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ST2 Biology > Cells as the basis of life > Flashcards

Cells as the basis of life Flashcards

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1
Q

What are the 3 key statements in The Cell Theory?

A

All cells come from pre-existing cells

All living things are made out of cells or products of cells

Cells are the smallest independent unit of life

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2
Q

Give an example of:
* A prokaryotic organism
* A single celled eukaryotic organism
* A multicellular eukaryotic organism

A
  • A prokaryotic organism
    Bacteria
  • A single celled eukaryotic organism
    Protists
  • A multicellular eukaryotic organism
    Plantae
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3
Q

List the common features of a eukaryotic and prokaryotic cells

A

Cell membrane
Ribosome
Cytoplasm
DNA

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4
Q

Compare prokaryotic and eukaryotic cells

size:

internal organisation:

shape and location of chromosomes:

A

Size:
prokaryote = smaller
eukaryote = larger

Internal organisation:
prokaryote = simple, no membrane-bound organelles
eukaryote = complex many membrane-bound organelles

Shape and location of chromosomes:
prokaryote = circular DNA, in cytoplasm
eukaryote = DNA arranged in linear chromosomes, in nucleus

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5
Q

State the function of Nucleus

A

Contains the genetic information of the cell (DNA in the form of chromosomes)

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6
Q

State the function of Nucleolus

A

Responsible for the production of ribosomes

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7
Q

State the function of mitochondrion

A

Site of aerobic respiration

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8
Q

Explain two features of the chloroplast that allow it to perform its function.

A

Function: site of photosynthesis

Contains chlorophyll
Has internal membranes that are highly folded
This increases their surface area
This allows a greater number of enzymes to be embedded in the membranes
This allows a greater rate of photosynthesis due to more reactions being able to take place at any given time
(more active sites available)
More enzymes and chlorophyll facilitate photosynthesis
This increases the efficiency of photosynthesis

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9
Q

state the function of vacuole

A

Storage of materials such as nutrients, water, and solutes

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10
Q

state the function of vesicle

A

Transportation of materials

e.g., newly synthesised proteins

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11
Q

state the functionm of golgi body

A

modification and packaging of cell products

e.g., proteins

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12
Q

state the function of Rough endoplasmic reticulum (RER)

A

site of protein synthesis and transportation

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13
Q

state the function of of smooth endoplasmic reticulum

A

synthesis and transport of lipids

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14
Q

state the function of ribosome

A

Protein synthesis from animo acid

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15
Q

state the function of cytoskeleton

A

Facilitate the movement of organelles into correct orientation, maintain the shape of cell

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16
Q

state the function of lysosome

A

Digestion and breakdown of excess worn out organelles and engulfed bacteria and viruses

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17
Q

Describe the fluid mosaic model

A

Fluid – flexible, allows the movement of molecules in and out of the cell

Mosaic – contains embedded proteins and other molecules pieced together like a mosaic

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18
Q

state the function of the cell membrane

A

To control the movement of molecules (materials, nutrients, and wastes) between the cell and its environment

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19
Q

Why do phospholipids arrange themselves into a bilayer?

A

Due to their chemical nature

Arranged so the hydrophilic heads face outwards, and hydrophobic tails turn inwards facing each other

20
Q
  • Give examples of types of proteins found in a cell membrane
A

Enzymes
Receptor proteins
Carrier proteins
Protein pumps
Protein channels

21
Q

Describe the process of exocytosis

A
  1. Golgi body packages material into vesicle
  2. Vesicle moves to the cell membrane and fuse with it
  3. Vesicle open outwards and expels the content into the external environment
    (movement of the cell membrane and vesicles is facilitated by the cytoskeleton)

EX. releasing of hormones into blood stream

22
Q

Describe the process of endocytosis

A
  1. Cell membrane surround and engulf molecules then fuse with it to form a vesicle and draw the molecules inside the cell
    (movement of the cell membrane and vesicles is facilitated by the cytoskeleton)

EX. single celled cells obtaining food

23
Q

Describe the process of crossing over and explain why it is important

A

Crossing over is the exchange of genetic material between the non-identical sister chromatids on different homologous pair of chromosomes

This creates new combinations of maternal and paternal alleles
It is important as it increases the chances of genetic variation which increases the chances of a population’s survival

24
Q

Describe independent assortment, stating what 2 stages of meiosis it occurs in

A
  • anaphase 1 & 2
  • The arrangement of homologous pair of chromosomes is random
  • Each of the homologous pair of chromosomes is arranged independently from the other pair
  • This greatly contributes to genetic variation by increasing the number of possible combinations of genes in the gamete cells
25
Q

Explain how mutations caused by carcinogens can upset normal controls of cell division.

A
  • Carcinogens increase the chances of a mutation occurring
  • A mutation causes a change in the gene that codes for a cell cycle regulator
  • This leads to changes in the shape and function of the regulator
  • This may lead to failure to stop a cell at a checkpoint or may lead to a damaged cell to pass through a checkpoint
26
Q

Explain how hormones and other proteins (CDK/Cyclin) may regulate the cell cycle and cell division.

A

Growth factors are types of hormones that regulate the cell cycle

Growth factors stimulate the cycle cell

  • Hormones bind to the membrane receptors and signal the cell to alter the levels of proteins produced
  • ## The level of proteins such as CDK and cyclin synthesised control whether a cell can go pass a checkpoint or not
  • CDK are enzymes
  • Cyclins bind to CDK to active them, the activated CDK acts as a signal to turn on certain processes
27
Q

Name the 3 things the G1 checkpoint checks for.

A
  • Check for cell size
  • Check for nutrients
  • Check for growth factors
28
Q

State the 2 things the G2 checkpoint checks for.

A
  • Check for correct DNA replication
  • Check for DNA damage
29
Q

What does the metaphase checkpoint check for?

A
  • Check for correct spindle attachment
30
Q

Describe the stages in the cell cycle:
G1 – Growth 1
S phase (DNA synthesis
G2 – Growth 2
M phase – Mitosis

A

G1 – Growth 1
- Cell physically grows larger and makes the molecular building blocks required in later steps
S phase (DNA synthesis
- cell synthesising a complete copy of the DNA in the nucleus via DNA replication

G2 – Growth 2
- creates proteins and copies organelles
- reorganise the content in preparation for mitosis
- cells grows more

M phase – Mitosis
- prophase, metaphase, anaphase, telophase, cytokinesis

31
Q

Describe and represent (draw) Binary fission in prokaryotic cells

A
  1. Bacterial DNA replication
  2. Each of the two copies of the circular DNA attaches to cell membrane
  3. Cell grows and in doing so the DNA moves from each other
  4. The cell membrane folds inwards to divide the cell into 2 (cytokinesis)
  5. 2 daughter cells produced, which are identical to each other and parent cell (have identical circular
32
Q

State the two processes within the cell cycle that ensure the production of genetically identical daughter

A
  • DNA replication
  • separation of identical sister chromatids
33
Q

Explain why the amount of DNA in a cell doubles before cell division

A

To make sure each daughter cell contains identical copy of the genetic material in its chromosomes and to be fully functional
This occurs during DNA replication

34
Q

Cells may divide for?
4 things

A
  • repair
  • growth
  • replacement
  • reproduction
35
Q

Explain why a different enzyme is needed to catalyse each step in a metabolic pathway.

A
  • Enzymes are specific to substrates due to complementary shapes
  • Enzyme has an active site that is complementary in shape to one substrate
  • Each step has a different substrate and so requires a different enzyme
36
Q

State and explain two benefits of chemical reactions occurring in small steps.

A

Avoid large changes in temperature
- only small amounts of heat is released at a time
- heat can be dissipated easily
- this maintains stable temperature
- large changes in optimal temperature would affect enzyme activity

OR

Efficient conversion of energy into ATP
- Large releases of energy would lead to more loss of energy as heat

37
Q

What is the definition of cell metabolism?

A
  • The total of the catabolic and anabolic reactions occurring in a cell
  • Is critical to the survival of a cell
38
Q

Describe how ATP is formed

state the cell activities in the form of ATP is required by cells for

A
  • Metabolic reactions such as cellular respiration releases energy
  • This means, there is a net release of energy from the breakdown of molecules
  • The produced energy is used to form ATP from ADP + Pi
    (ATP is formed when a phosphate is added to ADP (ADP + Pi) )
  • This energy is used for many cell activities such as :
  • Cell movement
  • Synthesis
  • Maintaining a stable environment
39
Q

Describe how energy is released from the conversion of ATP to ADP and Pi

A
  • When breaking the bond in ATP to form ADP and Pi (when a phosphate is removed from ATP), there is a net release of energy
  • The produced energy is used for many cell functions
40
Q

State:
- the word and chemical eqution of aerobic respiration
- location - where it occurs
- type of cells it occurs in

A

Glucose + oxygen –> carbon dioxide + water

C6H12O6 + 6O2 —> 6CO2 + 6H2O

location: Mitochondria
type of cells: plants & animals

41
Q

State:
- the word and chemical eqution of alcohol fermentation
- location - where it occurs
- type of cells it occurs in

A

Glucose —> ethanol + carbon dioxide

C6H12O6 –> 2C2H5OH + 2CO2

location: cytoplasm
type of cells: yeast, plants, some bacteria

42
Q

State:
- the word and chemical eqution of lactic acid fermentation
- location - where it occurs
- type of cells it occurs in

A

Glucose –> lactic acid
C6H12O6 —> 2C3H6O3

location: cytoplasm
type of cells: Animals

43
Q

Distinguish between autotrophs and heterotrophs

A

Autotroph:
Use light energy in photosynthesis to store chemical energy in carbohydrates (glucose)
e.g., Plant

Heterotroph:
Take in chemical energy in complex molecules produced by other organisms

e.g., Animal

44
Q

Use examples to explain why different materials move through the cell membrane by different mechanisms

Based on:
1. Nature of molecule (hydrophilic, hydrophobic, charged ions)
2. Size (small or large)
3. Direction (with or against concentration gradient)

A
  • Small hydrophobic molecules move in and out of the cell directly through cell membrane (lipid bilayer) via simple diffusion,
    e.g., oxygen
  • Small hydrophilic or charged ions move in and out the cell through protein channels embedded in the cell membrane via facilitated diffusion
    e.g., glucose or calcium ions
  • Large molecules move in and out the cell through endocytosis and exocytosis respectively, movement of cell membrane is facilitated by the cytoskeleton
    e.g.,
    exocytosis: secretion of wastes or newly synthesised proteins

endocytosis: single celled cells obtaining food

45
Q
  • How does surface area to volume ratio of the cell affect movement across a membrane?
A
  1. Size
    - Small cells have increased surface area to volume ratio than large cells
  2. Shape
    - Long and thin shaped cells have increased surface area to volume ratio
    -
    High surface increases the frequency and chances of successful collisions between particles, low volume decreases the distance travelled by particles, this increases the rate of transportation of molecules (e.g., osmosis/diffusion)
46
Q
  • How does the concentration gradient affect movement across a membrane?
A
  • Concentration gradient is the difference between the concentration intracellularly and extracellularly
  • The greater this difference, the steeper the concentration gradient
  • This increases the rate of the molecules’ movement

ST2 Biology (4 decks)

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