Transcript KS4 Movement In and Out of Cells

Contents
Movement In and Out of Cells
What is diffusion?
Diffusion and life processes
Active transport
Osmosis
Experiments: diffusion and osmosis
Multiple-choice quiz
1 of 44
Smells and liquids spreading out
Why can you smell cooked
food from a distance?
Why does the colour of
concentrated fruit drink change
when it is added to water?
Why can you smell
perfume or aftershave
when someone walks
past you?
2 of 44
Smells and liquids spreading out
Smelling cooked food or perfume and diluting juice in water
all involve things moving around and spreading out.
These processes are all examples of diffusion.
Diffusion involves the movement of molecules.
What type of molecules are moving in these examples?
3 of 44
Moving molecules
The molecules in every substance are always moving.
In which state are molecules able to spread out?
ice (solid)
water (liquid) water vapour (gas)
Diffusion involves the movement of gas and dissolved
molecules. Why don’t solid molecules diffuse?
4 of 44
Diffusion and changing concentrations
When smelling body spray where is the smell strongest
and where is the smell weakest?
Smell is strongest
at source.
Diffusion means the smell
spreads out and gets weaker
further away from the source.
How does the concentration of smell molecules change
during diffusion?
Smell molecules move from an area of high concentration
to an area of lower concentration. This is called a
concentration gradient.
5 of 44
Changing concentrations
Diffusion can be represented on a simple diagram.
Where will the molecules be after diffusion?
before diffusion
after diffusion
What has happened to the concentration of the molecules?
Diffusion is the movement of gas or dissolved molecules
from higher to lower concentration.
Molecules diffuse down a concentration gradient.
What does this mean?
6 of 44
Diffusion animation 1
7 of 44
Diffusion animation 2
8 of 44
Diffusion animation 3
9 of 44
Contents
Movement In and Out of Cells
What is diffusion?
Diffusion and life processes
Active transport
Osmosis
Experiments: diffusion and osmosis
Multiple-choice quiz
10 of 44
Why is diffusion so important?
Diffusion explains why you can smell smelly smells and
what happens when you dilute a concentrated fruit drink.
More importantly, diffusion is an essential process
that is going on inside your body right now and
keeping you alive!
Diffusion occurs in the organ systems that control your
breathing, circulation, digestion and other life processes.
11 of 44
Diffusion and life processes
Diffusion is the movement of gas or dissolved molecules.
What gas and dissolved
molecules do body cells need?
Your body’s survival depends
on oxygen and dissolved food
molecules getting into your cells.
How do these vital substances cross boundaries
within the body to get to where they are needed?
Oxygen and dissolved food molecules
must diffuse into and out of the blood
for transportation around the body.
Where does diffusion take place within the body?
12 of 44
Diffusion and breathing
Breathing involves the exchange of
gases in the lungs, a process which
occurs by diffusion.
What is the vital gas that
you breathe in?
oxygen
What is the waste gas that
you breathe out?
carbon dioxide
The lungs have a huge surface area to maximize the
exchange of oxygen and carbon dioxide with each breath.
Where in the lungs does gas exchange take place?
13 of 44
Diffusion and breathing
Gas exchange takes place in the alveoli, the tiny air sacs
at the end of the bronchioles.
What are these blood vessels around each alveolus called?
14 of 44
Diffusion and breathing – oxygen
Inhaling increases the concentration of oxygen molecules
in an alveolus.
At this point, how does this compare with the concentration
of oxygen in deoxygenated blood in the capillary?
When you inhale,
the concentration
of oxygen inside
each alveolus is
higher than in
deoxygenated
blood.
deoxygenated blood
from the body
oxygen
into alveoli
oxygenated blood
to the body
15 of 44
Diffusion and breathing – oxygen
How is the concentration of oxygen in the blood increased?
Oxygen molecules diffuse across the lining of the alveolus
into the blood in the capillary, moving from higher to lower
concentration.
diffusion
When you inhale,
the concentration
of oxygen inside
each alveolus is
higher than in
deoxygenated
blood.
deoxygenated blood
from the body
oxygen
into alveoli
oxygenated blood
to the body
16 of 44
Diffusion and breathing – carbon dioxide
Deoxygenated blood from the body is low in oxygen
but has high levels of carbon dioxide.
How does this compare with concentration of carbon dioxide
in the alveolus?
The concentration
of carbon dioxide
in deoxygenated
blood is higher
than in
deoxygenated
blood.
deoxygenated blood
from the body
oxygenated blood
to the body
17 of 44
Diffusion and breathing – carbon dioxide
How is the concentration of carbon dioxide in the blood
reduced?
Carbon dioxide molecules diffuse from the blood in the
capillary into the alveolus, moving from higher to lower
concentration.
diffusion
The concentration
of carbon dioxide
in deoxygenated
blood is higher
than in
deoxygenated
blood.
deoxygenated blood
from the body
carbon dioxide
out of alveoli
oxygenated blood
to the body
18 of 44
Gas exchange animation
19 of 44
Diffusion and digestion
Carbohydrates, proteins and fat are made up of large
molecules that cannot be used directly by the body.
Digestion breaks large food
molecules into smaller molecules
that can be used by the body.
Dissolved food molecules
then need to be transported
from the small intestine into
the bloodstream.
Where in the small intestine does
this diffusion take place?
20 of 44
Inside the small intestine
21 of 44
Cross-section of a villus
Each villus separates the digested food in the small intestine
from a network of capillaries.
22 of 44
Diffusion from the small intestine
Each villus has a surface layer that is one cell thick.
How does the concentration of dissolved food molecules in
the small intestine compare with the blood entering a villus?
The concentration of
dissolved food molecules
is higher in the small
intestine than in the
blood entering the villus.
inside the
small intestine
blood entering
villus
wall of small
intestine
23 of 44
blood leaving
villus
Diffusion from the small intestine
How is the concentration of dissolved food molecules in the
blood increased?
Dissolved food molecules diffuse from the small intestine
into the blood, moving from higher to lower concentration.
The concentration of
dissolved food molecules
is higher in the small
intestine than in the
blood entering the villus.
inside the
small intestine
diffusion
blood entering
villus
wall of small
intestine
24 of 44
blood leaving
villus
Diffusion in and out of cells
Oxygen and dissolved food molecules are transported to
the body’s cells in the bloodstream.
How does the concentration of these useful substances in
the blood compare with the concentration inside the cells?
The concentration of
oxygen and dissolved
food molecules
is higher in the blood
arriving at the cells
than inside the cells.
25 of 44
Diffusion in and out of cells
How do oxygen and dissolved food molecules pass
from the blood into the cells?
Oxygen and dissolved food molecules diffuse into the
body cells, moving from higher to lower concentration.
diffusion
The concentration of
oxygen and dissolved
food molecules
is higher in the blood
arriving at the cells
than inside the cells.
What process involving
these useful substances
takes place inside the cell?
26 of 44
Diffusion in and out of cells
The cells use the food and oxygen for respiration.
Carbon dioxide is the waste product of respiration and
will poison a cell if it is not removed. How is it removed?
diffusion
Carbon dioxide molecules
diffuse from the cells into
the bloodstream, moving
from higher to lower
concentration.
How is this waste carbon
dioxide removed from the
body?
27 of 44
Contents
Movement In and Out of Cells
What is diffusion?
Diffusion and life processes
Active transport
Osmosis
Experiments: diffusion and osmosis
Multiple-choice quiz
28 of 44
What is active transport?
Movement of substances in and out of cells by diffusion
involves molecules moving down a concentration gradient
from high to low concentration.
high concentration
diffusion
active transport
low concentration
Sometimes substances move into cells from low to high
concentration. This is called active transport.
Active transport needs energy to make it happen.
How do molecules move along the concentration gradient
during active transport?
29 of 44
Active transport and plants
Plants need mineral elements from the soil for healthy
growth. Minerals enter a plant though its roots.
The concentration of minerals in the soil is lower than that
inside a root hair cell, so how do minerals enter the root cell?
root hair
cell
mineral
element
soil
30 of 44
Active transport and plants
Minerals enter a root cell by active transport.
The plant uses energy to move minerals up the
concentration gradient from the soil into its root cells.
Why is it important for plants to use energy in this way?
active transport
root hair
cell
mineral
element
soil
31 of 44
Contents
Movement In and Out of Cells
What is diffusion?
Diffusion and life processes
Active transport
Osmosis
Experiments: diffusion and osmosis
Multiple-choice quiz
32 of 44
What is osmosis?
Osmosis is a special type of diffusion.
Diffusion involves gas or dissolved molecules, but osmosis
only involves the movement of water molecules.
water
molecule
Osmosis occurs across a semipermeable membrane
which has tiny holes in it.
These holes are small enough for water molecules to pass
through but larger molecules cannot pass through.
33 of 44
What happens during osmosis?
Osmosis is a type of diffusion, so what do you think
happens to water molecules during this process?
osmosis
water
molecule
semipermeable membrane
Osmosis is the movement of water molecules from a region
of high water concentration to a region of low water
concentration across a semipermeable membrane.
34 of 44
Osmosis experiment
A bag made from a semipermeable membrane is tied
to a glass tube and filled with a strong sugar solution.
This bag is placed in a weak sugar solution.
strong sugar
solution
weak sugar
solution
What happens to the water molecules in the weak solution?
What happens to the liquid inside the semipermeable bag?
35 of 44
Osmosis experiment
The volume of liquid in the semipermeable bag increases.
The liquid rises up the glass tube and then stops.
Why does this happen?
strong sugar
solution
weak sugar
solution
Water molecules diffuse across the membrane from the
weak sugar solution into the strong sugar solution.
This continues until the concentration is the same on both
sides of the membrane.
36 of 44
Osmosis animation 1
37 of 44
Osmosis animation 2
38 of 44
Contents
Movement In and Out of Cells
What is diffusion?
Diffusion and life processes
Active transport
Osmosis
Experiments: diffusion and osmosis
Multiple-choice quiz
39 of 44
Experiment to demonstrate diffusion
40 of 44
Experiment to investigate osmosis
41 of 44
Contents
Movement In and Out of Cells
What is diffusion?
Diffusion and life processes
Active transport
Osmosis
Experiments: diffusion and osmosis
Multiple-choice quiz
42 of 44
Multiple-choice quiz
43 of 44