AP Biology Discussion Notes

Tuesday 10/7/2014

Goals for the Day

1. Become familiar with the cell organelles and their functions.

2. Be able to describe the function of specific organelles, and which types of organisms have them

3. Describe how things are transported in/out of the cell

Question of the Day

What is osmosis & what kind of transport would it be considered?

Question of the Day

What is osmosis & what kind of transport would it be considered?

The “tonics”

Hypotonic

Isotonic

Hypertonic

Species of the day 10/6

Curculio spp.

• Acorn Weevil

Species of the day 10/6

Curculio spp.

• Acorn Weevil

Do the acorn and the weevil share the same cell parts? EXPLAIN your answer!

Structures of Plant Cells

Plants have three (for now) unique structures that are not found in animal cells:

• Cell Wall

• Chloroplasts

• Central Vacuole

Cell Wall• Provides Structure and Support• Contains cellulose ( in plants)• Contains _______ in Fungi• Contains ______________ in bacteria• Allows the cell to build pressure

Cell Walls of Plants• The cell wall is an extracellular structure that

distinguishes plant cells from animal cells

• Prokaryotes, fungi, and some protists also have cell walls

• The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water

• Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein

• Plant cell walls may have multiple layers– Primary cell wall: relatively thin and flexible– Middle lamella: thin layer between primary walls

of adjacent cells– Secondary cell wall (in some cells): added

between the plasma membrane and the primary cell wall

• Plasmodesmata are channels between adjacent plant cells

Secondarycell wallPrimarycell wallMiddlelamella

Central vacuoleCytosol

Plasma membrane

Plant cell walls

Plasmodesmata

1 m

Figure 6.28

Plasmodesmata in Plant Cells• Plasmodesmata are channels that

perforate plant cell walls• Through plasmodesmata, water and small

solutes (and sometimes proteins and RNA) can pass from cell to cell

Figure 6.31

Interiorof cell

Interiorof cell

0.5 m Plasmodesmata Plasma membranes

Cell walls

Central VacuoleCentral Vacuole:

Most of a plant cell’s volume is taken up by a large, membrane-bound space called the central vacuole.

The central vacuole stores water and may contain ions, nutrients, and wastes.

Peroxisomes: Oxidation• Peroxisomes are specialized metabolic

compartments bounded by a single membrane• Peroxisomes produce hydrogen peroxide and

convert it to water• Peroxisomes perform reactions with many

different functions

• What does that remind you of???

Figure 6.19

ChloroplastPeroxisome

Mitochondrion

1 m

Chloroplast

• Site of photosynthesis– Light Energy -> Chemical Energy

• Double-membraned• Stacks of thylakoids

Mitochondria

• Generate ATP from glucose– Generate ____________energy

• Site of cellular respiration• Double membraned—cristae

Mitochondria & Chloroplasts• Unique features:

• Both are energy-related organelles

• Have two membranes

• Have their own DNA

• Reproduce independently of the cell

• Have Ribosomes

Endosymbiotic (Endosymbiont)Theory

• What does endo mean?

• What is symbiosis?

Endosymbiotic Theory

• If mitochondria and chloroplasts originally came from independent prokaryotes, what would be true of their DNA? (What do you know about the DNA of prokaryotes compared to Eukaryotes?)

Endosymbiotic Theory

NucleusEndoplasmicreticulum

Nuclear envelope

Ancestor ofeukaryotic cells(host cell)

Engulfing of oxygen-using nonphotosyntheticprokaryote, whichbecomes a mitochondrion

Mitochondrion

Nonphotosyntheticeukaryote

Mitochondrion

At leastone cell

Photosynthetic eukaryote

Engulfing ofphotosyntheticprokaryote

Chloroplast

Figure 6.16

The cytoskeleton is a network of fibers that organizes structures

and activities in the cell• The cytoskeleton is a network of fibers

extending throughout the cytoplasm• It organizes the cell’s structures and activities,

anchoring many organelles• It is composed of three types of molecular

structures– Microtubules– Microfilaments– Intermediate filaments

Figure 6.20

10

m

Roles of the Cytoskeleton: Support and Motility

• The cytoskeleton helps to support the cell and maintain its shape

• It interacts with motor proteins to produce motility

• Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton

• Recent evidence suggests that the cytoskeleton may help regulate biochemical activities

Figure 6.21

ATPVesicle

(a)

Motor protein(ATP powered)

Microtubuleof cytoskeleton

Receptor formotor protein

0.25 m VesiclesMicrotubule

(b)

Components of the Cytoskeleton• Three main types of fibers make up the

cytoskeleton– Microtubules are the thickest of the three

components of the cytoskeleton– Microfilaments, also called actin filaments,

are the thinnest components– Intermediate filaments are fibers with

diameters in a middle range

Column of tubulin dimers

Tubulin dimer

25 nm

Actin subunit

7 nm

Keratin proteins

812 nm

Fibrous subunit (keratinscoiled together)

10 m 10 m 5 m

Table 6.1

Tubulin dimer

25 nm

Column of tubulin dimers

10 m

Table 6.1a

10 m

Actin subunit

7 nm

Table 6.1b

5 m

Keratin proteins

Fibrous subunit (keratinscoiled together)

812 nm

Table 6.1c

Microtubules• Microtubules are hollow rods about 25 nm in

diameter and about 200 nm to 25 microns long• Functions of microtubules

– Shaping the cell– Guiding movement of organelles– Separating chromosomes during cell division

Centrosomes and Centrioles• In many cells, microtubules grow out from

a centrosome near the nucleus• The centrosome is a “microtubule-

organizing center”• In animal cells, the centrosome has a pair

of centrioles, each with nine triplets of microtubules arranged in a ring

Centrosome

Longitudinalsection ofone centriole

Centrioles

Microtubule

0.25 m

Microtubules Cross sectionof the other centriole

Figure 6.22

Cilia & Flagella

• What would be the function in 1 word?

Organelles Organized

Species of the Day

• Resurrection Plant - Selaginella lepidophylla

• This plant belongs to the Lycophyta and has the oldest known lineage of any VASCULAR plant. Being as this plant represents one of the most primitive vascular plants.

Species of the Day

• Resurrection Plant - Selaginella lepidophylla

• Predict how long it would take for this plant to begin to be active again.