Eukaryotic cell structure Flashcards
Name all the parts to a eukaryotic cell nucleus and draw and label.
- Nuclear envelope.
- Nuclear pores.
- Nucleoplasm.
- Chromosomes.
- The nucleolus.
What’s the role of the nuclear envelope in the nucleus?
- A double membrane that surrounds the nucleus.
- Its outer membrane is continuous with the endoplasmic reticulum of the cell and often has ribosomes on it.
- Controls entries and exits of materials in and out of the nucleus.
- Contains the reactions taking place within it.
What’s the role of the nuclear pores in the nucleus?
- Allows large molecules e.g. mRNA out of the nucleus.
- There are about 3000 pores in each nucleus, 40-100nm in diameter.
What’s the role of the nucleoplasm in the nucleus?
- The granular, jelly-like material inside of the nuclear membrane or nuclear envelope
- Made up mostly of water, a mixture of various molecules, and dissolved ions.
- It helps to maintain the shape of the nucleus.
What’s the role of the chromosomes in the nucleus?
- Consists of protein bound, linear DNA.
What’s the role of the nucleolus in the nucleus?
- A small spherical region within the nucleoplasm.
- Manufactures rRNA and assembles the ribosomes.
- There might be more than one nucleolus in a nucleus.
What is the function of the nucleus?
- Acts as a control center of the cell through the production of mRNA and tRNA hence protein synthesis.
- Retain the genetic material of the cell in forms of DNA and chromosomes.
- Manufacture rRNA and ribosomes.
Name all the structures in the mitochondrion and draw and label the structure.
- A double membrane.
- Cristae.
- Matrix.
What is the role of the double membrane in the mitochondrion?
- Controls entry and exit of material.
- The inner part of the double membrane is folded to form extensions known as cristae.
What is the role of the cristae in the mitochondrion?
- They are extensions of the inner membrane, in some species, it goes across the whole width of the mitochondrion.
- They provide a LARGE SA for the attachment of enzymes and other proteins involved in respiration.
What is the role of the matrix in the mitochondrion?
- It makes up the rest of the mitochondrion.
- Contains protein, lipids, ribosomes, and DNA which allows mitochondrion to control the production of some of their own proteins.
- Many enzymes that are involved in respiration are found in the matrix.
Why are mitochondria important for our body?
- They are the sites of the aerobic stages of respiration. so they are responsible for the production of ATP from respiratory substrates e.g. glucose.
- Due to this, the number and size of mitochondria and their number of cristae are high in cells which has high levels of metabolic rate who requires a plentiful supply of ATP. E.g. muscle and epithelial cells- EC need a lot of ATP for absorbing substances from the intestines by active transport.
What are chloroplasts?
Organelles that carry out photosynthesis.
They vary in shape but usually disc-shaped, 2-10um long and 1um in diameter.
Draw and label the structure of the chloroplast and list the features within it.
- The chloroplast envelope.
- The grana.
- The stroma.
What is the role of the chloroplast envelope in the chloroplast?
- It’s the double plasma membrane which surrounds the organelle.
- It’s highly selective in what it allows to enter and leave the chloroplast.
What is the role of the grana (granum sing.) in the chloroplast?
- Grana are stacks of up to 100 disc-like structures called thylakoids.
- Within the thylakoids it contains chlorophyll.
- Some thylakoids have tubular extensions that join up with the thylakoids in adjacent grana.
- The grana are where the first stage of photosynthesis (light absorption) takes place.
What is the role of the stroma in the chloroplast?
- Stroma is a fluid-filled matrix where the 2nd stage of photosynthesis takes place (synthesis of sugar).
- Within the stroma, there are other structures e.g starch grains.
- It’s the solution that surrounds the grana.
How are chloroplasts adapted towards taking in sunlight to carry out photosynthesis?
- Many grana, large surface area for photosynthetic pigments, electron carriers and ATP synthase enzymes.
- Contains chloroplast DNA and ribosomes needed to make proteins for photosynthesis.
- Stroma - the fluid contains all the enzymes that’s needed for making sugars in the 2nd stage of photosynthesis.
What is the endoplasmic reticulum (ER) draw and label?
- ER is a 3-dimensional sheet-like membrane that spreads throughout the cytoplasm of the cell.
- It continues towards the outer nuclear membrane where the membranes include many tubules and flattened sacs called cisternae.
What are the 2 types of ER?
- Rough endoplasmic reticulum - RER - It has ribosomes present on the outer surfaces of the membrane.
- Smooth endoplasmic reticulum - SER - It lacks ribosomes on its surface and appear to be more tubular shaped.
What’re the functions of RER and SER?
- RER - provides a large SA for the synthesis of proteins and glycoproteins (simple protein with sugars attached).
- Provide a pathway for the transport of materials e.g. proteins throughout the cell.
- SER - synthesise, store and transport lipids.
- synthesise, store and transport carbohydrates.
Why do cells e.g. liver and secretory cells- epithelial cells that line the intestine have a very extensive ER?
They have a very extensive ER because they need to make and store a lot of carbohydrates, proteins, and lipids.
Where does the Golgi apparatus occur?
It occurs almost in all eukaryotic cells and similar to SER in structure but it’s more compact.
What does the Golgi apparatus consist of?
Stack of membranes that make up flattened sacs (cisternae), with small rounded structures called vesicles.
What does the Golgi apparatus do?
- The proteins produced by the ER is passed through the Golgi apparatus.
- The Golgi modifies these proteins by attaching a non-protein molecule e.g. carbohydrate.
- It ‘labels’ them so they can be accurately sorted out and be sent to their correct destination.
- When they are sorted, the proteins and lipids are transported in Golgi vesicles which are regularly pinched off from the ends of the Golgi cisternae.
- Those vesicles may move to the cell surface, where they fuse with the membrane and release their contents to the outside.
What are the functions of the Golgi apparatus?
- Add carbohydrates to proteins to form glycoproteins.
- Produce secretory enzymes, e.g. those secreted by the pancreas.
- Secret carbohydrates e.g. those used in making the cell walls of plants.
- Transport, modify and store lipids.
- Form lysosomes.
How are lysosomes formed?
- Lysosomes are formed when the vesicles produced by the Golgi apparatus contains enzymes e.g. protease, lipase.
What are lysozymes?
- Lysozymes are obtained in the lysosomes, they are the enzymes that hydrolyse the cell walls of certain bacteria.
How do lysosomes obtain the enzymes?
- They can contain up to 50 enzymes in a single lysosome
- They isolate these enzymes from the rest of the cells before releasing them, either to the outside or into a phagocytic vesicle within the cell.
What are the functions of a lysosome?
- Hydrolyse materials that are ingested by phagocytic cells e.g. bacteria.
- Release enzymes to the outside of the cell (exocytosis) so they can destroy the material around the cell.
- Digest worn out organelles so useful materials they are made of can be re-used.
- Completely break down cells after they have died (autolysis).
What are ribosomes?
They are small cytoplasmic granules found in all cells, may occur in the cytoplasm or associated with RER.
What are the 2 types of ribosomes?
- 80s - found in eukaryotic cells
- 70s - found in prokaryotic cells, mitochondria, and chloroplast.
Ribosomes have 2 subunits- one large and one small, each containing rRNA and proteins.
What are the functions of ribosomes?
- Site for protein synthesis.
- They assemble amino acids to form a specific protein.
What is the cell wall?
- Found in all plant cells, it consists of microfibrils of polysaccharide cellulose, embedded in a matrix.
- Cellulose microfibrils are quite strong so it can help yo support the cell wall.
What are the features of the cell wall?
- Consists of a number of polysaccharides e.g. cellulose.
- There’s a thin layer - middle lamella which marks the boundary between adjacent cell walls.
What are the functions of the cell wall?
- Provide strength to prevent the cell bursting under pressure created by the osmotic entry of water.
- Give mechanical strength to the plant as a whole.
- Allow water to pass along it so contributes to the movement of water through the plant.
What makes up the cell wall of algae?
- Either cellulose or glycoprotein or both.
What makes up the cell wall of fungi?
- Fungi’s cell wall does not contain cellulose but includes a mixture of a nitrogen-containing polysaccharide called Chitin, a polysaccharide called Glycan and Glycoproteins.
What are vacuoles?
- Fluid-filled sac bounded by a single membrane.
- Within matured plant cells, there’s usually a large central vacuole and the single membrane around it is called the tonoplast.
What substances does a plant vacuole contain?
Solutions of mineral salts, sugars, amino acids, wastes and sometimes pigments e.g. anthocyanins.
What are the functions of vacuoles?
- Support herbaceous plants and herbaceous parts of a woody plant, by making them turgid.
- Sugar and amino acids can act as a temporary food store.
- Pigments may colour petals to attract pollinating insects.
