Biology GCSE AQA - Cells and membranes

What organelles do both plants and animals have?

Nucleus, Cytoplasm, Cell Membrane

Give three differences between bacterial (prokaryotic) DNA and eukaryotic DNA

Bacteria don't have a nucleus. Bacterial DNA is single stranded. Bacterial DNA may be in the form of small loops called plasmids

How do you turn millimetres into micrometres?

x1000

Name 5 organelles found in an animal cell

Nucleus, Cell Membrane, Cytoplasm, Ribosome, Mitochondria

What happens in stage one of the cell cycle?

The cell grows and the number of organelles increases and DNA replicates

Name 2 organelles only found in plant cells

Chloroplasts and a vacuole

What is the difference between animal cell differentiation and plant cell differentiation?

Animal cells differentiate for a limited amount of time, whereas most plant cells can differentiate throughout the plants life

How have electron microscopes helped increase our understanding of sub-cellular structures?

They have a higher magnification and resolution than light microscopes so we can see smaller organelles, like ribosomes - which aren't visible under light microscopes

How can you calculate magnification

Magnification \= eyepiece x objective lens

How is DNA stored in a cell?

As chromosomes in the nucleus

What happens in stage 2 of the cell cycle?

Mitosis - one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides

What happens in stage 3 of the cell cycle?

The cells splits into two

What is mitosis used for?

Growth, Repair, Replacement and Asexual reproduction

What is a stem cell?

An undifferentiated cell

What is the role of stem cells in embryos?

At this point stem cells can differentiate into any cell type needed by the embryo

What is the role of stem cells in adults?

To replace body cells that die or are injured

What is the role of stem cells in the meristem?

The meristem is the only location that growth can happen in the plant. Meristem tissue can differentiate into many different types of cell throughout the plants life

Name two diseases that could be treated with stem cells

Diabetes and Paralysis

What is therapeutic cloning?

An embryo is made with the same genes as the patient. Stem cells from the embryo aren't rejected so they can be used for medical treatment

What is the role of the mitochondria?

Release energy by respiration

What is the role of the ribosome?

Make proteins

What is the role of the vacuole?

Stores cell sap

What is the role of the chloroplast?

Photosynthesis

How do you work out actual size of a magnified image?

Image size divided by magnification

Give a disadvantage of using embryonic stem cells

It destroys the embryo

Diffusion

The movement of molecules from an area of greater concentration to an area of lower concentration. Does not require energy. Example: Oxygen moves from the alveolar air space to blood around the lungs.

Osmosis

The movement of water across a semipermeable membrane through diffusion. Moving from an area of high concentration to low concentration.

Active transport

The movement of substances from an area of low concentration to an area of high concentration using a carrier protein. This movement is against the concentration gradient. As a result cells can absorb ions from very dilute solutions. It also enables cells to move substances, such as sugars or ions, from one place to another through the cell membrane.