Topic 2A - Cell Structure And Division Flashcards
What are eukaryotic and prokaryotic cells?
Eukaryotic cells are complex and include all animal and plant cells, as well as cells in algae and fungi. Prokaryotic cells are smaller and simpler.
What organelles do plant cells have?
Same organelles as animal cells but with:
A cellulose cell wall with plasmodesmata (channels for exchanging substances with adjacent cells)
A vacuole (compartment that contains cell sap)
Chloroplasts.
What do algal and fungal cells contain?
Algal cells are like plant cells, with the same organelles including a cell wall and chloroplasts.
Fungal cells are also like plant cells, but their cell walls are made of chitin.
They don’t have chloroplasts.
Describe the cell-surface membrane.
It regulates the movement of substances into and out of the cell. It also has receptor molecules which allow it to respond to chemicals like hormones.
Describe the nucleus.
A large organelle surrounded by a nuclear envelope, which contains many pores. The nucleus contains chromosomes (which are made from protein-bound linear DNA) and one or more structure called a nucleolus. The nucleus controls the cell’s activities my controlling the transcription of DNA. The pores allow substances like RNA to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.
Describe the mitochondrion.
They have a double membrane. The inner one is folded to form cristae. Inside is the matrix, which contains enzymes involved in respiration. It is the site of aerobic respiration where ATP is produced.
Describe the chloroplast
A small, flattened structure found in plant and algal cells. It’s surrounded by a double membrane, and also has membranes inside called thylakoid membranes. They are stacked up to form grana, which are linked together by lamellae.
Describe the Golgi apparatus.
A group of fluid-filled, membrane-bound flattened sacs. Vesicles are often seen at the edges of the sacs. It processes and packages new lipids and proteins. It also makes lysosomes.
What is a golgi vesicle?
Stores lipids and proteins made by the golgi apparatus and transports them out of the cell via the cell-surface membrane.
What is a lysosome?
A round organelle surrounded by a membrane. It contains hydrolytic/digestive enzymes which are kept separate from the cytoplasm and can be used to digest invading cells or to break down worn out components of the cell.
What is a ribosome?
A very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. It’s made up of proteins and RNA. It’s not surrounded by a membrane. The site where proteins are made.
What is RER
Covered with ribosomes, folds and processes proteins that have been made at the ribosomes.
What is SER?
Synthesises and processes lipids.
What does the cell wall do?
Supports cells and prevents them from changing shape.
What is the cell vacuole?
A membrane-bound organelle found in the cytoplasm of plant cells. It contains cell sap - a weak solution of sugar and salts. The surrounding membrane is called the tonoplast. It helps to maintain pressure inside the cell and keeps the cell rigid. This stops plants wilting. Also involved in the isolation of unwanted chemicals inside the cell.
What are specialised cells? How are epithelial cells in the small intestine specialised to absorb food efficiently?
In multicellular eukaryotic organisms, cells become specialised to carry out specific functions. A cell’s structure helps it to carry out its function. For example, the walls of the small intestine have lots of finger-like projections called villi. These increase surface area for absorption. The epithelial cells of the surface of villi have folds in their cell-surface membranes, called microvilli, which further increase the surface area.
They also have mitochondria to provide energy for the transport of digested food molecules into the cell.
What are tissues, organs and organ systems?
Specialised cells are grouped together to form tissues. A tissue is a group of cells working together to perform a particular function. Different tissues work together to form organs. Different organs make up an organ system.
What is the cell wall made up of in prokaryotes?
Murein, a glycoprotein.
What is a capsule and a plasmid?
Slime capsule helps to protect bacteria from attack by cells of the immune system. Plasmids are small loops of DNA that aren’t part of the main circular DNA molecule. They are not always present in prokaryotic cells.
What is a flagellum? Whats unique about the cytoplasm of a prokaryotic cell?
Tail to make the bacteria move. The cytoplasm has no membrane-bound organelles. It has ribosomes smaller than in eukaryotes.
Describe viruses.
They are nucleic acids surrounded by protein. They’re smaller than bacteria. Viruses contain a core of genetic material - either DNA or RNA. The protein coat around the core is called the capsid. They have attachment proteins which let the virus cling onto a suitable host cell.
How do prokaryotic cells replicate?
Binary fission. The cell replicates its genetic material, before physically splitting into two daughter cells.
The circular DNA and plasmids replicate. The main DNA loop is only replicated once, but plasmids can be replicated many times. The cell gets bigger and the DNA loops move to opposite poles of the cell. The cytoplasm begins to divide and new cell walls begin to form. The cytoplasm divides and two daughter cells are produced. Each daughter cell has one copy of the circular DNA, but variable number of copies of the plasmids.
How do viruses replicate?
They use their attachment proteins to bind to complementary receptor proteins on the surface of host cells. Different viruses have different attachment proteins and therefore require different receptor proteins on host cells. They inject their DNA or RNA into the host cell to use its machinery to replicate the viral particles.
What is magnification and resolution?
How much bigger the image is than the sample you are looking at.
Magnification = size of image/size of real object
Resolution is how well a microscope distinguishes between two points that are close together.