Chapter 4 - Transport Across Cell Membranes

Question 1

List the structures in the cell surface membrane:
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Answer 1

• cholesterol
• Chanel
• hydrophobic tail
• hydrophilic head
• Chanel protein molecule
• glycoprotein
• glycolipid
• protein molecules

Question 2

Define fluid Mosaic

Answer 2

Fluid is an individual phospholipid molecule that can move

Mosaic is a protein embedded in the phospholipid bilayer varieting in shape, size and pattern

Question 3

Describe cholesterol

Answer 3

• add strength
• hydrophobic
• reduce lateral movement
• membrane less fluid
• prevents leakage of water

Question 4

Describe hydrophobic tails and hydrophilic head

Answer 4

• repelled by water

* attracts water

Question 5

Describe phospholipid bilayer

Answer 5

• allows lipid – soluble substances to leave or into the cell
• Prevents water soluble entering and leaving
• Makes membrane flexible and self-healing

Question 6

Described channel protein molecules

Answer 6

• Allows water soluble ions to diffuse across membrane

* intrinic - active transport

Question 7

What three things are cell membrane made out of?

Answer 7

Proteins, lipids and carbohydrates

Question 8

Describe glycoprotein

Answer 8

• cell recognition
• carbohydrates + proteins
• receptor sites for proteins
• help attach cellaring form tissues

Question 9

What does the phospholipid stop from entering?

Answer 9

Charged and large

Question 10

What can pass through the bilayer?

Answer 10

Small and uncharged molecules

Question 11

Describe a glycolipid

Answer 11

• made of carbohydrate covalently bonded
• cell-surface receptor
• helps maintain stability
• help cells attach to form tissue

Question 12

Describe protein molecules

Answer 12

• mechanical support

* cell receptor for molecules

Question 13

How does a channel protein work?

Answer 13

Carrier proteins bind to ions or large molecules carrying them across against the concentration gradient.

Question 14

Explain why diffusion is higher at higher temperatures?

Answer 14

At a higher temperature, the kinetic energy has increased causing the rate of diffusion to increase as the more collisions

Question 15

What is diffusion?

Answer 15

• high to low concentration gradient

* no metabolic energy = passive transport

Question 16

Define Fick’s Law

Answer 16

• rate of diffusion in a given direction actors an exchange surface
• rate of diffusion = (surface x difference in concentration) / length of diffusion path

Question 17

What is facilitated diffusion?

Answer 17

• uses carrier/channel proteins
• high to low
• passive transport = no ATP used
• allows large and uncharged molecules

Question 18

What is osmosis?

Answer 18

• high to low
• water potential in the pressure created from water molecules
• water goes from a high water potential to a region of low (more negative) water potential

Question 19

What has the highest water potential?

Answer 19

• pure water

* 0kPa

Question 20

What is hypertonic?

Answer 20

Where water is drawn out of the cell to a solution which is more negative - cell swirls up

Question 21

What is isotonic?

Answer 21

Where there is an equal water potential

Question 22

What is hypotonic?

Answer 22

Where, the water drawn into the cell due to the solution having a lower negative potential than the cell - cell bursts

Question 23

What is active transport?

Answer 23

• transfers large and charged molecules
• phosphate group from the molecule ATP attaches to the carrier protein causing it to change shape
• low to high
• ATP from aerobic respiration (mitochondria + oxygen)

Question 24

What kind of transport across membranes which requires ATP energy?

Answer 24

Active transport

Question 25

Type of protein which moves molecules from one side of the membrane to another

Answer 25

Carrier protein

Question 26

Process describing the net movement of molecules from high to low concentration

Answer 26

Diffusion

Question 27

Bulk movement of substances into a cell by means of formation of a vesicle

Answer 27

Endocytosis

Question 28

Way in which substances and moves from the cell within a vesicle which fuses with the plasma membrane

Answer 28

Exocytosis

Question 29

Type of diffusion which requires carrier protein molecules to move molecules across the cell membrane

Answer 29

Facilitated diffusion

Question 30

Protein bound to polysaccharides

Answer 30

Glycoprotein

Question 31

A molecule which will mix with water but not with fat

Answer 31

Hydrophilic

Question 32

A molecule which will mix with fate but not with water

Answer 32

Hydrophobic

Question 33

These are used to increase the surface area of a cell to facilitate diffusion

Answer 33

Microvillie

Question 34

Describes a cell when water has left it causing the cytoplasm to shrink away from the cell wall

Answer 34

Plasmolyed

Question 35

Describe A cell which is pumped up full of water

Answer 35

Turgid

Question 36

What is the job of amylase and where is this enzyme produced?

Answer 36

* starch to sugar | * salivary glands/small intestine/pancreas

Question 37

What is the job of maltase and where is this enzyme produced?

Answer 37

* Maltose to glucose | * small intestine

Question 38

What is the job of sucrase and where is this enzyme produced?

Answer 38

* sucrose to fructose and glucose | * small intestine

Question 39

What is the job of lactase and where is this enzyme produced?

Answer 39

* lactose to galactose + glucose | * small intestine

Question 40

What is the job of protease and where is this enzyme produced?

Answer 40

* Proteins to amino acids | * stomach, small intestine and pancreases

Question 41

What is the job of lipase and where is this enzyme produced?

Answer 41

* lipids to fatty acid + glycerol | * small intestine, pancreases

Question 42

What is the small intestine adaptation for efficient absorption?

Answer 42

* microvilli * protein carrier/channels * diffusion/facilitated diffusion * active transport (co-transport) * length of diffusion pathway * capillary network

Question 43

What is co-transport?

Answer 43

Two molecules are actively transported or facilitated diffusion

Question 44

Describe co–transport

Answer 44

1) Na+ ions actively transport (using ATP) out of cell into blood 2) therefor low concentration of Na+ inside cell 3) therefore Na+ diffuse in from lumen of gut bringing glucose with it

Question 45

Explain how the transport of sodium ions is involved in the absorption of glucose by epithelial cells?

Answer 45

* Co-transport * sodium leaves the epithelial cells by active transport whilst a K+ enters * carries away by capillary network causing slow concentration of Na+ * diffused from a high to low concentration * glucose and Na+ enter at the same time

Question 46

Explain why the diffusion of chloride ions involve a membrane protein and the diffusion of oxygen does not

Answer 46

* diffusion of chloride ions involve carrier proteins * charges molecule cannot diffuse a cross bilayer * oxygen does not need membrane protein as small and uncharged can diffuse across the bilayer