Studied by 5 people
What do we use to see cells clearly?
A microscope
How do cells cooperate initially?
Sharing resources
How do cells cooperate as cell numbers increase?
Division of labour and specialisation
What is it called when an organism has two layers of cells?
Diploblastic
What is an example of an organism that has become specialised and how is it specialised?
A hydra, has a ring of tentacles around its mouth and has cells on its arms specialised to harpoon victims and inject them with a paralysing venom. The cells in its body cavity are specialised for digestion
How does a hydra reproduce asexually?
Budding
How do plants tend to communicate?
Chemically
How do complex animals communicate?
Chemically and electrically
What ability do cells lose as the become more specialised?
The ability to differentiate
What does differentiate mean?
The ability to become other types of cells
What is it called when an organism has three layers of cells?
Triploblastic
What is an example of cell differentiation in a complex animal?
Lizards that can regenerate their tail
What is a microscope with only one lens called?
A simple microscope
What is the name of a microscope with two or more lenses to increase magnifying power?
A compound microscope
What are the parts of a microscope?
Eyepiece lens, barrel, objective lens, stage, clip, diaphragm, light source, base, fine focus, coarse focus
What are the main three objective lenses used?
x4 (low), x10 (medium), x40 (high)
What does the coarse focus control?
Large movements of the stage
What does the fine focus control?
Very small movements of the stage
How is magnification calculated?
Eyepiece magnification x objective magnification
What is resolution?
The minimum size of an object that can be viewed clearly through a microscope
How did magnification affect the field of view on a microscope?
As the magnification increases, the field of view becomes smaller
How does magnification affect the depth of focus on a microscope?
As the magnification increases, the depth of focus decreases
What are the main differences between plant and animal cells?
Plant cells have a cell wall made of cellulose, and animal cells have no cell wall. Plant cells contain chloroplasts, and animal cells have no chloroplasts. Plant cells have a large permanent vacuole, and animal cells only have small non-permanent vacuoles
What do electron microscopes use as a source of illumination and what does this allow?
They use accelerated electrons as a source of illumination, giving much greater resolution, allowing for much greater magnification
Are electron micrographs 2D or 3D?
3D
How do specimens need to be viewed for electron microscopes?
In a vacuum to allow the free movement of electrons, and the slices must be extremely thin to allow the electrons to pass through
What is fixation?
Cutting cells and filling them with solid material to hold the membrane in place to avoid them bursting. This must be done without changing the cell shape or disrupting the contents
What is an artefact?
An object that is not a part of the cell, e.g. a sliver of the cutting blade
What is cell ultrastructure?
Components of the cell that are only visible using an electron microscope
What are the main organelles in an animal cell?
Nucleus, cell membrane, cytoplasm, mitochondria, ribosomes
What are the main organelles in a plant cell?
Cytoplasm, cell wall, cell membrane, ribosomes, vacuole, mitochondria, nucleus, centrioles
What are the other names of the cell membrane?
The plasma membrane and the phospholipid bilayer
What is the structure of the cell membrane?
The inner and outer surfaces are composed of phosphate groups, each of which has two lipid tails stretching towards the centre. Embedded in it are numerous proteins, some of which connect the outside and inside, while others only go part way or stick out
What are some functions of the cell membrane?
It acts as the boundary of the cell
Proteins on the surface help identify tue cell as part of the self so that it doesn’t get attacked by the body
It has receptors to allow hormones to attack and influence its activity
Active transport
The cell membrane is selectively permeable, what does this mean?
It only allows certain substances through
What is diffusion?
Small molecules such as oxygen and water can pass through the cell membrane. They diffuse from a higher concentration to a lower concentration
What does it mean if diffusion is a passive process?
It does not require energy
What is osmosis?
The diffusion of water across a selectively permeable membrane
What is active transport?
The proteins that connect the inside of the cell membrane to the outside can pump substances against the concentration gradient
Does active transport require energy?
Yes, supplied by ATP (adenosine triphosphate)
What is an example of active transport?
Plant root hairs pumping minerals from the soil into the roots
What is the fluid mosaic model?
The cell membrane is constantly moving, and is not a stationary structure like it appears to be in electron micrographs
What does cytoplasm consist of an contain?
Cystol, suspends all organelles inside the cell, apart from the nucleus
What are some examples of membrane-bound organelles within the cell?
Nucleus, mitochondria, chloroplasts, etc.
What is an example of an organelle within the cell that is not membrane-bound?
Ribosomes
What substances does the cytoplasm contain that are needed by the cell to carry out its functions?
Glucose, amino acids, lipids, proteins, enzymes, oxygen
What is the medium in which most chemical reactions of the cell take place?
The cytoplasm
What is glycolysis and where does it take place?
The first stage of respiration, where glucose is split, with the release of a small amount of energy. Takes place in the cytoplasm of cells
What is cytoplasmic streaming?
The obvious movement of cytoplasm in plant cells, where it forms a thin layer between the vacuole and cell membrane
What is the nucleus filled with?
A jelly-like substance called nucleoplasm
What does nucleoplasm contain?
Chromosomes, nucleotide bases and amino acids
What is the name of the phospholipid bilayer that surrounds the nucleus?
The nuclear envelope
What is the function of the nucleus?
It is the control centre of the cell
Where are the instructions contained in the nucleus?
In the genes
How many copies of each gene are in each cell?
Two, one from the father and one from the mother
Where are genes stored?
On the chromosomes
How many chromosomes do humans have?
46, consisting of 23 pairs
What are chromosomes made of?
Deoxyribonucleic acid (DNA) and proteins
What is a double helix?
Macromolecules form this shape, which is like a twisted ladder where alternate deoxyribose sugar and phosphate molecules form the sides and base pairs, held together by hydrogen bonds to form the rungs
What do chromosomes hold?
The genetic code for making proteins
What percentage of chromosomes are coding structures (genes)?
2%
What percentage of chromosomes are non-coding DNA, also known as junk DNA?
98%
What happens to chromosomes immediately prior to cell division?
The DNA coils around the histones many times in succession. Each coiling makes the chromosomes shorter and thicker until they are clearly visible
What happens to chromatids when coiling is completed?
Each chromatid is essentially identical to its partner and as soon as they are separated they become known as chromosomes
During coiling what, does each chromosome consist of?
Two roughly symmetrical strands called chromatids joined by a structure called the centromere
Where else is DNA found?
In mitochondria and chloroplasts
What are nuclear pores?
Gaps in the nuclear envelope that allow substances to enter and leave the nucleus
What enters the nucleus through the nuclear pores?
Proteins, amino acids, nucleotide bases
What leaves through the nuclear pores?
mRNA, rRNA, protein subunits that make ribosomes
What is the plural of nucleolus?
Nucleoli
What are nucleoli?
Darker staining areas within the nucleus
What do nucleoli produce?
Individual components, rRNA and proteins that combine on the cytoplasm to form ribosomes
What is the plural of mitochondrion?
Mitochondria
What do mitochondria consist of?
A smooth outer membrane and a folded inner membrane with a cavity between them
What is the name of the structures the inner membrane folds into?
Cristae
What is the jelly-like substance in the centre of mitochondria?
The matrix
What is found in the matrix?
Ribosomes and mitochondrial DNA
What are the ‘powerhouses’ of the cell and why?
Mitochondria, because they produce almost all of the energy required by the cell
What stage of aerobic respiration takes place in the matrix?
The second stage, Krebs cycle
What stage of respiration takes place on the large surface area of the cristae?
The final stage, the electron transport chain
What enzyme influences the final stage of respiration?
ATP synthase
How is ATP made?
By combining adenosine diphosphate (ADP) with a third phosphate
What is the equation for ATP?
ADP + P + energy = ATP
What does ATP do?
It stores and transports energy within cells
What happens to ATP when energy is required?
The ATP breaks down to ADP, releasing the third phosphate and the stored energy
What is the equation for when ATP breaks down?
ATP = ADP + P + energy
What is the process of ATP building up and breaking down called?
The ADP-ATP energy cycle
What were mitochondria derived from and what is the evidence for this?
A free-living prokaryotic organism that was taken in and formed a symbiotic relationship. The evidence is them having a double membrane and containing their own DNA, as well as ribosomes
What are the two types of ribosomes?
Free and bound
What are bound ribosomes attached to?
The endoplasmic reticulum
What are ribosomes made of?
Ribosomal RNA (rRNA) and proteins that were made in the nucleolus and assembled in the cystol
What do ribosomes do?
They build and manufacture proteins
How do ribosomes manufacture proteins?
They move along strands of mRNA, producing many copies of the specified protein
How do ribosomes determine the order in which to assemble the amino acids that make up the protein?
By reading the code nucleotide bases
When do proteins fold into their functional state?
As they are formed
What is the difference between what free and bound ribosomes produce?
Free ribosomes produce proteins used in the cystol. Bound ribosomes produce proteins that are packaged and exported from the cell
What are plastids?
A group of membrane-bound organelles only found in plant cells
What are leucoplasts?
Colourless organelles that store starch
What jelly-like substance fills the space between the inner and outer membrane of chloroplasts?
Stroma
What happens in the stroma?
The light-independent stage of photosynthesis (Calvin cycle)
Note
Flashcard