3.2.1.1 Structure of Eukaryotic Cells Flashcards
Nucleoplasm
Bulk of the nucleus formed from a granular jelly
Nucleoulus
Spherical region within the nucleus which manufactures RNA and assembles ribosomes
Nuclear envelope
Double stranded, it controls what goes in and out of the cell, reactions take place here and they contain ribosomes
Nuclear pores
These allow passage of large molecules e.g., mRNA
Chromatin in the nucleus
Linear DNA which is histone bound, this condenses to form visible chromosomes during nuclear division
List the functions of the nucleus
Produces mRNA and RNA for protein synthesis
DNA replication
Contains genetic information for primary structure of polypeptides
Double membrane (mitochondrion)
Controls entry and exit of substances in a cell and the inner of the 2 membranes fold to form cristae
Cristae
Extensions forming folds of the inner membranes, these provide a large surface area for enzymes involved in aerobic respiration e.g., ATP synthase
Matrix
Contains: proteins, lipids mitochondrial DNA and 70S ribosomes. By contains mitochondrial DNA, it allows mitochondria to produce its own proteins for respiration independent of a nucleus
Rough endoplasmic reticulum
Found on certain parts of the outer membrane of the nucleus
Contains ribosomes
Provides a large surface area for the synthesis of proteins
Packages proteins into vesicles and transports these to the Golgi apparatus ready for modification
Smooth endoplasmic reticulum
No ribsomes
Tube like appearance
Stores, transports and synthesis carbohydrates and lipids
State the definition of a eukaryotic cell (1)
(A cell that contains a) nucleus AND membrane-bound organelles
Accept membrane bound organelles AND nucleus
Ignore any reference to prokaryotic cells
Ignore any reference to examples of organelles
Ignore any reference to diagrams
Golgi apparatus
- Lipids and proteins formed in the RER and SER are passed through the GA in a strict sequence
- These are then modified by adding carbohydrates and lipids to them forming glycoproteins and glycolipids
- These modified proteins are then packaged into vesicles which are regularly ‘pinched off’ from the Golgi cistarne
- These vesicles then fuse or move towards the cell surface membrane where they release there contents during exocytosis
Ribosomes
Formed of ribosomal RNA and protein subunits needed to synthesise proteins. They may be found in the cytoplasm or attached to the membrane of the RER. There are 2 types:
1. 70S which are smaller and found in prokaryotic cells
2. 80S which are larger and found in eukaryotic cells
Cell surface membrane
- Controls passage of molecules in and out of the cell
- Made up of: carbohydrates, phospholipids and specific transport proteins arranged in ‘fluid mosaic model’
- All cell surface membranes have the same basic structure, however, the proportion of molecules varies depending on the function of the cell.
Draw and label a nucleus
See notes
Draw and label a mitochondrion
See notes
Draw and label a lysosome
See notes
Lysosomes are produced by which organelle?
Golgi apparatus
An important structure of a eukaryotic cell is lysosomes.
Describe the general behaviour and structure of lysosomes
- Contains and releases hydrolytic enzymes
- Contains and releases lyzozomes (enzyme)
- It is single membrane and in a spherical shape
- They isolate the hydrolytic enzymes before release so that there is no unwanted breakdown of the cells ultrastructure
List the functions of lysosomes
- Fuse with foreign materials ingested by phagocytic cells and release hydrolytic enzymes
- Release enzymes to the outside of the cell in exocytosis to break down molecules
- Breakdown damaged and worn out organelles so the useful molecules they’re built from can be restored
- Completely break down dead cells (autolysis)
Describe the role of organelles in eukaryotic cells for the production, transport and release of proteins (6)
- DNA in the nucleus codes for proteins
- Ribosomes/RER produce proteins
Allow synthesise proteins - Mitochondria produce ATP (for protein synthesis)
Reject any reference to energy - Golgi apparatus modify and package proteins
- Vesicles transport proteins
- Vesicles fuse with cell (surface) membrane during exocytosis
What do plant cells contain that animal cells do not?
- Large central vacuole containing cell sap
- Chloroplasts
- Cell wall
What is the main storage difference between animal and plant cells?
- Animal cells store carbohydrates as glycogen
- Plant cells store carbohydrates as starch
Draw out and label the structure of a chloroplast
Include:
- Inner membrane and outer membrane
- Granum
- Thylakoid
- Starch grain
- 70S ribosomes
- DNA
- Stoma
Describe the structure of a chloroplast
- Site of photosynthesis
- The chloroplast envelope is a double membrane, it is highly selective and controls what goes in and out.
- Inside, is the grana, these are stacks of (up to 100) disc shaped thylakoid which contain membranes
- Thylakoid membranes contain the photosynthetic pigment chlorophyl, the first stage of photosynthesis takes place here
- The stroma is a fluid filled matrix, which contains photosynthetic enzymes and starch grains. The second stage of photosynthesis takes place here
Outline the functions of a chloroplast
- The thylakoid membrane has a large surface area so that lots of (the photosynthetic pigment) chlorophyll can be stored
- Chloroplasts contain their own circular DNA and ribosomes so that they can form there own proteins for photosynthesis
Draw and label the structure of a cellulose cell wall
See notes
Describe the structure and functions of a cellulose cell wall
- Straight chains of beta glucose are held together by many (weak) hydrogen bonds forming microfibril
- These provide strength, stability and rigidity
- They prevent the cell from bursting due to pressure of water entry by osmosis
Draw and label the structure of a vacuole
See notes
Outline the structure and functions of a vacuole
- Fluid containing sack bound by a single membrane called a tonoplast
- Contains: mineral salts, waste, amino acids, sugars, and sometimes pigment
- It provides support - keeps the cell turgid
- Pigment attracts pollinating insects
State the differences a prokaryotic cell has compared to a eukaryotic cell (6)
- DNA is circular, not histone bound and contains no introns
- No true nucleus, DNA is found free in the cytoplasm
- Contains smaller 70S ribosomes
- Cell wall is made of glycoprotein meurin (plant cell walls are made of cellulose)
- No membrane-bound organelles
- Contains: capsule, one or more plasmids and one or more flagella
Outline how lysosomes break down vesicles (3)
-
Fuse(s) with vesicle
Reject converse - Release hydrolytic enzymes
Accept lyzozomes - Break down
Compare and contrast the DNA in eukaryotic cells with DNA in prokaryotic cells (5)
Comparisons
1. Nucleotide structure is identical;
Accept labelled diagram
- Nucleotides joined by phosphodiester bond;
OR
Deoxyribose joined to phosphate (in sugar, phosphate backbone);
- DNA in mitochondria / chloroplast same / similar (structure) to DNA in prokaryotes;
Contrasts
4. Eukaryotic DNA is longer;
- Eukaryotic DNA contains introns, prokaryotic DNA does not;
- Eukaryotic DNA is linear, prokaryotic DNA is circular;
- Eukaryotic DNA is associated with / bound to / protein / histones, prokaryotic DNA is not;
Give two types of molecules from which a ribosome is made (2)
- RNA/rRNA;
- Protein;
Reject tRNA and mRNA
Ignore amino acids
Outline the similarities in, and the differences between, the structures of chloroplasts and mitochondria (4)
Similarities
1. Double membrane;
2. Both contain (circular) DNA;
3. Both contain ribosomes;
Differences
4. Thylakoids/lamellae/grana v cristae;
5. Stroma v matrix;
6. Pigments v no pigments;
7. Starch grains v no starch grains;
- Ignore numbers in
front of ribosomes - Accept ‘chlorophyll
v no chlorophyll’
