Biology Journal 9/4/2015

Explain the science of the joke in this cartoon.

For Today’s Lab…1.Collect your data. 2.Clean up!!!

Clean the scales Wipe down the countertop The potato juice is sticky with

starches, so clean anything it touches!3.Exchange data with your group, or anyone else you need to in order to get a complete set of data.

5 trials for each of the 5 concentrations4.Work on your lab write up. It’s evidence!

In the Third Punic War (it took 3 tries) the Roman Army invaded the city of Carthage in 146 BC. They enslaved or killed everyone there and salted the Earth…

Why salt the Earth?

Biology Journal 11/12/2014

Osmosis

For Today’s Lab…1.Work in groups of 5. Each student in the group does a different % salt solution.2.Share all group data within the group. You should have all % solutions covered.3.Each student set up their own 5 cups. Put your name on it! Put your groups’ cups together (so somebody else can weigh your cups tomorrow if you’re gone)4.Once you have your set up, clean up!5.Once you’ve cleaned up, work on setting up your data tables, and the concluding questions.

Biology Journal 10/14/14

What is the job of the cell membrane? What do you think could happen to a cell if the membrane didn’t do its job?

Biology Journal 10/23/14

This unit has a lot of opposites. Do you know what these terms mean?

Endocytosis vs. Exocytosis

Active transport vs. Passive transport

Hydrophobic vs. Hydrophilic

Biology Journal 10/20/2014

Explain the science of the joke in this cartoon.

Biology Journal 10/21/2014

What are the parts of the cell membrane in this picture? What do these parts do?

Biology Journal 11/11/2014

1.3 Homework Quiz!1. What molecules make up most of the molecules in the cell membrane?

(a)proteins (b) phospholipids (c) receptors (d) RNA

2. Which kinds of cells have a cell membrane?

(a)eukaryotes (b) prokaryotes (c) plants (d) all cells have it

3. What is cholesterol?

4. Draw a picture of a phospholipid molecule and label which end is hydrophobic and hydrophilic

In the potato osmosis lab, what are the independent and dependent variables?

What will the units of our variables be? What will the uncertainty be?

What could be some of the control variables?

1.3 Membrane structure: The structure of biological membranes makes them fluid and dynamic.

Nature of science: Using models as representations of the real world—there are alternative models of membrane structure. Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model.

Understandings:Phospholipids form bilayers in water due to the amphipathic properties (hydrophobic and hydrophilic) of phospholipid molecules.Q: Define the prefix “hydro.” Define the suffixes “phobia” and “philia.” What is a lipid? What is a phosphate? Q: Define the words hydrophobic, hydrophilic, and phospholipid.Membrane proteins are diverse in terms of structure, position in the membrane and function.Cholesterol is a component of animal cell membranes. Q: What kind of molecule is cholesterol? Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.Q: Plant cell membranes don’t contain a high amount of cholesterol, but animal cells do. Why do you think this is?

Applications and skills:Drawing a 2-d model of the fluid mosaic model. A range of membrane proteins should be shown including glycoproteins.Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model.Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model.

Theory of knowledge: The explanation of the structure of the plasma membrane has changed over the years as new evidence and ways of analysis have come to light. Under what circumstances is it important to learn about theories that were later discredited?

Topic 1: Cell Biology (15 hours)

1.3 and 1.4 Membranes and 1.3 and 1.4 Membranes and Cell TransportCell Transport

What are membranes?

Isolate and control what enters/leaves

A site for chemical reactions

Membranes cover the surface of every cell, and also surround most organelles.

What does the What does the prefix prefix ““hydrohydro”” mean?mean?

What is a What is a phobia?phobia?

What is a What is a pedophile?pedophile?

Hydro = “water”Like in hydroelectric dam

phile = “attracted to”Like in audiophile

phobia = “does not like”Like in arachnophobia

Oil and water don’t mix. That’s because oil is what?

The hydrophilic and hydrophobic regions of the phospholipid molecule force it to constantly be in the bi-layer configuration.

Phospholipids arrange themselves so that the hydrophobic parts are not touching water and the hydrophilic parts are touching water.

The hydrophobic parts are not touching water and the hydrophilic parts are touching water.

Also in the membraneReceptors: Often glycoproteins or glycolipids. Serve in cell communication.

Channels / Transporters: Allow certain molecules to pass through

When clear electron micrographs of membranes became available, they appeared to show support for Davson–Danielli’s model, showing a three-layered structure.

2nd cell membrane

This was taken to be the phospholipid bilayer (light) surrounded by two layers of protein (dark).

1st cell membrane

intracellular space (blue)

1 light layer = phospholipid bilayer

2 dark layers: protein

Evidence for the Davson–Danielli model

Later, it was discovered that the light layer represented the phospholipid tails and the dark layers represented the phospholipid heads.

2nd cell membrane

1st cell membrane

intracellular space (blue)

1 light layer = phospholipid tails

2 dark layers: phospholipid heads

Evidence for the Davson–Danielli model

By the end of the 1960s, new evidence cast doubts on the viability of the Davson–Danielli model.

The amount and type of membrane proteins vary greatly between different cells.

It was unclear how the proteins in the model would permit the membrane to change shape without bonds being broken.

Membrane proteins are largely hydrophobic and therefore should not be found where the model positioned them: in the aqueous cytoplasm and extracellular environment.

Problems with the Davson–Danielli model

Evidence from freeze-fracturing

E-face: looking up at outer layer of membrane

This revealed a smooth surface with small bumps sticking out. These were later identified as proteins.

In 1966, biologist Daniel Branton used freeze-fracturing to split cell membranes between the two lipid layers, revealing a 3D view of the surface texture.

P-face: looking down on inner layer of membrane

Applications and skills:Drawing a 2-d model of the fluid mosaic model. A range of membrane proteins should be shown including glycoproteins.

The fluid mosaic model of the phospholipid bilayer

(aka transport protein, aka

channel)

What is diffusion?

Diffusion is the automatic movement of molecules from a high concentration to a low concentration.

Diffusion continues until equilibrium: when all of the concentrations are the same.

Where is the high concentration? Where is the low concentration?

These molecules pass through the cell membrane automatically.

Diffusion requires no energy from the cell.

Diffusion happens because of the random vibration and movement of molecules.

Diffusion happens in any liquid or gas. Why not solids?

Water is 55% to 75% of our body weight*

*People that are more lean have more water than people who have more fat because muscle cells hold more water than fat cells.

What is osmosis?

Osmosis is the diffusion of water.

Water diffuses so much in the bodies of living things that they give it a special name: osmosis.

Why do your fingers get Why do your fingers get wrinkly in a bathtub?wrinkly in a bathtub?

• Think about concentrations and Think about concentrations and osmosis…osmosis…

Protein Channels transport molecules that are too big to fit through the cell membrane.

Passive transport: through a channel; diffusion, it is automaticActive transport: through a channel; against diffusion, requires energy

Which type is in this picture?

At the end of 10 hour, when the bell rings, is At the end of 10 hour, when the bell rings, is that more like active or passive transport? that more like active or passive transport? Why?Why?

A 9 year old kid is told by her parents to put A 9 year old kid is told by her parents to put away all the toys into her toy box. Is that away all the toys into her toy box. Is that more like active or passive transport? Why?more like active or passive transport? Why?

Exocytosis: Packaging up molecules in a vesicle and sending them outside the cell

ItIt’’s kind of like taking out the s kind of like taking out the garbagegarbage

But, not everything released through exocytosis is garbage!

Brain cells release dopamine from vesicles. This makes you feel happy when good things happen…

Endocytosis: Taking in molecules from the outside and packaging them up in a vesicle.

Phagocytosis is when a cell engulfs or “eats” another cell.

A white blood cell engulfing some bacteria. Where might the bacteria be sent to once inside the cell?