BIOL 1030H Lecture Notes - Lecture 1: Membrane Lipids, Phospholipid, Homeostasis

38 views2 pages

bluebadger978

13 May 2018

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Introduction To Cells

●All organisms are made of either a single cell or an ensemble of cells.

Essential features of cells

1. A plasma membrane that creates a distinct boundary separating the cell interior from the

external environment

2. The ability to harness materials and energy from the environment.

3. The ability to store and transmit information

Cells are defined by membranes

●Membranes:

○ Separate the inside of the cell from the outside.

○Surround many internal structures.

Cell membranes are dynamic

●Lipids associated with each other by weak interactions called van der Waals forces

●Membrane lipids are able to move in the membrane (membrane is fluid) • Individual fatty

acid chains are also able to flex or bend.

● Fluidity depends on the fatty acids present (e.g., double bonds, and the length of the

tails).

Saturated vs. Unsaturated

●Saturated fatty acid chains lack double bonds, resulting in phospholipids with a straight

structure that favors tight packing.

●Unsaturated fatty acids have one or more double bonds that introduce kinks in the

phospholipids, reducing the tightness of packing

Plasma membrane

●Characteristics

○ Feature of all cells.

○Defines the cell boundary

○Separates internal contents from the surrounding environment

● Critical for homeostasis

○ Maintenance of a constant internal environment

Unlock document

This preview shows half of the first page of the document.
Unlock all 2 pages and 3 million more documents.

Already have an account? Log in

Document Summary

All organisms are made of either a single cell or an ensemble of cells. A plasma membrane that creates a distinct boundary separating the cell interior from the external environment. The ability to harness materials and energy from the environment. 2: the ability to store and transmit information. Separate the inside of the cell from the outside. Lipids associated with each other by weak interactions called van der waals forces. Membrane lipids are able to move in the membrane (membrane is fluid) individual fatty acid chains are also able to flex or bend. Fluidity depends on the fatty acids present (e. g. , double bonds, and the length of the tails). Saturated fatty acid chains lack double bonds, resulting in phospholipids with a straight structure that favors tight packing. Unsaturated fatty acids have one or more double bonds that introduce kinks in the phospholipids, reducing the tightness of packing. Separates internal contents from the surrounding environment.

Related Questions

1)(a) Saturated fatty acid tails have a different shape than unsaturated fatty acid tails. Briefly explain what this means in terms of chemical bonds.

(b) How does the difference in chemical bonds between saturated and unsaturated fatty acids affect the shape of these molecules.

(c) Cell membranes are made mostly of phospholipids (which contain fatty acids) that must maintain fluidity. What type of phospholipids would be better at maintaining fluidity: saturated phospholipids or unsaturated phospholipids? Explain your answer (and make sure your explanation relates to part b).

The table below shows the percent of each type of phospholipid fatty acid tail found in each type of the grass membranes on Oct. 2 and Dec. 8th. The first column in the table shows the length of the fatty acid tail and the number of double-bonds in the fatty acid. For example the fatty acid â16:0â would be a fatty acid that was 16 carbons long and had 0 double-bonds. The second and third columns show the percent of all phospholipid fatty acids that were of this type. For example, in grass collected on October 2nd, 23.9 % of the phospholipid fatty acids were 16 carbons long and had no double-bonds (16:0 type), and in the grass collected on Dec. 8^th, 21.0 % of the phospholipid fatty acids were 16 carbons long and had no double-bonds (16:0 type).

Fatty Acid composition of Phospholipids	October 2	December 8
Fatty Acid composition of Phospholipids	% of phospholipids	% of phospholipids
16:0	23.9	21.0
16.1	0.4	0.7
18:0	0.8	0.4
18:1	9.6	6.1
18:2	34.4	38.6
18:3	30.2	32.4
20:0	0.7	0.7

A. For each date the grass was collected, calculate the total percent of phospholipid fatty acids that were saturated fatty acids and the total percent of phospholipid fatty acids that were unsaturated fatty acids.

B. Draw a column graph that shows the total percent of phospholipid fatty acids that were saturated for each date that grass was collected and the total percent of phospholipids that were unsaturated for each date that grass were collected.

C. Why are the % of saturated and unsaturated fatty acid tails on the phospholipids of the Oct 2^nd collected grass and the Dec 8^th collected grass not the same? Use your understanding of membrane fluidity to address why these percentages have changed during this time period.

D. During this experiment the concentration of cholesterol found in the membranes of the grass was also measured. On Oct. 2^th the concentration of cholesterol was 1.10 umol/mg and on Dec. 8^th the concentration of cholesterol was 1.22 umol/mg. Why did the concentration of cholesterol change? Use your understanding of membrane fluidity to address why these concentrations have changed during this time period.

37.The major function of the cell wall is

(A) to facilitate cell divison (B) to serve as a diffusion barrier

(E) to serve as an anchor for proteins

38.Penicillin and vancomycin prevent cross-bridge formation between

(A) diaminopimelic acid and D-glutamic acid (B) L-alanine and D-alanine

(E) D-glutamic acid and D-alanine

39.An outer membrane is found in

(A) all cells (B) all prokaryotes

(E) all Gram-positive bacteria

40.The complex of DNA polymerase with its accessory components is called

(A) nucleoid (B) nucleus

(E) setpum

41.Which of the following is the bacterial homolog of tubulin?

(A) FtsZ (B) MreB

(E) MinD

42.Which of the following is an actin homolog that helps maintain cell shape?

(A) FtsZ (B) MreB

(E) MinD

43.Which of the following is least involved in photosynthesis?

(A) phycobilisomes (B) thylakoids

(E) stalks

44.Capsule is composed of

(A) nucleic acids (B) lipoproteins

(E) murein

45.Pili and fimbriae are composed of

(A) nucleic acids (B) lipopolysaccharides

(E) amino acids

46.Which of the following subcellular structures is involved in adherence?

(A) gas vesicles (B) storage granules

(E) phycobilisomes

47.As temperatures drop, membrane fluidity decreases. Which of the following changes to phospholipids will help maintain correct bacterial membrane fluidity under cold temperatures?

(A) Formation of lipid monolayer.

(B) An increase in the length of the fatty acid tails.

(D) An increase in saturated fatty acids.

(E) A switch from ester linkages between fatty acids and glycerol to ether linkages.

48.Which of the following statements regarding chemotaxis is true?

(A) Attractants cause counterclockwise rotation of the flagella that makes the cells tumble

(B) Attractants cause clockwise rotation of the flagella that makes the cells run

(D) Attractants cause clockwise rotation of the flagella that makes the cells tumble

(E) None of the above is true.

49.With 5 g of NaCl available, how much water is needed to make a solution at a concentration of 10 mg/mL?

(A) 0.5 mL (B) 5 mL

(E) 5 L

50.How much of 1 M glucose stock solution is needed to make a 500-mL solution containing 25 mM glucose?

(A) 12.5 Î¼L (B) 125 Î¼L

(E) 1.25 L

BIOL 1030H Lecture Notes - Lecture 1: Membrane Lipids, Phospholipid, Homeostasis

Document Summary

Get access

Related Documents

BIOL 1030H Lecture Notes - Lecture 1: Osmosis, Fluid Mosaic Model, Homeostasis

BIOA01H3 Lecture Notes - Lecture 8: Phospholipid, Covalent Bond

BIOA01H3 Lecture Notes - Lecture 2: Endoplasmic Reticulum, Cell Membrane, Nuclear Membrane

Related Questions