B2.1 Supplyimg The Cell Flashcards
What is diffusion?
The net movement of particles from a region of high concentration to a region of low concentration, down the concentration gradient
When does diffusion stop?
Until the concentration is the same everywhere and the gradient is 0
Is diffusion passive or active? Why?
Diffusion is passive because energy is not transferred
Give some examples of where diffusion occurs in the body
Glucose and oxygen for respiration diffuse into cells
Carbon dioxide diffuses out of respiring cells as it is poisonous
How does diffusion occur with cells?
The particles pass through the cell membrane to an area of low concentration
What factors affect the rate of diffusion and explain why
The shorter the distance particles need to move the faster the rate because it takes less time for the particles to travel
The steeper the concentration gradient, the greater the net movement of particles, eg CO2 concentration in a plant is low to increase the rate of diffusion
The larger the surface area the quicker the rate of diffusion because there is more space for particles to move, eg the small intestine is folded to increase surface area contact with blood stream
What is osmosis?
A special type of diffusion of water through a semi permeable membrane from an area of high water potential(lowest concentration of solute) to an area of low water potential
What is water potential?
The concentration of free water molecules. The more solute dissolved there is the lower the water potential
Highest water potential is 0
Why does osmosis occur?
So that water levels in cells stay constant
How does a selectively permeable membrane work?
Small holes called pores are small enough for water to pass through but not big enough for larger molecules to pass through
What happens to plant cells and animal cells when water potential is higher outside cell?
The plant cell takes up water and becomes turgid because pressure increases
Animal cells take in water, swell up and burst. This is called lysis
What happens if water potential is lower outside cells?
Plant cells lose water and their turgor pressure falls until they become flaccid. The cell collapses and becomes plasmolysed
Animal cells lose water and become crenated(crinkled)
What is active transport?
The movement of substances from an area of low concentration to an area of high concentration against the concentration gradient. It is active so energy is transferred
Why do cells that use active transport have a lot of mitochondria?
They need to respire to produce large quantities of ATP so the more mitochondrion the higher the rate of active transport
What are carrier proteins?
A protein that is across the width of the cell membrane. A particular molecule binds to the specific protein and then changes shape/rotates to move it into cells
What are some examples of active transport?
In digestion - there is more glucose in the blood than intestine
Plants and root cells - there is a lower concentration of nitrate ions and minerals in the soil so active transport is used to move it into cells
What is mitosis and what is the purpose of it?
Mitosis is the process in which cells divide to produce 2 identical daughter cells which are clones. It is used to replace worn out, damaged or dead cells and used for growth in children and everything
Describe the process of dna replication
The dna molecule unzips so that the bases on each stand are exposed
Free nucleotides in the nucleus line up using complementary base pairing
Dna bases are formed and 2 identical molecules of DNA are produced
Describe the steps in mitosis
Interphase - DNA replication
Prophase -
Metaphase - chromosomes align in the centre of the cell attached with spindle fibres
Anaphase - chromosomes separate and move to opposite pop,es
Telophase - 2 nuclei Reform at 2 ends of cell
Cytokenisis - subcellular structures divide and 2 daughter cells are formed
What is cell differentiation?
When cells become specialised to form a particular job and is more adapted to its function
Adaptations of a sperm cell
Flagellum - to propel the cell and has a lot of mitochondrion
Lots of mitochondria - for respiration to occur so that the flagella has energy to move
Acrosome - an Enzyme to break down the outer layer of the egg cell and transfer genetic material
Fat cell adaptations
Fat cells are specialised to store fat(energy) for use when food is short. They also provide insulation and protection.
They are adapted by having small cytoplasm so that they can expand
Red blood cell adaptations
Biconcave Disc shape - increases surface area to volume ration to speed up the rate of diffusion of oxygen and CO2
Haemoglobin- Protein that binds to oxygen to make oxyhemoglobin
No nucleus - more space for haemoglobin
Ciliated cells purpose and adaptations
Present in the airway to produce sticky mucus to trap bacteria and dirt
Cilia(hairs) to trap dirt and bacteria and sweep mucus away to the back of the throat
Palisade cells adaptations
Full of chloroplast
Shape to allow packing and maximising absorption of sunlight
What are stem cells and function?
Stem cells are undifferentiated cells which differentiate to any type of specialised cells
Where are stem cells found and how do adult ones differ from embryonic
Embryonic stem cells are found in embryos and they have the ability to differentiate into any cell type
Adult stem cells are found in body tissues like bone marrow and can differentiate into some cells but not all, eg stem cells in the marrow differentiate into blood cells
What are adult stem cell used for?
A repair mechanism to regenerate tissue and heal injuries
Where are stem cells found in plants?
They are found in meristems in shoot tips
They have different structures like no chloroplast and thin walls
Why can’t differentiated plant cells not divide through mitosis?
Cell walls are too thick
