Ultrastructure of a generalised cell Flashcards
What are all membranes thought to have?
The same structure
What are membranes composed of?
They are composed of phospholipids and proteins
What type of phosphate and lipid groups do phospholipids have?
A water-hating lipid group and a water-loving phosphate group
How are phospholipids arranged?
They are arranged into double layers (bilayers) The phosphates are on the exposed outer surfaces with the lipids in the middle
Name four functions of membranes
- retain the cell contents
- Recognise molecules that touch them
- Control what enters and leaves the cell
- Give some support to the cell
What is the nucleus surrounded by?
It is surrounded by a double membrane with numerous nuclear pores.
What does the double membrane with numerous nuclear pores surrounding the nucleus do?
They allow the controlled entry and exit of molecules into and out of the nucleus.
What does the nucleus contain?
It contains strands of deoxyribonucleic acid (DNA). and it is arranged into structures called chromosomes
Why is the nucleus of a stained cell darker than the other parts of the cell?
As the DNA in the nucleus readily absorbs many stains and becomes darkly coloured under the microscope.
What does every organism have a definite number of in each nucleus? Give this number for humans nuclei
A definite number of chromosomes. (humans have 46)
Where are genes located?
They are located randomly along chromosomes
Define chromatin
Chromatin is the name given to chromosomes when they are elongated and not dividing
What are genes? What do they control?
Genes are the structures that inform the cell how to make certain proteins.
They control features such as the number of fingers, colour of eyes and production of enzymes
What are genes also known as?
Units of inheritance
When cells are not dividing what do they look like?
They are very elongated and interwoven. In this form they are called chromatin
What do nuclear pores allow?
They allow a type of RNA called mRNA to pass in and out of the nucleus.
What does the nucleolus make?
It makes ribosomes
Where is the nucleolus located?
In an area in the nucleus that stains very darkly.
What is cytoplasm?
It is a jelly-like substance that surrounds the nucleus. A number of organelles are suspended in it.
What do mitochondria provide?
They supply energy to the cell
What cells produce lots of energy? Give an example in both animals and plants
Cells with many mitochondria produce lots of energy. An example is muscle and liver in animals, meristems in plants.
What cells produce less energy? Give an example in both animals and plants
Cells with few mitochondria produce less energy. An example is fat in humans, ground tissue in plants.
Mitochondria are the sites of what?
The sites of respiration
What are mitochondria surrounded by?
A double membrane.
Where is energy released in mitochondria?
It is on the inner membrane, especially the infoldings, that energy is released.
What affects cellular respiration in mitochondria?
The more infoldings that are present the greater the surface area for cellular respiration
What does each mitochondrion contain?
Its own loop of DNA
What causes the number of infoldings in mitochondria to increase?
Exercise
Answer the following in terms of chloroplasts:
- What are they surrounded by?
- What do they have that contains the green pigment chlorophyll?
- What do they also have similar to mitochondria?
- What are chloroplasts?
- Double membranes.
- They have membrane stacks that contain chlorophyll.
- They have a loop of DNA.
- Chloroplasts are green structures in plants in which photosynthesis takes place
Answer the following in terms of cell walls:
- What are they made of?
- Are they impermeable or permeable?
- What is the cell walls function?
- Cellulose (a structural polysaccharide)
- They are fully permeable.
- The function of the cell walls is to support and strengthen the cell.
What do plants have that animals don’t?
Chloroplasts, cell walls, a large vacuole
Answer the following in terms of ribosomes:
- What is the function of ribosomes?
- What are ribosomes made of?
- They work by combining what to form what?
- The function of ribosomes is to make proteins.
- They are made of RNA and protein.
- They work by combining a sequence of amino acids to from a protein.
Name all the parts of an animal cell (9)
Cell membrane Nucleus Nuclear membrane Nucleolus Chromatin Nuclear Pore Cytoplasm Ribosome Mitochondrion
Name all the parts of a plant cell (12)
Mitochondrion Cell wall Cell membrane Nucleus Cytoplasm Vacuole Chloroplast Ribosomes Nuclear pore Nucleolus Chromatin Nuclear membrane
Name the differences between a plant and animal cell
Plant Cells:
Have a cell wall, may have chloroplasts, have a large vacuole
Animal cells:
Don’t have a cell wall or chloroplasts or a large vacuole.
