Stage 2 Biology - Cells as the Basis of Life

Provide 3 pieces of evidence for endosymbiosis

+ Chloroplasts have a double membrane. The inner membrane was the original, prokaryotic membrane and the outer membrane is eukaryotic like, evident of the engulfing event

+ Chloroplasts replicate by binary fission, like prokaryotes

+ Chloroplasts contain their own circular DNA chromosomes like prokaryotes

+ Chloroplasts have their own ribosomes which are prokaryotic like

Explain why the cell membrane can be described as ‘fluid-mosiac’

The cell membrane consists of a semi-permeable bilayer of phospholipids, composed of a hydrophilic head and hydrophobic tail, embedded proteins and cholesterol. The arrangement of these components is described as a mosaic. The term fluid is used to describe the cell membrane as the components are constantly moving laterally and fluid. 

Compare the internal organisation of prokaryotes and eukaryotes

Eukaryotes have a nucleus, prokaryotes do not

Eukaryotes have membrane bound organelles

Compare the shape and location of chromosomes in a prokaryote and eukaryote

Chromosomes within a prokaryote are circular and are located in the nucleoid

Chromosomes within eukaryotes are linear and are located in the nucleus

Identify and explain the function of this organelle:

The organelle is a nucleus. The nucleus regulates cell activities, stores genetic material, the site of DNA replication and translation

Identify and explain the function of this organelle:

This organelle is a nucleolus. The nucleolus produces and assembles the cell's ribosomes and synthesises rRNA

Identify and explain the function of this organelle:

This organelle is a mitochondrion. Mitochondria are the site of aerobic respiration

Identify and explain the function of this organelle:

This organelle is a chloroplast. Chloroplast is the site of photosynthesis

Identify and explain the function of this organelle:

This organelle is a vacuole. Plant cells have 1 large vacuole that stores water and helps maintain the structure of the cell. Animal cells have many smaller vacuoles that store nutrients

Identify and explain the function of this organelle:

This organelle is the golgi body. The golgi body packages and processes vesicles containing proteins and lipids before they're transported

Identify and explain the function of these organelles:

These organelles are the smooth and rough endoplasmic reticulum. The smooth ER synthesises lipids. The rough ER has ribosomes attached that synthesise proteins

Identify and explain the function of this organelle:

This organelle is a ribosome. Ribosomes are the site of translation and protein synthesis

Identify and explain the function of this organelle:

This organelle is a lysosome. A lysosome is a membrane bound vesicle containing digestive enzymes that breaks down materials and foreign bodies

Identify and explain the function of this organelle:

This organelle is the cytoskeleton. The cytoskeleton aids in the movement of organelles and cellular membrane, the assembly of spindle fibres in mitosis and, in animal cells, provides support to the cell's shape

Distinguish between autotrophs and heterotrophs

Autotrophs produce their own energy by converting light energy into chemical energy.

Heterotrophs gain energy by consuming other organisms.

What is the chemical equation of photosynthesis

6CO2 + 6H2O → C6H12O6 + 6O2

What is the chemical equation of aerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

What is the chemical equation of fermentation/ anaerobic respiration in animal cells:

C6H12O6 —> 2C3H6O3

What is the chemical equation of fermentation/ anaerobic respiration in plant and yeast cells

C6H12O6 → 2C2H5OH + 2CO2

What cell type does photosynthesis occur in

Plant / Autotrophs

State where photosynthesis is located

Chloroplast

Explain why the internal membrane of chloroplast facilitates photosynthesis

The internal membranes of the chloroplast facilitate photosynthesis as they are folded to produce thylakoids (stacked into geranium). This folding  increases the surface area in which the chlorophyll pigments are located. Therefore, increasing the amount of trapped light which is needed for photosynthesis.

Describe the 2 parts of aerobic respiration

The glucose is broken down in the process of glycolysis in cytoplasm. This  creates 2 pyruvate. Because is O2 present the 2 pyruvate is transported into the mitochondria and is further completely combusted.

State the product of anaerobic respiration/ fermentation in animal cells

Lactic acid

State the product of anaerobic respiration/ fermentation in plant and yeast cells

Ethanol and carbon dioxide

Explain why aerobic respiration produces more energy than anaerobic respiration

Aerobic in a complete combustion of glucose as the glucose is broken down into 2 pyruvate. The presence of oxygen allows the 2 pyruvate to be further broken down inside mitochondria, releasing more energy.

Anaerobic is incomplete combustion as after glycolysis O2 is not present and therefore the Kerbs cycle in the mitochondria can not occur. The pyruvate is then turned into lactic acid or ethanol and carbon dioxide.

Explain the ATP/ADP cycle

ATP is a molecule with stored energy between the second and third phosphate. If a cell requires energy the bond between the second and third phosphate in ATP is broken which releases energy and forms ADP + Pi. Energy released from aerobic and anaerobic respiration can then be used to synthesise ATP by rebinding an inorganic phosphate to ADP.

Describe the process of diffusion

Diffusion is a process of passive transport in which small and uncharged molecules, moving with the concentration gradient pass through the semi-permeable cell membrane

Describe the process fo facilitated diffusion

Facilitated diffusion is a process of passive transport in which the movement of small uncharged particles, moving with the concentration gradient pass through channel proteins embedded within the cell membrane

Describe the process of osmosis

Osmosis if the diffusion of water particles, in which water molecules are transported across the cell membrane from a hypotonic solution (low solute) to a hypertonic solution(high solute concentration) facilitated by proteins call aquaporins.

Describe active transport

A process of transport in which energy is required to move large or charged molecules or molecules moving against the concentration gradient across the cell membrane through carrier proteins.

How does the internal membrane of the mitochondria facilitates aerobic respiration

The internal membrane of mitochondria facilitate the process of aerobic respiration as the folding of the internal membrane increases the surface area, allowing for more enzymes involved in aerobic respiration to be packed into the mitochondria, resulting in a higher rate of ATP synthesis.

Explain the process of endocytosis

Endocytosis is the process in which materials are transported into a cell During exocytosis a vesicle from extracellular space attaches to the cell membrane and creates an opening within the cell membrane and expelling the contents into the cell The vesicle then fuses with the cell membrane.

Explain the process of exocytosis

Exocytosis is the process in which cells export materials out of the cell. During exocytosis a vesicle packaged via the Golgi body is moved to the cell membrane via the cytoskeleton. The vesicle then fuses with the cell membrane and expels the contents out of the cell as the vesicle attaches to the cell membrane.

Why is DNA replicated before cell division

DNA is replicated before cell division to ensure that both daughter cells have the same amount of DNA and are genetically identical.

Explain the steps of binary fission

Binary fission occurs in prokaryote cells. In binary fission DNA are first replicated. The chromosomes then attach to the cell membrane and the cell elongates, separating the chromosomes. The cell wall and cell membrane begin to form. The cell then divides into two genetically identical daughter cells.

Describe the difference between sexual and asexual reproduction

Sexual reproduction is when a cell requires fertilisation before reproducing. Asexual reproduction does not have fertilisation

State and explain 2 events of genetic variation in meiosis

Crossing over and independent assortment are events in round one of meiosis that result in genetic variation. Crossing over occurs when homologous chromosomes are lined up and fragments from the maternal and paternal chromosomes are broken off and exchanged. Independent assortment describes the paternal and maternal chromosomes randomly line up of either side of the equator of the cell, resulting in the random assortment of genes.

What cell type does mitosis occur in

Eukaryotic

What are the 4 phases of mitosis

Prophase, metaphase, anaphase and telophase

Explain the phases of mitosis ad cytokinesis

During prophase DNA condenses around histones, the nuclear membrane breaks down and centrioles move towards opposite poles of the cell. During metaphase spindle fibres attach to the centromeres and align the chromosomes in the middle of the cell. During anaphase the spindle fibres contract and the sister chromatids are pulled apart During telophase the cell membrane begins to furrow and the nuclear membrane starts to reform. After mitosis cytokineses occurs the cell membrane is cleaved and 2 genetically identical daughter cells are produced.

State what happens in each stage of the cell cycle

G1 - Growth; S - DNA Replication; G2 - Growth; Mitosis; Cytokinesis