2.1 Cell structure Flashcards
What is the structure of the nucleus?
- Surrounded by a double membrane (nuclear envelope)
- Chromatin consists of DNA wound around histone proteins
What is the structure of the nucleus?
- Nuclear envelope separates contents of the nucleus from the cell
- Pores enable larger substances (mRNA) to leave the nucleus
- Inner/outer membranes fuse together so some dissolved substances can enter
- Chromosomes contain genes
What is the structure of the nucleolus?
- No membrane
- Contains RNA
What is the structure of the rough endoplasmic reticulum?
- System of membranes
- Fluid filled cavities
- Continuous with the nuclear membrane
What is the function of the rough endoplasmic reticulum?
- Intracellular transport system
- Cisternae forms channels for transport
- Large surface area for ribosomes
- Proteins pass through to cisternae and transported to golgi apparatus
What is the structure of the smooth endoplasmic reticullum?
- System of membranes containing fluid filled cavities
- No ribosomes
What is the functions of the smooth endoplasmic reticulum?
- Contains enzymes to catalyse reactions for lipid metabolism
- Used for the absorption, transport and synthesis of lipids
What is the structure of the Golgi apparatus?
- stack of membrane bounded flattened sacs
What are the functions of the Golgi Apparatus?
- Modify proteins (adding sugars, adding lipids, folding into a 3d shape)
- Package proteins into vesicles and pinched off (stored in cell, moved to plasma membrane, incorporated into or exported out of the cell)
What is the structure of the mitochondria?
- spherical/rod shape
- 2 membranes with a fluid filled gap
- inner membrane folded into cristae
- inner part is a fluid filled matrix
What is the function of the mitochondria?
- site of ATP during aerobic respiration
- self replicating
- where metabolic energy takes place
What is ATP?
energy currency
What is the structure of the chloroplast?
- Only in plant cells
- double membrane/envelope
- inner membrane with stacks of flattened membrane sacs called thylakoids containing chlorophyll
- contains loops of DNA and starch grains
What is a granum?
Stacks of thylakoids
What is a stroma?
Fluid filled matrix in the chloroplasts
What is the function of the chloroplast?
- site of photosynthesis
- light trapped by chlorophyll to make ATP and water
What is the structure of the vacuole?
- surrounded by a membrane called a tonoplast
- contains fluid
What is the function of the vacuole?
- only plant cells
- filled with water and solutes
- maintains stability
- when full pushes against cell wall to make it turgid
- supports plant in non-woody areas
What is the structure of lysosomes?
- small bags
- formed from golgi apparatus
- contains hydrolytic enzymes
- lots in phagocytic cells
What are hydrolytic enzymes?
Digestive
What is the function of lysosomes?
- keep powerful digestive enzymes from the rest of the cell
- ingest foreign matter and return components for reuse
What is the structure of the ribosome?
- Small and spherical
- made of RNA
- made in nucleolus as 2 separate subunits and passed through the nuclear and cell cytoplasm where it combines
- in cytoplasm of attached to rough endoplasmic reticulum
What is the function of ribosomes on the RER?
Synthesise proteins
What is the function of ribosomes in the cytoplasm?
Site of protein assembly
What is the structure of the centrioles?
- 2 bundles of microtubules at right angles
- made of tubulin protein subunits
- arranged in a cylinder
What is the function of the centrioles?
- Before cell division, spindles of tubulin threads form from centrioles (attach to chromosomes and pull apart with motor proteins during mitosis)
- form undulipodia and cilia
What is the structure of the cellulose cell wall?
- Outside of plasma membrane
- Bundles of cellulose fibres
What is the function of the cellulose cell wall?
- prevents plant cells bursting when turgid
- provide support and strength
- maintain cell shape
- permeable (allows solutions to pass through)
What are the 4 parts of the cytoskeleton?
- microfilaments
- intermediate filaments
- microtubule
- motor proteins
Describe Microfilaments
- subunits of actin
- polymers
- support
- mechanical strength
- allow cell movement
Describe Microtubules
- shape/support
- help movement
- track for motor proteins to travel along
- form spindle before division
- make up cilia, undulipodia and centriole
- made of tubulin
Describe Motor protiens
- 3 different types - myosins, kinesins, dyneins
- enzymes
- allow hydrolysis
- drag vesicles along the microtubules
Describe Intermediate Filaments
- variety of proteins
- anchor nucleus
- extend between cells in some tissues
- enables cell to cell signalling
Describe the steps for the translation and transcription of proteins
- mRNA is made by creating a copy of the genes code
- mRNA exits the nucleus through a nuclear pore
- mRNA attaches to a ribosome where the information is processed and a protein is created (translation)
- The protein is ‘‘pinched off’’ in vesicles and travels towards the golgi apparatus where it is modified
- Vesicles are pinched off from the golgi apparatus with the modified protein and travels towards the plasma membrane
- The vesicles fuses with the plasma membrane
- Exocytosis takes place and the proteins are released into the blood and taken to where they need to be
What are protrusions on a prokaryotic cell called?
Flagella
What are protrusions on a eukaryotic cell called?
Cilia and Undulipodia
Where are cilia found?
In the airways to the lungs in ciliated epithelial cells
What are the similarities of Eukaryotic and Prokaryotic cells?
- Have a plasma membrane, cytoplasm, DNA, ribosomes and RNA
What are the differences of Eukaryotic and Prokaryotic cells?
- Size (p smaller)
- Development of the cytoplasm (e better)
- Nucleus (p doesn’t have one)
- Membrane bound organelles (p none)
- What the walls are made of
- Size of ribosomes (p smaller)
- DNA
What are the walls made of in a prokaryotic cell?
Peptidoglycan
What are the walls made of in a eukaryotic cell?
Cellulose
What is the DNA like in a prokaryotic cell?
- Naked
- Not round around histone proteins - just floats in cytoplasm
- Circular
What is the DNA like in a eukaryotic cell?
- Wound around histone proteins
- In Nucleus
- Linear
What do some prokaryotes also have?
- protective waxy capsule around the cell wall
- small loops of DNA (plasmids) along with large loops
- flagella
- pili (hair like protrusions
- division of binary fission
What is the endosymbiont theory?
Eukaryotic cell evolved from prokaryotic cells 1.5 to 2 billion years ago. This happened when some prokaryotes with infolded membranes were engulfed by other prokaryotes but not digested creating a double membrane structure.
What is resolution?
The ability to distinguish between two separate points and enables to see things in greater detail
What is magnification?
The number of times larger an image is compared to the original object
How does a light microscope work?
Light from a mirror is reflected up through to a specimen into the lens producing a magnification
What is the magnification of a light microscope?
x500-x1500
What is the resolution of a light microscope?
Limited as can’t magnify while giving a detailed image
How does the golgi apparatus modify proteins?
- folding into 3D shapes
- add lipids
- add sugars
