B1: Cell Structure and Transport

Topics covered: White/Black - Organelles Yellow - Eukaryotic/Prokaryotic Red - Specialised Cells Blue - Sizes of Cells Purple - Magnification Green - Diffusion, Osmosis, Active Transport

Nucleus

Contains genetic information. Surrounded by nuclear membrane, and controls the cell.

Cytoplasm

Where chemical reactions happen in the cell.

Cell Membrane

Membrane around the contents of a cell that determine what can move in and out.

Cell Wall

Rigid structure around plant cells that strengthen the cell and hold its shape. Only present in plant cells.

Mitochondria

Site of aerobic respiration within a cell

Ribosomes

Site of protein synthesis (creation) within a cell

Permanent Vacuole

Space in the cytoplasm filled with cell sap. Only present in plant cells.

Chloroplasts

Where photosynthesis takes place. Usually has a green pigment and chlorophyll, only present in plant cells.

Eukaryotic Cell

Eukaryotic cells have a nucleus wrapped in a nuclear membrane. This is known as a true nucleus. All animal and plant cells are eukaryotic cells.

Prokaryotic Cells

Prokaryotic cells are a type of cell that do not have a nucleus. The DNA is free in the cytoplasm. Bacteria are a type of prokaryotic cells.

Plasmids

Small bits of DNA that carry extra genes. Only present in Prokaryotic cells.

Flagella

Used for movement. Only found in prokaryotic cells.

Size of a Plant cell

100µm

Size of an Animal Cell

10µm

Size of a Bacteria cell

1µm

Size of a Virus

50-100nm

What does it mean if a cell has become specialised?

A cell that has a special shape and features that help it to do it’s job.

Palisade Cell

Chloroplasts contain Chlorophyll.

Continuous Layers.

Large permanent Vacuole.

Root Hair Cell

Increase the surface area where water can enter the cell.

Vacuole speeds up water movement.

Active mitochondria.

Muscle Cell

Can contract.

Have lots of mitochondria to provide energy.

Sperm Cell

Large nucleus.

Contain digestive enzymes.

Many mitochondria.

Have a long tail.

Guard Cell

Half-Circle shape.

Found in pairs.

Red Blood Cell

Increased surface area (biconcave)

Packed with haemoglobin that binds to oxygen.

Have no nucleus.

Nerve Cell

Lots of dendrites to connect to other nerve cells.

Axon that carries the nerve impulse.

Endings pass impulse.

Egg Cell

Large in diameter.

Contain stored food.

Large nucleus.

23 chromosomes.

Magnification

The amount of times a specimen has been enlarged

Resolution

The minimum distance two objects need to be apart to be seen as separate (the clarity)

Light Microscopes

Work by sending a beam of light rays from a source underneath the sample of cells that you are looking at. The light passes through several glass lenses that magnify the image.

Electron Microscopes.

Bigger and more complex than light microscopes. Instead of using light, they send a beam of electrons through the cells. The electrons also pass through lenses but they are made of magnets, not glass. The image of the cells can be seen on a computer screen rather than an eyepiece.

Microscopy Calculation Triangle

Image Size = Actual Size x Magnification (I = AM)

What are cell walls made out of?

Cellulose

Why do nerve cells have a long axon?

So it can reach every part of your body.

What is transported in xylem cells?

Water and Minerals.

What is transported in Phloem cells?

Sugar and Amino Acids.

What is the proper name for the process of a cell becoming specialised?

Cell Differentiation

Advantages of using Light Microscopes

Less Expensive

Can view in colour

Specimen can be alive

Small and Portable

Advantages of using Electron microscopes

Greater Magnification

Greater Resolution

Diffusion

The net movement of molecules from a region of high concentration to a region of low concentration until equilibrium is reached.

Factors which affect the rate of Diffusion

Surface Area (large SA = larger rate of diffusion)

Concentration Gradient (greater concentration difference = faster diffusion)

Temperature (higher temperature = larger rate of diffusion due to kinetic energy)

Diffusion Distance (smaller distance = larger rate of diffusion)

Exchange Surfaces (5 of them)

Lungs (Exchange oxygen from the air with carbon dioxide in the blood)

Small Intestine (Exchanges fatty acids and glycerol)

Gills in fish (Exchange oxygen in water)

Roots in plants (Exchange water and nutrients from the soil)

Leaves in plants (Exchange Oxygen, Carbon Dioxide and water)

Osmosis

The movement of water from a dilute (high concentration) solution to a more concentrated (low concentration) solution through a partially permeable membrane that allows water to pass through.

Hypotonic Solution

Higher concentration of water outside of the cell than inside, so water will move into the cell via osmosis.

Isotonic Solution

There is the same concentration of water outside and inside the cell. Water will not move in or out.

Hypertonic Solution

There is a higher concentration of water inside of the cell, so water will move out of the cell via osmosis.

Animal + Plant Cells in Hypotonic Solutions

Animal cells will burst as there will be too much water moving in. Plant cells will fill up and become turgid but will not burst as the strong cell wall prevents bursting.

Animal + Plant Cells in Isotonic Solutions

Animal cells will stay the same as there is no net movement of water. Plant cells will become flaccid.

Animal + Plant Cells in Hypertonic Solutions

Animal cells will shrivel due to a lack of water (Crenation). In plant cells, the vacuole and cytoplasm will shrink away from the cell wall.

How to calculate % change in mass

Change in mass/Initial Mass

Intercept (Graph of Osmosis Practical)

The intercept is the point at which the line crossed the x axis. This is where there is 0 net change in mass, which means the concentration of water inside and outside of the cells is equal. This is how you can figure out the concentration of the solution.

Active Transport

The movement of molecules or ions from an area of low concentration to an area of high concentration using energy from respiration and carrier proteins.

Active Transport in Plant Roots

Allows mineral ions to be absorbed into plant root hair cells. They need to be absorbed via active transport as there is a higher concentration of mineral ions inside the root.

Active Transport in the Small Intestine

Sugars absorbed by the bloodstream from the gut are needed for Cell Respiration. They need to be absorbed via active transport because the concentration of glucose in the blood is higher than glucose in the gut.

SA:V Ratio

The smaller a cube (size), the larger the SA:V ratio. (Surface Area : Volume ratio)

How are Root Hair Cells adapted to carry out Active Transport?

Large permanent vacuole increases the speed of water from the soil across the cell.

Sticky-out part increases the surface area for water to move in.

Lots of mitochondria which transfer the energy needed for active transport of mineral ions.

Thin surface area over which things travel.

How are Small Intestine Cells adapted to carry out Active Transport?

Lots of mitochondria, transferring the energy needed for Active Transport.

‘Villi’ or ‘microvilli’ are small folds which increase surface area for glucose to be absorbed.

Thin cell membrane (one cell thick)

High blood supply which maintains a steep concentration gradient.