Cell Biology
- Created by: Jmsmcn
- Created on: 14-09-17 15:20
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- Cell Biology
- Active transport
- This is when molecules move from an area of lower concentration to an area of higher concentration
- E.g. in root hair cells there are more minerals in the cell than outside but they move inwards
- It happens in humans in the kidneys and when we take in glucose from the gut
- It uses energy to do this
- We need active transport to survive
- If there is a lower concentration of nutrients in the gut nothing will be absorbed
- Active transport is used so that the minerals can be taken around the body via blood.
- If there is a lower concentration of nutrients in the gut nothing will be absorbed
- This is when molecules move from an area of lower concentration to an area of higher concentration
- Chromosomes and Mitosis
- Nucleus contains genetic information in chromosomes
- Chromosomes are coiled up DNA
- They contain genes which determine characteristics (hair colour)
- Two copies of each chromosome (one from father one from mother)
- 23 pairs
- The cell cycle: how organisms produce new cells
- The part where the cell divides is called mitosis
- Used to grow or replace cells
- End up with 2 identical cells
- The cell duplicated the DNA making X shaped chromosomes
- Each arm of the X is identical
- The chromosome arms are pulled apart and go to opposite ends
- membrans form around the chromosmes forming nuclei
- then the cytoplasm and cell membranes divide
- membrans form around the chromosmes forming nuclei
- Osmosis
- Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
- A partially permeable membrane is a membrane with very small holes that only tiny molecules can fit through
- Water moves both ways (as it moves randomly)
- But there is a net flow from one side to the other because there are more water molecules on one side
- This has the effect of diluting a solution
- Cell Differentiation and Specialisation
- differentiation is when a cell change to be specialized
- They develop different subcellular structures
- Most differntiation occurs when organisms devlop
- Most animal cells cannot change again when the have differentiated
- Cells that differentiate in mature animals are mainly used to repair and replace cells
- a lot of plant cells can change lots of time
- un-differentiated cells are called stem cells
- Most animal cells cannot change again when the have differentiated
- Sperm cells are specialized for reproduction
- Has a long tail and a streamlined head to help it swim
- Lots of mitochondria for energy
- Has enzymes to digest the egg cell membrane
- Only has 23 chromosomes
- Nerve cells ae specilised for signalling
- Long to cover distance
- Branched connections at end to form a network
- Muscle cells are specialized for contraction
- Long so they have space to contract
- Lots of mitochondria for energy
- Root hair cells are specialized for absorbing water
- Large surface area to absorb water
- Phloem and Xylem cells are specialized for transport
- Cells are long so they can cover distances
- differentiation is when a cell change to be specialized
- Exchange Surfaces
- Organisms absorb things they need from the environment and they put waste products into the environment via exchange surfaces
- Oxygen and carbon dioxide are transferred in gas exchange
- Urea diffuses from cells into the blood for removal via urine
- How easy it is for an organism to exchange substance depends in the surface area to volume ratio
- Do do this you find the surface area and the volume in the same unit (e.g. cm squared and cm cubed) and simplify it down or put it as a decimal
- Multi-cellular organisms need efficient exchange surfaces.
- This is because they have quite low surface area to volume ratios
- They have adapted to have: a thin membrane, large surface area, lots of blood vessels, they are well ventilated (for gas exchange)
- In single celled organisms substance diffuse straight into where they are needed so they do not need to adapt as much
- Organisms absorb things they need from the environment and they put waste products into the environment via exchange surfaces
- Binary Fission
- This is how prokaryotic cells split in two
- DNA strand and plasmids replicate
- The cell gets bigger and the DNA strands move apart
- The cytoplasm begins to divide and cell walls form
- The cytoplasm divides and two cells are produced, each cell has one strand of DNA and a variable number of plasmids
- The cytoplasm begins to divide and cell walls form
- The cell gets bigger and the DNA strands move apart
- DNA strand and plasmids replicate
- Bacteria can divide very quickly in the right enviroment
- E.Coli takes as little as 20 mintues
- But in bad conditions the bacteria will not replicate and will begin to die
- This is how prokaryotic cells split in two
- Diffusion
- Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration
- Diffusion happens in both solution and gases because the particles are able to move around
- The large the difference in concentration and the higher the temperature the faster the rate of diffusion is
- Cell membranes allow certain things to move in and out of the cell
- Only very samll things can difuse though it
- Oxygen, glucose, amino acids, and water
- Big molecules cannot fit though the membrane
- Only very samll things can difuse though it
- The molecules go from where there is lots to where there is not much
- Cell membranes allow certain things to move in and out of the cell
- Only very samll things can difuse though it
- Oxygen, glucose, amino acids, and water
- Big molecules cannot fit though the membrane
- Only very samll things can difuse though it
- The larger the surface area of the cell the faster the diffusion rate (more particles can fit through)
- Cell membranes allow certain things to move in and out of the cell
- Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration
- Microscopy
- Light microscopes use light and lenses to magnify the specimen
- Can see subcellular structures such as nuclei
- Electron microscopes use electrons to form an image
- Can see the internal structure of mitochondria and chloroplasts
- Has a higher resolution and magnification
- Resolution is the ability to distinguish between two points
- Magnification = image size/real size
- Light microscopes use light and lenses to magnify the specimen
- Exchanging Substances
- Gas exchange happens in the lungs
- The lungs contain millions of alveoli where gas exchange takes place
- The alveoli are specialized to maximise exchange surfaces: large surface area, moist lining, very thin wall, a good blood supply (thin walls around the blood supply)
- The lungs contain millions of alveoli where gas exchange takes place
- The small intestines absorb nutrients
- They are covered in villi - these are tiny projections lining the gut
- They increase the surface area - speeding up the time taken for nutrients to be absorbed
- They have a single layer of surface cells, and a very good blood supply
- They increase the surface area - speeding up the time taken for nutrients to be absorbed
- They are covered in villi - these are tiny projections lining the gut
- The structure of leaves maximises gas diffusion
- Carbon dioxide diffuses into the leaves air spaces and then into the cells
- The air spaces maximise the surface area of the cells themselves
- The gases diffuse in and put of the stomata
- The guard cells control the size of the stoma
- If there is not much water it closes to stop water being released.
- The guard cells control the size of the stoma
- The flattened shape of the leaf increases the surface area
- Carbon dioxide diffuses into the leaves air spaces and then into the cells
- Gills have a large surface area for gas exchange
- Oxygen diffuses from the water (and carbon dioxide to it) into the blood as the water is passed out through the gills
- Each gill is made of lots of plates called gill filaments - this increases the surface area
- The gill filaments are covered in even smaller lamellae
- the lamellea have lots of blood capillaries and a thin layer of cells
- The blood flows in the opposite direction to the water keeping the concentration gradient high
- There is always a higher concentration of oxygen in the water
- The blood flows in the opposite direction to the water keeping the concentration gradient high
- the lamellea have lots of blood capillaries and a thin layer of cells
- The gill filaments are covered in even smaller lamellae
- Gas exchange happens in the lungs
- Stem Cells
- Embryonic stem cells can turn into any type of cell
- Stem cells are un-differentiated
- They are found in early human embroys
- Adults have stem cells but only in certain places
- Bone Marrow
- Thye can only turn into ceratin cells (auch as red bllod cells)
- Can be used in medicine to replace faulty cells
- An embryo could be made by cloning so the stem cells have the same genes
- This means the cells won't be rejected
- However this is controversial as some feel human embryos have rights
- Some people say saving lives is more important
- However this is controversial as some feel human embryos have rights
- Often embryos used are wasted from fertility clinics
- An embryo could be made by cloning so the stem cells have the same genes
- Stem cells can prouce identical plants
- Stem cells are found in the part where growth occurs
- They can be used to produce clones
- The clones can have desirable features for farmers
- the clones can be used to stop species going extinct
- They can be used to produce clones
- Stem cells are found in the part where growth occurs
- Embryonic stem cells can turn into any type of cell
- Cells
- All living things are made of cells
- Cells can be Prokaryotic or Eukaryotic
- Eukaryotic are complex and include animal and plant cells
- Animal cells have a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes
- Nucleus: contains genetic material, controls the cell
- Cytoplasm: where chemical reactions happen, contains enzymes
- Cell membrane: holds the cell together, controls what goes in and out
- Mitochondria: where respiration happens
- Where proteins are made
- Plant cells have animals subcellular structures and a cell wall, permanent vacuole, and chloroplasts
- Cell wall: supports and strengthens the cell
- Permanent vacuole: contains cell sap
- Chloroplasts: where photo-synthesis happens contain chlorophyll which absorbs light
- Animal cells have a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes
- Prokaryotic are smaller and simpler and include bacteria
- Bacteria has a cell membrane, cell wall, cytoplasm, single strand of DNA, plasmids
- They do not contain a nucleus but they have a strand of DNA floating in the cytoplasm
- Plasmids are small rings of DNA (not all bacteria have them)
- They do not have mitochondria or chloroplasts
- Bacteria has a cell membrane, cell wall, cytoplasm, single strand of DNA, plasmids
- Eukaryotic are complex and include animal and plant cells
- Active transport
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