Biological membranes

Fluid mosaic model

Theory of cell membrane structure with proteins embedded in a sea of phospholipids

Explain why some cells don’t take up a solution during active transport

EQ

Cells are dead

No ATP to take up stain

Describe the effect of high temperatures on the structure of the yeast cell membranes

EQ

Phospholipids vibrate more

More gaps in membrane

Bilayer becomes more fluid

Describe the arrangement and functions of two named components of a cell surface membrane

EQ

Proteins for facilitated diffusion

Barrier to polar and large molecules

What is meant by cell signalling

EQ

Communication between cells

Explain how cell surface membranes contribute to the process of cell signalling

EQ

Exocytosis

Glycoproteins have receptors

Shape of receptors adn signal are complementary

Cell surface membrane allows century of some signal molecules

State one role of membranes inside cells

EQ

Site for enzyme attachment

List 3 components of cell surface membrane

EQ

Phospholipids

Proteins

Cholesterol

Active transport definition

EQ

Movement of molecules from a low to high concentration

ATP required

State 2 examples of active transport in cells

EQ

Ions into root hair cells

H+ ions out of companion cells

What mechanism is involved in this

Calcium ions entering a nerve cell down a concentration gradient

Facilitated diffusion

Describe the route that water molecules take through the cell surface membrane

EQ

Between phospholipids

Through aquaporins

Explain why plant cells don’t burst when they are left in pure water

EQ

Cell wall provides strength

Explain why facilitated diffusion requires no energy

EQ

Uses only the kinetic energy of a particle

Down concentration gradient

Via protein channels

Explain why glucose cannot pass through a membrane by simple diffusion

EQ

Too large

Phospholipids act as a barrier

State and explalin how one property of the phospholipid bilayer contributes to the stability of the membrane

EQ

Hydrophobic fatty acid tails point inward to form bilayer

Outline the roles of membranes within cells

EQ

Compartmentalisation

Site of chemical reactions

Explain the role of the membrane in the rough endoplasmic reticulum

Hold ribosomes

Compartmentalisation

Where do the independent variable and the dependant variable go on a table?

EQ

IV first column

DV second column

Suggest and explain why a low PH might cause the red pigment to leak out the beetroot cells

EQ

Denatures proteins

Membrane permeability is reduced

Outline how students could modify their investigation to get a more accurate value for the pH at which the red pigment begins to leak out the beetroot cells.

EQ

Use PH buffer with range with smaller intervals

Test more values between x and y

Explain why progesterone can move across membranes

EQ

Non polar so diffuses through phospholipid bilayer

What 3 molecules have up ATP

Adenine

Ribose

Phosphate groups

How does the fluid mosaic model describe the structure of a plasma membrane.

EQ

Phospholipid bilayer

Hydrophobic tails inwards

Hydrophilic heads outwards

Explain how the structure of phospholipid molecules allows for the formation of plasma membranes

EQ

Hydrophilic phosphate heads facing outwards

Hydrophobic fatty acid tails point inwards

Phospholipid bilayer

Describe the structure of the rough endoplasmic reticulum
EQ

Phospholipid bilayer

Covered with ribosomes

Cisternae

For which macromolecules foes a plant need both nitrogen andd phosphorous

EQ

DNA

How would flooding affect the soils water potential

EQ

Lower water potential

What type of graph is needle for absorbance and concentration of ethanol axis

Line graph

Explain how carrying out replicates would improve an investigation

EQ

Calculate mean

Improvement repeatability

As temperature increases the absorbance increases

Pigment leaves the cell

Temperature doesn’t increase much from 0 to 30

How would using smaller intervals improve an investigation

EQ

More accurate

What do you have to remember when a question asks why something can pass through a membrane

EQ

Can DIFFUSE through phospholipid bilayer

How do you make a practical more precise

EQ

Repeats to calculate a mean

Smaller intervals

What should you include in a hypothesis?

Anomalies

General trend of graph

How do you increase the thickness of a Viking tube?

EQ

Use 2 visiting tubes

What is the role of a universal indicator?

EQ

Measure end point

Where does the DV and IV go on a graph?

EQ

IV-x axis

DV-y axis

How can you improve the VALIDITY of data?

EQ

Repeats

Smaller intervals

One control variable-most prominent

How does using smaller intervals increase the validity of data?

EQ

Allows trend to be identified more clearly

Effect of boiling on a plasma membrane so…

EQ

Damages plasma membrane

No osmosis

how you can modify a procedure to improve accuracy

EQ

Test smaller intervals of ——-between — and ——

Explain the effect of ethanol on a plasma membrane

EQ

Dissolves phospholipid bilayer

No osmosis

How can students reduce the uncertainty of their data

EQ

Use more accurate apparatus

Explain the importance of osmosis in plant support

EQ

Water enters vacuole

Pressure against cell wall

Turgid cells support plant cells

Uncertainty of a ruler

2 uncertainties

So double value they give you

HIGHER WATER POTENTIAL

HIGHER SOLUTE POTENTIAL

If a questions asks you to describe two solutions compositions

Suggest a practical error in an osmosis experiment that could have caused an anomaly

EQ

Inadequate drying

More mass of one than other different pieces

How do you use data to determine the water potential of a potato

Data-concentration and change in mass

EQ

No change in mass when water potential of solution is identical to water potential of potato

Analysis of data

Plot graph of concentration against sucrose and find where intercepts x acis

What is a limitation of a practical procedure in an investigation of changing surface area of a potato cube?

EQ

Inconsistency of surface area-difficult to cut smaller cubes accurately

Why is rate of movement of molecules from a plasma membrane to the center of living cells often greater than seen in procedures

EQ

Involvement of cytoskeleton

What other factor will change if you change the concentration of sucrose solutions?

EQ

Water potential

Why do you use line graphs

EQ

Water bath

Timer

What is dialysis tubing

Partially permeable membrane like tube

Outline the method that the students would use to carry out an investigation into the effect of temperature on the diffusion rate in their model cells

EQ

Add 25cm3 of glucose solution to the dialysis tubing

Knot the tubing

Place in a water bath and remove the sample after 10 minutes

Add Benedict’s to test for glucose

Repeat for different temperatures

Evaluate questions remember:

Refer to control variables

Refer to why data is correct

Refer to why data is incorrect

Refer to any reasons why the data would be incorrect-COMMON EXAMPLE IS SAMPLE SIZE

State how hydrogen peroxide could affect the plasma membrane

EQ

Changes fluidity of the membrane

Denatures proteins

Beetroot investigation of temperature and absorbency control variables

EQ

Shape of beetroot

Volume of ethanol

Type of beetroot

Why do you have to control the variety of the beetroot in experiment?

EQ

To control pigment concentration as different beetroots have different water potentials

Formula for serial dilutions

EQ

Concentration 1 x volume 1 = concentration 2 x volume 2

Rearrange for different values

What is the volume 2 in serial dilution formula?

EQ

Total volume that you need to make each serial dilution to

What is the concentration 2 in the serial dilution formula

EQ

Concentration you are trying to make for the next serial dilution

EQ

A

EQ

C

How does frozen beetroot affect the percentage absorbance and why?

EQ

Percentage absorbance is higher

Ice damages membrane

Where do the labels go on a graph of percentage absorbance -colorimeter experiment

EQ-sort of

Concentration of substance on y axis

Absorbance on x axis

Explain the shape of this graph

EQ-beetroot experiment

Ethanol increases the permeability of the membrane

Levels off as no more pigment is released

Effect of cholesterol on a membrane at higher temperatures

EQ

Decreases fluidity

EQ

Solution lowers water potential of soil

Water moves out of cells by osmosis

How are mineral ions transported into a plant?

Where are they transported to?

EQ

Active transport of minerals into the xylem

What does a proportional graph mean?

EQ-sort of

As one value increases the other increases by the same factor

Glycolipid

Phospholipid chain with a. Chain of carbohydrate molecules attached

What is an intrinsic protein

Integral protein

Glycoprotein

Protein with a chain of carbohydrate molecules attached

Are phosphate groups polar

Yes

Explain the difference between the mean results obtained at the 0.0 mol dm-3 and 0.8 mol dm-3 sucrose concentrations

EQ

Gain in mass at 0.01mol due to higher water potential inside cells

Mean loss at 0.8 due to lower water potential than inside cells

How do anomalies affect the precision of data

EQ

Reduces repeatability of the data

Increases standard deviation of data

Plasma membrane

Cell surface membrane

What do you have to remember when doing serial dilutions

EQ

Mix the contents after adding water and solution

Describe the plasmas membrane

Partially permeable

If a question asks how you compare 2 sets of data how do you do this

EQ

Draw 2 graphs

Draw a line of best fit for both graphs

Analyse

Roles of membranes at surface of cells

Separates cells components from external environment

Regulates transport of materials in and out of cell

CELL SIGNALLING

site of chemical reactions

B

Find surface area to volume ratio

Greatest surface area to volume ratio diffuses the fastest

C

D

Which does cell to cell signalling:

Intracellular membranes

Extracellular membranes

Extracellular only

What is the effect of cholesterol dependant on

EQ

Temperature

At lower temperatures how does cholesterol affect the fluidity of a membrane

EQ

Increases fluidity

What goes on the axis on a percentage absorbance temperature graph for beetroot experiment?

EQ

Percentage absorbance on x axis

Temperature on y axis

Where are receptors on steroid hormones and why are they there?

EQ

Inside cells as steroids can cross the plasma membrane

How do you calculate percentage uncertainty with these 2 values

Mass uncertainty

EQ

Uncertainty per instrument

Divided by

Change in mass

Multiplied by 100

Why do plasma membranes have antigens at the surface of cells

So that immune system recognises the cell as itself

Purpose of plasma membranes inside cells

Chloroplasts-reactions of photosynthesis

Small intestine-digestive enzymes on plasma membrane

Why are there digestive enzymes on the plasma membrane of epithelial cells in the small intestine

Catalyse breakdown of sugars

What type of proteins are the channel and carrier proteins

Integral proteins

Why are glycocalyx on the outside of the membrane

Very hydrophilic and attract water with dissolved solutes helps cells interact with water environment

Glycocalyx definition

Carbohydrate molecules