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Science 10 AP: Biology > Cell Membranes > Flashcards

Cell Membranes Flashcards

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1
Q

What are the four functions of the cell membrane?

A
  1. Transport raw materials into the cell
  2. Transport manufactures products and wastes out of the cell
  3. Prevent unwanted matter from entering the cell
  4. Prevent the escape of matter needed to perform cellular functions
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2
Q

What are the three structural parts of the cell membrane?

A
  1. Phospholipid bilayer
  2. Proteins
  3. Cholesterol
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3
Q

What is the phospholipid bilayer and its properties?

A

It consists of a hydrophilic (water-loving) polar head. This is made of phosphates.

It has two tails that are hydrophobic (water-fearing) and non-polar. These are lipids.

As a result, they’ll arrange two of the tails touching the other two tails. It is an excellent barrier as extracellular fluid and cytoplasm are mostly water. It protects both water and non-water things.

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4
Q

What are proteins and their properties?

A

These are embedded through the membrane and are “potato lumps/blobs”.

They:
*a) move substances across the membrane
b) carry out chemical reactions (act as enzymes)
c) some have “marker” molecules (carbohydrate chains) on the surface to allow cells to recognize each other
d) allow messenger molecules (hormones) to attach
e) assist in cell-to-cell communication and help control cell function

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5
Q

Proteins in the cell membrane can be split into two types. What are they?

A
  • Peripheral proteins are partially embedded inside or on the outside surface. You can only see on one side, not on the other. For everything else: enzyme, markers, attach to hormones, cell-to-cell communication
  • Integral proteins extend through the entire bilayer and project from both sides. They move things in and out since it goes all the way through.
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6
Q

What are the two parts of the fluid-mosaic model?

A

Cell membrane molecules are in constant motion (drifting past each other). This allows the cell membrane to be:
a) membrane flexibility
b) cells ability to change shape

  • Mosaic refers to the pattern made by the proteins and phospholipid heads.
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7
Q

What is chloestrol and what is its function?

A

Steroid (type of carbon-containing) molecule that first in between phospholipids—mostly the lipid part (the tail)—and ensures the membrane stays fluid.

It is good because we do not want it too packed.

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8
Q

Which type of lipid (fat) is “bendy” and which is “straight”?

A

Saturated lipid: Straight
Unsaturated lipid: bendy

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9
Q

What are the two functions of the cell membrane?

A
  1. Biological barrier
  2. Selective filter
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10
Q

How does the cell membrane act as a biological barrier?

A
  • A cell membrane prevents many materials from entering the cell. Examples include salts, proteins, viruses/prions, sugars, ions, and bacteria.
  • Most organelles are surrounded by membranes with the same structure as a cell membrane (except prokaryotes which have no inner membranes. An example is a vesicle.
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11
Q

What is apoptosis?

A

When a lysosome bursts and releases its digestive enzymes into the cell, it results in cell destruction. It is programmed cell suicide.

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12
Q

How does the cell membrane act as a selective filter?

A

Cell membranes are selectively permeable, allowing some materials to cross while excluding others. They can select:
a) by particle size
- small enough to enter (O2, CO2, H2O)
- too large to cross (sugars)
b) particular materials to transport across
- proteins bind to chemicals based on shape, size, or charge

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13
Q

Define the three “levels of permeability”.

A

Impermeable = none gets through
Semi-permeable = some things get through
Permeable = all gets through

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14
Q

What are the three “causes” of the transport across cell membranes?

A

1) Selective Transport = Movement of only certain substances across the cell membrane
2) Particle Model of Matter = All matter is made up of tiny particles
3) Brownian Motion = In a liquid or gas, all the particles are in constant, random motion. This is why they go across the cell membrane.

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15
Q

What is the concentration gradient?

A

The difference in concentration between two areas for any given molecule produces a gradient, or path of movement, in which molecules move toward areas where the concentration of particles is lower.
- Molecules always move down the concentration gradient
- “Difference in concentration”

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16
Q

What is equilibrium?

A

A state at which molecules are evenly distributed (the concentration is equal throughout the medium)
- Molecules continue moving, but equilibrium is maintained
- Concentration stays the same

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17
Q

What are the two types of transport across membranes?

A

1) Passive Transport
2) Active Transport

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18
Q

Explain the three types of Passive Transport (transport #1) and the general definition.

A

Movement across cell membranes without an input of energy (no ATP).

1) (Simple) Diffusion
2) Osmosis
3) Facilitated DIffusion

Requires only heat energy.

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19
Q

How can molecules move without ATP then?

A
  • Brownian Motion
  • Concentration Gradient
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20
Q

What is (simple) diffusion? (first type of passive transport)

A

The net movement of particles from an area of high concentration to an area of low concentration.
* down the concentration gradient
* no energy is expended
* does not only necessarily only apply to membranes
- In a cell, very small particles can cross the membrane by moving between the phospholipid molecules
- Small, uncharged, particles, especially gases
ex: O2 and CO2

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21
Q

Why does oxygen diffusing into the cell never reach equilibrium?

A

We use it up (cellular respiration) -> CO2

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22
Q

Describe the concentration gradient of carbon dioxide across the cell membrane.

A

stuff can move
High (mitochondria) -> Low
Inside -> Outside

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23
Q

What is the formula for concentration?

A

Stuff / Volume (in our case, water)

stuff per volume.

24
Q

Predict the solute diffusion.

5% NaCl | 10% Glucose

A

2.5% NaCl | 2.5% NaCl
5% Gluc. | 5% Glucose

25
Q

What is osmosis (the second type of passive transport)?

A

In a case where the stuff can’t move, we move the H2O (the volume)

The diffusion of water molecules across a membrane. Water molecules move from where they are highly concentrated to where they are less concentrated.

  • Solutions are described in terms of their concentration relative to another solution.
  • Concentration of solutions is given based on SOLUTE amount. Not the amount of water. LOTS SOLUTE = LESS WATER.
26
Q

What are the description words of osmosis?

A

These are comparison words like shorter and taller.

  • Hypotonic
  • Hypertonic
  • Isotonic
27
Q

What are hypotonic solutions?

A

Lower concentration of solute (more water)

A hypotonic solution [outside of the cell] has a lower concentration of solute inside the cell.

Water is more present outside the cell and water will move into the cell. The cell swells.

28
Q

What are hypertonic solutions?

A

Higher concentration of solute (less water)

A hypertonic solution [outside of the cell] has a higher concentration of solute compared to inside the cell.

Water is more present inside the cell and water will move out of the cell. The cell shrinks.

29
Q

What is the osmosis rule?

A

If the solute can’t move, water always moves to the hypertonic solution until it reaches equilibrium/isotonic.

30
Q

What is an isotonic solution?

A

The same concentration of solute on both sides.

Isotonic solutions have the same concentration of solute on both sides of the cell membrane.

Equilibrium has been reached. Water moves in an out at the same rate.

31
Q

The cell is 5% salt. The outside solution is 10% salt. Which way will the water move?

A

The water will move out of the cell. The cell is hypotonic compared to the solution.

The outside solution is hypertonic.

32
Q

The cell is 90% water. The outside solution is 100% water. Which way will the water move?

A

The cell is 10% solute. The outside solution is 0% solute.

The water will move into the cell. The cell is hypertonic compared to the solution.

The outside solution is hypotonic.

33
Q

What is facilitated diffusion (the third type of passive transport)?

A

Diffusion of molecules across the cell membrane using transport proteins.

This is necessary for glucose, ions (charged), and other substances that cannot cross the membrane by simple diffusion. Still, no input energy.

Water sometimes also needs help, so osmosis is kind of facilitated.

34
Q

What are transport proteins and what are the two types?

A

Transport proteins have 3D shapes that make them highly selective, recognizing atoms or molecules by shape, size, or charge.

a) Carrier proteins
b) Channel proteins

35
Q

Explain carrier proteins.

A

Facilitate the diffusion of glucose across the membrane.

Glucose fits into a groove on the carrier; the protein changes shape and glucose is released into the cell on the other side of the membrane. “Keyhole”.

They recognize size and shape

36
Q

Explain channel proteins.

A

Have tunnel-like pores filled with water that allow charged ions into and out of the cell.

Channel proteins are hollow to allow tiny ions through.

They recognize small and charged.

37
Q

What is electrochemical attraction (extra fourth type)?

A

Facilitated diffusion of ions. Charged particles through pores.

38
Q

Explain active transport (transport #2) and the two types.

A

Transport that requires input energy (ATP).

  1. Active Transport (uhh…)
  2. Bulk Transport

Requies chemical energy and heat.

39
Q

What is active transport (as a part of active transport) (A.T. #1)?

A

Movement of molecules and ions against the concentration gradient.
- Requires ATP energy and carrier proteins to pump these molecules from an area of low solute concentration to an area of high solute concentration.
- Used to accumulate nutrients, or remove toxic materials or wastes.

*Most cells use 40% of their energy on active transport; kidney cells use 90% of their energy on using active transport to filter wastes out of the blood.

Essentially same as carrier protein’s process except with ATP and a pump.

40
Q

What is bulk transport? (A.T. #2) What are the two types of bulk transport?

A

The use of vesicles to facilitate the movement of substances that are too large (groups) to enter or exit the cell via transport proteins. Very often requires ATP!

a) Endocytosis
b) Exocytosis
c) Receptor-Mediated

41
Q

What is endocytosis? (B.T. #1)

A

(Into cell) The cell membrane forms a pocket around the material to be transported, then either pinches off as a vesicle (transport) or vacuole (storage). For ingested material.

When a new vesicle enters the cytoplasm, it may fuse with a lysosome and the enzymes digest the materials.

42
Q

What is phagocytosis? (endocytosis section 1)

A

When cells “eat” by taking in large particles or other cells.

Large chunks.

43
Q

What is pinocytosis? (endocytosis section 2)

A

When cells “drink” by taking in droplets of fluids.

Water and small ions.

44
Q

What is receptor-mediated endocytosis (R.M.E.)? (endocytosis section 3)

A

Receptors (proteins), like antennae, detect specific compounds or cells and bind with them, triggering endocytosis.

Examples of molecules entering by R.M.E. include cholesterol and HIV.

45
Q

What is exocytosis? (B.T. #2)*

A

(Out of cell) The reverse of endocytosis, whereby the membrane of vesicles or vacuoles fuses with the cell membrane and stored contents are expelled from the cell.

These materials may include water, enzymes, or hormones.

46
Q

Give three examples of membranes at work.

A

1) Reverse osmosis
2) Kidney dialysis
3) Controlled delivery of medications

47
Q

How does reverse osmosis work?

A
  • Water purification
  • Uses pressure to force contaminated water through a membrane with fine pores that will not allow bacteria, salts, and other dissolved molecules through, resulting in water with fewer impurities
48
Q

How does kidney dialysis work?

A
  • Filters toxic wastes that accumulate in the blood while retaining necessary protein, glucose, amino acids, and ions.
    The patient’s blood is pumped through dialysis tubing, a synthetic, semi-permeable membrane. When immersed in a salt solution, needed salts do not diffuse, but wastes, which are hypertonic to the dialysate (salt solution), diffuse out of the blood.
49
Q

How does controlled delivery of medications work?

A

a) Medications can be placed in a flat transdermal patch (over the skin) that sticks to the skin. A semi-permeable membrane lining the inner surface allows drugs to diffuse out of the patch at a slow, constant, rate.

Examples include nicotine, motion sickness drugs, pain relievers, hormones (birth control)

b) Liposomes are artificial vesicles that can safely transport medications from one part of the body to another.
- used to transport anti-cancer medications to tumours in cancer patients
- liposomes, coated with the gene needed to cure cystic fibrosis, are sprayed into the patient’s nostrils.

50
Q

Why could a human-amoeba never exist?

A
  1. Substances could diffuse into the cell in less than a second, but would take more than a week to reach the center of the cell
  2. It would have a very low surface area-to-volume ratio, making it difficult for adequate amounts of oxygen to diffuse in

SA = 6l^2, V = l^3

51
Q

Explain cell size and function.

A

Particles entering the cell must diffuse through the cytoplasm down concentration gradients to be used. The downfall is that this takes time.

Concentration gradients within a cell are much smaller than concentration gradients across the cell membrane.

Larger concentration gradients = faster diffusion

To maximize efficiency, cells must have a high surface area-to-volume ratio. This is the relative magnitude of the cell’s surface area to its volume.

So, there is a problem if the cell becomes too big.

SA = 6l^2, V = l^3
SA is absorption
V is what it needs to support

52
Q

What do scientists believe was the reason that the Paleozoic Era could sustain the existence of giant insects?

A

They have no circulatory system, and the greater the concentration gradient, the deeper O2 can diffuse.

53
Q

Explain Surface Area-to-Volume Ratio.

A

As a cell grows, volume increases faster than surface area.

SA = 6l^2, V = l^3

SA = cell membrane (transport potential)
V = everything else (organelles) (energy-resource needs)

If a cell doubled in size, it would require 8 times as many nutrients and produce 8 times as much waste, but it’s surface area would only have increased 4 times.

Result:
1. Not enough SA for oxygen, nutrient, and waste exchange
2. Cell would starve
3. Cell would be poisoned from a buildup of toxic waste

54
Q

Give two examples of cell shapes that increase SA-V ratios.

A
  • Microvilli in the digestive system for absorbing nutrients from food
  • Plan root hairs absorbing nutrients
55
Q

How do some organisms function at enormous sizes?

A

They are multicellular and grow by adding more cells instead of growing larger cells. This results in rapid diffusion within cells and cell specialization.

56
Q

What is cell specialization?

A

In multicellular organisms, cells are organized into tissues that do specific jobs.

57
Q

What structure carries out RME?

A

Proteins

Science 10 AP: Biology (8 decks)

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