Cells Flashcards
Cell-surface plasma membrane
Structure and function
The membrane found on the surface of animal cells and just inside the cell wall of plant cells. Made mainly of proteins and lipids.
The cell membrane regulates the passage of substances into and out of the cell. Also has receptor molecules which allow it to respond to chemicals like hormones.
Nucleus
Structure and function
A large organelle surrounded by a nuclear envelope double membrane that contains many pores. The nucleus contains chromosomes and one or more nucleoli.
The nucleus controls the cells activities. DNA contains instructions to make proteins. The pores allow substances like RNA to move between the nucleus and cytoplasm. The nucleolus makes ribosomes.
Mitochondrion
Structure and function
Generally oval shaped with a double membrane. The inner membrane is folded into cristae. Within this is the matrix, which contains enzymes involved in respiration.
Mitochondria are the site of aerobic respiration, where ATP is produced. They’re found in large numbers in cells that are very active and require a lot of energy, such as muscle cells and liver cells.
Chloroplasts
Structure and function
Chloroplasts are a small, flattened structure found in plant and algal cells. They are surrounded by a double membrane, as well as having membranes within the organelle called thylakoids. These thylakoids are stacked up to form grana. Grana are linked together by lamellae- thin, flat pieces of thylakoid membrane.
Chloroplasts are the site of photosynthesis. The light dependent stage of photosynthesis occurs in the grana and the light independent stage occurs in the stroma.
Golgi apparatus
Structure and function
A group of fluid-filled, membrane-bound, flattened sacs. Vesicles are often seen at the edges of the secs.
The Golgi apparatus processes and packages new lipids and proteins. It also makes lysosomes.
Golgi vesicles
Structure and function
Small fluid-filled sacs in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus.
Stores lipids and proteins made by the Golgi apparatus and transports them out of the cel via the cell-surface membrane.
Lysosome
Structure and function
A round organelle surrounded by a membrane, with no clear internal structure. A type of Golgi vesicle.
Contains digestive enzymes called lysozymes, that are kept separate from the cytoplasm by the surrounding membrane. Lysozymes can be used to digest invading cells or break down worn out components of the cell.
Ribosome
Structure and function
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 and is not surrounded by a membrane.
The site of protein synthesis
Rough Endoplasmic Reticulum
Structure and function
A system of membranes enclosing a fluid-filled space. The surface is covered with ribosomes.
Folds and processes proteins that have been made at the ribosomes
Smooth Endoplasmic Reticulum
Structure and function
A system of membranes enclosing a fluid-filled space, but with no ribosomes on its surface.
Synthesises and processes lipids.
Cell wall
Structure and function
A rigid structure that surrounds cells in plants, algae and fungi. In plants and algae, it’s made mainly of cellulose, while in fungi it’s made of chitin.
Cell vacuole
Structure and function
A membrane-bound organelle found in the cytoplasm of plant cells. It contains cell sap- a weak solution of salts and sugar. The surrounding membrane is called the tonoplast.
Helps to maintain pressure inside the cell and keep the cell rigid. This stops plants wilting. Also involved in the isolation of unwanted chemicals inside the cell
Give 3 specialisations of epithelial cells in the small intestine to absorb food efficiently
- They have microvilli facing the small intestine, which are tiny, finger-like projections that greatly increase the surface area for diffusion and active transport.
- The epithelial cells themselves are situated at the surface of villi, which are finger-like projections from the walls of the small intestines that increase the surface area.
- The epithelial cells have lots of mitochondria to provide energy for the transport of digested food molecules into the cell.
What is the difference between the cytoplasm of eukaryotic cells and prokaryotic cells?
The cytoplasm of prokaryotic cells has no membrane-bound organelles. It has ribosomes, but they’re smaller than those in eukaryotes.
What is a shared characteristic between prokaryotes and eukaryotes?
They have a plasma membrane mainly made of proteins and lipids, which controls the movement of substances into and out of the cell.
What is a flagellum?
A long, hair-like structure that protrudes from some prokaryotes and rotates to make the prokaryote move, like the tail of a sperm cell. Some prokaryotes don’t have flagella and some have multiple.
Where is the DNA in a prokaryotic cell?
Prokaryotes do not have a nucleus. Instead, the DNA floats free in the cytoplasm. It is circular DNA, present as one long coiled up strand. It is not attached to histone proteins.
What is different about the cell wall of prokaryotic cells?
The cell wall has the same function (supporting the cell and maintaining its shape) but it is made of a polymer called murein. Murein is a glycoprotein (protein with a carbohydrate attached)
