area?

Volume n3, surface area n2

What limits the size of cells?

Surface area to volume ratio

What happens if cells were bigger?

Nutrient deficiency, waste buildup

Why are most cells microscopic?

Geometric relationships

What are prokaryotic cells lacking?

Nucleus

What do eukaryotic cells have?

Nucleus

What is absent in prokaryotic cells?

Internal compartmentalization

What structures do eukaryotic cells possess?

Membrane-bound organelles

Differences in gene expression between prokaryotes and eukaryotes

Transcription and translation locations

What is the difference between prokaryotes and eukaryotes?

Eukaryotes have a nucleus, prokaryotes do not.

What is an example of a prokaryote?

Bacteria

What is an example of a eukaryote?

Plants and animals

What is the function of the nucleus in a eukaryote?

Contains genetic material

What defines all cells?

Cell membrane

What are the major lipids in cell membranes?

Phospholipids

What regions do phospholipids have?

Hydrophobic and hydrophilic

What is the nature of the 'head group' in phospholipids?

Polar

What is the nature of the 'tails' in phospholipids?

Nonpolar

What is the major type of lipid in cell membranes?

Phospholipids

What characteristic do phospholipids have?

Amphipathic

What does the hydrophilic region of phospholipids consist of?

Glycerol, phosphate, polar group

What is found in the hydrophobic region of phospholipids?

Fatty acid tail

What are micelles formed by?

Phospholipids with large heads

What type of structure do detergents form?

Micelles

What forms bilayers and liposomes?

Phospholipids with small heads

What do phospholipids form with large head groups and one tail?

Micelles

What structure do phospholipids form with smaller heads and two tails?

Bilayer

What factors influence the arrangement of phospholipids?

Size of polar head groups

What do phospholipids form when in water?

Liposome

What constitutes the structure of a liposome?

Bilayer

Why are membranes described as 'self-healing'?

Spontaneously reform

What do phospholipids form in a test tube?

Liposomes

Why are membranes self-healing?

Phospholipid rearrangement

What is found in the membrane?

Lipids and proteins

What type of movement do lipids have in the membrane?

Lateral movement

What affects lipid movement in the membrane?

Phospholipid tails

Unsaturated vs. Saturated

Unsaturated is more fluid

Fatty acid length effect

Shorter = more fluid

Temperature effect on membrane

Increased temp = more fluid

Van der Waals interactions role

Stabilizes membrane

What forces associate lipids?

Van der Waals forces

What property allows membrane lipids to move?

Weak interactions

What effect does membrane fluidity have?

Dynamic membranes

What is the structure of saturated fatty acids?

No double bonds

What distinguishes unsaturated fatty acids?

Contains double bonds

Where is cholesterol found?

Animal cell membranes

What regions does cholesterol have?

Polar and nonpolar

How does cholesterol affect membrane fluidity at normal temperature?

Reduces fluidity

What does cholesterol interact with?

Phospholipid fatty acid tails

What is cholesterol?

Component of animal cell membranes

What is the structure of cholesterol?

Amphipathic with hydroxyl group

How does cholesterol affect membrane fluidity?

Increases or decreases with temperature

What is the effect of cholesterol at normal cell temperature?

Reduces mobility and fluidity

How does cholesterol function at high temperatures?

Forms VDW forces

How does cholesterol function at low temperatures?

Prevents tight packing

How does cholesterol affect phospholipid movement at high temperatures?

Forms VDW forces

What is the effect of cholesterol at low temperatures?

Prevents tight packing

What do transporters do in the membrane?

Move ions and molecules

What is the function of receptors in the membrane?

Receive signals

What role do enzymes play in the membrane?

Catalyze chemical reactions

What do anchors do in the membrane?

Attach to other proteins

What do most membranes contain?

Proteins and lipids

What is the function of transporters?

Move ions or molecules

How do channels function?

Allow molecules to move

What do carriers do?

Facilitate movement by changing shape

What do receptors do?

Receive signals

Function of enzymes?

Catalyze reactions

What do anchors attach to?

Other proteins

Role of anchors?

Maintain structure and shape

What are integral membrane proteins?

Permanently associated, cross membrane

What are peripheral membrane proteins?

Temporarily associated with membrane

What are the two types of membrane proteins?

Integral and peripheral

How are integral membrane proteins associated with cell membranes?

Permanently associated

Can integral membrane proteins be separated from the membrane?

No, without destruction

What do transmembrane proteins do?

Span the entire lipid bilayer

How are peripheral membrane proteins associated with the membrane?

Temporarily associated

What type of interactions associate peripheral membrane proteins with the membrane?

Weak noncovalent interactions

Where can peripheral membrane proteins be located?

Internal or external side

What defines an integral membrane protein?

Ends in cytoplasm and extracellular space

What evidence supports the Fluid Mosaic Model?

Fluorescently labeled proteins