Lesson 3 - Eukaryotic cell structure Flashcards
Prokaryotic structure
Single-celled organisms with a simple structure of just a single undivided internal area called the cytoplasm.
What makes up Cytoplasm?
Cortosyl. This is made up of water, salts and organic molecules
Eukaryotic cells
Make up multicellular organisms such as plants, animals and fungi.
Have a more complicated internal structure, containing a membrane bound nucleus (nucleoplasm) and cytoplasm, which contains many membrane bound cellular components.
Simply, what does metabolism involve?
Synthesis (building up) and breaking down of molecules
What is required for a chemical reaction in cells?
Enzymes and specific reaction conditions
Cell membranes?
Selectively permeable and control movement of substances into and out of the cell and organelles. Membranes are effective barriers in controlling which substances enter and exit cells. They are fragile.
Organelles in eukaryotic cells?
- Nucleus
- Nucleolus
- Vesicles
- Microtubule network
- Golgi apparatus
- Mitochondria
- Secretory vesicles
- Cytoskeleton
- Smooth endoplasmic reticulum
- Rough endoplasmic reticulum
- Centriole
- Ribosome
- Cytosol
- Cell-surface membrane
Nucleus:
The nucleus contains coded genetic information in the form of DNA molecules.
Biggest organelle in the cell.
What is the purpose of DNA?
Directs the synthesis of all proteins required by the cell (although protein synthesis occurs outside of the nucleus in the ribosomes).
DNA controls the metabolic activities of the cell, as many of these are proteins are the enzymes necessary for metabolism to take place.
Where is DNA contained?
Nuclear envelope to protect it from damage in the cytoplasm. The nuclear envelope contains nuclear pores that allow molecules to move into and out of the nucleus. DNA itself is too large to leave the nucleus to the site of protein synthesis in the cytoplasm. So instead it is transcribed into smaller RNA molecules, which are exported via the nuclear pores.
Chromosomes?
DNA associates with proteins called histones to form a complex called chromatin. Chromatin coils and condenses to form structures known as chromosomes. These only become visible when the cells are preparing to divide.
Nucleolus?
An area within the nucleus that is responsible for producing ribosomes. Composed of proteins and RNA. RNA is used to produce ribosomal RNA (rRNA) which is then combined with proteins to form the ribosomes necessary for protein synthesis.
Mitochondria
Essential organelles in almost every eukaryotic cell. Site of the final stages of cellular respiration.
How does aerobic respiration happen?
Energy stored in the bonds of the complex, organic molecules is made available for the cell to use by the production of the molecule ATP.
The number of mitochondria in a cell is generally a reflection of the amount of energy it uses, so very active cells usually have a lot of mitochondria.
Structure of mitochondria?
Have double membrane. Inner membrane is highly folded to form structures called cristae and the fluid interior called the matrix.
The membrane forming cristae contains the enzymes used in aerobic respiration.
Reproduction of mitochondria?
Mitochondria also contain small amount of DNA, called mitochondrial DNA. Mitochondria can produce their own enzymes and reproduce themselves.
Vesicles
Vesicles are membranous sacs that have storage and transport roles.
The consist simply of a single membrane with fluid inside. Vesicles are used to transport materials inside the cell
Lysosomes
Specialised forms of vesicles:
- Contain hydrolytic enzymes. They are responsible for breaking down waste material in cells, including old organelles.
- Important role in immune system as they are responsible for breaking down pathogens ingested by phagocytic cells. They also play an important role in programmed cell death or apoptosis.
Cytoskeleton:
Cytoskeleton is present throughout the cytoplasm of all eukaryotic cells. Network of fibres necessary for the shape and stability of a cell. Organelles are held in place by cytoskeleton and it controls cell movement and the movement of organelles within the cell.
3 components of cytoskeleton:
Microfilaments:
Microtubules:
Intermediate fibres:
Microfilaments: in cytoskeleton
Contractile fibres formed from the protein actin.
These are responsible for cell movement and also cell contraction during cytokinesis (the process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells.
Microtubules:
Globular tubulin proteins polymerise to form tubes that are used to form a scaffold-like structure that determines the shape of a cell.
They also act as tracks for the movement of organelles, including vesicles, around the cell. Spindle fibres, which have a role in the physical segregation of chromosomes in cell division, are composed of microtubules.
Intermediate fibres:
These fibres give mechanical strength to cells and help maintain their integrity.
When does mRNA travel to free ribosomes?
If protein stays in the cytoplasm
When do mRNA travel to RER?
If protein is secreted from cell
Nucleoplasm
Contains enzymes and nucleotides needed for synthesis of DNA and RNA
Nuclear envelope is made up of
phospholipid bilayers
Dark material in Nucleus
Chromatin
How are chromosomes formed?
DNA tightly wrapped around proteins called histones to form chromatin
Fungi cell wall made up of?
Chitin Polysaccharide
Cilia:
Hair like projections out of cells:
Can be mobile or stationary.
Mobile help move substances in a sweeping motion.
Sensory organs like nose
Centrioles
Made of microtubles in pairs to form centrosome. Involved in the production of spindle fibres and organisation of chromosomes in cell division.
Name of folded membranes on RER and SER?
Cisternae
Functions of lysosome?
- Hydrolyse phagocytic cells
- Completely break down dead cells
- Exocytosis (release enzymes outside of the cell to destroy material)
- Digest worn out cells for reuse of materials
Chloroplasts:
- Surrounded by double membrane
- Contains thykaloids (folded membranes imbedded with pigments)
- Fluid filled stroma contains enzymes for photosynthesis
Cell wall:
- Middle lamella
- Primary cell wall
- Plasma membrane
Cell membrane
Phospholipid bilayer
- molecules embedded within and attached to outside.
What do plant cell walls contain that allow them to connect to neighbouring cells?
plasmodesmata
Purpose of the vacuole:
- Keeps cell turgid
- Stores food reserves
- Maintains pressure within the cell
- Stores waste products
Cell theory:
- Cells are the smallest living unit in all organisms.
- All living things are made of cells.
- All cells come from other pre-existing cells.
