The cell Topic 1 1st year Flashcards
What is a cell?
A cell is the basic unit of life.
True or false.
All cells in the body are different.
True. The cells that make up our kidneys are different from the ones that make up our skin. Although cells are different they all have the same basic plan.
What does the cell theory state?
1) A new cell arises from pre-existing cells
2)Each cell is a basic living unit
3) All organisms are made up of one or more cells.
What do we call organisms which are made up of 1 cell, and organisms which are made up of many cells? Give an example of each.
Unicellular and multicellular
unicellular: bacteria
multicellular: plant
True or false. Cells in multicellular organisms become specialised.
This means that specialized cells have a distinct shape and a particular function
Ex: sperm or red blood cell
How can we further classify cells? The ones which do not contain a membrane-bound nucleus and no membrane-bound organelles. And the ones which do?
Prokaryotic
Eukaryotic
Give an example of a prokaryote and a eukaryote.
Prokaryote: bacteria (more primitive)
Eukaryote: animal or human (more complex)
What are viruses?
Viruses: particles which do not have a cellular structure but they depend on host cells to replicate
What is an organelle?
An organized structure is found in cells with a distinctive shape and function. Ex: mitochondria or chloroplast
Describe the structure and function of the bacterial cell wall.
a permeable structure surrounding the cell membrane. This means that substances can pass freely through it.
Made up of peptidoglycan (murein) which is a polymer made up of sugars and amino acids.
Strong and rigid: does not burst when the cell absorbs water
Describe the function of the cell membrane in bacterial cells
Thin and flexible layer surrounds the cell.
The cell membrane is semi-permeable because it regulates the exchange of substances into and out of the cell. (and it controls what enters or leaves the cell)
Nutrients are allowed to leave and waste products are allowed to leave
Describe the function of the cytoplasm in the bacterial cell
An aqueous jelly-like substance where chemical reactions occur and organelles are suspended in it
Describe the structure and function of the genetic material of the bacterial cell
bacteria have a single-stranded nucleic acid. It is a coiled structure attached to the plasma membrane which floats in the cytoplasm
What are ribosomes?
structures made up of RNA and proteins,sites of protein syntheis
What is the purpose of the slimy capsule in bacteria?
A slimy secretion found in some bacteria which offers protection
What is the purpose of the flagella?
Usd for motility. A hollow structure is found at the base of the bacteria.Moves around in a rotating-like way
Made up of flagellin (protein)
What are plasmids in bacteria?
Tiny circles of self-replicating DNA which provide the bacteria with a survivable advantage
Plasmids can also be exchanged between living cells.
What is a spore?
These are thick protective coats which form when there are bad conditions present,like dryness,heat pr poisions. This provides protection to the bacteria
They can stay in the spare for a long time until conditions have “left”
Draw a well-labelled diagram if a bacterial cell
Why do large organisms consist of many cells instead of 1 large cell?
Exchange of nutrients and waste products are exchanged between the cell membrane and the cell’s external environment
If an organism was just made up of 1 type of cell only, this would cause 2 major problems.
distance of the cell from its centre to the surface
surface area of the cell:
If the cell si going to increase in size more oxygen and nutrients are needed.and more waste products are produced
Cell size limits cell functioning,becase it limits the exchange of nutrients and wastes between the cell and its environment
Describe the surface area of small organisms vs. large organisims
Small organisms: large surface area to volume ratio. (cytoplasm comes into contact with the outside)
Large organisms: small surface area to volume ratio. (however large organisms have developed complex organ systems like the circulatory system and the respiratory system)
The cells deep within the organism are not getting oxygen and nutrients because the cell size is limited
Because of this now the surface area to volume ratio has increased.
What is the nucleus? (in eukaryotic cells)
The largest and spherical organelle in the cell. contains chromatin and nucleolus
It controls everything that takes place inside of the cell: protein synthesis or cell division + chemical reactions take place inside of the cell. Contains the genetic material
It is surrounded by a nuclear envelope which contains pores + inner and the outer membrane.
What is the purpose of the pores in the nuclear envelope?
It allows communication between the nucleus and the cytoplasm
Describe the structure of the pores in the nuclear membrane.
The pores fuse with the inner and outer membranes
The outer membrane is continuous with the endoplasmic reticulum (can be covered with ribosomes)
What is chromatin?
Coils of DNA which are bound to basic proteins called histones
Chromatin can stain easily. 9chromatin means coloured material)
During nuclear division, they can be seen easily if stained because it condense into more tightly threads called chromosomes.
What are the 2 types of chromatin?
Heterochromatin and Euchromatin
Euchromatin: located towards the centre of the nucleus and contains loose coiled chromatin
Heterochromatin: stains intensely, located near the nuclear envelope, tightly coiled chromatin
What is the nucleolus?
Rounded darkly stained strcture in the nucleus which contains DNA and RNA
Mention a function of the nucleolus.
It makes ribosomes (manufactures ribosomal RNA)
In a eukaryotic cell, we also have a cell membrane, cytoplasm. Mention its functions.
Cell membrane: thin flexible layer which keeps together the cell’s internal contents. It is semi-permeable which means that it controls what enters or leaves the cell, and it regulates the exchange of nutrients and waste products between the cell’s cytoplasm and the external environment
Cytoplasm: an aqueous jelly-like substance where chemical reactions occur, organelles are suspended in it
What is the protoplasm and cytosol?
Protoplasm: nucleus + cytoplasm
Cytosol: the intracellular fluid
Draw a labelled diagram of the nucleus.
What is the endoplasmic reticulum?
It is made up of flattened cavities called cisternae made up of parallel membranes
What are the 2 types of endoplasmic reticulum?
Rough (with ribosomes)
Smooth (no ribosomes)
What is the function of the rough endoplasmic reticulum?
Concerned with the modification and transport of proteins which are made by the ribosomes on its surface