Cells as the basis of life Flashcards
What are the 3 key statements in The Cell Theory?
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
Give an example of:
* A prokaryotic organism
* A single celled eukaryotic organism
* A multicellular eukaryotic organism
- A prokaryotic organism
Bacteria - A single celled eukaryotic organism
Protists - A multicellular eukaryotic organism
Plantae
List the common features of a eukaryotic and prokaryotic cells
Cell membrane
Ribosome
Cytoplasm
DNA
Compare prokaryotic and eukaryotic cells
size:
internal organisation:
shape and location of chromosomes:
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
State the function of Nucleus
Contains the genetic information of the cell (DNA in the form of chromosomes)
State the function of Nucleolus
Responsible for the production of ribosomes
State the function of mitochondrion
Site of aerobic respiration
Explain two features of the chloroplast that allow it to perform its function.
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
state the function of vacuole
Storage of materials such as nutrients, water, and solutes
state the function of vesicle
Transportation of materials
e.g., newly synthesised proteins
state the functionm of golgi body
modification and packaging of cell products
e.g., proteins
state the function of Rough endoplasmic reticulum (RER)
site of protein synthesis and transportation
state the function of of smooth endoplasmic reticulum
synthesis and transport of lipids
state the function of ribosome
Protein synthesis from animo acid
state the function of cytoskeleton
Facilitate the movement of organelles into correct orientation, maintain the shape of cell
state the function of lysosome
Digestion and breakdown of excess worn out organelles and engulfed bacteria and viruses
Describe the fluid mosaic model
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
state the function of the cell membrane
To control the movement of molecules (materials, nutrients, and wastes) between the cell and its environment
Why do phospholipids arrange themselves into a bilayer?
Due to their chemical nature
Arranged so the hydrophilic heads face outwards, and hydrophobic tails turn inwards facing each other
- Give examples of types of proteins found in a cell membrane
Enzymes
Receptor proteins
Carrier proteins
Protein pumps
Protein channels
Describe the process of exocytosis
- Golgi body packages material into vesicle
- Vesicle moves to the cell membrane and fuse with it
- 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
Describe the process of endocytosis
- 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
Describe the process of crossing over and explain why it is important
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
Describe independent assortment, stating what 2 stages of meiosis it occurs in
- 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
Explain how mutations caused by carcinogens can upset normal controls of cell division.
- 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
Explain how hormones and other proteins (CDK/Cyclin) may regulate the cell cycle and cell division.
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
Name the 3 things the G1 checkpoint checks for.
- Check for cell size
- Check for nutrients
- Check for growth factors
State the 2 things the G2 checkpoint checks for.
- Check for correct DNA replication
- Check for DNA damage
What does the metaphase checkpoint check for?
- Check for correct spindle attachment
Describe the stages in the cell cycle:
G1 – Growth 1
S phase (DNA synthesis
G2 – Growth 2
M phase – Mitosis
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
Describe and represent (draw) Binary fission in prokaryotic cells
- Bacterial DNA replication
- Each of the two copies of the circular DNA attaches to cell membrane
- Cell grows and in doing so the DNA moves from each other
- The cell membrane folds inwards to divide the cell into 2 (cytokinesis)
- 2 daughter cells produced, which are identical to each other and parent cell (have identical circular
State the two processes within the cell cycle that ensure the production of genetically identical daughter
- DNA replication
- separation of identical sister chromatids
Explain why the amount of DNA in a cell doubles before cell division
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
Cells may divide for?
4 things
- repair
- growth
- replacement
- reproduction
Explain why a different enzyme is needed to catalyse each step in a metabolic pathway.
- 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
State and explain two benefits of chemical reactions occurring in small steps.
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
What is the definition of cell metabolism?
- The total of the catabolic and anabolic reactions occurring in a cell
- Is critical to the survival of a cell
Describe how ATP is formed
state the cell activities in the form of ATP is required by cells for
- 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
Describe how energy is released from the conversion of ATP to ADP and Pi
- 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
State:
- the word and chemical eqution of aerobic respiration
- location - where it occurs
- type of cells it occurs in
Glucose + oxygen –> carbon dioxide + water
C6H12O6 + 6O2 —> 6CO2 + 6H2O
location: Mitochondria
type of cells: plants & animals
State:
- the word and chemical eqution of alcohol fermentation
- location - where it occurs
- type of cells it occurs in
Glucose —> ethanol + carbon dioxide
C6H12O6 –> 2C2H5OH + 2CO2
location: cytoplasm
type of cells: yeast, plants, some bacteria
State:
- the word and chemical eqution of lactic acid fermentation
- location - where it occurs
- type of cells it occurs in
Glucose –> lactic acid
C6H12O6 —> 2C3H6O3
location: cytoplasm
type of cells: Animals
Distinguish between autotrophs and heterotrophs
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
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)
- 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
- How does surface area to volume ratio of the cell affect movement across a membrane?
- Size
- Small cells have increased surface area to volume ratio than large cells - 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)
- How does the concentration gradient affect movement across a membrane?
- 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
