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Biology > Cell Function > Flashcards

Cell Function Flashcards

Module 1

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1
Q

Why there are movements in and out of cells?

A
  • Because substances required by cells for their functioning need to move into the internal environment of cells; and waste substances and cellular products need to pass out of cells into the external environement.
  • These substance move from the internal environment to the external environment by passing through cell membrane.
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2
Q

The permeability of a cell membrane to a molecule depends on which characteristics of molecules:

A
  • Size
  • Electrical charge
  • Lipid solubility
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3
Q

Definition of hypertonic environment

A

Hypertonic environment (solutions with much more salty) when compared to external:
+ Higher concentration of soluble particles
+ Lower concentration of water

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4
Q

What happen to the cell with external environment is hypertonic?

A

They will be shrinked:
- Soluble molecules cannot pass membrane to reach equilibrium but water molecules can
- Water outside are obstructed to pass the membrane, but water inside do not
=> water will begin rushing out of the cell

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5
Q

Definition of hypotonic environment

A
  • Much more watery:
    + Higher concentrarion of water
    + Lower concentration of salty
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6
Q

What happen to the cell with external environment is hypertonic

A
  • More water will rush in easy and aren’t obstructed by solute particles.
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7
Q

What is concentration gradient?

A
  • The difference in concentration between two planes
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8
Q

Outline factors that affect the rate of diffusion.

A
  • Concentration gradient
  • Temperature (higher temperature, more energy to diffuse quicker)
  • Surface area
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9
Q

Definition of diffusion

A
  • Diffusion is the movement of substances from a region of high concentration to a region of low concentration, until equilibrium is reached
  • Diffusion is also described as movement of a substance down a concentration gradient.
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10
Q

Why diffusion is considered as a passive transport?

A

Because this movement happens spontaneously without the use of energy

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11
Q

Which direction do the particles pass through the cell membrane?

A

From the region of higher concentration to the region of lower concentration.

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12
Q

Definition of osmosis

A

Osmosis is the diffusion of water. It is the movement of water from a high concentration to a low concentration. (Passive transport)

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13
Q

What are limitations of diffusion through cell membrane

A
  • Large molecules and charged particles often cannot diffuse across a cell membrane.
  • No matter how large the concentration gradient is, these substances will not diffusion due to their sizes.
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14
Q

Definition of facilitated diffusion

A
  • Facilitated diffusion is a form of passive transport
  • It is a diffusion of a substance using a channel or carrier protein.
  • A channel protein forms a channel, or canal, across the cell membrane. Channels allow some charged particles to diffuse across the membrane. This is how water diffuses across a cell membrane. Channels can transport one or more different substances.
  • Carrier proteins form a passage across the cell membrane like channel proteins. Carrier proteins help some large substances diffuse across the membrane (eg. glucose). Carrier proteins are more selective than channels, only transports one specific substance.
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15
Q

What is tonicity?

A

Tonicity is a measure to compare the concentration in terms of the solute, not the solvent.
- Hypertonic solution (more solute than other solutions)
- Hypotonic solution (less solute than other solutions)
- Isotonic (same concentration as another solution)

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16
Q

What happen to cells’ shape with cell wall when put in hypotonic or hypertonic solutions

A
  • The water still moving in or out of cell put the cell wall is rigid. Hence, it does not shrink when water leaves the cells and it does not burst when water enters the cell.
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17
Q

What happen to the cell membrane of plant cell when put it in hypertonic solution?

A

The cell membrane shrinks (as the cell wall is rigid). This is called plasmolysis.

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18
Q

Definition of osmotic pressure

A
  • The concentration of dissolved substances in a cell gives the cell a certain osmotic pressure.
  • Osmotic pressure is the force, or pressure, exerted by the ‘cell solution’ that prevents water flow into the cell.
  • In order words, osmotic pressure resists osmosis of water.
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19
Q

What happen to the cell membrane of plant cell when put it in hypertonic solution?

A

The cell membrane is caused to push up against the cell wall. It puts pressure on the cell wall. This pressure is called turgor pressure.

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20
Q

What is osmoregulation?

A

When osmotic pressure in a cell is not enough to resist osmosis. Cells try to regulate their osmosis pressure. This is called osmoregulation.
- This is a homeostatis mechanism. I.e. it is a mechanism that attempts to keep balance in organism.

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21
Q

Distinguish a permeable and selectively permeable membrane

A
  • Permeable: it allows any types of molecules pass through
  • Selectively permeable: some can pass/ some cannot; and this membrane acts as a “filter”
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22
Q

Define active transport

A
  • Active transport is the transport of substances moving from low concentration to high concentration
  • The moment goes against a concentration gradient and involves movement across a cell membrane that has receptors for the molecules.
  • It requires energy in the form of ATP
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23
Q

Examples of active transport in plant cells

A
  • Some pumps in the cells of their roots that help extract salts and minerals for the soil.
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24
Q

Examples of active transport in animal cells

A
  • Occurs in the digestive system to extract glucose in the small intestines
  • To pump hydrogen ions in the stomach
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25
Q

What is a special pump that occured in most body cells

A

Sodium - potassium pump

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26
Q

Processes and function related to sodium - potassium pump

A
  • The pump actively transports 2 potassium ions into the cell while actively transporting 3 sodium ions out of the cells.
  • Pumping sodium out of cells is important to maintaining fluid balance and volume of cells.
  • If too much sodium is inside a cell, water will rush into the cell => swell and burst
  • The sodium-potassium pump also helps with conducting nerve signals. This pump also helps nerve cells accumulate potassium. High levels of potassium inside the cell help the nerve send signals along nerve fibres.
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27
Q

Definition of endocytosis

A
  • When a large particle has to be moved into a cell, the cell membrane can change its shape and engulf the particle by the process of endocytosis.
    + If solid particle is engulfed -> Phagocytosis (cell eating)
    + If fluid is engulfed -> pinocytosis (cell drinking)
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28
Q

Example of endocytosis

A
  • Amoeba changes shape by sending out membrane projections fill with cytoplasm that surround the prey.
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29
Q

Definition of exocytosis

A
  • Some substances such as antibodies, neurotransmitters and enzymes are contained within vesicles inside of the cell.
  • Cells also produce waste products that need to be moved out of the cell
  • Exocytosis is the process by which these substances are transported to external environement of the cell.
  • During exocytosis, a membrane-bound vesicle moves to the cell membrane, fuses with it and then releases its contents to the exterior of the cell.
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29
Q

What is the result of endocytosis?

A
  • This results in the formation of a vesicle which then stores or transports the material within the cytoplasm.
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30
Q

Identify three types of substances that are removed from the cell.

A
  • Hormones, toxins, and wastes
31
Q

How does SA:V ratio affect the rate of function of some organelles?

A

The more SA:V ratio, the higher rate of function of that organelle.

31
Q

In which ways do substances needed by living cells for their function.

A

These substances are used in two ways:
+ As essential building blocks from which cells and living tissues are made
+ As a source of stored energy for the cell

32
Q

Listing all types of carbohydrates

A

Monosaccharides - Disaccharides - Polysaccharides

33
Q

Structure of lipids

A
  • Contain many carbon (C) and hydrogen (H) atoms with a few oxygen (O) atoms.
  • The fats and oils in the cells of organisms are typically composed of triglycerides molecules (glycerol molecule attach to three chains of fatty acids)
34
Q

Function of lids in cells

A
  • Energy storage
  • Structural component of membranes
  • Essential structural parts of hormones, which are chemical messengers produced by cells (e.g. steroids)
35
Q

What made up proteins?

A
  • Proteins are made up of elements C, H, O, N, and sometimes S. These elements combine to form amino acids, which are building block of proteins
  • There are about 20 different amino acids: they can be put together in chains of up to 300 amino acids to form a peptide/polypeptide chain.
  • Proteins are made up of one or more of these polypeptide chains twisted together into a particular shape.
  • DNA in the nucleus of cell controls the sequence and arrangement of the amino acids (this determine the type of protein)
36
Q

Function of proteins in cells

A
  • They form structural components in cells in tissues
  • They are important structural components of cell membranes
  • Some proteins have a functional role, such as enzymes, which control all the metabolic reactions in the cell; and hormones, which control the functioning of other cells.
  • Proteins occur suspended in the protoplasm of cells with other macromolecules to form an important structural part of all membranes within the cell.
37
Q

How many ‘essential’ animo acids in animal cells?

A

Nine, and they are essential because they cannot be synthesised by cell in the body.

38
Q

How main types of nucleic acids

A

Two: DNA and RNA

39
Q

Define DNA and RNA

A
  • DNA is a double-stranded molecule that stores information that controls the cell. It is the main chemical making up the nucleus. Small amounts are also found in mitochondria and chloroplasts.
  • RNA is found in small amounts in the nucleus and in larger amounts in the cytoplasm.
40
Q

What bases are contained by DNA and RNA

A
  • DNA nucleotides contain the four bases Adenine, Guanine, Cytosine and Thymine (they also contain the sugar deoxyribose)
  • DNA nucleotides are required by cells to make DNA during replication.
  • RNA nucleotides contain four bases Adenine, Guanine, Cytosine and Uracil (they also contain the sugar ribose)
  • RNA nucleotides are required for cells to make ribosomes and to make RNA so that cells can make protein.
41
Q

The waste substances needs to be removed to ensure balance is maintained in the organism => Known as excretion

A

Informative sentence

42
Q

Which types of substances can be exerted by passive or active transport through cell membrane?

A
  • Passive - osmosis of water molecules, simple diffusion of O2, CO2, ammonia and alcohol; facilitated diffusion of urea, glucose and ions.
  • Active - Urea, toxins and ions being removed against their concentration gradient and out of the cell.
43
Q

What are autotrophs?

A
  • Most autotrophs, including plants and algae, are photosynthetic. They use solar energy and inorganic molecules for producing energy-rich organic compounds.
  • Autotrophs use energy and inorganic molecules from their environment to produce the organic compounds they need in a process called carbon fixation.
44
Q

What are heterotrophs?

A
  • Including animals, fungi and some bacteria and protists - obtain organic compounds by eating other organisms or their products
45
Q

Define Enzymes

A
  • Enzymes are protein molecules that control all metabolic reactions in living cells
  • Without enzymes the reaction that occur in cells would be so slow as the hardly processed at all.
  • Enzymes act as biological catalysts, controlling the rate of each step of the complex chemical reactions that take place in cells.
  • Enzymes would stay unchanged at the end of the reaction and can be reused at anytime
46
Q

Define metabolism

A
  • It is the sum of all chemical reactions occuring within a living organism
  • Over 1000 different reactions can take place in each cell
  • A specific enzyme catalyses each of these reactions
  • There are as many enzymes in living organisms as there are types of chemical reactions.
47
Q

Mechanism that enzymes function

A
  • Enzymes speed up reactions by lowering the activation energy required for the reaction.
  • They do this by combining with the reactant and holding them in a way that makes the reaction are more likely to occur
48
Q

Properties of enzymes

A
  • Composed of protein molecules that are often highly folded to create a particular chemical shape.
    The surface of the enzyme with a specific shape is called the active site.
49
Q

How enzymes work?

A
  • The reactants also known as the substrates, in a chemical reaction temporarily bind with an active site of enzymes.
  • When this occurs , a substrate-enzyme complex is formed and the reaction proceeds.
  • The products of the reaction are then released from the active site of the enzyme.
50
Q

Describe Induced Fit Model.

A
  • This model is based on the realisation that proteins are not rigid.
  • The binding of a substrate to the active site of an enzyme induces the enzyme to alter its shape slightly, to fit more tightly around the substrate
51
Q

Describe Lock-and-Key Model

A
  • Substrate molecule was thought to be rigid ad reciprocally shaped and fits exactly into the active site, like a key into a lock.
  • Once this substrate-enzyme complex has formed, the close proximity of molecules allows the reaction to be rapidly catalysed and the products of the reaction are released.
52
Q

Outline factors affecting enzyme activity

A
  • Temperature Sensitivity:
    + The heat can cause the enzyme to denature - this change in the structure and shape of the molecule due to excessive heat is irreversible.
    + Excessive cold also causes the enzyme to change shape and its function to slow down or stop, but this change is often reversible (có thể quay lại)
  • pH-sensitive:
    + Each enzyme has its own narrow range of pH within its functions most efficiently.
    + Levels of alkalinity or acidity outside the optimum pH for an enzyme have a similar effect to that of temperature change.
  • Substrate Concentration:
    + The higher the substrate concentration, the greater the rate of enzyme reaction, until available enzymes are being used to catalyse reactions. This point is known as the saturation point.
    + Increasing the substrate concentration beyond the saturation point will not increase the rate of reaction, since all enzymes are working at their maximum turnover rate. The only way to increase the reaction rate would be to increase the enzyme concentration.
53
Q

Pepsin is found in the stomach where it breaks down complex proteins into long peptide chains. Trypsin is found in the small intestine and continues the digestion of proteins. Trypsin breaks down the long peptide chains into short ones. Explain why pepsin no longer functions when it enters into the small intestine.

A

Because the pH in small intestine is about 6 - 7.4 pH. However, pepsin functions not too efficiently or may not function in this pH.

54
Q

Discuss why enzymes are important for the maintenance of life

A
  • Enzymes help cell provide sustainably and enough quantities of important substances to body (water, nutrients, …)
55
Q

Which factors can determine whether enzymatic reactions can occur?

A
  • Inhibitors, phosphorylation, cofactors and coenzymes
56
Q

What are cofactors and coenzymes?

A
  • Cofactors are additional components required by some enzymes to catalyse a reaction.
  • Coenzymes are small, non-protein organic cofactors, such as vitamins, ADP, NADH and NADPH
  • Coenzymes are needed for reactions in biochemical pathways, including cellular respiration and photosynthesis.
57
Q

Photosynthesis formula by word equation

A

Carbon dioxide + Water (light energy, chlorophyll) ===> glucose + oxygen

58
Q

Balanced overall chemical equation of photosynthesis

A

6CO2 + 6H2O (light energy, chlorophyll) ===> C6H12O6 + 6O2

59
Q

Describe phase 1 of photosynthesis (light dependent stage)

A
  • The light-dependent stage (photolysis) occurs in the GRANA of chloroplasts.
  • It involves the absorption of light energy by the chlorophyll in the thylakoid membranes of the chloroplast
  • This energy is used to split the water molecules into Hydrogen and Oxygen.
  • The oxygen is released into the atmosphere and the hydrogen ions are carried to the next phase.
  • ATP is also formed at this stage
60
Q

Describe phase 2 of photosynthesis (light-independent stage) - Calvin Cycle

A
  • This phase is also known as carbon fixation occurs in the stroma of the chloroplasts.
  • It involved combining the carbon dioxide (diffuse through stomata) with the hydrogen ions produced in the photolysis stage to form glucose
  • The ATP formed in the photolysis stage is required to provide the energy from this reaction
  • No light is required in this stage
61
Q

Glucose produced by photosynthesis can be converted by plants into complex carbohydrates, lipids or proteins. These end products are stored by the plants and are the source of organic nutrients, not only for plants themselves but also for consumer organisms that eat the plants.

A

Informative sentences

62
Q

Describe CAM photosynthesis (crassulacean acid metabolism)

A
  • Plants can open stomata at night to inhale (exchange) CO2 inside and store it in vacuoles with the form of malic acid (by enzyme PEP carboxylase) and the stomata will not open during daytime in order to conserve water.
  • During the daytime, malic acid is broken down to release CO2, then is used in Calvin Cycle to produce glucose with the light energy.
63
Q

What products does the breakdown of glucose molecules result in?

A
  • Carbon dioxide
  • Water
  • Energy
64
Q

Outline main stages of cellular respiration.

A

Two main stages:
1. Glycolysis
2. Aerobic or anaerobic respiration

65
Q

Describe the glycolysis stage.

A

The glycolysis stage is the first stage, which splits the glucose molecule into two parts and does not require oxygen.
- This occurs in the cytosol of cell and uses two ATP molecules o break down glucose, but then produces four more ATP -> Gain 2 ATP

66
Q

Describe the anaerobic respiration stage

A
  • Organisms (bacteria, archaea), live in environments lacking oxygen. They may use anaerobic respiration to produce energy in the lack of oxygen
  • During anaerobic respiration, there is no further formation of ATP. The purpose is to prevent the accumulation of pyruvate (which allows glycolysis to occur). If pyruvate accumulates then glycolysis slows and no energy is available to the cell.
67
Q

Describe aerobic respiration stage

A
  • Occurs when oxygen is available.
  • Aerobic respiration occurs in the mitochondria and converts ADP to ATP.
  • During aerobic respiration, the two pyruvate molecules are produced in the glycolysis and then broken down to produce CO2, water and 36 ATP.
68
Q

Two main stages of Aerobic Respiration are

A

Krebs Cycle and Eletron transport system

69
Q

Formula for cellular respiration in cells

A
  • Notation: C6H12O6 + 6O2 ===> 6CO2 + 6H2O + 36ATP
  • Word: Glucose + Oxygen ===> Carbon dioxide + Water + Energy (thermal + ATP)
70
Q

Outline input, output, ATP molecules formed from one glucose molecule, and location of GLYCOLYSIS

A
  • Input: C6H12O6
  • Output: 2 pyruvate acid
  • ATP produced: 2ATP
  • Location: cytoplasm
71
Q

Outline input, output, ATP molecules formed from one glucose molecule, and location of SECOND STAGE OF AEROBIC CELLULAR RESPIRATION

A
  • Input: ADP, NAD+, FAD, pyruvates
  • Output: ATP, NADH, FADH_2
  • ATP produced: 28-36 ATP
  • Location: mitochondria
72
Q

Outline input, output, ATP molecules formed from one glucose molecule, and location of ALCOHOL FERMENTATION

A
  • Input: pyruvates
  • Output: C2H5OH + CO2
  • ATP produced: 0 ATP
  • Location: mitochondria
73
Q

Outline input, output, ATP molecules formed from one glucose molecule, and location of LACTIC ACID FERMENTATION

A
  • Input: pyruvates
  • Output: lactic acid
  • ATP produced: 0 ATP
  • Location: mitochondria

Biology (6 decks)

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