Cells (chap 1) -olevel pure biology

What is a cell?

The basic building blocks of life

What is protoplasm consisting of?

Nucleus, cell membrane, cytoplasm

Cytoplasm

-Contains organelles

-where most cellular activities take place

cell membrane

-controls movement of substances in and out of the cell

- made of lipids and proteins

-is a partially permeable membrane and only allows small and soluble molecules to pass through

nucleus

-surrounded by nuclear membrane that separates it from the cytoplasm

-controls cell activities

-essential for cell division

-chromosomes -long thread like substance

-made of DNA which contains hereditary information

-when the cell is dividing, chromosomes condense and shorten to become thick, rod-shaped structures

what is a organelle

a cellular structure that performs specific functions within the cell

rough ER

-a network of flattened spaces lined with a membrane and its outer surface is continuous with the nuclear membrane

-there are ribosomes attached to its surface hence it appears rough

-is involved in protein synthesis and transport of proteins

smooth ER

-more tubular than rough ER

-synthesises substances such as fats and steroids

-is involved in detoxification

ribosomes

-involved in protein synthesis

-either attach itself to RER or lie freely in the cytoplasm

-attached to RER: make proteins that are usually transported out of the cell

-in cytoplasm: make proteins that are used within the cytoplasm of that cell

golgi body

-consists of a stack of flattened spaces surrounded by membranes

-chemically modifies substances made by the ER

-stores and packages these substances in vesicles for secretion out of the cell

mithocondria

-site of aerobic respiration

-food substances are broken down to release energy for cellular activities

chloroplasts

-contain chlorophyll which is essential for photosynthesis

-can only be found in leaf cells

vacuole

-fluid filled space enclosed by a partially permeable membrane

-store substances within a cell

-plant cell: has a large central vacuole containing dissolved substances such as sugars, minerals salts and amino acids

-animal cell: has numerous small vacuoles that contain water and food substances. exist temporarily

cell wall

-fully permeable

- made of cellulose

-gives the cell a fixed shape

-only found in plant cells

what is differentiation

the process by which a cell becomes specialised for a specific function

adaptations of a red blood cell

-contains haemogloblin which binds to oxygen to form oxyhaemogloblin to transport oxygen around the body

-has a circular biconcave shape which increases surface area-to-volume ratio so oxygen can diffuse in and out at a higher rate

-has no nucleus to allow the cell to store more haemogloblin for more transport of oxygen

-is flexible and can squeeze through capillaries easily

adaptations of root hair cell

-has a long and narrow extension to increase surface area-to-volume ratio to absorb water and mineral salts at a higher rate

adaptations of muscle cell

-contains many nuclei for more cell division

-contains many mitochondria to provide more energy for contraction of muscle cell

-has contractile protein fibres to contract and relax to bring about movement

how substances made by ER are moved out of the cell

1. proteins made by ribosomes in the RER are packaged into vesicles. they pinch off from the RER and move to the golgi body.

2. these vesicles fuse with the golgi body and release their contents into the Golgi body. the substances made by the ER may be modified inside the Golgi body.

3. secretory vesicles containing these modified substances are pinched off from the Golgi body. they then move to the cell membrane.

4. the secretory vesicles fuse with the cell membrane and their contents are released out of the cell.