Topic 1 - Cell biology (2) Flashcards
14 20 21 (differentiation, diffusion, osmosis
What is the process called by which cells become specialised?
cell differentiation
What is cell differentiation?
the process by which a cell changes to become specialised for its job
What happens when cells differentiate?
What does this allow them to do?
- they develop different subcellular structures
- turn into different types of cells
- this allows them to carry out specific funtions
When does most differentiation happen in both plants and animals?
- most differentiation occurs as an organism develops
- In most animal cells, the ability to differentiate is lost at an early stage, after they become specialised
- however, lots of plant cells don’t ever lose this ability
What is the function of cells that differentiate in mature animals?
repairing and replacing cells (such as in skin or blood cells)
What are undifferentiated cells called?
stem cells
SPERM CELLS:
What is their function?
How are they adapted to this?
- REPRODUCTION - get the male DNA to the female DNA
- It has a long tail and a streamlined head to help it swim to the egg
- there are lots of mitochondria in the cell to provide the energy needed
- carries enzymes in its head to digest through the egg cell membrane
NERVE CELLS:
What is their function?
How are they adapted to this?
- RAPID SIGNALLING - carry electrical signals from one part of the body to anothe
- These are long (to cover more distance)
- branched connections at their ends to connect to other nerve cells and form a network throughout the body
MUSCLES:
What is their function?
How are they adapted to this?
- CONTRACTION - to contract quickly
- they are long (so they have space to contract)
- contain lots of mitochondria to generate the energy needed for contraction
ROOT HAIR CELLS:
What is their function?
How are they adapted to this?
- absorbing water and minerals
- they are on the surface of plant roots and grow into long ‘hairs’ that stick out into the soil - this gives the plant a large surface area for absorbing water and mineral ions out of the soil
PHLOEM + XYLEM CELLS:
What is their function?
How are they adapted to this?
- TRANSPORTING SUBSTANCES - form phloem and xylem tubes which transport subsances like food and water around plants (to form tubes, the cells are joined end to end)
- xylem cells are hollow in the centre and phloem cells have very few subcellular structures, so that stuff can flow through them
DIFFUSION:
What is the definition of diffusion?
the spreading out of particles from an area of higher concetration to an area of lower concentration
DIFFUSION:
In what substances does diffusion occur? WHY?
- in both solutions and gases
- the particles in these substances are free to move about randomly
DIFFUSION:
What are two key ways to increase the rate of diffusion?
- larger concentration gradient
- higher temperature
DIFFUSION:
What is the concentration gradient?
the difference in concentration of substances
DIFFUSION:
How does a higher temperature lead to a faster diffusion rate?
the particles have more energy, so move around faster
DIFFUSION:
How do dissolves substances move in and out of cells?
via diffusion across cell membrames
DIFFUSION:
What type of molecules diffuse across cell membranes?
- only very small molecules can diffuse through cell membranes
- things like oxygen (needed for respiration), glucose, amino acids and water
DIFFUSION:
Name some molecules that can’t diffuse through cell membranes?
Big molecules like starch and proteins
DIFFUSION:
What causes a net (overall) movement of particles across a cell membrane?
- particles move about randomly so they go in both ways
- if there is a lo more particles of one side of the membrane, there’s a net movemnt of particles from that side
DIFFUSION:
What change too the cell mambrane can lead to a faster rate of diffusion?
the larger the surface area of the cell membrane, the faster the diffusion rate, because more particles can pass through at once
OSMOSIS:
What is the definition of osmosis?
the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
OSMOSIS:
What is a partially permeable membrane?
a membrane with very small holes in it so only tiny molecules (like water) can pass through them and bigger molecules (like sucrose) can’t
OSMOSIS:
Why do water molecules pass both ways through a membrane during osmosis?
water molecules move about randomly all the time
