Biology Abitur Lernzettel / Biology exam preparation -
Topics for Q1 - Cell Biology, Neurobiology and Metabolism
Table of Contents
Cell Biology
Prokaryotic and eukaryotic cells
Structure and function of the nucleus
Plasmids and genetic material
Cell organelles and their functions
Membrane Transport
Passive transport and diffusion
Facilitated diffusion and channel proteins
Osmosis and water movement
Active transport and ATP usage
Carrier proteins and transport mechanisms
ATP and Energy Processes
Structure and function of ATP
Energy release through hydrolysis
Role of ATP in cellular processes
Membrane Potential
Resting membrane potential
Sodium-potassium pump
Ion gradients and leak channels
Neurobiology and Synaptic Transmission
Structure of synapses
Transmission of nerve impulses
Role of neurotransmitters
Excitatory and inhibitory signals
Neuroactive Substances
Agonists and antagonists
Reuptake inhibition
Enzyme inhibition
Neurotoxins and their effects
1
,1. Prokaryotic and eukaryotic cells
The nucleus is a structure within the cytoplasm, that is surrounded by a membrane and contains
most of the genetic information of the cell. Cells can be classified into two basic types based on the
presence or absence of a nucleus: prokaryotic cells, which lack a nucleus, and eukaryotic cells, which
contain a nucleus.
1. Prokaryotes:
Prokaryotes are organisms that lack a distinct nucleus and other membrane-bound organelles due
to the absence of internal membranes. The DNA of prokaryotic cells is located in the cytoplasm
rather than being enclosed within a nuclear membrane. Prokaryotes are typically found in single-
celled organisms, such as bacteria.
Prokaryotes have two types of DNA:
1. Single chromosome:
The single prokaryotic chromosome is coiled and concentrated in a region called the nucleoid.
Because prokaryotes have only one chromosome, they possess only one copy of each gene. Before
cell division, a copy of the chromosome is made through a process called binary fission.
2. Plasmids:
Prokaryotic bacteria may also contain circular, double-stranded DNA molecules called plasmids.
These structures are separate from the main chromosome of the cell and carry genes that provide
additional advantages, such as antibiotic resistance. Plasmids are not typically found in eukaryotic
cells.
Features of Plasmids:
-Naked DNA - not associated with histone proteins
-Not responsible for normal life processes - these are controlled by the nucleoid chromosome
-Commonly contain survival characteristics, e.g. antibiotic resistance
-Can be passed between prokaryotes
-Can be incorporated into the nucleoid chromosome
2. Eukaryotes:
Eukaryotes are organisms or cells that contain a nucleus and various other organelles not found in
prokaryotes. An organelle is a structure within the cytoplasm that performs a specific function in the
cell. For example, eukaryotic cells contain mitochondria, which provide energy, and vacuoles, which
store substances. Ribosomes, responsible for producing proteins, are present in both eukaryotic and
prokaryotic cells. Eukaryotic cells are generally larger than prokaryotic cells and are typically found
in multicellular organisms.
2
, 2. Transportation through the membrane
1. Passive Transport:
-Occurs via simple diffusion or facilitated diffusion (require no or very little energy in the form of
ATP)
Simple diffusion:
-Substances or molecules move down a concentration gradient -> from an area of high concentration
to an area of low concentration
-Carbon dioxide, Oxygen, Ethanol (hydrophobic in nature, therefore they can easily diffuse through)
Facilitated diffusion:
-Molecules or particles move from regions of higher concentration to regions of lower concentration
with the help of transport molecules
-Polar molecules/charged ions cannot diffuse through the membrane since they are charged
molecules and would be repelled by the hydrophobic, non-polar part of the lipid bilayer
Transmembrane channels/proteins: They act as a transporter for polar, charged, and medium sized
molecules. They form a passage through the lipid bilayer, allowing these molecules to cross the
membrane, otherwise they would be repelled by the hydrophilic part of the phospholipid bilayer.
Types of passive transport:
Protein channels:
Channel proteins form open pores through which molecules of the appropriate size (e.g., Ion
channels, for example, allow the passage of inorganic ions such as Na+, K+, Ca2+, and Cl- across) can
freely cross the membrane. Channels proteins operate via passive diffusion, where molecules move
down a concentration gradient (from high to low concentration) with the help of transport proteins.
Both sides of the membrane can remain open at the same time.
Osmosis:
Water molecules cross the cell membrane through osmosis. Osmosis is the passive movement of
water from an area of lower solute concentration to an area of higher solute concentration across a
semipermeable membrane. Accordingly, solutes cannot cross the phospholipid bilayer of the cell
membrane on their own. Hence they are often dissolved in water molecules, which helps facilitate
their movement across the semipermeable membrane. The majority of water transport occurs
through specialized protein channels called aquaporins, which increase the rate of water movement.
Osmosis is a passive process, which is why it needs no or only very little energy in the form of ATP.
3
Topics for Q1 - Cell Biology, Neurobiology and Metabolism
Table of Contents
Cell Biology
Prokaryotic and eukaryotic cells
Structure and function of the nucleus
Plasmids and genetic material
Cell organelles and their functions
Membrane Transport
Passive transport and diffusion
Facilitated diffusion and channel proteins
Osmosis and water movement
Active transport and ATP usage
Carrier proteins and transport mechanisms
ATP and Energy Processes
Structure and function of ATP
Energy release through hydrolysis
Role of ATP in cellular processes
Membrane Potential
Resting membrane potential
Sodium-potassium pump
Ion gradients and leak channels
Neurobiology and Synaptic Transmission
Structure of synapses
Transmission of nerve impulses
Role of neurotransmitters
Excitatory and inhibitory signals
Neuroactive Substances
Agonists and antagonists
Reuptake inhibition
Enzyme inhibition
Neurotoxins and their effects
1
,1. Prokaryotic and eukaryotic cells
The nucleus is a structure within the cytoplasm, that is surrounded by a membrane and contains
most of the genetic information of the cell. Cells can be classified into two basic types based on the
presence or absence of a nucleus: prokaryotic cells, which lack a nucleus, and eukaryotic cells, which
contain a nucleus.
1. Prokaryotes:
Prokaryotes are organisms that lack a distinct nucleus and other membrane-bound organelles due
to the absence of internal membranes. The DNA of prokaryotic cells is located in the cytoplasm
rather than being enclosed within a nuclear membrane. Prokaryotes are typically found in single-
celled organisms, such as bacteria.
Prokaryotes have two types of DNA:
1. Single chromosome:
The single prokaryotic chromosome is coiled and concentrated in a region called the nucleoid.
Because prokaryotes have only one chromosome, they possess only one copy of each gene. Before
cell division, a copy of the chromosome is made through a process called binary fission.
2. Plasmids:
Prokaryotic bacteria may also contain circular, double-stranded DNA molecules called plasmids.
These structures are separate from the main chromosome of the cell and carry genes that provide
additional advantages, such as antibiotic resistance. Plasmids are not typically found in eukaryotic
cells.
Features of Plasmids:
-Naked DNA - not associated with histone proteins
-Not responsible for normal life processes - these are controlled by the nucleoid chromosome
-Commonly contain survival characteristics, e.g. antibiotic resistance
-Can be passed between prokaryotes
-Can be incorporated into the nucleoid chromosome
2. Eukaryotes:
Eukaryotes are organisms or cells that contain a nucleus and various other organelles not found in
prokaryotes. An organelle is a structure within the cytoplasm that performs a specific function in the
cell. For example, eukaryotic cells contain mitochondria, which provide energy, and vacuoles, which
store substances. Ribosomes, responsible for producing proteins, are present in both eukaryotic and
prokaryotic cells. Eukaryotic cells are generally larger than prokaryotic cells and are typically found
in multicellular organisms.
2
, 2. Transportation through the membrane
1. Passive Transport:
-Occurs via simple diffusion or facilitated diffusion (require no or very little energy in the form of
ATP)
Simple diffusion:
-Substances or molecules move down a concentration gradient -> from an area of high concentration
to an area of low concentration
-Carbon dioxide, Oxygen, Ethanol (hydrophobic in nature, therefore they can easily diffuse through)
Facilitated diffusion:
-Molecules or particles move from regions of higher concentration to regions of lower concentration
with the help of transport molecules
-Polar molecules/charged ions cannot diffuse through the membrane since they are charged
molecules and would be repelled by the hydrophobic, non-polar part of the lipid bilayer
Transmembrane channels/proteins: They act as a transporter for polar, charged, and medium sized
molecules. They form a passage through the lipid bilayer, allowing these molecules to cross the
membrane, otherwise they would be repelled by the hydrophilic part of the phospholipid bilayer.
Types of passive transport:
Protein channels:
Channel proteins form open pores through which molecules of the appropriate size (e.g., Ion
channels, for example, allow the passage of inorganic ions such as Na+, K+, Ca2+, and Cl- across) can
freely cross the membrane. Channels proteins operate via passive diffusion, where molecules move
down a concentration gradient (from high to low concentration) with the help of transport proteins.
Both sides of the membrane can remain open at the same time.
Osmosis:
Water molecules cross the cell membrane through osmosis. Osmosis is the passive movement of
water from an area of lower solute concentration to an area of higher solute concentration across a
semipermeable membrane. Accordingly, solutes cannot cross the phospholipid bilayer of the cell
membrane on their own. Hence they are often dissolved in water molecules, which helps facilitate
their movement across the semipermeable membrane. The majority of water transport occurs
through specialized protein channels called aquaporins, which increase the rate of water movement.
Osmosis is a passive process, which is why it needs no or only very little energy in the form of ATP.
3
