Cells Flashcards
What is a eukaryotic cell?
Contain nuclei and membrane bound organelles, e.g plant, animal, fungi and protoctists
What is a prokaryotic cell?
Contain no true nucleus, DNA is found free in the cytoplasm, and have no membrane bound organelles, e.g bacteria
Differences between prokaryotes and eukaryotes
Prokaryotes: no nucleus, no membrane bound organelles, 70S ribosomes, circular DNA not associated with histone proteins, murein cell wall, only unicellular, contains plasmids and may have capsule
Eukaryotes: nucleus, membrane bound organelles, 80S ribosomes, linear DNA associated with histone proteins, cellulose cell wall, can be multicellular, no plasmids, no capsule.
What is tissue?
group of similar cells that work together for a specific function, e.g muscle tissue
What are organs?
a group of different tissues working together to perform a particular function, e.g muscle to churn and mix stomach contents
What is an organ system?
A group of different organs working together to carry out a major function in the body, e.g digestive system
What is the structure if a nucleus?
-surrounded by a nuclear envelope which is a double membrane
-nuclear pores are small channels that span the nuclear envelope and let substances enter and exit the nucleus, e.g mRNA
-chromatin is DNA wrapped around proteins, makes up the inside of the nucleus
-the nucleolus is a small spherical region which manufactures ribosomal RNA and assembles ribosomes
What is the function of the nucleus?
contains the cells DNA and controls the cells activities through production of mRNA, tRNA, and also assembles ribosomes
What is the structure of a ribosome?
-have two subunits, one large and one small
-made of only protein and rRNA
-found free in cytoplasm or associated with the rough ER
What is the function of ribosomes?
protein synthesis
What is the structure of the rough endoplasmic reticulum?
-continuous with the outer membrane of the nucleus
-forms an interconnected network of flattened membrane-enclosed scans called cisternae
-forms flats sheets called lamellae
-ribosomes present on the outer surfaces of membrane
What is the function of the rough endoplasmic reticulum?
protein synthesis
What is the structure of the smooth endoplasmic reticulum?
-tubelike structure
-lacks ribosomes on the surface
What is the function of the smooth endoplasmic reticulum?
-synthesises, stores and transports lipids
-synthesises, stores and transports carbohydrates
What is the structure of the golgi apparatus?
- consists of a stack of membranes that make up flattened sacs called cisternae
What is the function of the golgi apparatus?
-proteins and lipids produced by the ER are passed through
-modifies these proteins, e.g addition of carbohydrates to form glycoproteins
-‘labels’ them to be sent to their destinations
-proteins and lipids sent into vesicles which are regularly pinched off ends, they may move to the cell surface where they fuse with the membrane and release contents
What is the structure of lysosomes?
-contain enzymes such as protease, lipase and lysozymes
-they isolate these enzymes from the rest of the cell before releasing then either to the outside of the cell or into a phagocytic vesicle
What is the function of lysosomes?
-hydrolyse material ingested by phagocytic cells
- release enzymes outside of the cell to destroy material outside of the cell
- digest worn out organelles
What is the structure of mitochondria?
- usually ‘rod-shaped’
- surrounded by double membrane that controls the entry and exit of materials
- the inner membrane is folded to form extensions called cristae, this creates a large surface area tor attachment of enzymes and proteins involved in respiration
- the matrix is found in the middle which contains enzymes and proteins involved in respiration
What is the function of mitochondria?
-site of respiration
-responsible for the production of ATP
What is the structure of a vacuole?
-fluid filled sac bound by a single membrane, tonoplast
-contains solution of mineral salts, sugars,amino acids and pigments
What is the function of a vacuole?
-supports plants by making them turgid
-pigments may colour petals to attract pollinators
What is the structure of chloroplasts?
-the stroma is a fluid filled matrix and contains enzymes and proteins needed to make sugars in the second stage of photosynthesis
-starch grains are found in the stroma
-chloroplasts contain DNA and ribosomes so can quickly manufacture proteins needed for photosynthesis
What is the function of chloroplasts?
carry out photosynthesis
What is the structure of the cell wall?
-made of microfibrils of cellulose
-thin layer of in the middle called lamella, which marks the boundary between adjacent cell walls and cements adjacent cells together
What is the function of a cell wall?
-provides mechanical strength to plant
-gives mechanical strength in order to prevent the cell from bursting
-allows water to pass along it
