1.1.3
Ultrastructure of Eukaryotic Cells
The Nucleus
The Nucleus
The nucleus is a big organelle that contains the cell’s DNA and is surrounded by a nuclear envelope. The largest sub-structure within the nucleus is the nucleolus.


Structure of the nuclear envelope
Structure of the nuclear envelope
- The nuclear envelope is a double-membrane structure that has a number of pores.
- Both the inner and outer membranes of the nuclear envelope are phospholipid bilayers.


Function of the nuclear envelope
Function of the nuclear envelope
- The pores in the nuclear envelope control the passage of ions, molecules and RNA between the nucleoplasm and cytoplasm.


Structure of the nucleus
Structure of the nucleus
- The nucleoplasm is the semi-solid fluid inside the nucleus, where we find the chromatin and the nucleolus.
- In eukaryotes, the nucleus contains linear chromosomes that are made up of DNA.
- There is an area within the nucleus called the nucleolus (plural = nucleoli).


Function of the nucleus
Function of the nucleus
- The nucleus controls the actions of the cell.
- DNA in the nucleus contains instructions for the synthesis of proteins.
- Ribosomal RNA is joined together with associated proteins in the nucleolus to assemble the ribosomal subunits.


Structure of the nucleolus
Structure of the nucleolus
- The nucleolus is the largest sub-structure within the nucleus.
- The nucleolus is made of proteins, RNA and DNA.


Function of the nucleolus
Function of the nucleolus
- The main role of the nucleolus is to act as the site at which ribosomes are made.
- The nucleolus also has secondary roles, such as immobilising proteins and forming signal recognition particles.
Mitochondria and Chloroplasts
Mitochondria and Chloroplasts
Mitochondria produce adenosine triphosphate (ATP) via aerobic respiration. Chloroplasts are plant cell organelles that carry out photosynthesis.


Structure of mitochondria
Structure of mitochondria
- Mitochondria are oval-shaped, double-membrane organelles that have their own ribosomes and DNA.
- Each membrane is a phospholipid bilayer embedded with proteins.
- The inner layer of the membrane has folds called cristae.
- The area surrounded by the folds is called the mitochondrial matrix.
- The mitochondrial matrix contains enzymes used for respiration.


Function of mitochondria
Function of mitochondria
- Mitochondria make ATP via aerobic respiraton.
- Muscle cells have a very high concentration of mitochondria because they are highly active and need a lot of energy to keep the body moving.


Structure of chloroplasts
Structure of chloroplasts
- Chloroplasts have their own circular DNA, ribosomes and have inner and outer membranes.
- The space enclosed by the inner membrane contains a set of interconnected and stacked fluid-filled membrane sacs called thylakoids.
- Each stack of thylakoids is called a granum (plural = grana).
- Grana are linked by lamellae.
- Lamellae are flat, thin parts of thylakoid membrane.
- The fluid enclosed by the inner membrane that surrounds the grana is called the stroma.


Function of chloroplasts
Function of chloroplasts
- Photosynthesis is the series of reactions that use carbon dioxide, water and light energy to make glucose and oxygen.
- This process happens in chloroplasts and allows plants to make their own food (e.g. sugars).
- Chloroplasts are found in plant and algal cells but not in animal cells.
The Golgi Apparatus and Golgi Vesicles
The Golgi Apparatus and Golgi Vesicles
The Golgi apparatus releases Golgi vesicles. Lysosomes are a special type of Golgi vesicle.


Structure of Golgi apparatus
Structure of Golgi apparatus
- The Golgi apparatus is a series of flattened membranous sacs.


Function of Golgi apparatus
Function of Golgi apparatus
- Transport vesicles form from the endoplasmic reticulum and fuse with the Golgi apparatus.
- The transport vesicles empty proteins and lipids into the lumen of the Golgi apparatus.
- As the proteins and lipids travel through the Golgi, they are sorted, packaged and tagged so that they can be sent to the right place.


Structure of Golgi vesicles
Structure of Golgi vesicles
- Golgi vesicles are membrane-bound, fluid-filled vesicles located in the cytoplasm.
- They are small, round and are seen in a high density near the edges of the sacs.
- Lysosomes are a type of Golgi vesicle.


Function of Golgi vesicles
Function of Golgi vesicles
- Golgi vesicles store and transport modified proteins and lipids from the Golgi apparatus to target cells.
- Lysosomes are a special type of Golgi vesicle. They contain enzymes called lysozymes.
- Lysozymes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids and old organelles.
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
Jump to other topics
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
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