Cells

Cells

Cell Structure & Function

• Cytoplasm is found inside the cell and contains all the other cell structures

• The large nucleus is surrounded by a nuclear membrane to separate it from the cytoplasm

• The cell membrane surrounds the cell

• The cell wall is made of cellulose and surrounds the cell membrane in plant cells

Cell Structure & Function

• Mitochondria (singular: mitochondrion) are organelles found throughout the cytoplasm

• Chloroplasts are organelles found in the cytoplasm that are packed with the pigment chlorophyll and so are green in colour

• Ribosomes are tiny structures that can be free within the cytoplasm or attached to a system of membranes inside the cell

• Vacuoles are large vesicles that take up a large part of the interior of plant cells

specialised cells

• Specialised cells are those which have developed certain characteristics in order to perform particular functions

• Cells specialise by undergoing differentiation: a process that involves the cell gaining new structures within the cell in order for it to be suited to its function

• Cells can either differentiate once early on or have the ability to differentiate their whole lives (these are called stem cells) In animals, most cells only differentiate once, but in plants many cells retain the ability

Stem cells

• Many tissues in the human body contain a small number of undifferentiated cells

• These are called stem cells and their function is to divide and produce new differentiated cells within the tissue for growth and repair

• Adult stem cells from bone marrow are quite useful in medicine as they can be directed to differentiate into several different cell types (unlike adult stem cells from other tissues which can only differentiate into related cell types)

Stem cells are also found in great numbers in embryonic tissue as there is a large amount of development and differentiation going on during foetal development Scientists can clone these embryonic stem cells and direct them to differentiate into almost any cell type

Multiple Choice

Site of aerobic respiration

• mitochondria

• ribosomes

• nucleus

• vacuole

Multiple Choice

site of protein synthesis

• mitochondria

• ribosomes

• nucleus

• vacuole

Multiple Choice

provides cell with support

• cell membrane

• cell wall

• nucleus

• chloroplasts

Multiple Choice

controls what enters and leaves the cell

• cell wall

• cell membrane

• vacuole

• nucleus

Multiple Choice

needed for photosynthesis

• cell wall

• vacuole

• nucelus

• chloroplasts

Multiple Choice

all chemical reactions take place here

• cytoplasm

• cell membrane

• nucleus

• vacuole

Multiple Choice

used as storage and to provide extra support

• cytoplasm

• vacuole

• ribosomes

• nucleus

Open Ended

what is a stem cell?

Movement Across Membranes

• All cells are surrounded by a cell membrane which is partially permeable

• Molecules can move in and out of cells by diffusion or active transport

• Water can move in and out of cells by osmosis

What Affects Rate of Movement?

• Surface Area to Volume Ratio

  The bigger a cell or structure is, the smaller its surface area to volume ratio is, slowing down the rate at which substances can move across its surface

• Many cells which are adapted for diffusion have increased surface area in some way – eg root hair cells in plants (which absorb water and mineral ions) and cells lining the ileum in animals (which absorb the products of digestion)

What Affects Rate of Movement?

• Distance

  The smaller the distance molecules have to travel the faster transport will occur

• This is why blood capillaries and alveoli have walls which are only one cell thick, ensuring the rate of diffusion across them is as fast as possible

What Affects Rate of Movement?

• Temperature

  The higher the temperature, the faster molecules move as they have more energy

• This results in more collisions against the cell membrane and therefore a faster rate of movement across them

What Affects Rate of Movement?

• Concentration Gradient

  The greater the difference in concentration either side of the membrane, the faster movement across it will occur

• This is because on the side with the higher concentration, more random collisions against the membrane will occur

Fill in the Blank

by which two process' do molecules pass in and out of cells?

Fill in the Blank

by which process does water move in and out of cells?

Fill in the Blank

Which process sees particles move against a concentration gradient ? (low to high)

Open Ended

How does surface are affect the net movement of particles?

Open Ended

How does does distance affect the net movement of particles?

Open Ended

How does temperature affect the rate of movement?

Open Ended

How does concentration affect the rate of movement?

Fill in the Blank

Which type of particle movement is happening in the diagram?

Fill in the Blank

Where in the body is this happening?

Open Ended

Explain what is happening in the diagram in terms of molecule movement